Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

5 files changed, 2618 insertions, 0 deletions

diff --git a/third_party/rust/prost/src/encoding.rs b/third_party/rust/prost/src/encoding.rs
new file mode 100644
index 0000000000..252358685c
--- /dev/null
+++ b/third_party/rust/prost/src/encoding.rs
@@ -0,0 +1,1770 @@
+//! Utility functions and types for encoding and decoding Protobuf types.
+//!
+//! Meant to be used only from `Message` implementations.
+
+#![allow(clippy::implicit_hasher, clippy::ptr_arg)]
+
+use alloc::collections::BTreeMap;
+use alloc::format;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::cmp::min;
+use core::convert::TryFrom;
+use core::mem;
+use core::str;
+use core::u32;
+use core::usize;
+
+use ::bytes::{Buf, BufMut, Bytes};
+
+use crate::DecodeError;
+use crate::Message;
+
+/// Encodes an integer value into LEB128 variable length format, and writes it to the buffer.
+/// The buffer must have enough remaining space (maximum 10 bytes).
+#[inline]
+pub fn encode_varint<B>(mut value: u64, buf: &mut B)
+where
+    B: BufMut,
+{
+    // Safety notes:
+    //
+    // - ptr::write is an unsafe raw pointer write. The use here is safe since the length of the
+    //   uninit slice is checked.
+    // - advance_mut is unsafe because it could cause uninitialized memory to be advanced over. The
+    //   use here is safe since each byte which is advanced over has been written to in the
+    //   previous loop iteration.
+    unsafe {
+        let mut i;
+        'outer: loop {
+            i = 0;
+
+            let uninit_slice = buf.chunk_mut();
+            for offset in 0..uninit_slice.len() {
+                i += 1;
+                let ptr = uninit_slice.as_mut_ptr().add(offset);
+                if value < 0x80 {
+                    ptr.write(value as u8);
+                    break 'outer;
+                } else {
+                    ptr.write(((value & 0x7F) | 0x80) as u8);
+                    value >>= 7;
+                }
+            }
+
+            buf.advance_mut(i);
+            debug_assert!(buf.has_remaining_mut());
+        }
+
+        buf.advance_mut(i);
+    }
+}
+
+/// Decodes a LEB128-encoded variable length integer from the buffer.
+pub fn decode_varint<B>(buf: &mut B) -> Result<u64, DecodeError>
+where
+    B: Buf,
+{
+    let bytes = buf.chunk();
+    let len = bytes.len();
+    if len == 0 {
+        return Err(DecodeError::new("invalid varint"));
+    }
+
+    let byte = unsafe { *bytes.get_unchecked(0) };
+    if byte < 0x80 {
+        buf.advance(1);
+        Ok(u64::from(byte))
+    } else if len > 10 || bytes[len - 1] < 0x80 {
+        let (value, advance) = unsafe { decode_varint_slice(bytes) }?;
+        buf.advance(advance);
+        Ok(value)
+    } else {
+        decode_varint_slow(buf)
+    }
+}
+
+/// Decodes a LEB128-encoded variable length integer from the slice, returning the value and the
+/// number of bytes read.
+///
+/// Based loosely on [`ReadVarint64FromArray`][1].
+///
+/// ## Safety
+///
+/// The caller must ensure that `bytes` is non-empty and either `bytes.len() >= 10` or the last
+/// element in bytes is < `0x80`.
+///
+/// [1]: https://github.com/google/protobuf/blob/3.3.x/src/google/protobuf/io/coded_stream.cc#L365-L406
+#[inline]
+unsafe fn decode_varint_slice(bytes: &[u8]) -> Result<(u64, usize), DecodeError> {
+    // Fully unrolled varint decoding loop. Splitting into 32-bit pieces gives better performance.
