1 files changed, 79 insertions, 0 deletions
diff --git a/third_party/rust/h2/src/frame/util.rs b/third_party/rust/h2/src/frame/util.rs
new file mode 100644
index 0000000000..6bee7bd9bb
--- /dev/null
+++ b/third_party/rust/h2/src/frame/util.rs
@@ -0,0 +1,79 @@
+use std::fmt;
+
+use super::Error;
+use bytes::Bytes;
+
+/// Strip padding from the given payload.
+///
+/// It is assumed that the frame had the padded flag set. This means that the
+/// first byte is the length of the padding with that many
+/// 0 bytes expected to follow the actual payload.
+///
+/// # Returns
+///
+/// A slice of the given payload where the actual one is found and the length
+/// of the padding.
+///
+/// If the padded payload is invalid (e.g. the length of the padding is equal
+/// to the total length), returns `None`.
+pub fn strip_padding(payload: &mut Bytes) -> Result<u8, Error> {
+    let payload_len = payload.len();
+    if payload_len == 0 {
+        // If this is the case, the frame is invalid as no padding length can be
+        // extracted, even though the frame should be padded.
+        return Err(Error::TooMuchPadding);
+    }
+
+    let pad_len = payload[0] as usize;
+
+    if pad_len >= payload_len {
+        // This is invalid: the padding length MUST be less than the
+        // total frame size.
+        return Err(Error::TooMuchPadding);
+    }
+
+    let _ = payload.split_to(1);
+    let _ = payload.split_off(payload_len - pad_len - 1);
+
+    Ok(pad_len as u8)
+}
+
+pub(super) fn debug_flags<'a, 'f: 'a>(
+    fmt: &'a mut fmt::Formatter<'f>,
+    bits: u8,
+) -> DebugFlags<'a, 'f> {
+    let result = write!(fmt, "({:#x}", bits);
+    DebugFlags {
+        fmt,
+        result,
+        started: false,
+    }
+}
+
+pub(super) struct DebugFlags<'a, 'f: 'a> {
+    fmt: &'a mut fmt::Formatter<'f>,
+    result: fmt::Result,
+    started: bool,
+}
+
+impl<'a, 'f: 'a> DebugFlags<'a, 'f> {
+    pub(super) fn flag_if(&mut self, enabled: bool, name: &str) -> &mut Self {
+        if enabled {
+            self.result = self.result.and_then(|()| {
+                let prefix = if self.started {
+                    " | "
+                } else {
+                    self.started = true;
+                    ": "
+                };
+
+                write!(self.fmt, "{}{}", prefix, name)
+            });
+        }
+        self
+    }
+
+    pub(super) fn finish(&mut self) -> fmt::Result {
+        self.result.and_then(|()| write!(self.fmt, ")"))
+    }
+}