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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /library/core/src/fmt
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/core/src/fmt')
-rw-r--r--library/core/src/fmt/builders.rs939
-rw-r--r--library/core/src/fmt/float.rs226
-rw-r--r--library/core/src/fmt/mod.rs2664
-rw-r--r--library/core/src/fmt/nofloat.rs15
-rw-r--r--library/core/src/fmt/num.rs683
-rw-r--r--library/core/src/fmt/rt/v1.rs45
6 files changed, 4572 insertions, 0 deletions
diff --git a/library/core/src/fmt/builders.rs b/library/core/src/fmt/builders.rs
new file mode 100644
index 000000000..32d1a4e55
--- /dev/null
+++ b/library/core/src/fmt/builders.rs
@@ -0,0 +1,939 @@
+#![allow(unused_imports)]
+
+use crate::fmt::{self, Debug, Formatter};
+
+struct PadAdapter<'buf, 'state> {
+ buf: &'buf mut (dyn fmt::Write + 'buf),
+ state: &'state mut PadAdapterState,
+}
+
+struct PadAdapterState {
+ on_newline: bool,
+}
+
+impl Default for PadAdapterState {
+ fn default() -> Self {
+ PadAdapterState { on_newline: true }
+ }
+}
+
+impl<'buf, 'state> PadAdapter<'buf, 'state> {
+ fn wrap<'slot, 'fmt: 'buf + 'slot>(
+ fmt: &'fmt mut fmt::Formatter<'_>,
+ slot: &'slot mut Option<Self>,
+ state: &'state mut PadAdapterState,
+ ) -> fmt::Formatter<'slot> {
+ fmt.wrap_buf(move |buf| slot.insert(PadAdapter { buf, state }))
+ }
+}
+
+impl fmt::Write for PadAdapter<'_, '_> {
+ fn write_str(&mut self, mut s: &str) -> fmt::Result {
+ while !s.is_empty() {
+ if self.state.on_newline {
+ self.buf.write_str(" ")?;
+ }
+
+ let split = match s.find('\n') {
+ Some(pos) => {
+ self.state.on_newline = true;
+ pos + 1
+ }
+ None => {
+ self.state.on_newline = false;
+ s.len()
+ }
+ };
+ self.buf.write_str(&s[..split])?;
+ s = &s[split..];
+ }
+
+ Ok(())
+ }
+}
+
+/// A struct to help with [`fmt::Debug`](Debug) implementations.
+///
+/// This is useful when you wish to output a formatted struct as a part of your
+/// [`Debug::fmt`] implementation.
+///
+/// This can be constructed by the [`Formatter::debug_struct`] method.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Foo {
+/// bar: i32,
+/// baz: String,
+/// }
+///
+/// impl fmt::Debug for Foo {
+/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+/// fmt.debug_struct("Foo")
+/// .field("bar", &self.bar)
+/// .field("baz", &self.baz)
+/// .finish()
+/// }
+/// }
+///
+/// assert_eq!(
+/// format!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() }),
+/// "Foo { bar: 10, baz: \"Hello World\" }",
+/// );
+/// ```
+#[must_use = "must eventually call `finish()` on Debug builders"]
+#[allow(missing_debug_implementations)]
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub struct DebugStruct<'a, 'b: 'a> {
+ fmt: &'a mut fmt::Formatter<'b>,
+ result: fmt::Result,
+ has_fields: bool,
+}
+
+pub(super) fn debug_struct_new<'a, 'b>(
+ fmt: &'a mut fmt::Formatter<'b>,
+ name: &str,
+) -> DebugStruct<'a, 'b> {
+ let result = fmt.write_str(name);
+ DebugStruct { fmt, result, has_fields: false }
+}
+
+impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
+ /// Adds a new field to the generated struct output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Bar {
+ /// bar: i32,
+ /// another: String,
+ /// }
+ ///
+ /// impl fmt::Debug for Bar {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_struct("Bar")
+ /// .field("bar", &self.bar) // We add `bar` field.
+ /// .field("another", &self.another) // We add `another` field.
+ /// // We even add a field which doesn't exist (because why not?).
+ /// .field("not_existing_field", &1)
+ /// .finish() // We're good to go!
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Bar { bar: 10, another: "Hello World".to_string() }),
+ /// "Bar { bar: 10, another: \"Hello World\", not_existing_field: 1 }",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut Self {
+ self.result = self.result.and_then(|_| {
+ if self.is_pretty() {
+ if !self.has_fields {
+ self.fmt.write_str(" {\n")?;
+ }
+ let mut slot = None;
+ let mut state = Default::default();
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
+ writer.write_str(name)?;
+ writer.write_str(": ")?;
+ value.fmt(&mut writer)?;
+ writer.write_str(",\n")
+ } else {
+ let prefix = if self.has_fields { ", " } else { " { " };
+ self.fmt.write_str(prefix)?;
+ self.fmt.write_str(name)?;
+ self.fmt.write_str(": ")?;
+ value.fmt(self.fmt)
+ }
+ });
+
+ self.has_fields = true;
+ self
+ }
+
+ /// Marks the struct as non-exhaustive, indicating to the reader that there are some other
+ /// fields that are not shown in the debug representation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Bar {
+ /// bar: i32,
+ /// hidden: f32,
+ /// }
+ ///
+ /// impl fmt::Debug for Bar {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_struct("Bar")
+ /// .field("bar", &self.bar)
+ /// .finish_non_exhaustive() // Show that some other field(s) exist.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Bar { bar: 10, hidden: 1.0 }),
+ /// "Bar { bar: 10, .. }",
+ /// );
+ /// ```
+ #[stable(feature = "debug_non_exhaustive", since = "1.53.0")]
+ pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
+ self.result = self.result.and_then(|_| {
+ if self.has_fields {
+ if self.is_pretty() {
+ let mut slot = None;
+ let mut state = Default::default();
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
+ writer.write_str("..\n")?;
+ self.fmt.write_str("}")
+ } else {
+ self.fmt.write_str(", .. }")
+ }
+ } else {
+ self.fmt.write_str(" { .. }")
+ }
+ });
+ self.result
+ }
+
+ /// Finishes output and returns any error encountered.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Bar {
+ /// bar: i32,
+ /// baz: String,
+ /// }
+ ///
+ /// impl fmt::Debug for Bar {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_struct("Bar")
+ /// .field("bar", &self.bar)
+ /// .field("baz", &self.baz)
+ /// .finish() // You need to call it to "finish" the
+ /// // struct formatting.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Bar { bar: 10, baz: "Hello World".to_string() }),
+ /// "Bar { bar: 10, baz: \"Hello World\" }",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn finish(&mut self) -> fmt::Result {
+ if self.has_fields {
+ self.result = self.result.and_then(|_| {
+ if self.is_pretty() { self.fmt.write_str("}") } else { self.fmt.write_str(" }") }
+ });
+ }
+ self.result
+ }
+
+ fn is_pretty(&self) -> bool {
+ self.fmt.alternate()
+ }
+}
+
+/// A struct to help with [`fmt::Debug`](Debug) implementations.
+///
+/// This is useful when you wish to output a formatted tuple as a part of your
+/// [`Debug::fmt`] implementation.
+///
+/// This can be constructed by the [`Formatter::debug_tuple`] method.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Foo(i32, String);
+///
+/// impl fmt::Debug for Foo {
+/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+/// fmt.debug_tuple("Foo")
+/// .field(&self.0)
+/// .field(&self.1)
+/// .finish()
+/// }
+/// }
+///
+/// assert_eq!(
+/// format!("{:?}", Foo(10, "Hello World".to_string())),
+/// "Foo(10, \"Hello World\")",
+/// );
+/// ```
+#[must_use = "must eventually call `finish()` on Debug builders"]
+#[allow(missing_debug_implementations)]
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub struct DebugTuple<'a, 'b: 'a> {
+ fmt: &'a mut fmt::Formatter<'b>,
+ result: fmt::Result,
+ fields: usize,
+ empty_name: bool,
+}
+
+pub(super) fn debug_tuple_new<'a, 'b>(
+ fmt: &'a mut fmt::Formatter<'b>,
+ name: &str,
+) -> DebugTuple<'a, 'b> {
+ let result = fmt.write_str(name);
+ DebugTuple { fmt, result, fields: 0, empty_name: name.is_empty() }
+}
+
+impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
+ /// Adds a new field to the generated tuple struct output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32, String);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_tuple("Foo")
+ /// .field(&self.0) // We add the first field.
+ /// .field(&self.1) // We add the second field.
+ /// .finish() // We're good to go!
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(10, "Hello World".to_string())),
+ /// "Foo(10, \"Hello World\")",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut Self {
+ self.result = self.result.and_then(|_| {
+ if self.is_pretty() {
+ if self.fields == 0 {
+ self.fmt.write_str("(\n")?;
+ }
+ let mut slot = None;
+ let mut state = Default::default();
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
+ value.fmt(&mut writer)?;
+ writer.write_str(",\n")
+ } else {
+ let prefix = if self.fields == 0 { "(" } else { ", " };
+ self.fmt.write_str(prefix)?;
+ value.fmt(self.fmt)
+ }
+ });
+
+ self.fields += 1;
+ self
+ }
+
+ /// Finishes output and returns any error encountered.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32, String);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_tuple("Foo")
+ /// .field(&self.0)
+ /// .field(&self.1)
+ /// .finish() // You need to call it to "finish" the
+ /// // tuple formatting.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(10, "Hello World".to_string())),
+ /// "Foo(10, \"Hello World\")",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn finish(&mut self) -> fmt::Result {
+ if self.fields > 0 {
+ self.result = self.result.and_then(|_| {
+ if self.fields == 1 && self.empty_name && !self.is_pretty() {
+ self.fmt.write_str(",")?;
+ }
+ self.fmt.write_str(")")
+ });
+ }
+ self.result
+ }
+
+ fn is_pretty(&self) -> bool {
+ self.fmt.alternate()
+ }
+}
+
+struct DebugInner<'a, 'b: 'a> {
+ fmt: &'a mut fmt::Formatter<'b>,
+ result: fmt::Result,
+ has_fields: bool,
+}
+
+impl<'a, 'b: 'a> DebugInner<'a, 'b> {
+ fn entry(&mut self, entry: &dyn fmt::Debug) {
+ self.result = self.result.and_then(|_| {
+ if self.is_pretty() {
+ if !self.has_fields {
+ self.fmt.write_str("\n")?;
+ }
+ let mut slot = None;
+ let mut state = Default::default();
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
+ entry.fmt(&mut writer)?;
+ writer.write_str(",\n")
+ } else {
+ if self.has_fields {
+ self.fmt.write_str(", ")?
+ }
+ entry.fmt(self.fmt)
+ }
+ });
+
+ self.has_fields = true;
+ }
+
+ fn is_pretty(&self) -> bool {
+ self.fmt.alternate()
+ }
+}
+
+/// A struct to help with [`fmt::Debug`](Debug) implementations.
+///
+/// This is useful when you wish to output a formatted set of items as a part
+/// of your [`Debug::fmt`] implementation.
+///
+/// This can be constructed by the [`Formatter::debug_set`] method.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Foo(Vec<i32>);
+///
+/// impl fmt::Debug for Foo {
+/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+/// fmt.debug_set().entries(self.0.iter()).finish()
+/// }
+/// }
+///
+/// assert_eq!(
+/// format!("{:?}", Foo(vec![10, 11])),
+/// "{10, 11}",
+/// );
+/// ```
+#[must_use = "must eventually call `finish()` on Debug builders"]
+#[allow(missing_debug_implementations)]
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub struct DebugSet<'a, 'b: 'a> {
+ inner: DebugInner<'a, 'b>,
+}
+
+pub(super) fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b> {
+ let result = fmt.write_str("{");
+ DebugSet { inner: DebugInner { fmt, result, has_fields: false } }
+}
+
+impl<'a, 'b: 'a> DebugSet<'a, 'b> {
+ /// Adds a new entry to the set output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>, Vec<u32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_set()
+ /// .entry(&self.0) // Adds the first "entry".
+ /// .entry(&self.1) // Adds the second "entry".
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+ /// "{[10, 11], [12, 13]}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
+ self.inner.entry(entry);
+ self
+ }
+
+ /// Adds the contents of an iterator of entries to the set output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>, Vec<u32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_set()
+ /// .entries(self.0.iter()) // Adds the first "entry".
+ /// .entries(self.1.iter()) // Adds the second "entry".
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+ /// "{10, 11, 12, 13}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
+ where
+ D: fmt::Debug,
+ I: IntoIterator<Item = D>,
+ {
+ for entry in entries {
+ self.entry(&entry);
+ }
+ self
+ }
+
+ /// Finishes output and returns any error encountered.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_set()
+ /// .entries(self.0.iter())
+ /// .finish() // Ends the struct formatting.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11])),
+ /// "{10, 11}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn finish(&mut self) -> fmt::Result {
+ self.inner.result.and_then(|_| self.inner.fmt.write_str("}"))
+ }
+}
+
+/// A struct to help with [`fmt::Debug`](Debug) implementations.
+///
+/// This is useful when you wish to output a formatted list of items as a part
+/// of your [`Debug::fmt`] implementation.
+///
+/// This can be constructed by the [`Formatter::debug_list`] method.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Foo(Vec<i32>);
+///
+/// impl fmt::Debug for Foo {
+/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+/// fmt.debug_list().entries(self.0.iter()).finish()
+/// }
+/// }
+///
+/// assert_eq!(
+/// format!("{:?}", Foo(vec![10, 11])),
+/// "[10, 11]",
+/// );
+/// ```
+#[must_use = "must eventually call `finish()` on Debug builders"]
+#[allow(missing_debug_implementations)]
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub struct DebugList<'a, 'b: 'a> {
+ inner: DebugInner<'a, 'b>,
+}
+
+pub(super) fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a, 'b> {
+ let result = fmt.write_str("[");
+ DebugList { inner: DebugInner { fmt, result, has_fields: false } }
+}
+
+impl<'a, 'b: 'a> DebugList<'a, 'b> {
+ /// Adds a new entry to the list output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>, Vec<u32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_list()
+ /// .entry(&self.0) // We add the first "entry".
+ /// .entry(&self.1) // We add the second "entry".
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+ /// "[[10, 11], [12, 13]]",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
+ self.inner.entry(entry);
+ self
+ }
+
+ /// Adds the contents of an iterator of entries to the list output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>, Vec<u32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_list()
+ /// .entries(self.0.iter())
+ /// .entries(self.1.iter())
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
+ /// "[10, 11, 12, 13]",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
+ where
+ D: fmt::Debug,
+ I: IntoIterator<Item = D>,
+ {
+ for entry in entries {
+ self.entry(&entry);
+ }
+ self
+ }
+
+ /// Finishes output and returns any error encountered.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_list()
+ /// .entries(self.0.iter())
+ /// .finish() // Ends the struct formatting.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![10, 11])),
+ /// "[10, 11]",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn finish(&mut self) -> fmt::Result {
+ self.inner.result.and_then(|_| self.inner.fmt.write_str("]"))
+ }
+}
+
+/// A struct to help with [`fmt::Debug`](Debug) implementations.
+///
+/// This is useful when you wish to output a formatted map as a part of your
+/// [`Debug::fmt`] implementation.
