Merging upstream version 1.70.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 117 insertions, 107 deletions

diff --git a/library/core/src/num/dec2flt/parse.rs b/library/core/src/num/dec2flt/parse.rs
index 1a90e0d20..b0a23835c 100644
--- a/library/core/src/num/dec2flt/parse.rs
+++ b/library/core/src/num/dec2flt/parse.rs
@@ -1,6 +1,6 @@
 //! Functions to parse floating-point numbers.
 
-use crate::num::dec2flt::common::{is_8digits, AsciiStr, ByteSlice};
+use crate::num::dec2flt::common::{is_8digits, ByteSlice};
 use crate::num::dec2flt::float::RawFloat;
 use crate::num::dec2flt::number::Number;
 
@@ -26,24 +26,39 @@ fn parse_8digits(mut v: u64) -> u64 {
 }
 
 /// Parse digits until a non-digit character is found.
-fn try_parse_digits(s: &mut AsciiStr<'_>, x: &mut u64) {
+fn try_parse_digits(mut s: &[u8], mut x: u64) -> (&[u8], u64) {
     // may cause overflows, to be handled later
-    s.parse_digits(|digit| {
-        *x = x.wrapping_mul(10).wrapping_add(digit as _);
+
+    while s.len() >= 8 {
+        let num = s.read_u64();
+        if is_8digits(num) {
+            x = x.wrapping_mul(1_0000_0000).wrapping_add(parse_8digits(num));
+            s = &s[8..];
+        } else {
+            break;
+        }
+    }
+
+    s = s.parse_digits(|digit| {
+        x = x.wrapping_mul(10).wrapping_add(digit as _);
     });
+
+    (s, x)
 }
 
 /// Parse up to 19 digits (the max that can be stored in a 64-bit integer).
-fn try_parse_19digits(s: &mut AsciiStr<'_>, x: &mut u64) {
+fn try_parse_19digits(s_ref: &mut &[u8], x: &mut u64) {
+    let mut s = *s_ref;
+
     while *x < MIN_19DIGIT_INT {
-        if let Some(&c) = s.as_ref().first() {
+        // FIXME: Can't use s.split_first() here yet,
+        // see https://github.com/rust-lang/rust/issues/109328
+        if let [c, s_next @ ..] = s {
             let digit = c.wrapping_sub(b'0');
+
             if digit < 10 {
                 *x = (*x * 10) + digit as u64; // no overflows here
-                // SAFETY: cannot be empty
-                unsafe {
-                    s.step();
-                }
+                s = s_next;
             } else {
                 break;
             }
@@ -51,46 +66,26 @@ fn try_parse_19digits(s: &mut AsciiStr<'_>, x: &mut u64) {
             break;
         }
     }
-}
 
-/// Try to parse 8 digits at a time, using an optimized algorithm.
-fn try_parse_8digits(s: &mut AsciiStr<'_>, x: &mut u64) {
-    // may cause overflows, to be handled later
-    if let Some(v) = s.read_u64() {
-        if is_8digits(v) {
-            *x = x.wrapping_mul(1_0000_0000).wrapping_add(parse_8digits(v));
-            // SAFETY: already ensured the buffer was >= 8 bytes in read_u64.
-            unsafe {
-                s.step_by(8);
-            }
-            if let Some(v) = s.read_u64() {
-                if is_8digits(v) {
-                    *x = x.wrapping_mul(1_0000_0000).wrapping_add(parse_8digits(v));
-                    // SAFETY: already ensured the buffer was >= 8 bytes in try_read_u64.
-                    unsafe {
-                        s.step_by(8);
-                    }
-                }
-            }
-        }
-    }
+    *s_ref = s;
 }
 
