1 files changed, 105 insertions, 0 deletions
diff --git a/third_party/rust/generic-array/src/hex.rs b/third_party/rust/generic-array/src/hex.rs
new file mode 100644
index 0000000000..33c796f3c9
--- /dev/null
+++ b/third_party/rust/generic-array/src/hex.rs
@@ -0,0 +1,105 @@
+//! Generic array are commonly used as a return value for hash digests, so
+//! it's a good idea to allow to hexlify them easily. This module implements
+//! `std::fmt::LowerHex` and `std::fmt::UpperHex` traits.
+//!
+//! Example:
+//!
+//! ```rust
+//! # #[macro_use]
+//! # extern crate generic_array;
+//! # extern crate typenum;
+//! # fn main() {
+//! let array = arr![u8; 10, 20, 30];
+//! assert_eq!(format!("{:x}", array), "0a141e");
+//! # }
+//! ```
+//!
+
+use core::{fmt, str, ops::Add, cmp::min};
+
+use typenum::*;
+
+use crate::{ArrayLength, GenericArray};
+
+static LOWER_CHARS: &'static [u8] = b"0123456789abcdef";
+static UPPER_CHARS: &'static [u8] = b"0123456789ABCDEF";
+
+impl<T: ArrayLength<u8>> fmt::LowerHex for GenericArray<u8, T>
+where
+    T: Add<T>,
+    <T as Add<T>>::Output: ArrayLength<u8>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);
+        let max_hex = (max_digits >> 1) + (max_digits & 1);
+
+        if T::USIZE < 1024 {
+            // For small arrays use a stack allocated
+            // buffer of 2x number of bytes
+            let mut res = GenericArray::<u8, Sum<T, T>>::default();
+
+            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {
+                res[i * 2] = LOWER_CHARS[(c >> 4) as usize];
+                res[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];
+            });
+
+            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;
+        } else {
+            // For large array use chunks of up to 1024 bytes (2048 hex chars)
+            let mut buf = [0u8; 2048];
+            let mut digits_left = max_digits;
+
+            for chunk in self[..max_hex].chunks(1024) {
+                chunk.iter().enumerate().for_each(|(i, c)| {
+                    buf[i * 2] = LOWER_CHARS[(c >> 4) as usize];
+                    buf[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];
+                });
+
+                let n = min(chunk.len() * 2, digits_left);
+                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;
+                digits_left -= n;
+            }
+        }
+        Ok(())
+    }
+}
+
+impl<T: ArrayLength<u8>> fmt::UpperHex for GenericArray<u8, T>
+where
+    T: Add<T>,
+    <T as Add<T>>::Output: ArrayLength<u8>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);
+        let max_hex = (max_digits >> 1) + (max_digits & 1);
+
+        if T::USIZE < 1024 {
+            // For small arrays use a stack allocated
+            // buffer of 2x number of bytes
+            let mut res = GenericArray::<u8, Sum<T, T>>::default();
+
+            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {
+                res[i * 2] = UPPER_CHARS[(c >> 4) as usize];
+                res[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];
+            });
+
+            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;
+        } else {
+            // For large array use chunks of up to 1024 bytes (2048 hex chars)
+            let mut buf = [0u8; 2048];
+            let mut digits_left = max_digits;
+
+            for chunk in self[..max_hex].chunks(1024) {
+                chunk.iter().enumerate().for_each(|(i, c)| {
+                    buf[i * 2] = UPPER_CHARS[(c >> 4) as usize];
+                    buf[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];
+                });
+
+                let n = min(chunk.len() * 2, digits_left);
+                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;
+                digits_left -= n;
+            }
+        }
+        Ok(())
+    }
+}