+///
+/// This can be constructed by the [`Formatter::debug_map`] method.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Foo(Vec<(String, i32)>);
+///
+/// impl fmt::Debug for Foo {
+/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+/// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
+/// }
+/// }
+///
+/// assert_eq!(
+/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+/// "{\"A\": 10, \"B\": 11}",
+/// );
+/// ```
+#[must_use = "must eventually call `finish()` on Debug builders"]
+#[allow(missing_debug_implementations)]
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub struct DebugMap<'a, 'b: 'a> {
+ fmt: &'a mut fmt::Formatter<'b>,
+ result: fmt::Result,
+ has_fields: bool,
+ has_key: bool,
+ // The state of newlines is tracked between keys and values
+ state: PadAdapterState,
+}
+
+pub(super) fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b> {
+ let result = fmt.write_str("{");
+ DebugMap { fmt, result, has_fields: false, has_key: false, state: Default::default() }
+}
+
+impl<'a, 'b: 'a> DebugMap<'a, 'b> {
+ /// Adds a new entry to the map output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_map()
+ /// .entry(&"whole", &self.0) // We add the "whole" entry.
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// "{\"whole\": [(\"A\", 10), (\"B\", 11)]}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut Self {
+ self.key(key).value(value)
+ }
+
+ /// Adds the key part of a new entry to the map output.
+ ///
+ /// This method, together with `value`, is an alternative to `entry` that
+ /// can be used when the complete entry isn't known upfront. Prefer the `entry`
+ /// method when it's possible to use.
+ ///
+ /// # Panics
+ ///
+ /// `key` must be called before `value` and each call to `key` must be followed
+ /// by a corresponding call to `value`. Otherwise this method will panic.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_map()
+ /// .key(&"whole").value(&self.0) // We add the "whole" entry.
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// "{\"whole\": [(\"A\", 10), (\"B\", 11)]}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_map_key_value", since = "1.42.0")]
+ pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut Self {
+ self.result = self.result.and_then(|_| {
+ assert!(
+ !self.has_key,
+ "attempted to begin a new map entry \
+ without completing the previous one"
+ );
+
+ if self.is_pretty() {
+ if !self.has_fields {
+ self.fmt.write_str("\n")?;
+ }
+ let mut slot = None;
+ self.state = Default::default();
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut self.state);
+ key.fmt(&mut writer)?;
+ writer.write_str(": ")?;
+ } else {
+ if self.has_fields {
+ self.fmt.write_str(", ")?
+ }
+ key.fmt(self.fmt)?;
+ self.fmt.write_str(": ")?;
+ }
+
+ self.has_key = true;
+ Ok(())
+ });
+
+ self
+ }
+
+ /// Adds the value part of a new entry to the map output.
+ ///
+ /// This method, together with `key`, is an alternative to `entry` that
+ /// can be used when the complete entry isn't known upfront. Prefer the `entry`
+ /// method when it's possible to use.
+ ///
+ /// # Panics
+ ///
+ /// `key` must be called before `value` and each call to `key` must be followed
+ /// by a corresponding call to `value`. Otherwise this method will panic.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_map()
+ /// .key(&"whole").value(&self.0) // We add the "whole" entry.
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// "{\"whole\": [(\"A\", 10), (\"B\", 11)]}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_map_key_value", since = "1.42.0")]
+ pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut Self {
+ self.result = self.result.and_then(|_| {
+ assert!(self.has_key, "attempted to format a map value before its key");
+
+ if self.is_pretty() {
+ let mut slot = None;
+ let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut self.state);
+ value.fmt(&mut writer)?;
+ writer.write_str(",\n")?;
+ } else {
+ value.fmt(self.fmt)?;
+ }
+
+ self.has_key = false;
+ Ok(())
+ });
+
+ self.has_fields = true;
+ self
+ }
+
+ /// Adds the contents of an iterator of entries to the map output.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_map()
+ /// // We map our vec so each entries' first field will become
+ /// // the "key".
+ /// .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// "{\"A\": 10, \"B\": 11}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn entries<K, V, I>(&mut self, entries: I) -> &mut Self
+ where
+ K: fmt::Debug,
+ V: fmt::Debug,
+ I: IntoIterator<Item = (K, V)>,
+ {
+ for (k, v) in entries {
+ self.entry(&k, &v);
+ }
+ self
+ }
+
+ /// Finishes output and returns any error encountered.
+ ///
+ /// # Panics
+ ///
+ /// `key` must be called before `value` and each call to `key` must be followed
+ /// by a corresponding call to `value`. Otherwise this method will panic.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// fmt.debug_map()
+ /// .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
+ /// .finish() // Ends the struct formatting.
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// "{\"A\": 10, \"B\": 11}",
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn finish(&mut self) -> fmt::Result {
+ self.result.and_then(|_| {
+ assert!(!self.has_key, "attempted to finish a map with a partial entry");
+
+ self.fmt.write_str("}")
+ })
+ }
+
+ fn is_pretty(&self) -> bool {
+ self.fmt.alternate()
+ }
+}
diff --git a/library/core/src/fmt/float.rs b/library/core/src/fmt/float.rs
new file mode 100644
index 000000000..89d5fac30
--- /dev/null
+++ b/library/core/src/fmt/float.rs
@@ -0,0 +1,226 @@
+use crate::fmt::{Debug, Display, Formatter, LowerExp, Result, UpperExp};
+use crate::mem::MaybeUninit;
+use crate::num::flt2dec;
+use crate::num::fmt as numfmt;
+
+#[doc(hidden)]
+trait GeneralFormat: PartialOrd {
+ /// Determines if a value should use exponential based on its magnitude, given the precondition
+ /// that it will not be rounded any further before it is displayed.
+ fn already_rounded_value_should_use_exponential(&self) -> bool;
+}
+
+macro_rules! impl_general_format {
+ ($($t:ident)*) => {
+ $(impl GeneralFormat for $t {
+ fn already_rounded_value_should_use_exponential(&self) -> bool {
+ let abs = $t::abs_private(*self);
+ (abs != 0.0 && abs < 1e-4) || abs >= 1e+16
+ }
+ })*
+ }
+}
+
+impl_general_format! { f32 f64 }
+
+// Don't inline this so callers don't use the stack space this function
+// requires unless they have to.
+#[inline(never)]
+fn float_to_decimal_common_exact<T>(
+ fmt: &mut Formatter<'_>,
+ num: &T,
+ sign: flt2dec::Sign,
+ precision: usize,
+) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ let mut buf: [MaybeUninit<u8>; 1024] = MaybeUninit::uninit_array(); // enough for f32 and f64
+ let mut parts: [MaybeUninit<numfmt::Part<'_>>; 4] = MaybeUninit::uninit_array();
+ let formatted = flt2dec::to_exact_fixed_str(
+ flt2dec::strategy::grisu::format_exact,
+ *num,
+ sign,
+ precision,
+ &mut buf,
+ &mut parts,
+ );
+ fmt.pad_formatted_parts(&formatted)
+}
+
+// Don't inline this so callers that call both this and the above won't wind
+// up using the combined stack space of both functions in some cases.
+#[inline(never)]
+fn float_to_decimal_common_shortest<T>(
+ fmt: &mut Formatter<'_>,
+ num: &T,
+ sign: flt2dec::Sign,
+ precision: usize,
+) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ // enough for f32 and f64
+ let mut buf: [MaybeUninit<u8>; flt2dec::MAX_SIG_DIGITS] = MaybeUninit::uninit_array();
+ let mut parts: [MaybeUninit<numfmt::Part<'_>>; 4] = MaybeUninit::uninit_array();
+ let formatted = flt2dec::to_shortest_str(
+ flt2dec::strategy::grisu::format_shortest,
+ *num,
+ sign,
+ precision,
+ &mut buf,
+ &mut parts,
+ );
+ fmt.pad_formatted_parts(&formatted)
+}
+
+fn float_to_decimal_display<T>(fmt: &mut Formatter<'_>, num: &T) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ let force_sign = fmt.sign_plus();
+ let sign = match force_sign {
+ false => flt2dec::Sign::Minus,
+ true => flt2dec::Sign::MinusPlus,
+ };
+
+ if let Some(precision) = fmt.precision {
+ float_to_decimal_common_exact(fmt, num, sign, precision)
+ } else {
+ let min_precision = 0;
+ float_to_decimal_common_shortest(fmt, num, sign, min_precision)
+ }
+}
+
+// Don't inline this so callers don't use the stack space this function
+// requires unless they have to.
+#[inline(never)]
+fn float_to_exponential_common_exact<T>(
+ fmt: &mut Formatter<'_>,
+ num: &T,
+ sign: flt2dec::Sign,
+ precision: usize,
+ upper: bool,
+) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ let mut buf: [MaybeUninit<u8>; 1024] = MaybeUninit::uninit_array(); // enough for f32 and f64
+ let mut parts: [MaybeUninit<numfmt::Part<'_>>; 6] = MaybeUninit::uninit_array();
+ let formatted = flt2dec::to_exact_exp_str(
+ flt2dec::strategy::grisu::format_exact,
+ *num,
+ sign,
+ precision,
+ upper,
+ &mut buf,
+ &mut parts,
+ );
+ fmt.pad_formatted_parts(&formatted)
+}
+
+// Don't inline this so callers that call both this and the above won't wind
+// up using the combined stack space of both functions in some cases.
+#[inline(never)]
+fn float_to_exponential_common_shortest<T>(
+ fmt: &mut Formatter<'_>,
+ num: &T,
+ sign: flt2dec::Sign,
+ upper: bool,
+) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ // enough for f32 and f64
+ let mut buf: [MaybeUninit<u8>; flt2dec::MAX_SIG_DIGITS] = MaybeUninit::uninit_array();
+ let mut parts: [MaybeUninit<numfmt::Part<'_>>; 6] = MaybeUninit::uninit_array();
+ let formatted = flt2dec::to_shortest_exp_str(
+ flt2dec::strategy::grisu::format_shortest,
+ *num,
+ sign,
+ (0, 0),
+ upper,
+ &mut buf,
+ &mut parts,
+ );
+ fmt.pad_formatted_parts(&formatted)
+}
+
+// Common code of floating point LowerExp and UpperExp.
+fn float_to_exponential_common<T>(fmt: &mut Formatter<'_>, num: &T, upper: bool) -> Result
+where
+ T: flt2dec::DecodableFloat,
+{
+ let force_sign = fmt.sign_plus();
+ let sign = match force_sign {
+ false => flt2dec::Sign::Minus,
+ true => flt2dec::Sign::MinusPlus,
+ };
+
+ if let Some(precision) = fmt.precision {
+ // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
+ float_to_exponential_common_exact(fmt, num, sign, precision + 1, upper)
+ } else {
+ float_to_exponential_common_shortest(fmt, num, sign, upper)
+ }
+}
+
+fn float_to_general_debug<T>(fmt: &mut Formatter<'_>, num: &T) -> Result
+where
+ T: flt2dec::DecodableFloat + GeneralFormat,
+{
+ let force_sign = fmt.sign_plus();
+ let sign = match force_sign {
+ false => flt2dec::Sign::Minus,
+ true => flt2dec::Sign::MinusPlus,
+ };
+
+ if let Some(precision) = fmt.precision {
+ // this behavior of {:.PREC?} predates exponential formatting for {:?}
+ float_to_decimal_common_exact(fmt, num, sign, precision)
+ } else {
+ // since there is no precision, there will be no rounding
+ if num.already_rounded_value_should_use_exponential() {
+ let upper = false;
+ float_to_exponential_common_shortest(fmt, num, sign, upper)
+ } else {
+ let min_precision = 1;
+ float_to_decimal_common_shortest(fmt, num, sign, min_precision)
+ }
+ }
+}
+
+macro_rules! floating {
+ ($ty:ident) => {
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl Debug for $ty {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ float_to_general_debug(fmt, self)
+ }
+ }
+
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl Display for $ty {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ float_to_decimal_display(fmt, self)
+ }
+ }
+
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl LowerExp for $ty {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ float_to_exponential_common(fmt, self, false)
+ }
+ }
+
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl UpperExp for $ty {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ float_to_exponential_common(fmt, self, true)
+ }
+ }
+ };
+}
+
+floating! { f32 }
+floating! { f64 }
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
new file mode 100644
index 000000000..372141e09
--- /dev/null
+++ b/library/core/src/fmt/mod.rs
@@ -0,0 +1,2664 @@
+//! Utilities for formatting and printing strings.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use crate::cell::{Cell, Ref, RefCell, RefMut, SyncUnsafeCell, UnsafeCell};
+use crate::char::EscapeDebugExtArgs;
+use crate::iter;
+use crate::marker::PhantomData;
+use crate::mem;
+use crate::num::fmt as numfmt;
+use crate::ops::Deref;
+use crate::result;
+use crate::str;
+
+mod builders;
+#[cfg(not(no_fp_fmt_parse))]
+mod float;
+#[cfg(no_fp_fmt_parse)]
+mod nofloat;
+mod num;
+
+#[stable(feature = "fmt_flags_align", since = "1.28.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Alignment")]
+/// Possible alignments returned by `Formatter::align`
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Alignment {
+ #[stable(feature = "fmt_flags_align", since = "1.28.0")]
+ /// Indication that contents should be left-aligned.
+ Left,
+ #[stable(feature = "fmt_flags_align", since = "1.28.0")]
+ /// Indication that contents should be right-aligned.
+ Right,
+ #[stable(feature = "fmt_flags_align", since = "1.28.0")]
+ /// Indication that contents should be center-aligned.
+ Center,
+}
+
+#[stable(feature = "debug_builders", since = "1.2.0")]
+pub use self::builders::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
+
+#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+#[doc(hidden)]
+pub mod rt {
+ pub mod v1;
+}
+
+/// The type returned by formatter methods.
+///
+/// # Examples
+///
+/// ```
+/// use std::fmt;
+///
+/// #[derive(Debug)]
+/// struct Triangle {
+/// a: f32,
+/// b: f32,
+/// c: f32
+/// }
+///
+/// impl fmt::Display for Triangle {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// write!(f, "({}, {}, {})", self.a, self.b, self.c)
+/// }
+/// }
+///
+/// let pythagorean_triple = Triangle { a: 3.0, b: 4.0, c: 5.0 };
+///
+/// assert_eq!(format!("{pythagorean_triple}"), "(3, 4, 5)");
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub type Result = result::Result<(), Error>;
+
+/// The error type which is returned from formatting a message into a stream.
+///
+/// This type does not support transmission of an error other than that an error
+/// occurred. Any extra information must be arranged to be transmitted through
+/// some other means.
+///
+/// An important thing to remember is that the type `fmt::Error` should not be
+/// confused with [`std::io::Error`] or [`std::error::Error`], which you may also
+/// have in scope.
+///
+/// [`std::io::Error`]: ../../std/io/struct.Error.html
+/// [`std::error::Error`]: ../../std/error/trait.Error.html
+///
+/// # Examples
+///
+/// ```rust
+/// use std::fmt::{self, write};
+///
+/// let mut output = String::new();
+/// if let Err(fmt::Error) = write(&mut output, format_args!("Hello {}!", "world")) {
+/// panic!("An error occurred");
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct Error;
+
+/// A trait for writing or formatting into Unicode-accepting buffers or streams.
+///
+/// This trait only accepts UTF-8–encoded data and is not [flushable]. If you only
+/// want to accept Unicode and you don't need flushing, you should implement this trait;
+/// otherwise you should implement [`std::io::Write`].
+///
+/// [`std::io::Write`]: ../../std/io/trait.Write.html
+/// [flushable]: ../../std/io/trait.Write.html#tymethod.flush
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Write {
+ /// Writes a string slice into this writer, returning whether the write
+ /// succeeded.
+ ///
+ /// This method can only succeed if the entire string slice was successfully
+ /// written, and this method will not return until all data has been
+ /// written or an error occurs.
+ ///
+ /// # Errors
+ ///
+ /// This function will return an instance of [`Error`] on error.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt::{Error, Write};
+ ///
+ /// fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
+ /// f.write_str(s)
+ /// }
+ ///
+ /// let mut buf = String::new();
+ /// writer(&mut buf, "hola").unwrap();
+ /// assert_eq!(&buf, "hola");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn write_str(&mut self, s: &str) -> Result;
+
+ /// Writes a [`char`] into this writer, returning whether the write succeeded.