 /// Parse the scientific notation component of a float.
-fn parse_scientific(s: &mut AsciiStr<'_>) -> Option<i64> {
-    let mut exponent = 0_i64;
+fn parse_scientific(s_ref: &mut &[u8]) -> Option<i64> {
+    let mut exponent = 0i64;
     let mut negative = false;
-    if let Some(&c) = s.as_ref().get(0) {
+
+    let mut s = *s_ref;
+
+    if let Some((&c, s_next)) = s.split_first() {
         negative = c == b'-';
         if c == b'-' || c == b'+' {
-            // SAFETY: s cannot be empty
-            unsafe {
-                s.step();
-            }
+            s = s_next;
         }
     }
-    if s.first_isdigit() {
-        s.parse_digits(|digit| {
+
+    if matches!(s.first(), Some(&x) if x.is_ascii_digit()) {
+        *s_ref = s.parse_digits(|digit| {
             // no overflows here, saturate well before overflow
             if exponent < 0x10000 {
                 exponent = 10 * exponent + digit as i64;
@@ -98,6 +93,7 @@ fn parse_scientific(s: &mut AsciiStr<'_>) -> Option<i64> {
         });
         if negative { Some(-exponent) } else { Some(exponent) }
     } else {
+        *s_ref = s;
         None
     }
 }
@@ -106,28 +102,29 @@ fn parse_scientific(s: &mut AsciiStr<'_>) -> Option<i64> {
 ///
 /// This creates a representation of the float as the
 /// significant digits and the decimal exponent.
-fn parse_partial_number(s: &[u8], negative: bool) -> Option<(Number, usize)> {
-    let mut s = AsciiStr::new(s);
-    let start = s;
+fn parse_partial_number(mut s: &[u8]) -> Option<(Number, usize)> {
     debug_assert!(!s.is_empty());
 
     // parse initial digits before dot
     let mut mantissa = 0_u64;
-    let digits_start = s;
-    try_parse_digits(&mut s, &mut mantissa);
-    let mut n_digits = s.offset_from(&digits_start);
+    let start = s;
+    let tmp = try_parse_digits(s, mantissa);
+    s = tmp.0;
+    mantissa = tmp.1;
+    let mut n_digits = s.offset_from(start);
 
     // handle dot with the following digits
     let mut n_after_dot = 0;
     let mut exponent = 0_i64;
     let int_end = s;
-    if s.first_is(b'.') {
-        // SAFETY: s cannot be empty due to first_is
-        unsafe { s.step() };
+
+    if let Some((&b'.', s_next)) = s.split_first() {
+        s = s_next;
         let before = s;
-        try_parse_8digits(&mut s, &mut mantissa);
-        try_parse_digits(&mut s, &mut mantissa);
-        n_after_dot = s.offset_from(&before);
+        let tmp = try_parse_digits(s, mantissa);
+        s = tmp.0;
+        mantissa = tmp.1;
+        n_after_dot = s.offset_from(before);
         exponent = -n_after_dot as i64;
     }
 
@@ -138,65 +135,60 @@ fn parse_partial_number(s: &[u8], negative: bool) -> Option<(Number, usize)> {
 
     // handle scientific format
     let mut exp_number = 0_i64;
-    if s.first_is2(b'e', b'E') {
-        // SAFETY: s cannot be empty
-        unsafe {
-            s.step();
+    if let Some((&c, s_next)) = s.split_first() {
+        if c == b'e' || c == b'E' {
+            s = s_next;
+            // If None, we have no trailing digits after exponent, or an invalid float.
+            exp_number = parse_scientific(&mut s)?;
+            exponent += exp_number;
         }
-        // If None, we have no trailing digits after exponent, or an invalid float.
-        exp_number = parse_scientific(&mut s)?;
-        exponent += exp_number;
     }
 
-    let len = s.offset_from(&start) as _;
+    let len = s.offset_from(start) as _;
 
     // handle uncommon case with many digits
     if n_digits <= 19 {
-        return Some((Number { exponent, mantissa, negative, many_digits: false }, len));
+        return Some((Number { exponent, mantissa, negative: false, many_digits: false }, len));
     }
 
