merge `hex` & `debug` into `fmt` (#357)

1 files changed, 49 insertions, 0 deletions

diff --git a/src/fmt/debug.rs b/src/fmt/debug.rs
new file mode 100644
index 0000000..f6a08b8
--- /dev/null
+++ b/src/fmt/debug.rs
@@ -0,0 +1,49 @@
+use core::fmt::{Debug, Formatter, Result};
+
+use crate::{Bytes, BytesMut};
+use super::BytesRef;
+
+/// Alternative implementation of `std::fmt::Debug` for byte slice.
+///
+/// Standard `Debug` implementation for `[u8]` is comma separated
+/// list of numbers. Since large amount of byte strings are in fact
+/// ASCII strings or contain a lot of ASCII strings (e. g. HTTP),
+/// it is convenient to print strings as ASCII when possible.
+impl Debug for BytesRef<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        write!(f, "b\"")?;
+        for &b in self.0 {
+            // https://doc.rust-lang.org/reference/tokens.html#byte-escapes
+            if b == b'\n' {
+                write!(f, "\\n")?;
+            } else if b == b'\r' {
+                write!(f, "\\r")?;
+            } else if b == b'\t' {
+                write!(f, "\\t")?;
+            } else if b == b'\\' || b == b'"' {
+                write!(f, "\\{}", b as char)?;
+            } else if b == b'\0' {
+                write!(f, "\\0")?;
+            // ASCII printable
+            } else if b >= 0x20 && b < 0x7f {
+                write!(f, "{}", b as char)?;
+            } else {
+                write!(f, "\\x{:02x}", b)?;
+            }
+        }
+        write!(f, "\"")?;
+        Ok(())
+    }
+}
+
+impl Debug for Bytes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        Debug::fmt(&BytesRef(&self.as_ref()), f)
+    }
+}
+
+impl Debug for BytesMut {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        Debug::fmt(&BytesRef(&self.as_ref()), f)
+    }
+}