+ ///
+ /// A single [`char`] may be encoded as more than one byte.
+ /// This method can only succeed if the entire byte sequence was successfully
+ /// written, and this method will not return until all data has been
+ /// written or an error occurs.
+ ///
+ /// # Errors
+ ///
+ /// This function will return an instance of [`Error`] on error.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt::{Error, Write};
+ ///
+ /// fn writer<W: Write>(f: &mut W, c: char) -> Result<(), Error> {
+ /// f.write_char(c)
+ /// }
+ ///
+ /// let mut buf = String::new();
+ /// writer(&mut buf, 'a').unwrap();
+ /// writer(&mut buf, 'b').unwrap();
+ /// assert_eq!(&buf, "ab");
+ /// ```
+ #[stable(feature = "fmt_write_char", since = "1.1.0")]
+ fn write_char(&mut self, c: char) -> Result {
+ self.write_str(c.encode_utf8(&mut [0; 4]))
+ }
+
+ /// Glue for usage of the [`write!`] macro with implementors of this trait.
+ ///
+ /// This method should generally not be invoked manually, but rather through
+ /// the [`write!`] macro itself.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt::{Error, Write};
+ ///
+ /// fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
+ /// f.write_fmt(format_args!("{s}"))
+ /// }
+ ///
+ /// let mut buf = String::new();
+ /// writer(&mut buf, "world").unwrap();
+ /// assert_eq!(&buf, "world");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn write_fmt(mut self: &mut Self, args: Arguments<'_>) -> Result {
+ write(&mut self, args)
+ }
+}
+
+#[stable(feature = "fmt_write_blanket_impl", since = "1.4.0")]
+impl<W: Write + ?Sized> Write for &mut W {
+ fn write_str(&mut self, s: &str) -> Result {
+ (**self).write_str(s)
+ }
+
+ fn write_char(&mut self, c: char) -> Result {
+ (**self).write_char(c)
+ }
+
+ fn write_fmt(&mut self, args: Arguments<'_>) -> Result {
+ (**self).write_fmt(args)
+ }
+}
+
+/// Configuration for formatting.
+///
+/// A `Formatter` represents various options related to formatting. Users do not
+/// construct `Formatter`s directly; a mutable reference to one is passed to
+/// the `fmt` method of all formatting traits, like [`Debug`] and [`Display`].
+///
+/// To interact with a `Formatter`, you'll call various methods to change the
+/// various options related to formatting. For examples, please see the
+/// documentation of the methods defined on `Formatter` below.
+#[allow(missing_debug_implementations)]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Formatter<'a> {
+ flags: u32,
+ fill: char,
+ align: rt::v1::Alignment,
+ width: Option<usize>,
+ precision: Option<usize>,
+
+ buf: &'a mut (dyn Write + 'a),
+}
+
+impl<'a> Formatter<'a> {
+ /// Creates a new formatter with default settings.
+ ///
+ /// This can be used as a micro-optimization in cases where a full `Arguments`
+ /// structure (as created by `format_args!`) is not necessary; `Arguments`
+ /// is a little more expensive to use in simple formatting scenarios.
+ ///
+ /// Currently not intended for use outside of the standard library.
+ #[unstable(feature = "fmt_internals", reason = "internal to standard library", issue = "none")]
+ #[doc(hidden)]
+ pub fn new(buf: &'a mut (dyn Write + 'a)) -> Formatter<'a> {
+ Formatter {
+ flags: 0,
+ fill: ' ',
+ align: rt::v1::Alignment::Unknown,
+ width: None,
+ precision: None,
+ buf,
+ }
+ }
+}
+
+// NB. Argument is essentially an optimized partially applied formatting function,
+// equivalent to `exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result`.
+
+extern "C" {
+ type Opaque;
+}
+
+/// This struct represents the generic "argument" which is taken by the Xprintf
+/// family of functions. It contains a function to format the given value. At
+/// compile time it is ensured that the function and the value have the correct
+/// types, and then this struct is used to canonicalize arguments to one type.
+#[derive(Copy, Clone)]
+#[allow(missing_debug_implementations)]
+#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+#[doc(hidden)]
+pub struct ArgumentV1<'a> {
+ value: &'a Opaque,
+ formatter: fn(&Opaque, &mut Formatter<'_>) -> Result,
+}
+
+/// This struct represents the unsafety of constructing an `Arguments`.
+/// It exists, rather than an unsafe function, in order to simplify the expansion
+/// of `format_args!(..)` and reduce the scope of the `unsafe` block.
+#[allow(missing_debug_implementations)]
+#[doc(hidden)]
+#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+pub struct UnsafeArg {
+ _private: (),
+}
+
+impl UnsafeArg {
+ /// See documentation where `UnsafeArg` is required to know when it is safe to
+ /// create and use `UnsafeArg`.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ #[inline(always)]
+ pub unsafe fn new() -> Self {
+ Self { _private: () }
+ }
+}
+
+// This guarantees a single stable value for the function pointer associated with
+// indices/counts in the formatting infrastructure.
+//
+// Note that a function defined as such would not be correct as functions are
+// always tagged unnamed_addr with the current lowering to LLVM IR, so their
+// address is not considered important to LLVM and as such the as_usize cast
+// could have been miscompiled. In practice, we never call as_usize on non-usize
+// containing data (as a matter of static generation of the formatting
+// arguments), so this is merely an additional check.
+//
+// We primarily want to ensure that the function pointer at `USIZE_MARKER` has
+// an address corresponding *only* to functions that also take `&usize` as their
+// first argument. The read_volatile here ensures that we can safely ready out a
+// usize from the passed reference and that this address does not point at a
+// non-usize taking function.
+#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
+ // SAFETY: ptr is a reference
+ let _v: usize = unsafe { crate::ptr::read_volatile(ptr) };
+ loop {}
+};
+
+macro_rules! arg_new {
+ ($f: ident, $t: ident) => {
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ #[inline]
+ pub fn $f<'b, T: $t>(x: &'b T) -> ArgumentV1<'_> {
+ Self::new(x, $t::fmt)
+ }
+ };
+}
+
+#[rustc_diagnostic_item = "ArgumentV1Methods"]
+impl<'a> ArgumentV1<'a> {
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ #[inline]
+ pub fn new<'b, T>(x: &'b T, f: fn(&T, &mut Formatter<'_>) -> Result) -> ArgumentV1<'b> {
+ // SAFETY: `mem::transmute(x)` is safe because
+ // 1. `&'b T` keeps the lifetime it originated with `'b`
+ // (so as to not have an unbounded lifetime)
+ // 2. `&'b T` and `&'b Opaque` have the same memory layout
+ // (when `T` is `Sized`, as it is here)
+ // `mem::transmute(f)` is safe since `fn(&T, &mut Formatter<'_>) -> Result`
+ // and `fn(&Opaque, &mut Formatter<'_>) -> Result` have the same ABI
+ // (as long as `T` is `Sized`)
+ unsafe { ArgumentV1 { formatter: mem::transmute(f), value: mem::transmute(x) } }
+ }
+
+ arg_new!(new_display, Display);
+ arg_new!(new_debug, Debug);
+ arg_new!(new_octal, Octal);
+ arg_new!(new_lower_hex, LowerHex);
+ arg_new!(new_upper_hex, UpperHex);
+ arg_new!(new_pointer, Pointer);
+ arg_new!(new_binary, Binary);
+ arg_new!(new_lower_exp, LowerExp);
+ arg_new!(new_upper_exp, UpperExp);
+
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ pub fn from_usize(x: &usize) -> ArgumentV1<'_> {
+ ArgumentV1::new(x, USIZE_MARKER)
+ }
+
+ fn as_usize(&self) -> Option<usize> {
+ // We are type punning a bit here: USIZE_MARKER only takes an &usize but
+ // formatter takes an &Opaque. Rust understandably doesn't think we should compare
+ // the function pointers if they don't have the same signature, so we cast to
+ // usizes to tell it that we just want to compare addresses.
+ if self.formatter as usize == USIZE_MARKER as usize {
+ // SAFETY: The `formatter` field is only set to USIZE_MARKER if
+ // the value is a usize, so this is safe
+ Some(unsafe { *(self.value as *const _ as *const usize) })
+ } else {
+ None
+ }
+ }
+}
+
+// flags available in the v1 format of format_args
+#[derive(Copy, Clone)]
+enum FlagV1 {
+ SignPlus,
+ SignMinus,
+ Alternate,
+ SignAwareZeroPad,
+ DebugLowerHex,
+ DebugUpperHex,
+}
+
+impl<'a> Arguments<'a> {
+ /// When using the format_args!() macro, this function is used to generate the
+ /// Arguments structure.
+ #[doc(hidden)]
+ #[inline]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ #[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
+ pub const fn new_v1(pieces: &'a [&'static str], args: &'a [ArgumentV1<'a>]) -> Arguments<'a> {
+ if pieces.len() < args.len() || pieces.len() > args.len() + 1 {
+ panic!("invalid args");
+ }
+ Arguments { pieces, fmt: None, args }
+ }
+
+ /// This function is used to specify nonstandard formatting parameters.
+ ///
+ /// An `UnsafeArg` is required because the following invariants must be held
+ /// in order for this function to be safe:
+ /// 1. The `pieces` slice must be at least as long as `fmt`.
+ /// 2. Every [`rt::v1::Argument::position`] value within `fmt` must be a
+ /// valid index of `args`.
+ /// 3. Every [`Count::Param`] within `fmt` must contain a valid index of
+ /// `args`.
+ #[doc(hidden)]
+ #[inline]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ #[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
+ pub const fn new_v1_formatted(
+ pieces: &'a [&'static str],
+ args: &'a [ArgumentV1<'a>],
+ fmt: &'a [rt::v1::Argument],
+ _unsafe_arg: UnsafeArg,
+ ) -> Arguments<'a> {
+ Arguments { pieces, fmt: Some(fmt), args }
+ }
+
+ /// Estimates the length of the formatted text.
+ ///
+ /// This is intended to be used for setting initial `String` capacity
+ /// when using `format!`. Note: this is neither the lower nor upper bound.
+ #[doc(hidden)]
+ #[inline]
+ #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+ pub fn estimated_capacity(&self) -> usize {
+ let pieces_length: usize = self.pieces.iter().map(|x| x.len()).sum();
+
+ if self.args.is_empty() {
+ pieces_length
+ } else if !self.pieces.is_empty() && self.pieces[0].is_empty() && pieces_length < 16 {
+ // If the format string starts with an argument,
+ // don't preallocate anything, unless length
+ // of pieces is significant.
+ 0
+ } else {
+ // There are some arguments, so any additional push
+ // will reallocate the string. To avoid that,
+ // we're "pre-doubling" the capacity here.
+ pieces_length.checked_mul(2).unwrap_or(0)
+ }
+ }
+}
+
+/// This structure represents a safely precompiled version of a format string
+/// and its arguments. This cannot be generated at runtime because it cannot
+/// safely be done, so no constructors are given and the fields are private
+/// to prevent modification.
+///
+/// The [`format_args!`] macro will safely create an instance of this structure.
+/// The macro validates the format string at compile-time so usage of the
+/// [`write()`] and [`format()`] functions can be safely performed.
+///
+/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
+/// and `Display` contexts as seen below. The example also shows that `Debug`
+/// and `Display` format to the same thing: the interpolated format string
+/// in `format_args!`.
+///
+/// ```rust
+/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
+/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
+/// assert_eq!("1 foo 2", display);
+/// assert_eq!(display, debug);
+/// ```
+///
+/// [`format()`]: ../../std/fmt/fn.format.html
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Arguments")]
+#[derive(Copy, Clone)]
+pub struct Arguments<'a> {
+ // Format string pieces to print.
+ pieces: &'a [&'static str],
+
+ // Placeholder specs, or `None` if all specs are default (as in "{}{}").
+ fmt: Option<&'a [rt::v1::Argument]>,
+
+ // Dynamic arguments for interpolation, to be interleaved with string
+ // pieces. (Every argument is preceded by a string piece.)
+ args: &'a [ArgumentV1<'a>],
+}
+
+impl<'a> Arguments<'a> {
+ /// Get the formatted string, if it has no arguments to be formatted.
+ ///
+ /// This can be used to avoid allocations in the most trivial case.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt::Arguments;
+ ///
+ /// fn write_str(_: &str) { /* ... */ }
+ ///
+ /// fn write_fmt(args: &Arguments) {
+ /// if let Some(s) = args.as_str() {
+ /// write_str(s)
+ /// } else {
+ /// write_str(&args.to_string());
+ /// }
+ /// }
+ /// ```
+ ///
+ /// ```rust
+ /// assert_eq!(format_args!("hello").as_str(), Some("hello"));
+ /// assert_eq!(format_args!("").as_str(), Some(""));
+ /// assert_eq!(format_args!("{}", 1).as_str(), None);
+ /// ```
+ #[stable(feature = "fmt_as_str", since = "1.52.0")]
+ #[rustc_const_unstable(feature = "const_arguments_as_str", issue = "none")]
+ #[must_use]
+ #[inline]
+ pub const fn as_str(&self) -> Option<&'static str> {
+ match (self.pieces, self.args) {
+ ([], []) => Some(""),
+ ([s], []) => Some(s),
+ _ => None,
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Debug for Arguments<'_> {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ Display::fmt(self, fmt)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Display for Arguments<'_> {
+ fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+ write(fmt.buf, *self)
+ }
+}
+
+/// `?` formatting.
+///
+/// `Debug` should format the output in a programmer-facing, debugging context.
+///
+/// Generally speaking, you should just `derive` a `Debug` implementation.
+///
+/// When used with the alternate format specifier `#?`, the output is pretty-printed.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// This trait can be used with `#[derive]` if all fields implement `Debug`. When
+/// `derive`d for structs, it will use the name of the `struct`, then `{`, then a
+/// comma-separated list of each field's name and `Debug` value, then `}`. For
+/// `enum`s, it will use the name of the variant and, if applicable, `(`, then the
+/// `Debug` values of the fields, then `)`.
+///
+/// # Stability
+///
+/// Derived `Debug` formats are not stable, and so may change with future Rust
+/// versions. Additionally, `Debug` implementations of types provided by the
+/// standard library (`libstd`, `libcore`, `liballoc`, etc.) are not stable, and
+/// may also change with future Rust versions.
+///
+/// # Examples
+///
+/// Deriving an implementation:
+///
+/// ```
+/// #[derive(Debug)]
+/// struct Point {
+/// x: i32,
+/// y: i32,
+/// }
+///
+/// let origin = Point { x: 0, y: 0 };
+///
+/// assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");
+/// ```
+///
+/// Manually implementing:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Point {
+/// x: i32,
+/// y: i32,
+/// }
+///
+/// impl fmt::Debug for Point {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// f.debug_struct("Point")
+/// .field("x", &self.x)
+/// .field("y", &self.y)
+/// .finish()
+/// }
+/// }
+///
+/// let origin = Point { x: 0, y: 0 };
+///
+/// assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");
+/// ```
+///
+/// There are a number of helper methods on the [`Formatter`] struct to help you with manual
+/// implementations, such as [`debug_struct`].
+///
+/// [`debug_struct`]: Formatter::debug_struct
+///
+/// Types that do not wish to use the standard suite of debug representations
+/// provided by the `Formatter` trait (`debug_struct`, `debug_tuple`,
+/// `debug_list`, `debug_set`, `debug_map`) can do something totally custom by
+/// manually writing an arbitrary representation to the `Formatter`.