     n_digits -= 19;
     let mut many_digits = false;
-    let mut p = digits_start;
-    while p.first_is2(b'0', b'.') {
-        // SAFETY: p cannot be empty due to first_is2
-        unsafe {
-            // '0' = b'.' + 2
-            n_digits -= p.first_unchecked().saturating_sub(b'0' - 1) as isize;
-            p.step();
+    let mut p = start;
+    while let Some((&c, p_next)) = p.split_first() {
+        if c == b'.' || c == b'0' {
+            n_digits -= c.saturating_sub(b'0' - 1) as isize;
+            p = p_next;
+        } else {
+            break;
         }
     }
     if n_digits > 0 {
         // at this point we have more than 19 significant digits, let's try again
         many_digits = true;
         mantissa = 0;
-        let mut s = digits_start;
+        let mut s = start;
         try_parse_19digits(&mut s, &mut mantissa);
         exponent = if mantissa >= MIN_19DIGIT_INT {
             // big int
-            int_end.offset_from(&s)
+            int_end.offset_from(s)
         } else {
-            // SAFETY: the next byte must be present and be '.'
-            // We know this is true because we had more than 19
-            // digits previously, so we overflowed a 64-bit integer,
-            // but parsing only the integral digits produced less
-            // than 19 digits. That means we must have a decimal
-            // point, and at least 1 fractional digit.
-            unsafe { s.step() };
+            s = &s[1..];
             let before = s;
             try_parse_19digits(&mut s, &mut mantissa);
-            -s.offset_from(&before)
+            -s.offset_from(before)
         } as i64;
         // add back the explicit part
         exponent += exp_number;
     }
 
-    Some((Number { exponent, mantissa, negative, many_digits }, len))
+    Some((Number { exponent, mantissa, negative: false, many_digits }, len))
 }
 
-/// Try to parse a non-special floating point number.
-pub fn parse_number(s: &[u8], negative: bool) -> Option<Number> {
-    if let Some((float, rest)) = parse_partial_number(s, negative) {
+/// Try to parse a non-special floating point number,
+/// as well as two slices with integer and fractional parts
+/// and the parsed exponent.
+pub fn parse_number(s: &[u8]) -> Option<Number> {
+    if let Some((float, rest)) = parse_partial_number(s) {
         if rest == s.len() {
             return Some(float);
         }
@@ -204,30 +196,48 @@ pub fn parse_number(s: &[u8], negative: bool) -> Option<Number> {
     None
 }
 
-/// Parse a partial representation of a special, non-finite float.
-fn parse_partial_inf_nan<F: RawFloat>(s: &[u8]) -> Option<(F, usize)> {
-    fn parse_inf_rest(s: &[u8]) -> usize {
-        if s.len() >= 8 && s[3..].as_ref().starts_with_ignore_case(b"inity") { 8 } else { 3 }
-    }
-    if s.len() >= 3 {
-        if s.starts_with_ignore_case(b"nan") {
-            return Some((F::NAN, 3));
-        } else if s.starts_with_ignore_case(b"inf") {
-            return Some((F::INFINITY, parse_inf_rest(s)));
-        }
-    }
-    None
-}
-
 /// Try to parse a special, non-finite float.
-pub fn parse_inf_nan<F: RawFloat>(s: &[u8], negative: bool) -> Option<F> {
-    if let Some((mut float, rest)) = parse_partial_inf_nan::<F>(s) {
-        if rest == s.len() {
-            if negative {
-                float = -float;
-            }
-            return Some(float);
-        }
+pub(crate) fn parse_inf_nan<F: RawFloat>(s: &[u8], negative: bool) -> Option<F> {
+    // Since a valid string has at most the length 8, we can load
+    // all relevant characters into a u64 and work from there.
+    // This also generates much better code.
+
+    let mut register;
+    let len: usize;
+
+    // All valid strings are either of length 8 or 3.
+    if s.len() == 8 {
+        register = s.read_u64();
+        len = 8;
+    } else if s.len() == 3 {
+        let a = s[0] as u64;
+        let b = s[1] as u64;
+        let c = s[2] as u64;
+        register = (c << 16) | (b << 8) | a;
+        len = 3;
+    } else {
+        return None;
     }
-    None
+
+    // Clear out the bits which turn ASCII uppercase characters into
+    // lowercase characters. The resulting string is all uppercase.
+    // What happens to other characters is irrelevant.
+    register &= 0xDFDFDFDFDFDFDFDF;
+
+    // u64 values corresponding to relevant cases
+    const INF_3: u64 = 0x464E49; // "INF"
+    const INF_8: u64 = 0x5954494E49464E49; // "INFINITY"
+    const NAN: u64 = 0x4E414E; // "NAN"
+
+    // Match register value to constant to parse string.
+    // Also match on the string length to catch edge cases
+    // like "inf\0\0\0\0\0".
+    let float = match (register, len) {
+        (INF_3, 3) => F::INFINITY,
+        (INF_8, 8) => F::INFINITY,
+        (NAN, 3) => F::NAN,
+        _ => return None,
+    };
+
+    if negative { Some(-float) } else { Some(float) }
 }