+
+    let mut b: u8;
+    let mut part0: u32;
+    b = *bytes.get_unchecked(0);
+    part0 = u32::from(b);
+    if b < 0x80 {
+        return Ok((u64::from(part0), 1));
+    };
+    part0 -= 0x80;
+    b = *bytes.get_unchecked(1);
+    part0 += u32::from(b) << 7;
+    if b < 0x80 {
+        return Ok((u64::from(part0), 2));
+    };
+    part0 -= 0x80 << 7;
+    b = *bytes.get_unchecked(2);
+    part0 += u32::from(b) << 14;
+    if b < 0x80 {
+        return Ok((u64::from(part0), 3));
+    };
+    part0 -= 0x80 << 14;
+    b = *bytes.get_unchecked(3);
+    part0 += u32::from(b) << 21;
+    if b < 0x80 {
+        return Ok((u64::from(part0), 4));
+    };
+    part0 -= 0x80 << 21;
+    let value = u64::from(part0);
+
+    let mut part1: u32;
+    b = *bytes.get_unchecked(4);
+    part1 = u32::from(b);
+    if b < 0x80 {
+        return Ok((value + (u64::from(part1) << 28), 5));
+    };
+    part1 -= 0x80;
+    b = *bytes.get_unchecked(5);
+    part1 += u32::from(b) << 7;
+    if b < 0x80 {
+        return Ok((value + (u64::from(part1) << 28), 6));
+    };
+    part1 -= 0x80 << 7;
+    b = *bytes.get_unchecked(6);
+    part1 += u32::from(b) << 14;
+    if b < 0x80 {
+        return Ok((value + (u64::from(part1) << 28), 7));
+    };
+    part1 -= 0x80 << 14;
+    b = *bytes.get_unchecked(7);
+    part1 += u32::from(b) << 21;
+    if b < 0x80 {
+        return Ok((value + (u64::from(part1) << 28), 8));
+    };
+    part1 -= 0x80 << 21;
+    let value = value + ((u64::from(part1)) << 28);
+
+    let mut part2: u32;
+    b = *bytes.get_unchecked(8);
+    part2 = u32::from(b);
+    if b < 0x80 {
+        return Ok((value + (u64::from(part2) << 56), 9));
+    };
+    part2 -= 0x80;
+    b = *bytes.get_unchecked(9);
+    part2 += u32::from(b) << 7;
+    if b < 0x80 {
+        return Ok((value + (u64::from(part2) << 56), 10));
+    };
+
+    // We have overrun the maximum size of a varint (10 bytes). Assume the data is corrupt.
+    Err(DecodeError::new("invalid varint"))
+}
+
+/// Decodes a LEB128-encoded variable length integer from the buffer, advancing the buffer as
+/// necessary.
+#[inline(never)]
+fn decode_varint_slow<B>(buf: &mut B) -> Result<u64, DecodeError>
+where
+    B: Buf,
+{
+    let mut value = 0;
+    for count in 0..min(10, buf.remaining()) {
+        let byte = buf.get_u8();
+        value |= u64::from(byte & 0x7F) << (count * 7);
+        if byte <= 0x7F {
+            return Ok(value);
+        }
+    }
+
+    Err(DecodeError::new("invalid varint"))
+}
+
+/// Additional information passed to every decode/merge function.
+///
+/// The context should be passed by value and can be freely cloned. When passing
+/// to a function which is decoding a nested object, then use `enter_recursion`.
+#[derive(Clone, Debug)]
+pub struct DecodeContext {
+    /// How many times we can recurse in the current decode stack before we hit
+    /// the recursion limit.
+    ///
+    /// The recursion limit is defined by `RECURSION_LIMIT` and cannot be
+    /// customized. The recursion limit can be ignored by building the Prost
+    /// crate with the `no-recursion-limit` feature.
+    #[cfg(not(feature = "no-recursion-limit"))]
+    recurse_count: u32,
+}
+
+impl Default for DecodeContext {
+    #[cfg(not(feature = "no-recursion-limit"))]
+    #[inline]
+    fn default() -> DecodeContext {
+        DecodeContext {
+            recurse_count: crate::RECURSION_LIMIT,
+        }
+    }
+
+    #[cfg(feature = "no-recursion-limit")]
+    #[inline]
+    fn default() -> DecodeContext {
+        DecodeContext {}
+    }
+}
+
+impl DecodeContext {
+    /// Call this function before recursively decoding.
+    ///
+    /// There is no `exit` function since this function creates a new `DecodeContext`
+    /// to be used at the next level of recursion. Continue to use the old context
+    // at the previous level of recursion.
+    #[cfg(not(feature = "no-recursion-limit"))]
+    #[inline]
+    pub(crate) fn enter_recursion(&self) -> DecodeContext {
+        DecodeContext {
+            recurse_count: self.recurse_count - 1,
+        }
+    }
+
+    #[cfg(feature = "no-recursion-limit")]
+    #[inline]
+    pub(crate) fn enter_recursion(&self) -> DecodeContext {
+        DecodeContext {}
+    }
+
+    /// Checks whether the recursion limit has been reached in the stack of
+    /// decodes described by the `DecodeContext` at `self.ctx`.