+///
+/// ```
+/// # use std::fmt;
+/// # struct Point {
+/// # x: i32,
+/// # y: i32,
+/// # }
+/// #
+/// impl fmt::Debug for Point {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// write!(f, "Point [{} {}]", self.x, self.y)
+/// }
+/// }
+/// ```
+///
+/// `Debug` implementations using either `derive` or the debug builder API
+/// on [`Formatter`] support pretty-printing using the alternate flag: `{:#?}`.
+///
+/// Pretty-printing with `#?`:
+///
+/// ```
+/// #[derive(Debug)]
+/// struct Point {
+/// x: i32,
+/// y: i32,
+/// }
+///
+/// let origin = Point { x: 0, y: 0 };
+///
+/// assert_eq!(format!("The origin is: {origin:#?}"),
+/// "The origin is: Point {
+/// x: 0,
+/// y: 0,
+/// }");
+/// ```
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_on_unimplemented(
+ on(
+ crate_local,
+ label = "`{Self}` cannot be formatted using `{{:?}}`",
+ note = "add `#[derive(Debug)]` to `{Self}` or manually `impl {Debug} for {Self}`"
+ ),
+ message = "`{Self}` doesn't implement `{Debug}`",
+ label = "`{Self}` cannot be formatted using `{{:?}}` because it doesn't implement `{Debug}`"
+)]
+#[doc(alias = "{:?}")]
+#[rustc_diagnostic_item = "Debug"]
+#[rustc_trivial_field_reads]
+pub trait Debug {
+ /// Formats the value using the given formatter.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Position {
+ /// longitude: f32,
+ /// latitude: f32,
+ /// }
+ ///
+ /// impl fmt::Debug for Position {
+ /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// f.debug_tuple("")
+ /// .field(&self.longitude)
+ /// .field(&self.latitude)
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// let position = Position { longitude: 1.987, latitude: 2.983 };
+ /// assert_eq!(format!("{position:?}"), "(1.987, 2.983)");
+ ///
+ /// assert_eq!(format!("{position:#?}"), "(
+ /// 1.987,
+ /// 2.983,
+ /// )");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+// Separate module to reexport the macro `Debug` from prelude without the trait `Debug`.
+pub(crate) mod macros {
+ /// Derive macro generating an impl of the trait `Debug`.
+ #[rustc_builtin_macro]
+ #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
+ #[allow_internal_unstable(core_intrinsics, fmt_helpers_for_derive)]
+ pub macro Debug($item:item) {
+ /* compiler built-in */
+ }
+}
+#[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
+#[doc(inline)]
+pub use macros::Debug;
+
+/// Format trait for an empty format, `{}`.
+///
+/// `Display` is similar to [`Debug`], but `Display` is for user-facing
+/// output, and so cannot be derived.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Implementing `Display` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Point {
+/// x: i32,
+/// y: i32,
+/// }
+///
+/// impl fmt::Display for Point {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// write!(f, "({}, {})", self.x, self.y)
+/// }
+/// }
+///
+/// let origin = Point { x: 0, y: 0 };
+///
+/// assert_eq!(format!("The origin is: {origin}"), "The origin is: (0, 0)");
+/// ```
+#[rustc_on_unimplemented(
+ on(
+ any(_Self = "std::path::Path", _Self = "std::path::PathBuf"),
+ label = "`{Self}` cannot be formatted with the default formatter; call `.display()` on it",
+ note = "call `.display()` or `.to_string_lossy()` to safely print paths, \
+ as they may contain non-Unicode data"
+ ),
+ message = "`{Self}` doesn't implement `{Display}`",
+ label = "`{Self}` cannot be formatted with the default formatter",
+ note = "in format strings you may be able to use `{{:?}}` (or {{:#?}} for pretty-print) instead"
+)]
+#[doc(alias = "{}")]
+#[rustc_diagnostic_item = "Display"]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Display {
+ /// Formats the value using the given formatter.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Position {
+ /// longitude: f32,
+ /// latitude: f32,
+ /// }
+ ///
+ /// impl fmt::Display for Position {
+ /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// write!(f, "({}, {})", self.longitude, self.latitude)
+ /// }
+ /// }
+ ///
+ /// assert_eq!("(1.987, 2.983)",
+ /// format!("{}", Position { longitude: 1.987, latitude: 2.983, }));
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `o` formatting.
+///
+/// The `Octal` trait should format its output as a number in base-8.
+///
+/// For primitive signed integers (`i8` to `i128`, and `isize`),
+/// negative values are formatted as the two’s complement representation.
+///
+/// The alternate flag, `#`, adds a `0o` in front of the output.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `i32`:
+///
+/// ```
+/// let x = 42; // 42 is '52' in octal
+///
+/// assert_eq!(format!("{x:o}"), "52");
+/// assert_eq!(format!("{x:#o}"), "0o52");
+///
+/// assert_eq!(format!("{:o}", -16), "37777777760");
+/// ```
+///
+/// Implementing `Octal` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::Octal for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = self.0;
+///
+/// fmt::Octal::fmt(&val, f) // delegate to i32's implementation
+/// }
+/// }
+///
+/// let l = Length(9);
+///
+/// assert_eq!(format!("l as octal is: {l:o}"), "l as octal is: 11");
+///
+/// assert_eq!(format!("l as octal is: {l:#06o}"), "l as octal is: 0o0011");
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Octal {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `b` formatting.
+///
+/// The `Binary` trait should format its output as a number in binary.
+///
+/// For primitive signed integers ([`i8`] to [`i128`], and [`isize`]),
+/// negative values are formatted as the two’s complement representation.
+///
+/// The alternate flag, `#`, adds a `0b` in front of the output.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with [`i32`]:
+///
+/// ```
+/// let x = 42; // 42 is '101010' in binary
+///
+/// assert_eq!(format!("{x:b}"), "101010");
+/// assert_eq!(format!("{x:#b}"), "0b101010");
+///
+/// assert_eq!(format!("{:b}", -16), "11111111111111111111111111110000");
+/// ```
+///
+/// Implementing `Binary` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::Binary for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = self.0;
+///
+/// fmt::Binary::fmt(&val, f) // delegate to i32's implementation
+/// }
+/// }
+///
+/// let l = Length(107);
+///
+/// assert_eq!(format!("l as binary is: {l:b}"), "l as binary is: 1101011");
+///
+/// assert_eq!(
+/// format!("l as binary is: {l:#032b}"),
+/// "l as binary is: 0b000000000000000000000001101011"
+/// );
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Binary {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `x` formatting.
+///
+/// The `LowerHex` trait should format its output as a number in hexadecimal, with `a` through `f`
+/// in lower case.
+///
+/// For primitive signed integers (`i8` to `i128`, and `isize`),
+/// negative values are formatted as the two’s complement representation.
+///
+/// The alternate flag, `#`, adds a `0x` in front of the output.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `i32`:
+///
+/// ```
+/// let x = 42; // 42 is '2a' in hex
+///
+/// assert_eq!(format!("{x:x}"), "2a");
+/// assert_eq!(format!("{x:#x}"), "0x2a");
+///
+/// assert_eq!(format!("{:x}", -16), "fffffff0");
+/// ```
+///
+/// Implementing `LowerHex` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::LowerHex for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = self.0;
+///
+/// fmt::LowerHex::fmt(&val, f) // delegate to i32's implementation
+/// }
+/// }
+///
+/// let l = Length(9);
+///
+/// assert_eq!(format!("l as hex is: {l:x}"), "l as hex is: 9");
+///
+/// assert_eq!(format!("l as hex is: {l:#010x}"), "l as hex is: 0x00000009");
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait LowerHex {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `X` formatting.
+///
+/// The `UpperHex` trait should format its output as a number in hexadecimal, with `A` through `F`
+/// in upper case.
+///
+/// For primitive signed integers (`i8` to `i128`, and `isize`),
+/// negative values are formatted as the two’s complement representation.
+///
+/// The alternate flag, `#`, adds a `0x` in front of the output.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `i32`:
+///
+/// ```
+/// let x = 42; // 42 is '2A' in hex
+///
+/// assert_eq!(format!("{x:X}"), "2A");
+/// assert_eq!(format!("{x:#X}"), "0x2A");
+///
+/// assert_eq!(format!("{:X}", -16), "FFFFFFF0");
+/// ```
+///
+/// Implementing `UpperHex` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::UpperHex for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = self.0;
+///
+/// fmt::UpperHex::fmt(&val, f) // delegate to i32's implementation
+/// }
+/// }
+///
+/// let l = Length(i32::MAX);
+///
+/// assert_eq!(format!("l as hex is: {l:X}"), "l as hex is: 7FFFFFFF");
+///
+/// assert_eq!(format!("l as hex is: {l:#010X}"), "l as hex is: 0x7FFFFFFF");
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait UpperHex {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `p` formatting.
+///
+/// The `Pointer` trait should format its output as a memory location. This is commonly presented
+/// as hexadecimal.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `&i32`:
+///
+/// ```
+/// let x = &42;
+///
+/// let address = format!("{x:p}"); // this produces something like '0x7f06092ac6d0'
+/// ```
+///
+/// Implementing `Pointer` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::Pointer for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// // use `as` to convert to a `*const T`, which implements Pointer, which we can use
+///
+/// let ptr = self as *const Self;
+/// fmt::Pointer::fmt(&ptr, f)
+/// }
+/// }
+///
+/// let l = Length(42);
+///
+/// println!("l is in memory here: {l:p}");
+///
+/// let l_ptr = format!("{l:018p}");
+/// assert_eq!(l_ptr.len(), 18);
+/// assert_eq!(&l_ptr[..2], "0x");
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_diagnostic_item = "Pointer"]
+pub trait Pointer {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[rustc_diagnostic_item = "pointer_trait_fmt"]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `e` formatting.
+///
+/// The `LowerExp` trait should format its output in scientific notation with a lower-case `e`.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `f64`:
+///
+/// ```
+/// let x = 42.0; // 42.0 is '4.2e1' in scientific notation
+///
+/// assert_eq!(format!("{x:e}"), "4.2e1");
+/// ```
+///
+/// Implementing `LowerExp` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::LowerExp for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = f64::from(self.0);
+/// fmt::LowerExp::fmt(&val, f) // delegate to f64's implementation
+/// }
+/// }
+///
+/// let l = Length(100);
+///
+/// assert_eq!(
+/// format!("l in scientific notation is: {l:e}"),
+/// "l in scientific notation is: 1e2"
+/// );
+///
+/// assert_eq!(
+/// format!("l in scientific notation is: {l:05e}"),
+/// "l in scientific notation is: 001e2"
+/// );
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait LowerExp {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// `E` formatting.
+///
+/// The `UpperExp` trait should format its output in scientific notation with an upper-case `E`.
+///
+/// For more information on formatters, see [the module-level documentation][module].
+///
+/// [module]: ../../std/fmt/index.html
+///
+/// # Examples
+///
+/// Basic usage with `f64`:
+///
+/// ```
+/// let x = 42.0; // 42.0 is '4.2E1' in scientific notation
+///
+/// assert_eq!(format!("{x:E}"), "4.2E1");
+/// ```
+///
+/// Implementing `UpperExp` on a type:
+///
+/// ```
+/// use std::fmt;
+///
+/// struct Length(i32);
+///
+/// impl fmt::UpperExp for Length {
+/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+/// let val = f64::from(self.0);
+/// fmt::UpperExp::fmt(&val, f) // delegate to f64's implementation
+/// }
+/// }
+///
+/// let l = Length(100);
+///
+/// assert_eq!(
+/// format!("l in scientific notation is: {l:E}"),
+/// "l in scientific notation is: 1E2"
+/// );
+///
+/// assert_eq!(
+/// format!("l in scientific notation is: {l:05E}"),
+/// "l in scientific notation is: 001E2"
+/// );
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait UpperExp {
+ /// Formats the value using the given formatter.
+ #[stable(feature = "rust1", since = "1.0.0")]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+/// The `write` function takes an output stream, and an `Arguments` struct
+/// that can be precompiled with the `format_args!` macro.
+///
+/// The arguments will be formatted according to the specified format string
+/// into the output stream provided.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::fmt;
+///
+/// let mut output = String::new();
+/// fmt::write(&mut output, format_args!("Hello {}!", "world"))
+/// .expect("Error occurred while trying to write in String");
+/// assert_eq!(output, "Hello world!");
+/// ```
+///
+/// Please note that using [`write!`] might be preferable. Example:
+///
+/// ```
+/// use std::fmt::Write;
+///
+/// let mut output = String::new();
+/// write!(&mut output, "Hello {}!", "world")
+/// .expect("Error occurred while trying to write in String");
+/// assert_eq!(output, "Hello world!");
+/// ```
+///
+/// [`write!`]: crate::write!
+#[stable(feature = "rust1", since = "1.0.0")]
+pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
+ let mut formatter = Formatter::new(output);
+ let mut idx = 0;
+
+ match args.fmt {
+ None => {
+ // We can use default formatting parameters for all arguments.
+ for (i, arg) in args.args.iter().enumerate() {
+ // SAFETY: args.args and args.pieces come from the same Arguments,
+ // which guarantees the indexes are always within bounds.
+ let piece = unsafe { args.pieces.get_unchecked(i) };
+ if !piece.is_empty() {
+ formatter.buf.write_str(*piece)?;
+ }
+ (arg.formatter)(arg.value, &mut formatter)?;
+ idx += 1;
+ }
+ }
+ Some(fmt) => {
+ // Every spec has a corresponding argument that is preceded by
+ // a string piece.
+ for (i, arg) in fmt.iter().enumerate() {
+ // SAFETY: fmt and args.pieces come from the same Arguments,
+ // which guarantees the indexes are always within bounds.
+ let piece = unsafe { args.pieces.get_unchecked(i) };
+ if !piece.is_empty() {
+ formatter.buf.write_str(*piece)?;
+ }
+ // SAFETY: arg and args.args come from the same Arguments,
+ // which guarantees the indexes are always within bounds.
+ unsafe { run(&mut formatter, arg, args.args) }?;
+ idx += 1;
+ }
+ }
+ }
+
+ // There can be only one trailing string piece left.
+ if let Some(piece) = args.pieces.get(idx) {
+ formatter.buf.write_str(*piece)?;
+ }
+
+ Ok(())
+}
+
+unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV1<'_>]) -> Result {
+ fmt.fill = arg.format.fill;
+ fmt.align = arg.format.align;
+ fmt.flags = arg.format.flags;
+ // SAFETY: arg and args come from the same Arguments,
+ // which guarantees the indexes are always within bounds.
+ unsafe {
+ fmt.width = getcount(args, &arg.format.width);
+ fmt.precision = getcount(args, &arg.format.precision);
+ }
+
+ // Extract the correct argument
+ debug_assert!(arg.position < args.len());
+ // SAFETY: arg and args come from the same Arguments,
+ // which guarantees its index is always within bounds.
+ let value = unsafe { args.get_unchecked(arg.position) };
+
+ // Then actually do some printing
+ (value.formatter)(value.value, fmt)
+}
+
+unsafe fn getcount(args: &[ArgumentV1<'_>], cnt: &rt::v1::Count) -> Option<usize> {
+ match *cnt {
+ rt::v1::Count::Is(n) => Some(n),
+ rt::v1::Count::Implied => None,
+ rt::v1::Count::Param(i) => {
+ debug_assert!(i < args.len());
+ // SAFETY: cnt and args come from the same Arguments,
+ // which guarantees this index is always within bounds.
+ unsafe { args.get_unchecked(i).as_usize() }
+ }
+ }
+}
+
+/// Padding after the end of something. Returned by `Formatter::padding`.
+#[must_use = "don't forget to write the post padding"]
+pub(crate) struct PostPadding {
+ fill: char,
+ padding: usize,
+}
+
+impl PostPadding {
+ fn new(fill: char, padding: usize) -> PostPadding {
+ PostPadding { fill, padding }
+ }
+
+ /// Write this post padding.
+ pub(crate) fn write(self, f: &mut Formatter<'_>) -> Result {
+ for _ in 0..self.padding {
+ f.buf.write_char(self.fill)?;
+ }
+ Ok(())
+ }
+}
+
+impl<'a> Formatter<'a> {
+ fn wrap_buf<'b, 'c, F>(&'b mut self, wrap: F) -> Formatter<'c>
+ where
+ 'b: 'c,
+ F: FnOnce(&'b mut (dyn Write + 'b)) -> &'c mut (dyn Write + 'c),
+ {
+ Formatter {
+ // We want to change this
+ buf: wrap(self.buf),
+
+ // And preserve these
+ flags: self.flags,
+ fill: self.fill,
+ align: self.align,
+ width: self.width,
+ precision: self.precision,
+ }
+ }
+
+ // Helper methods used for padding and processing formatting arguments that
+ // all formatting traits can use.
+
+ /// Performs the correct padding for an integer which has already been
+ /// emitted into a str. The str should *not* contain the sign for the
+ /// integer, that will be added by this method.
+ ///
+ /// # Arguments
+ ///
+ /// * is_nonnegative - whether the original integer was either positive or zero.
+ /// * prefix - if the '#' character (Alternate) is provided, this
+ /// is the prefix to put in front of the number.
+ /// * buf - the byte array that the number has been formatted into
+ ///
+ /// This function will correctly account for the flags provided as well as
+ /// the minimum width. It will not take precision into account.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo { nb: i32 }
+ ///
+ /// impl Foo {
+ /// fn new(nb: i32) -> Foo {
+ /// Foo {
+ /// nb,
+ /// }
+ /// }
+ /// }
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// // We need to remove "-" from the number output.
+ /// let tmp = self.nb.abs().to_string();
+ ///
+ /// formatter.pad_integral(self.nb >= 0, "Foo ", &tmp)
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{}", Foo::new(2)), "2");
+ /// assert_eq!(&format!("{}", Foo::new(-1)), "-1");
+ /// assert_eq!(&format!("{}", Foo::new(0)), "0");
+ /// assert_eq!(&format!("{:#}", Foo::new(-1)), "-Foo 1");
+ /// assert_eq!(&format!("{:0>#8}", Foo::new(-1)), "00-Foo 1");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn pad_integral(&mut self, is_nonnegative: bool, prefix: &str, buf: &str) -> Result {
+ let mut width = buf.len();
+
+ let mut sign = None;
+ if !is_nonnegative {
+ sign = Some('-');
+ width += 1;
+ } else if self.sign_plus() {
+ sign = Some('+');
+ width += 1;
+ }
+
+ let prefix = if self.alternate() {
+ width += prefix.chars().count();
+ Some(prefix)
+ } else {
+ None
+ };
+
+ // Writes the sign if it exists, and then the prefix if it was requested
+ #[inline(never)]
+ fn write_prefix(f: &mut Formatter<'_>, sign: Option<char>, prefix: Option<&str>) -> Result {
+ if let Some(c) = sign {
+ f.buf.write_char(c)?;
+ }
+ if let Some(prefix) = prefix { f.buf.write_str(prefix) } else { Ok(()) }
+ }
+
+ // The `width` field is more of a `min-width` parameter at this point.
+ match self.width {
+ // If there's no minimum length requirements then we can just
+ // write the bytes.
+ None => {
+ write_prefix(self, sign, prefix)?;
+ self.buf.write_str(buf)
+ }
+ // Check if we're over the minimum width, if so then we can also
+ // just write the bytes.
+ Some(min) if width >= min => {
+ write_prefix(self, sign, prefix)?;
+ self.buf.write_str(buf)
+ }
+ // The sign and prefix goes before the padding if the fill character
+ // is zero
+ Some(min) if self.sign_aware_zero_pad() => {
+ let old_fill = crate::mem::replace(&mut self.fill, '0');
+ let old_align = crate::mem::replace(&mut self.align, rt::v1::Alignment::Right);
+ write_prefix(self, sign, prefix)?;
+ let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
+ self.buf.write_str(buf)?;
+ post_padding.write(self)?;
+ self.fill = old_fill;
+ self.align = old_align;
+ Ok(())
+ }
+ // Otherwise, the sign and prefix goes after the padding
+ Some(min) => {
+ let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
+ write_prefix(self, sign, prefix)?;
+ self.buf.write_str(buf)?;
+ post_padding.write(self)
+ }
+ }
+ }
+
+ /// This function takes a string slice and emits it to the internal buffer
+ /// after applying the relevant formatting flags specified. The flags
+ /// recognized for generic strings are:
+ ///
+ /// * width - the minimum width of what to emit
+ /// * fill/align - what to emit and where to emit it if the string
+ /// provided needs to be padded
+ /// * precision - the maximum length to emit, the string is truncated if it
+ /// is longer than this length
+ ///
+ /// Notably this function ignores the `flag` parameters.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo;
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// formatter.pad("Foo")
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{Foo:<4}"), "Foo ");
+ /// assert_eq!(&format!("{Foo:0>4}"), "0Foo");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn pad(&mut self, s: &str) -> Result {
+ // Make sure there's a fast path up front
+ if self.width.is_none() && self.precision.is_none() {
+ return self.buf.write_str(s);
+ }
+ // The `precision` field can be interpreted as a `max-width` for the
+ // string being formatted.
+ let s = if let Some(max) = self.precision {
+ // If our string is longer that the precision, then we must have
+ // truncation. However other flags like `fill`, `width` and `align`
+ // must act as always.
+ if let Some((i, _)) = s.char_indices().nth(max) {
+ // LLVM here can't prove that `..i` won't panic `&s[..i]`, but
+ // we know that it can't panic. Use `get` + `unwrap_or` to avoid
+ // `unsafe` and otherwise don't emit any panic-related code
+ // here.
+ s.get(..i).unwrap_or(s)
+ } else {
+ &s
+ }
+ } else {
+ &s
+ };
+ // The `width` field is more of a `min-width` parameter at this point.
+ match self.width {
+ // If we're under the maximum length, and there's no minimum length
+ // requirements, then we can just emit the string
+ None => self.buf.write_str(s),
+ Some(width) => {
+ let chars_count = s.chars().count();
+ // If we're under the maximum width, check if we're over the minimum
+ // width, if so it's as easy as just emitting the string.
+ if chars_count >= width {
+ self.buf.write_str(s)
+ }
+ // If we're under both the maximum and the minimum width, then fill
+ // up the minimum width with the specified string + some alignment.
+ else {
+ let align = rt::v1::Alignment::Left;
+ let post_padding = self.padding(width - chars_count, align)?;
+ self.buf.write_str(s)?;
+ post_padding.write(self)
+ }
+ }
+ }
+ }
+
+ /// Write the pre-padding and return the unwritten post-padding. Callers are
+ /// responsible for ensuring post-padding is written after the thing that is
+ /// being padded.
+ pub(crate) fn padding(
+ &mut self,
+ padding: usize,
+ default: rt::v1::Alignment,
+ ) -> result::Result<PostPadding, Error> {
+ let align = match self.align {
+ rt::v1::Alignment::Unknown => default,
+ _ => self.align,
+ };
+
+ let (pre_pad, post_pad) = match align {
+ rt::v1::Alignment::Left => (0, padding),
+ rt::v1::Alignment::Right | rt::v1::Alignment::Unknown => (padding, 0),
+ rt::v1::Alignment::Center => (padding / 2, (padding + 1) / 2),
+ };
+
+ for _ in 0..pre_pad {
+ self.buf.write_char(self.fill)?;
+ }
+
+ Ok(PostPadding::new(self.fill, post_pad))
+ }
+
+ /// Takes the formatted parts and applies the padding.
+ /// Assumes that the caller already has rendered the parts with required precision,
+ /// so that `self.precision` can be ignored.
+ fn pad_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
+ if let Some(mut width) = self.width {
+ // for the sign-aware zero padding, we render the sign first and
+ // behave as if we had no sign from the beginning.
+ let mut formatted = formatted.clone();
+ let old_fill = self.fill;
+ let old_align = self.align;
+ let mut align = old_align;
+ if self.sign_aware_zero_pad() {
+ // a sign always goes first
+ let sign = formatted.sign;
+ self.buf.write_str(sign)?;
+
+ // remove the sign from the formatted parts
+ formatted.sign = "";
+ width = width.saturating_sub(sign.len());
+ align = rt::v1::Alignment::Right;
+ self.fill = '0';
+ self.align = rt::v1::Alignment::Right;
+ }
+
+ // remaining parts go through the ordinary padding process.
+ let len = formatted.len();
+ let ret = if width <= len {
+ // no padding
+ self.write_formatted_parts(&formatted)
+ } else {
+ let post_padding = self.padding(width - len, align)?;
+ self.write_formatted_parts(&formatted)?;
+ post_padding.write(self)
+ };
+ self.fill = old_fill;
+ self.align = old_align;
+ ret
+ } else {
+ // this is the common case and we take a shortcut
+ self.write_formatted_parts(formatted)
+ }
+ }
+
+ fn write_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
+ fn write_bytes(buf: &mut dyn Write, s: &[u8]) -> Result {
+ // SAFETY: This is used for `numfmt::Part::Num` and `numfmt::Part::Copy`.
+ // It's safe to use for `numfmt::Part::Num` since every char `c` is between
+ // `b'0'` and `b'9'`, which means `s` is valid UTF-8.
+ // It's also probably safe in practice to use for `numfmt::Part::Copy(buf)`
+ // since `buf` should be plain ASCII, but it's possible for someone to pass
+ // in a bad value for `buf` into `numfmt::to_shortest_str` since it is a
+ // public function.
+ // FIXME: Determine whether this could result in UB.
+ buf.write_str(unsafe { str::from_utf8_unchecked(s) })
+ }
+
+ if !formatted.sign.is_empty() {
+ self.buf.write_str(formatted.sign)?;
+ }
+ for part in formatted.parts {
+ match *part {
+ numfmt::Part::Zero(mut nzeroes) => {
+ const ZEROES: &str = // 64 zeroes
+ "0000000000000000000000000000000000000000000000000000000000000000";
+ while nzeroes > ZEROES.len() {
+ self.buf.write_str(ZEROES)?;
+ nzeroes -= ZEROES.len();
+ }
+ if nzeroes > 0 {
+ self.buf.write_str(&ZEROES[..nzeroes])?;
+ }
+ }
+ numfmt::Part::Num(mut v) => {
+ let mut s = [0; 5];
+ let len = part.len();
+ for c in s[..len].iter_mut().rev() {
+ *c = b'0' + (v % 10) as u8;
+ v /= 10;
+ }
+ write_bytes(self.buf, &s[..len])?;
+ }
+ numfmt::Part::Copy(buf) => {
+ write_bytes(self.buf, buf)?;
+ }
+ }
+ }
+ Ok(())
+ }
+
+ /// Writes some data to the underlying buffer contained within this
+ /// formatter.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo;
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// formatter.write_str("Foo")
+ /// // This is equivalent to:
+ /// // write!(formatter, "Foo")
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{Foo}"), "Foo");
+ /// assert_eq!(&format!("{Foo:0>8}"), "Foo");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn write_str(&mut self, data: &str) -> Result {
+ self.buf.write_str(data)
+ }
+
+ /// Writes some formatted information into this instance.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// formatter.write_fmt(format_args!("Foo {}", self.0))
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{}", Foo(-1)), "Foo -1");
+ /// assert_eq!(&format!("{:0>8}", Foo(2)), "Foo 2");
+ /// ```
+ #[stable(feature = "rust1", since = "1.0.0")]
+ pub fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result {
+ write(self.buf, fmt)
+ }
+
+ /// Flags for formatting
+ #[must_use]
+ #[stable(feature = "rust1", since = "1.0.0")]
+ #[deprecated(
+ since = "1.24.0",
+ note = "use the `sign_plus`, `sign_minus`, `alternate`, \
+ or `sign_aware_zero_pad` methods instead"
+ )]
+ pub fn flags(&self) -> u32 {
+ self.flags
+ }
+
+ /// Character used as 'fill' whenever there is alignment.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo;
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// let c = formatter.fill();
+ /// if let Some(width) = formatter.width() {
+ /// for _ in 0..width {
+ /// write!(formatter, "{c}")?;
+ /// }
+ /// Ok(())
+ /// } else {
+ /// write!(formatter, "{c}")
+ /// }
+ /// }
+ /// }
+ ///
+ /// // We set alignment to the right with ">".
+ /// assert_eq!(&format!("{Foo:G>3}"), "GGG");
+ /// assert_eq!(&format!("{Foo:t>6}"), "tttttt");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn fill(&self) -> char {
+ self.fill
+ }
+
+ /// Flag indicating what form of alignment was requested.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// extern crate core;
+ ///
+ /// use std::fmt::{self, Alignment};
+ ///
+ /// struct Foo;
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// let s = if let Some(s) = formatter.align() {
+ /// match s {
+ /// Alignment::Left => "left",
+ /// Alignment::Right => "right",
+ /// Alignment::Center => "center",
+ /// }
+ /// } else {
+ /// "into the void"
+ /// };
+ /// write!(formatter, "{s}")
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{Foo:<}"), "left");
+ /// assert_eq!(&format!("{Foo:>}"), "right");
+ /// assert_eq!(&format!("{Foo:^}"), "center");
+ /// assert_eq!(&format!("{Foo}"), "into the void");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags_align", since = "1.28.0")]
+ pub fn align(&self) -> Option<Alignment> {
+ match self.align {
+ rt::v1::Alignment::Left => Some(Alignment::Left),
+ rt::v1::Alignment::Right => Some(Alignment::Right),
+ rt::v1::Alignment::Center => Some(Alignment::Center),
+ rt::v1::Alignment::Unknown => None,
+ }
+ }
+
+ /// Optionally specified integer width that the output should be.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// if let Some(width) = formatter.width() {
+ /// // If we received a width, we use it
+ /// write!(formatter, "{:width$}", &format!("Foo({})", self.0), width = width)
+ /// } else {
+ /// // Otherwise we do nothing special
+ /// write!(formatter, "Foo({})", self.0)
+ /// }
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:10}", Foo(23)), "Foo(23) ");
+ /// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn width(&self) -> Option<usize> {
+ self.width
+ }
+
+ /// Optionally specified precision for numeric types. Alternatively, the
+ /// maximum width for string types.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(f32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// if let Some(precision) = formatter.precision() {
+ /// // If we received a precision, we use it.
+ /// write!(formatter, "Foo({1:.*})", precision, self.0)
+ /// } else {
+ /// // Otherwise we default to 2.
+ /// write!(formatter, "Foo({:.2})", self.0)
+ /// }
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:.4}", Foo(23.2)), "Foo(23.2000)");
+ /// assert_eq!(&format!("{}", Foo(23.2)), "Foo(23.20)");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn precision(&self) -> Option<usize> {
+ self.precision
+ }
+
+ /// Determines if the `+` flag was specified.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// if formatter.sign_plus() {
+ /// write!(formatter,
+ /// "Foo({}{})",
+ /// if self.0 < 0 { '-' } else { '+' },
+ /// self.0)
+ /// } else {
+ /// write!(formatter, "Foo({})", self.0)
+ /// }
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:+}", Foo(23)), "Foo(+23)");
+ /// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn sign_plus(&self) -> bool {
+ self.flags & (1 << FlagV1::SignPlus as u32) != 0
+ }
+
+ /// Determines if the `-` flag was specified.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// if formatter.sign_minus() {
+ /// // You want a minus sign? Have one!
+ /// write!(formatter, "-Foo({})", self.0)
+ /// } else {
+ /// write!(formatter, "Foo({})", self.0)
+ /// }
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:-}", Foo(23)), "-Foo(23)");
+ /// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn sign_minus(&self) -> bool {
+ self.flags & (1 << FlagV1::SignMinus as u32) != 0
+ }
+
+ /// Determines if the `#` flag was specified.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// if formatter.alternate() {
+ /// write!(formatter, "Foo({})", self.0)
+ /// } else {
+ /// write!(formatter, "{}", self.0)
+ /// }
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:#}", Foo(23)), "Foo(23)");
+ /// assert_eq!(&format!("{}", Foo(23)), "23");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn alternate(&self) -> bool {
+ self.flags & (1 << FlagV1::Alternate as u32) != 0
+ }
+
+ /// Determines if the `0` flag was specified.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::fmt;
+ ///
+ /// struct Foo(i32);
+ ///
+ /// impl fmt::Display for Foo {
+ /// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// assert!(formatter.sign_aware_zero_pad());
+ /// assert_eq!(formatter.width(), Some(4));
+ /// // We ignore the formatter's options.
+ /// write!(formatter, "{}", self.0)
+ /// }
+ /// }
+ ///
+ /// assert_eq!(&format!("{:04}", Foo(23)), "23");
+ /// ```
+ #[must_use]
+ #[stable(feature = "fmt_flags", since = "1.5.0")]
+ pub fn sign_aware_zero_pad(&self) -> bool {
+ self.flags & (1 << FlagV1::SignAwareZeroPad as u32) != 0
+ }
+
+ // FIXME: Decide what public API we want for these two flags.
+ // https://github.com/rust-lang/rust/issues/48584
+ fn debug_lower_hex(&self) -> bool {
+ self.flags & (1 << FlagV1::DebugLowerHex as u32) != 0
+ }
+
+ fn debug_upper_hex(&self) -> bool {
+ self.flags & (1 << FlagV1::DebugUpperHex as u32) != 0
+ }
+
+ /// Creates a [`DebugStruct`] builder designed to assist with creation of
+ /// [`fmt::Debug`] implementations for structs.
+ ///
+ /// [`fmt::Debug`]: self::Debug
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt;
+ /// use std::net::Ipv4Addr;
+ ///
+ /// struct Foo {
+ /// bar: i32,
+ /// baz: String,
+ /// addr: Ipv4Addr,
+ /// }
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_struct("Foo")
+ /// .field("bar", &self.bar)
+ /// .field("baz", &self.baz)
+ /// .field("addr", &format_args!("{}", self.addr))
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// "Foo { bar: 10, baz: \"Hello World\", addr: 127.0.0.1 }",
+ /// format!("{:?}", Foo {
+ /// bar: 10,
+ /// baz: "Hello World".to_string(),
+ /// addr: Ipv4Addr::new(127, 0, 0, 1),
+ /// })
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn debug_struct<'b>(&'b mut self, name: &str) -> DebugStruct<'b, 'a> {
+ builders::debug_struct_new(self, name)
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_struct_fields_finish` is more general, but this is faster for 1 field.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_field1_finish<'b>(
+ &'b mut self,
+ name: &str,
+ name1: &str,
+ value1: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_struct_new(self, name);
+ builder.field(name1, value1);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_struct_fields_finish` is more general, but this is faster for 2 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_field2_finish<'b>(
+ &'b mut self,
+ name: &str,
+ name1: &str,
+ value1: &dyn Debug,
+ name2: &str,
+ value2: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_struct_new(self, name);
+ builder.field(name1, value1);
+ builder.field(name2, value2);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_struct_fields_finish` is more general, but this is faster for 3 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_field3_finish<'b>(
+ &'b mut self,
+ name: &str,
+ name1: &str,
+ value1: &dyn Debug,
+ name2: &str,
+ value2: &dyn Debug,
+ name3: &str,
+ value3: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_struct_new(self, name);
+ builder.field(name1, value1);
+ builder.field(name2, value2);
+ builder.field(name3, value3);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_struct_fields_finish` is more general, but this is faster for 4 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_field4_finish<'b>(
+ &'b mut self,
+ name: &str,
+ name1: &str,
+ value1: &dyn Debug,
+ name2: &str,
+ value2: &dyn Debug,
+ name3: &str,
+ value3: &dyn Debug,
+ name4: &str,
+ value4: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_struct_new(self, name);
+ builder.field(name1, value1);
+ builder.field(name2, value2);
+ builder.field(name3, value3);
+ builder.field(name4, value4);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_struct_fields_finish` is more general, but this is faster for 5 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_field5_finish<'b>(
+ &'b mut self,
+ name: &str,
+ name1: &str,
+ value1: &dyn Debug,
+ name2: &str,
+ value2: &dyn Debug,
+ name3: &str,
+ value3: &dyn Debug,
+ name4: &str,
+ value4: &dyn Debug,
+ name5: &str,
+ value5: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_struct_new(self, name);
+ builder.field(name1, value1);
+ builder.field(name2, value2);
+ builder.field(name3, value3);
+ builder.field(name4, value4);
+ builder.field(name5, value5);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// For the cases not covered by `debug_struct_field[12345]_finish`.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_struct_fields_finish<'b>(
+ &'b mut self,
+ name: &str,
+ names: &[&str],
+ values: &[&dyn Debug],
+ ) -> Result {
+ assert_eq!(names.len(), values.len());
+ let mut builder = builders::debug_struct_new(self, name);
+ for (name, value) in iter::zip(names, values) {
+ builder.field(name, value);
+ }
+ builder.finish()
+ }
+
+ /// Creates a `DebugTuple` builder designed to assist with creation of
+ /// `fmt::Debug` implementations for tuple structs.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt;
+ /// use std::marker::PhantomData;
+ ///
+ /// struct Foo<T>(i32, String, PhantomData<T>);
+ ///
+ /// impl<T> fmt::Debug for Foo<T> {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_tuple("Foo")
+ /// .field(&self.0)
+ /// .field(&self.1)
+ /// .field(&format_args!("_"))
+ /// .finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// "Foo(10, \"Hello\", _)",
+ /// format!("{:?}", Foo(10, "Hello".to_string(), PhantomData::<u8>))
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn debug_tuple<'b>(&'b mut self, name: &str) -> DebugTuple<'b, 'a> {
+ builders::debug_tuple_new(self, name)
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_tuple_fields_finish` is more general, but this is faster for 1 field.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_field1_finish<'b>(&'b mut self, name: &str, value1: &dyn Debug) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ builder.field(value1);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_tuple_fields_finish` is more general, but this is faster for 2 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_field2_finish<'b>(
+ &'b mut self,
+ name: &str,
+ value1: &dyn Debug,
+ value2: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ builder.field(value1);
+ builder.field(value2);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_tuple_fields_finish` is more general, but this is faster for 3 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_field3_finish<'b>(
+ &'b mut self,
+ name: &str,
+ value1: &dyn Debug,
+ value2: &dyn Debug,
+ value3: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ builder.field(value1);
+ builder.field(value2);
+ builder.field(value3);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_tuple_fields_finish` is more general, but this is faster for 4 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_field4_finish<'b>(
+ &'b mut self,
+ name: &str,
+ value1: &dyn Debug,
+ value2: &dyn Debug,
+ value3: &dyn Debug,
+ value4: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ builder.field(value1);
+ builder.field(value2);
+ builder.field(value3);
+ builder.field(value4);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// `debug_tuple_fields_finish` is more general, but this is faster for 5 fields.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_field5_finish<'b>(
+ &'b mut self,
+ name: &str,
+ value1: &dyn Debug,
+ value2: &dyn Debug,
+ value3: &dyn Debug,
+ value4: &dyn Debug,
+ value5: &dyn Debug,
+ ) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ builder.field(value1);
+ builder.field(value2);
+ builder.field(value3);
+ builder.field(value4);
+ builder.field(value5);
+ builder.finish()
+ }
+
+ /// Used to shrink `derive(Debug)` code, for faster compilation and smaller binaries.
+ /// For the cases not covered by `debug_tuple_field[12345]_finish`.
+ #[doc(hidden)]
+ #[unstable(feature = "fmt_helpers_for_derive", issue = "none")]
+ pub fn debug_tuple_fields_finish<'b>(
+ &'b mut self,
+ name: &str,
+ values: &[&dyn Debug],
+ ) -> Result {
+ let mut builder = builders::debug_tuple_new(self, name);
+ for value in values {
+ builder.field(value);
+ }
+ builder.finish()
+ }
+
+ /// Creates a `DebugList` builder designed to assist with creation of
+ /// `fmt::Debug` implementations for list-like structures.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_list().entries(self.0.iter()).finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(format!("{:?}", Foo(vec![10, 11])), "[10, 11]");
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn debug_list<'b>(&'b mut self) -> DebugList<'b, 'a> {
+ builders::debug_list_new(self)
+ }
+
+ /// Creates a `DebugSet` builder designed to assist with creation of
+ /// `fmt::Debug` implementations for set-like structures.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<i32>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_set().entries(self.0.iter()).finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(format!("{:?}", Foo(vec![10, 11])), "{10, 11}");
+ /// ```
+ ///
+ /// [`format_args!`]: crate::format_args
+ ///
+ /// In this more complex example, we use [`format_args!`] and `.debug_set()`
+ /// to build a list of match arms:
+ ///
+ /// ```rust
+ /// use std::fmt;
+ ///
+ /// struct Arm<'a, L: 'a, R: 'a>(&'a (L, R));
+ /// struct Table<'a, K: 'a, V: 'a>(&'a [(K, V)], V);
+ ///
+ /// impl<'a, L, R> fmt::Debug for Arm<'a, L, R>
+ /// where
+ /// L: 'a + fmt::Debug, R: 'a + fmt::Debug
+ /// {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// L::fmt(&(self.0).0, fmt)?;
+ /// fmt.write_str(" => ")?;
+ /// R::fmt(&(self.0).1, fmt)
+ /// }
+ /// }
+ ///
+ /// impl<'a, K, V> fmt::Debug for Table<'a, K, V>
+ /// where
+ /// K: 'a + fmt::Debug, V: 'a + fmt::Debug
+ /// {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_set()
+ /// .entries(self.0.iter().map(Arm))
+ /// .entry(&Arm(&(format_args!("_"), &self.1)))
+ /// .finish()
+ /// }
+ /// }
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn debug_set<'b>(&'b mut self) -> DebugSet<'b, 'a> {
+ builders::debug_set_new(self)
+ }
+
+ /// Creates a `DebugMap` builder designed to assist with creation of
+ /// `fmt::Debug` implementations for map-like structures.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use std::fmt;
+ ///
+ /// struct Foo(Vec<(String, i32)>);
+ ///
+ /// impl fmt::Debug for Foo {
+ /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+ /// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
+ /// }
+ /// }
+ ///
+ /// assert_eq!(
+ /// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
+ /// r#"{"A": 10, "B": 11}"#
+ /// );
+ /// ```
+ #[stable(feature = "debug_builders", since = "1.2.0")]
+ pub fn debug_map<'b>(&'b mut self) -> DebugMap<'b, 'a> {
+ builders::debug_map_new(self)
+ }
+}
+
+#[stable(since = "1.2.0", feature = "formatter_write")]
+impl Write for Formatter<'_> {
+ fn write_str(&mut self, s: &str) -> Result {
+ self.buf.write_str(s)
+ }
+
+ fn write_char(&mut self, c: char) -> Result {
+ self.buf.write_char(c)
+ }
+
+ fn write_fmt(&mut self, args: Arguments<'_>) -> Result {
+ write(self.buf, args)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Display for Error {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Display::fmt("an error occurred when formatting an argument", f)
+ }
+}
+
+// Implementations of the core formatting traits
+
+macro_rules! fmt_refs {
+ ($($tr:ident),*) => {
+ $(
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl<T: ?Sized + $tr> $tr for &T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result { $tr::fmt(&**self, f) }
+ }
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl<T: ?Sized + $tr> $tr for &mut T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result { $tr::fmt(&**self, f) }
+ }
+ )*
+ }
+}
+
+fmt_refs! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
+
+#[unstable(feature = "never_type", issue = "35121")]
+impl Debug for ! {
+ fn fmt(&self, _: &mut Formatter<'_>) -> Result {
+ *self
+ }
+}
+
+#[unstable(feature = "never_type", issue = "35121")]
+impl Display for ! {
+ fn fmt(&self, _: &mut Formatter<'_>) -> Result {
+ *self
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Debug for bool {
+ #[inline]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Display::fmt(self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Display for bool {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Display::fmt(if *self { "true" } else { "false" }, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Debug for str {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.write_char('"')?;
+ let mut from = 0;
+ for (i, c) in self.char_indices() {
+ let esc = c.escape_debug_ext(EscapeDebugExtArgs {
+ escape_grapheme_extended: true,
+ escape_single_quote: false,
+ escape_double_quote: true,
+ });
+ // If char needs escaping, flush backlog so far and write, else skip
+ if esc.len() != 1 {
+ f.write_str(&self[from..i])?;
+ for c in esc {
+ f.write_char(c)?;
+ }
+ from = i + c.len_utf8();
+ }
+ }
+ f.write_str(&self[from..])?;
+ f.write_char('"')
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Display for str {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.pad(self)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Debug for char {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.write_char('\'')?;
+ for c in self.escape_debug_ext(EscapeDebugExtArgs {
+ escape_grapheme_extended: true,
+ escape_single_quote: true,
+ escape_double_quote: false,
+ }) {
+ f.write_char(c)?
+ }
+ f.write_char('\'')
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Display for char {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ if f.width.is_none() && f.precision.is_none() {
+ f.write_char(*self)
+ } else {
+ f.pad(self.encode_utf8(&mut [0; 4]))
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Pointer for *const T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ // Cast is needed here because `.addr()` requires `T: Sized`.
+ pointer_fmt_inner((*self as *const ()).addr(), f)
+ }
+}
+
+/// Since the formatting will be identical for all pointer types, use a non-monomorphized
+/// implementation for the actual formatting to reduce the amount of codegen work needed.
+///
+/// This uses `ptr_addr: usize` and not `ptr: *const ()` to be able to use this for
+/// `fn(...) -> ...` without using [problematic] "Oxford Casts".
+///
+/// [problematic]: https://github.com/rust-lang/rust/issues/95489
+pub(crate) fn pointer_fmt_inner(ptr_addr: usize, f: &mut Formatter<'_>) -> Result {
+ let old_width = f.width;
+ let old_flags = f.flags;
+
+ // The alternate flag is already treated by LowerHex as being special-
+ // it denotes whether to prefix with 0x. We use it to work out whether
+ // or not to zero extend, and then unconditionally set it to get the
+ // prefix.
+ if f.alternate() {
+ f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
+
+ if f.width.is_none() {
+ f.width = Some((usize::BITS / 4) as usize + 2);
+ }
+ }
+ f.flags |= 1 << (FlagV1::Alternate as u32);
+
+ let ret = LowerHex::fmt(&ptr_addr, f);
+
+ f.width = old_width;
+ f.flags = old_flags;
+
+ ret
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Pointer for *mut T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Pointer::fmt(&(*self as *const T), f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Pointer for &T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Pointer::fmt(&(*self as *const T), f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Pointer for &mut T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Pointer::fmt(&(&**self as *const T), f)
+ }
+}
+
+// Implementation of Display/Debug for various core types
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Debug for *const T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Pointer::fmt(self, f)
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Debug for *mut T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Pointer::fmt(self, f)
+ }
+}
+
+macro_rules! peel {
+ ($name:ident, $($other:ident,)*) => (tuple! { $($other,)* })
+}
+
+macro_rules! tuple {
+ () => ();
+ ( $($name:ident,)+ ) => (
+ maybe_tuple_doc! {
+ $($name)+ @
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl<$($name:Debug),+> Debug for ($($name,)+) where last_type!($($name,)+): ?Sized {
+ #[allow(non_snake_case, unused_assignments)]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ let mut builder = f.debug_tuple("");
+ let ($(ref $name,)+) = *self;
+ $(
+ builder.field(&$name);
+ )+
+
+ builder.finish()
+ }
+ }
+ }
+ peel! { $($name,)+ }
+ )
+}
+
+macro_rules! maybe_tuple_doc {
+ ($a:ident @ #[$meta:meta] $item:item) => {
+ #[cfg_attr(not(bootstrap), doc(fake_variadic))]
+ #[doc = "This trait is implemented for tuples up to twelve items long."]
+ #[$meta]
+ $item
+ };
+ ($a:ident $($rest_a:ident)+ @ #[$meta:meta] $item:item) => {
+ #[doc(hidden)]
+ #[$meta]
+ $item
+ };
+}
+
+macro_rules! last_type {
+ ($a:ident,) => { $a };
+ ($a:ident, $($rest_a:ident,)+) => { last_type!($($rest_a,)+) };
+}
+
+tuple! { E, D, C, B, A, Z, Y, X, W, V, U, T, }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Debug> Debug for [T] {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.debug_list().entries(self.iter()).finish()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Debug for () {
+ #[inline]
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.pad("()")
+ }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Debug for PhantomData<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.debug_struct("PhantomData").finish()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: Copy + Debug> Debug for Cell<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.debug_struct("Cell").field("value", &self.get()).finish()
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Debug> Debug for RefCell<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ match self.try_borrow() {
+ Ok(borrow) => f.debug_struct("RefCell").field("value", &borrow).finish(),
+ Err(_) => {
+ // The RefCell is mutably borrowed so we can't look at its value
+ // here. Show a placeholder instead.
+ struct BorrowedPlaceholder;
+
+ impl Debug for BorrowedPlaceholder {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.write_str("<borrowed>")
+ }
+ }
+
+ f.debug_struct("RefCell").field("value", &BorrowedPlaceholder).finish()
+ }
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Debug> Debug for Ref<'_, T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Debug::fmt(&**self, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized + Debug> Debug for RefMut<'_, T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Debug::fmt(&*(self.deref()), f)
+ }
+}
+
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<T: ?Sized> Debug for UnsafeCell<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.debug_struct("UnsafeCell").finish_non_exhaustive()
+ }
+}
+
+#[unstable(feature = "sync_unsafe_cell", issue = "95439")]
+impl<T: ?Sized> Debug for SyncUnsafeCell<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ f.debug_struct("SyncUnsafeCell").finish_non_exhaustive()
+ }
+}
+
+// If you expected tests to be here, look instead at the core/tests/fmt.rs file,
+// it's a lot easier than creating all of the rt::Piece structures here.
+// There are also tests in the alloc crate, for those that need allocations.
diff --git a/library/core/src/fmt/nofloat.rs b/library/core/src/fmt/nofloat.rs
new file mode 100644
index 000000000..cfb94cd9d
--- /dev/null
+++ b/library/core/src/fmt/nofloat.rs
@@ -0,0 +1,15 @@
+use crate::fmt::{Debug, Formatter, Result};
+
+macro_rules! floating {
+ ($ty:ident) => {
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl Debug for $ty {
+ fn fmt(&self, _fmt: &mut Formatter<'_>) -> Result {
+ panic!("floating point support is turned off");
+ }
+ }
+ };
+}
+
+floating! { f32 }
+floating! { f64 }
diff --git a/library/core/src/fmt/num.rs b/library/core/src/fmt/num.rs
new file mode 100644
index 000000000..25789d37c
--- /dev/null
+++ b/library/core/src/fmt/num.rs
@@ -0,0 +1,683 @@
+//! Integer and floating-point number formatting
+
+use crate::fmt;
+use crate::mem::MaybeUninit;
+use crate::num::fmt as numfmt;
+use crate::ops::{Div, Rem, Sub};
+use crate::ptr;
+use crate::slice;
+use crate::str;
+
+#[doc(hidden)]
+trait DisplayInt:
+ PartialEq + PartialOrd + Div<Output = Self> + Rem<Output = Self> + Sub<Output = Self> + Copy
+{
+ fn zero() -> Self;
+ fn from_u8(u: u8) -> Self;
+ fn to_u8(&self) -> u8;
+ fn to_u16(&self) -> u16;
+ fn to_u32(&self) -> u32;
+ fn to_u64(&self) -> u64;
+ fn to_u128(&self) -> u128;
+}
+
+macro_rules! impl_int {
+ ($($t:ident)*) => (
+ $(impl DisplayInt for $t {
+ fn zero() -> Self { 0 }
+ fn from_u8(u: u8) -> Self { u as Self }
+ fn to_u8(&self) -> u8 { *self as u8 }
+ fn to_u16(&self) -> u16 { *self as u16 }
+ fn to_u32(&self) -> u32 { *self as u32 }
+ fn to_u64(&self) -> u64 { *self as u64 }
+ fn to_u128(&self) -> u128 { *self as u128 }
+ })*
+ )
+}
+macro_rules! impl_uint {
+ ($($t:ident)*) => (
+ $(impl DisplayInt for $t {
+ fn zero() -> Self { 0 }
+ fn from_u8(u: u8) -> Self { u as Self }
+ fn to_u8(&self) -> u8 { *self as u8 }
+ fn to_u16(&self) -> u16 { *self as u16 }
+ fn to_u32(&self) -> u32 { *self as u32 }
+ fn to_u64(&self) -> u64 { *self as u64 }
+ fn to_u128(&self) -> u128 { *self as u128 }
+ })*
+ )
+}
+
+impl_int! { i8 i16 i32 i64 i128 isize }
+impl_uint! { u8 u16 u32 u64 u128 usize }
+
+/// A type that represents a specific radix
+#[doc(hidden)]
+trait GenericRadix: Sized {
+ /// The number of digits.
+ const BASE: u8;
+
+ /// A radix-specific prefix string.
+ const PREFIX: &'static str;
+
+ /// Converts an integer to corresponding radix digit.
+ fn digit(x: u8) -> u8;
+
+ /// Format an integer using the radix using a formatter.
+ fn fmt_int<T: DisplayInt>(&self, mut x: T, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // The radix can be as low as 2, so we need a buffer of at least 128
+ // characters for a base 2 number.
+ let zero = T::zero();
+ let is_nonnegative = x >= zero;
+ let mut buf = [MaybeUninit::<u8>::uninit(); 128];
+ let mut curr = buf.len();
+ let base = T::from_u8(Self::BASE);
+ if is_nonnegative {
+ // Accumulate each digit of the number from the least significant
+ // to the most significant figure.
+ for byte in buf.iter_mut().rev() {
+ let n = x % base; // Get the current place value.
+ x = x / base; // Deaccumulate the number.
+ byte.write(Self::digit(n.to_u8())); // Store the digit in the buffer.
+ curr -= 1;
+ if x == zero {
+ // No more digits left to accumulate.
+ break;
+ };
+ }
+ } else {
+ // Do the same as above, but accounting for two's complement.
+ for byte in buf.iter_mut().rev() {
+ let n = zero - (x % base); // Get the current place value.
+ x = x / base; // Deaccumulate the number.
+ byte.write(Self::digit(n.to_u8())); // Store the digit in the buffer.
+ curr -= 1;
+ if x == zero {
+ // No more digits left to accumulate.
+ break;
+ };
+ }
+ }
+ let buf = &buf[curr..];
+ // SAFETY: The only chars in `buf` are created by `Self::digit` which are assumed to be
+ // valid UTF-8
+ let buf = unsafe {
+ str::from_utf8_unchecked(slice::from_raw_parts(
+ MaybeUninit::slice_as_ptr(buf),
+ buf.len(),
+ ))
+ };
+ f.pad_integral(is_nonnegative, Self::PREFIX, buf)
+ }
+}
+
+/// A binary (base 2) radix
+#[derive(Clone, PartialEq)]
+struct Binary;
+
+/// An octal (base 8) radix
+#[derive(Clone, PartialEq)]
+struct Octal;
+
+/// A hexadecimal (base 16) radix, formatted with lower-case characters
+#[derive(Clone, PartialEq)]
+struct LowerHex;
+
+/// A hexadecimal (base 16) radix, formatted with upper-case characters
+#[derive(Clone, PartialEq)]
+struct UpperHex;
+
+macro_rules! radix {
+ ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
+ impl GenericRadix for $T {
+ const BASE: u8 = $base;
+ const PREFIX: &'static str = $prefix;
+ fn digit(x: u8) -> u8 {
+ match x {
+ $($x => $conv,)+
+ x => panic!("number not in the range 0..={}: {}", Self::BASE - 1, x),
+ }
+ }
+ }
+ }
+}
+
+radix! { Binary, 2, "0b", x @ 0 ..= 1 => b'0' + x }
+radix! { Octal, 8, "0o", x @ 0 ..= 7 => b'0' + x }
+radix! { LowerHex, 16, "0x", x @ 0 ..= 9 => b'0' + x, x @ 10 ..= 15 => b'a' + (x - 10) }
+radix! { UpperHex, 16, "0x", x @ 0 ..= 9 => b'0' + x, x @ 10 ..= 15 => b'A' + (x - 10) }
+
+macro_rules! int_base {
+ (fmt::$Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl fmt::$Trait for $T {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ $Radix.fmt_int(*self as $U, f)
+ }
+ }
+ };
+}
+
+macro_rules! integer {
+ ($Int:ident, $Uint:ident) => {
+ int_base! { fmt::Binary for $Int as $Uint -> Binary }
+ int_base! { fmt::Octal for $Int as $Uint -> Octal }
+ int_base! { fmt::LowerHex for $Int as $Uint -> LowerHex }
+ int_base! { fmt::UpperHex for $Int as $Uint -> UpperHex }
+
+ int_base! { fmt::Binary for $Uint as $Uint -> Binary }
+ int_base! { fmt::Octal for $Uint as $Uint -> Octal }
+ int_base! { fmt::LowerHex for $Uint as $Uint -> LowerHex }
+ int_base! { fmt::UpperHex for $Uint as $Uint -> UpperHex }
+ };
+}
+integer! { isize, usize }
+integer! { i8, u8 }
+integer! { i16, u16 }
+integer! { i32, u32 }
+integer! { i64, u64 }
+integer! { i128, u128 }
+macro_rules! debug {
+ ($($T:ident)*) => {$(
+ #[stable(feature = "rust1", since = "1.0.0")]
+ impl fmt::Debug for $T {
+ #[inline]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ if f.debug_lower_hex() {
+ fmt::LowerHex::fmt(self, f)
+ } else if f.debug_upper_hex() {
+ fmt::UpperHex::fmt(self, f)
+ } else {
+ fmt::Display::fmt(self, f)
+ }
+ }
+ }
+ )*};
+}
+debug! {
+ i8 i16 i32 i64 i128 isize
+ u8 u16 u32 u64 u128 usize
+}
+
+// 2 digit decimal look up table
+static DEC_DIGITS_LUT: &[u8; 200] = b"0001020304050607080910111213141516171819\
+ 2021222324252627282930313233343536373839\
+ 4041424344454647484950515253545556575859\
+ 6061626364656667686970717273747576777879\
+ 8081828384858687888990919293949596979899";
+
+macro_rules! impl_Display {
+ ($($t:ident),* as $u:ident via $conv_fn:ident named $name:ident) => {
+ fn $name(mut n: $u, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // 2^128 is about 3*10^38, so 39 gives an extra byte of space
+ let mut buf = [MaybeUninit::<u8>::uninit(); 39];
+ let mut curr = buf.len() as isize;
+ let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
+ let lut_ptr = DEC_DIGITS_LUT.as_ptr();
+
+ // SAFETY: Since `d1` and `d2` are always less than or equal to `198`, we
+ // can copy from `lut_ptr[d1..d1 + 1]` and `lut_ptr[d2..d2 + 1]`. To show
+ // that it's OK to copy into `buf_ptr`, notice that at the beginning
+ // `curr == buf.len() == 39 > log(n)` since `n < 2^128 < 10^39`, and at
+ // each step this is kept the same as `n` is divided. Since `n` is always
+ // non-negative, this means that `curr > 0` so `buf_ptr[curr..curr + 1]`
+ // is safe to access.
+ unsafe {
+ // need at least 16 bits for the 4-characters-at-a-time to work.
+ assert!(crate::mem::size_of::<$u>() >= 2);
+
+ // eagerly decode 4 characters at a time
+ while n >= 10000 {
+ let rem = (n % 10000) as isize;
+ n /= 10000;
+
+ let d1 = (rem / 100) << 1;
+ let d2 = (rem % 100) << 1;
+ curr -= 4;
+
+ // We are allowed to copy to `buf_ptr[curr..curr + 3]` here since
+ // otherwise `curr < 0`. But then `n` was originally at least `10000^10`
+ // which is `10^40 > 2^128 > n`.
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
+ }
+
+ // if we reach here numbers are <= 9999, so at most 4 chars long
+ let mut n = n as isize; // possibly reduce 64bit math
+
+ // decode 2 more chars, if > 2 chars
+ if n >= 100 {
+ let d1 = (n % 100) << 1;
+ n /= 100;
+ curr -= 2;
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+ }
+
+ // decode last 1 or 2 chars
+ if n < 10 {
+ curr -= 1;
+ *buf_ptr.offset(curr) = (n as u8) + b'0';
+ } else {
+ let d1 = n << 1;
+ curr -= 2;
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+ }
+ }
+
+ // SAFETY: `curr` > 0 (since we made `buf` large enough), and all the chars are valid
+ // UTF-8 since `DEC_DIGITS_LUT` is
+ let buf_slice = unsafe {
+ str::from_utf8_unchecked(
+ slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
+ };
+ f.pad_integral(is_nonnegative, "", buf_slice)
+ }
+
+ $(#[stable(feature = "rust1", since = "1.0.0")]
+ impl fmt::Display for $t {
+ #[allow(unused_comparisons)]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ let is_nonnegative = *self >= 0;
+ let n = if is_nonnegative {
+ self.$conv_fn()
+ } else {
+ // convert the negative num to positive by summing 1 to it's 2 complement
+ (!self.$conv_fn()).wrapping_add(1)
+ };
+ $name(n, is_nonnegative, f)
+ }
+ })*
+ };
+}
+
+macro_rules! impl_Exp {
+ ($($t:ident),* as $u:ident via $conv_fn:ident named $name:ident) => {
+ fn $name(
+ mut n: $u,
+ is_nonnegative: bool,
+ upper: bool,
+ f: &mut fmt::Formatter<'_>
+ ) -> fmt::Result {
+ let (mut n, mut exponent, trailing_zeros, added_precision) = {
+ let mut exponent = 0;
+ // count and remove trailing decimal zeroes
+ while n % 10 == 0 && n >= 10 {
+ n /= 10;
+ exponent += 1;
+ }
+
+ let (added_precision, subtracted_precision) = match f.precision() {
+ Some(fmt_prec) => {
+ // number of decimal digits minus 1
+ let mut tmp = n;
+ let mut prec = 0;
+ while tmp >= 10 {
+ tmp /= 10;
+ prec += 1;
+ }
+ (fmt_prec.saturating_sub(prec), prec.saturating_sub(fmt_prec))
+ }
+ None => (0, 0)
+ };
+ for _ in 1..subtracted_precision {
+ n /= 10;
+ exponent += 1;
+ }
+ if subtracted_precision != 0 {
+ let rem = n % 10;
+ n /= 10;
+ exponent += 1;
+ // round up last digit
+ if rem >= 5 {
+ n += 1;
+ }
+ }
+ (n, exponent, exponent, added_precision)
+ };
+
+ // 39 digits (worst case u128) + . = 40
+ // Since `curr` always decreases by the number of digits copied, this means
+ // that `curr >= 0`.
+ let mut buf = [MaybeUninit::<u8>::uninit(); 40];
+ let mut curr = buf.len() as isize; //index for buf
+ let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
+ let lut_ptr = DEC_DIGITS_LUT.as_ptr();
+
+ // decode 2 chars at a time
+ while n >= 100 {
+ let d1 = ((n % 100) as isize) << 1;
+ curr -= 2;
+ // SAFETY: `d1 <= 198`, so we can copy from `lut_ptr[d1..d1 + 2]` since
+ // `DEC_DIGITS_LUT` has a length of 200.
+ unsafe {
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+ }
+ n /= 100;
+ exponent += 2;
+ }
+ // n is <= 99, so at most 2 chars long
+ let mut n = n as isize; // possibly reduce 64bit math
+ // decode second-to-last character
+ if n >= 10 {
+ curr -= 1;
+ // SAFETY: Safe since `40 > curr >= 0` (see comment)
+ unsafe {
+ *buf_ptr.offset(curr) = (n as u8 % 10_u8) + b'0';
+ }
+ n /= 10;
+ exponent += 1;
+ }
+ // add decimal point iff >1 mantissa digit will be printed
+ if exponent != trailing_zeros || added_precision != 0 {
+ curr -= 1;
+ // SAFETY: Safe since `40 > curr >= 0`
+ unsafe {
+ *buf_ptr.offset(curr) = b'.';
+ }
+ }
+
+ // SAFETY: Safe since `40 > curr >= 0`
+ let buf_slice = unsafe {
+ // decode last character
+ curr -= 1;
+ *buf_ptr.offset(curr) = (n as u8) + b'0';
+
+ let len = buf.len() - curr as usize;
+ slice::from_raw_parts(buf_ptr.offset(curr), len)
+ };
+
+ // stores 'e' (or 'E') and the up to 2-digit exponent
+ let mut exp_buf = [MaybeUninit::<u8>::uninit(); 3];
+ let exp_ptr = MaybeUninit::slice_as_mut_ptr(&mut exp_buf);
+ // SAFETY: In either case, `exp_buf` is written within bounds and `exp_ptr[..len]`
+ // is contained within `exp_buf` since `len <= 3`.
+ let exp_slice = unsafe {
+ *exp_ptr.offset(0) = if upper { b'E' } else { b'e' };
+ let len = if exponent < 10 {
+ *exp_ptr.offset(1) = (exponent as u8) + b'0';
+ 2
+ } else {
+ let off = exponent << 1;
+ ptr::copy_nonoverlapping(lut_ptr.offset(off), exp_ptr.offset(1), 2);
+ 3
+ };
+ slice::from_raw_parts(exp_ptr, len)
+ };
+
+ let parts = &[
+ numfmt::Part::Copy(buf_slice),
+ numfmt::Part::Zero(added_precision),
+ numfmt::Part::Copy(exp_slice)
+ ];
+ let sign = if !is_nonnegative {
+ "-"
+ } else if f.sign_plus() {
+ "+"
+ } else {
+ ""
+ };
+ let formatted = numfmt::Formatted{sign, parts};
+ f.pad_formatted_parts(&formatted)
+ }
+
+ $(
+ #[stable(feature = "integer_exp_format", since = "1.42.0")]
+ impl fmt::LowerExp for $t {
+ #[allow(unused_comparisons)]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ let is_nonnegative = *self >= 0;
+ let n = if is_nonnegative {
+ self.$conv_fn()
+ } else {
+ // convert the negative num to positive by summing 1 to it's 2 complement
+ (!self.$conv_fn()).wrapping_add(1)
+ };
+ $name(n, is_nonnegative, false, f)
+ }
+ })*
+ $(
+ #[stable(feature = "integer_exp_format", since = "1.42.0")]
+ impl fmt::UpperExp for $t {
+ #[allow(unused_comparisons)]
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ let is_nonnegative = *self >= 0;
+ let n = if is_nonnegative {
+ self.$conv_fn()
+ } else {
+ // convert the negative num to positive by summing 1 to it's 2 complement
+ (!self.$conv_fn()).wrapping_add(1)
+ };
+ $name(n, is_nonnegative, true, f)
+ }
+ })*
+ };
+}
+
+// Include wasm32 in here since it doesn't reflect the native pointer size, and
+// often cares strongly about getting a smaller code size.
+#[cfg(any(target_pointer_width = "64", target_arch = "wasm32"))]
+mod imp {
+ use super::*;
+ impl_Display!(
+ i8, u8, i16, u16, i32, u32, i64, u64, usize, isize
+ as u64 via to_u64 named fmt_u64
+ );
+ impl_Exp!(
+ i8, u8, i16, u16, i32, u32, i64, u64, usize, isize
+ as u64 via to_u64 named exp_u64
+ );
+}
+
+#[cfg(not(any(target_pointer_width = "64", target_arch = "wasm32")))]
+mod imp {
+ use super::*;
+ impl_Display!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named fmt_u32);
+ impl_Display!(i64, u64 as u64 via to_u64 named fmt_u64);
+ impl_Exp!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named exp_u32);
+ impl_Exp!(i64, u64 as u64 via to_u64 named exp_u64);
+}
+impl_Exp!(i128, u128 as u128 via to_u128 named exp_u128);
+
+/// Helper function for writing a u64 into `buf` going from last to first, with `curr`.
+fn parse_u64_into<const N: usize>(mut n: u64, buf: &mut [MaybeUninit<u8>; N], curr: &mut isize) {
+ let buf_ptr = MaybeUninit::slice_as_mut_ptr(buf);
+ let lut_ptr = DEC_DIGITS_LUT.as_ptr();
+ assert!(*curr > 19);
+
+ // SAFETY:
+ // Writes at most 19 characters into the buffer. Guaranteed that any ptr into LUT is at most
+ // 198, so will never OOB. There is a check above that there are at least 19 characters
+ // remaining.
+ unsafe {
+ if n >= 1e16 as u64 {
+ let to_parse = n % 1e16 as u64;
+ n /= 1e16 as u64;
+
+ // Some of these are nops but it looks more elegant this way.
+ let d1 = ((to_parse / 1e14 as u64) % 100) << 1;
+ let d2 = ((to_parse / 1e12 as u64) % 100) << 1;
+ let d3 = ((to_parse / 1e10 as u64) % 100) << 1;
+ let d4 = ((to_parse / 1e8 as u64) % 100) << 1;
+ let d5 = ((to_parse / 1e6 as u64) % 100) << 1;
+ let d6 = ((to_parse / 1e4 as u64) % 100) << 1;
+ let d7 = ((to_parse / 1e2 as u64) % 100) << 1;
+ let d8 = ((to_parse / 1e0 as u64) % 100) << 1;
+
+ *curr -= 16;
+
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1 as isize), buf_ptr.offset(*curr + 0), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d2 as isize), buf_ptr.offset(*curr + 2), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d3 as isize), buf_ptr.offset(*curr + 4), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d4 as isize), buf_ptr.offset(*curr + 6), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d5 as isize), buf_ptr.offset(*curr + 8), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d6 as isize), buf_ptr.offset(*curr + 10), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d7 as isize), buf_ptr.offset(*curr + 12), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d8 as isize), buf_ptr.offset(*curr + 14), 2);
+ }
+ if n >= 1e8 as u64 {
+ let to_parse = n % 1e8 as u64;
+ n /= 1e8 as u64;
+
+ // Some of these are nops but it looks more elegant this way.
+ let d1 = ((to_parse / 1e6 as u64) % 100) << 1;
+ let d2 = ((to_parse / 1e4 as u64) % 100) << 1;
+ let d3 = ((to_parse / 1e2 as u64) % 100) << 1;
+ let d4 = ((to_parse / 1e0 as u64) % 100) << 1;
+ *curr -= 8;
+
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1 as isize), buf_ptr.offset(*curr + 0), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d2 as isize), buf_ptr.offset(*curr + 2), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d3 as isize), buf_ptr.offset(*curr + 4), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d4 as isize), buf_ptr.offset(*curr + 6), 2);
+ }
+ // `n` < 1e8 < (1 << 32)
+ let mut n = n as u32;
+ if n >= 1e4 as u32 {
+ let to_parse = n % 1e4 as u32;
+ n /= 1e4 as u32;
+
+ let d1 = (to_parse / 100) << 1;
+ let d2 = (to_parse % 100) << 1;
+ *curr -= 4;
+
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1 as isize), buf_ptr.offset(*curr + 0), 2);
+ ptr::copy_nonoverlapping(lut_ptr.offset(d2 as isize), buf_ptr.offset(*curr + 2), 2);
+ }
+
+ // `n` < 1e4 < (1 << 16)
+ let mut n = n as u16;
+ if n >= 100 {
+ let d1 = (n % 100) << 1;
+ n /= 100;
+ *curr -= 2;
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1 as isize), buf_ptr.offset(*curr), 2);
+ }
+
+ // decode last 1 or 2 chars
+ if n < 10 {
+ *curr -= 1;
+ *buf_ptr.offset(*curr) = (n as u8) + b'0';
+ } else {
+ let d1 = n << 1;
+ *curr -= 2;
+ ptr::copy_nonoverlapping(lut_ptr.offset(d1 as isize), buf_ptr.offset(*curr), 2);
+ }
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for u128 {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt_u128(*self, true, f)
+ }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for i128 {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ let is_nonnegative = *self >= 0;
+ let n = if is_nonnegative {
+ self.to_u128()
+ } else {
+ // convert the negative num to positive by summing 1 to it's 2 complement
+ (!self.to_u128()).wrapping_add(1)
+ };
+ fmt_u128(n, is_nonnegative, f)
+ }
+}
+
+/// Specialized optimization for u128. Instead of taking two items at a time, it splits
+/// into at most 2 u64s, and then chunks by 10e16, 10e8, 10e4, 10e2, and then 10e1.
+/// It also has to handle 1 last item, as 10^40 > 2^128 > 10^39, whereas
+/// 10^20 > 2^64 > 10^19.
+fn fmt_u128(n: u128, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // 2^128 is about 3*10^38, so 39 gives an extra byte of space
+ let mut buf = [MaybeUninit::<u8>::uninit(); 39];
+ let mut curr = buf.len() as isize;
+
+ let (n, rem) = udiv_1e19(n);
+ parse_u64_into(rem, &mut buf, &mut curr);
+
+ if n != 0 {
+ // 0 pad up to point
+ let target = (buf.len() - 19) as isize;
+ // SAFETY: Guaranteed that we wrote at most 19 bytes, and there must be space
+ // remaining since it has length 39
+ unsafe {
+ ptr::write_bytes(
+ MaybeUninit::slice_as_mut_ptr(&mut buf).offset(target),
+ b'0',
+ (curr - target) as usize,
+ );
+ }
+ curr = target;
+
+ let (n, rem) = udiv_1e19(n);
+ parse_u64_into(rem, &mut buf, &mut curr);
+ // Should this following branch be annotated with unlikely?
+ if n != 0 {
+ let target = (buf.len() - 38) as isize;
+ // The raw `buf_ptr` pointer is only valid until `buf` is used the next time,
+ // buf `buf` is not used in this scope so we are good.
+ let buf_ptr = MaybeUninit::slice_as_mut_ptr(&mut buf);
+ // SAFETY: At this point we wrote at most 38 bytes, pad up to that point,
+ // There can only be at most 1 digit remaining.
+ unsafe {
+ ptr::write_bytes(buf_ptr.offset(target), b'0', (curr - target) as usize);
+ curr = target - 1;
+ *buf_ptr.offset(curr) = (n as u8) + b'0';
+ }
+ }
+ }
+
+ // SAFETY: `curr` > 0 (since we made `buf` large enough), and all the chars are valid
+ // UTF-8 since `DEC_DIGITS_LUT` is
+ let buf_slice = unsafe {
+ str::from_utf8_unchecked(slice::from_raw_parts(
+ MaybeUninit::slice_as_mut_ptr(&mut buf).offset(curr),
+ buf.len() - curr as usize,
+ ))
+ };
+ f.pad_integral(is_nonnegative, "", buf_slice)
+}
+
+/// Partition of `n` into n > 1e19 and rem <= 1e19
+///
+/// Integer division algorithm is based on the following paper:
+///
+/// T. Granlund and P. Montgomery, “Division by Invariant Integers Using Multiplication”
+/// in Proc. of the SIGPLAN94 Conference on Programming Language Design and
+/// Implementation, 1994, pp. 61–72
+///
+fn udiv_1e19(n: u128) -> (u128, u64) {
+ const DIV: u64 = 1e19 as u64;
+ const FACTOR: u128 = 156927543384667019095894735580191660403;
+
+ let quot = if n < 1 << 83 {
+ ((n >> 19) as u64 / (DIV >> 19)) as u128
+ } else {
+ u128_mulhi(n, FACTOR) >> 62
+ };
+
+ let rem = (n - quot * DIV as u128) as u64;
+ (quot, rem)
+}
+
+/// Multiply unsigned 128 bit integers, return upper 128 bits of the result
+#[inline]
+fn u128_mulhi(x: u128, y: u128) -> u128 {
+ let x_lo = x as u64;
+ let x_hi = (x >> 64) as u64;
+ let y_lo = y as u64;
+ let y_hi = (y >> 64) as u64;
+
+ // handle possibility of overflow
+ let carry = (x_lo as u128 * y_lo as u128) >> 64;
+ let m = x_lo as u128 * y_hi as u128 + carry;
+ let high1 = m >> 64;
+
+ let m_lo = m as u64;
+ let high2 = (x_hi as u128 * y_lo as u128 + m_lo as u128) >> 64;
+
+ x_hi as u128 * y_hi as u128 + high1 + high2
+}
diff --git a/library/core/src/fmt/rt/v1.rs b/library/core/src/fmt/rt/v1.rs
new file mode 100644
index 000000000..37202b277
--- /dev/null
+++ b/library/core/src/fmt/rt/v1.rs
@@ -0,0 +1,45 @@
+//! This is an internal module used by the ifmt! runtime. These structures are
+//! emitted to static arrays to precompile format strings ahead of time.
+//!
+//! These definitions are similar to their `ct` equivalents, but differ in that
+//! these can be statically allocated and are slightly optimized for the runtime
+#![allow(missing_debug_implementations)]
+
+#[derive(Copy, Clone)]
+pub struct Argument {
+ pub position: usize,
+ pub format: FormatSpec,
+}
+
+#[derive(Copy, Clone)]
+pub struct FormatSpec {
+ pub fill: char,
+ pub align: Alignment,
+ pub flags: u32,
+ pub precision: Count,
+ pub width: Count,
+}
+
+/// Possible alignments that can be requested as part of a formatting directive.
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Alignment {
+ /// Indication that contents should be left-aligned.
+ Left,
+ /// Indication that contents should be right-aligned.
+ Right,
+ /// Indication that contents should be center-aligned.
+ Center,
+ /// No alignment was requested.
+ Unknown,
+}
+
+/// Used by [width](https://doc.rust-lang.org/std/fmt/#width) and [precision](https://doc.rust-lang.org/std/fmt/#precision) specifiers.
+#[derive(Copy, Clone)]
+pub enum Count {
+ /// Specified with a literal number, stores the value
+ Is(usize),
+ /// Specified using `$` and `*` syntaxes, stores the index into `args`
+ Param(usize),
+ /// Not specified
+ Implied,
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-01 17:59:38 +0000