+    ///
+    /// Returns `Ok<()>` if it is ok to continue recursing.
+    /// Returns `Err<DecodeError>` if the recursion limit has been reached.
+    #[cfg(not(feature = "no-recursion-limit"))]
+    #[inline]
+    pub(crate) fn limit_reached(&self) -> Result<(), DecodeError> {
+        if self.recurse_count == 0 {
+            Err(DecodeError::new("recursion limit reached"))
+        } else {
+            Ok(())
+        }
+    }
+
+    #[cfg(feature = "no-recursion-limit")]
+    #[inline]
+    #[allow(clippy::unnecessary_wraps)] // needed in other features
+    pub(crate) fn limit_reached(&self) -> Result<(), DecodeError> {
+        Ok(())
+    }
+}
+
+/// Returns the encoded length of the value in LEB128 variable length format.
+/// The returned value will be between 1 and 10, inclusive.
+#[inline]
+pub fn encoded_len_varint(value: u64) -> usize {
+    // Based on [VarintSize64][1].
+    // [1]: https://github.com/google/protobuf/blob/3.3.x/src/google/protobuf/io/coded_stream.h#L1301-L1309
+    ((((value | 1).leading_zeros() ^ 63) * 9 + 73) / 64) as usize
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[repr(u8)]
+pub enum WireType {
+    Varint = 0,
+    SixtyFourBit = 1,
+    LengthDelimited = 2,
+    StartGroup = 3,
+    EndGroup = 4,
+    ThirtyTwoBit = 5,
+}
+
+pub const MIN_TAG: u32 = 1;
+pub const MAX_TAG: u32 = (1 << 29) - 1;
+
+impl TryFrom<u64> for WireType {
+    type Error = DecodeError;
+
+    #[inline]
+    fn try_from(value: u64) -> Result<Self, Self::Error> {
+        match value {
+            0 => Ok(WireType::Varint),
+            1 => Ok(WireType::SixtyFourBit),
+            2 => Ok(WireType::LengthDelimited),
+            3 => Ok(WireType::StartGroup),
+            4 => Ok(WireType::EndGroup),
+            5 => Ok(WireType::ThirtyTwoBit),
+            _ => Err(DecodeError::new(format!(
+                "invalid wire type value: {}",
+                value
+            ))),
+        }
+    }
+}
+
+/// Encodes a Protobuf field key, which consists of a wire type designator and
+/// the field tag.
+#[inline]
+pub fn encode_key<B>(tag: u32, wire_type: WireType, buf: &mut B)
+where
+    B: BufMut,
+{
+    debug_assert!((MIN_TAG..=MAX_TAG).contains(&tag));
+    let key = (tag << 3) | wire_type as u32;
+    encode_varint(u64::from(key), buf);
+}
+
+/// Decodes a Protobuf field key, which consists of a wire type designator and
+/// the field tag.
+#[inline(always)]
+pub fn decode_key<B>(buf: &mut B) -> Result<(u32, WireType), DecodeError>
+where
+    B: Buf,
+{
+    let key = decode_varint(buf)?;
+    if key > u64::from(u32::MAX) {
+        return Err(DecodeError::new(format!("invalid key value: {}", key)));
+    }
+    let wire_type = WireType::try_from(key & 0x07)?;
+    let tag = key as u32 >> 3;
+
+    if tag < MIN_TAG {
+        return Err(DecodeError::new("invalid tag value: 0"));
+    }
+
+    Ok((tag, wire_type))
+}
+
+/// Returns the width of an encoded Protobuf field key with the given tag.
+/// The returned width will be between 1 and 5 bytes (inclusive).
+#[inline]
+pub fn key_len(tag: u32) -> usize {
+    encoded_len_varint(u64::from(tag << 3))
+}
+
+/// Checks that the expected wire type matches the actual wire type,
+/// or returns an error result.
+#[inline]
+pub fn check_wire_type(expected: WireType, actual: WireType) -> Result<(), DecodeError> {
+    if expected != actual {
+        return Err(DecodeError::new(format!(
+            "invalid wire type: {:?} (expected {:?})",
+            actual, expected
+        )));
+    }
+    Ok(())
+}
+
+/// Helper function which abstracts reading a length delimiter prefix followed
+/// by decoding values until the length of bytes is exhausted.
+pub fn merge_loop<T, M, B>(
+    value: &mut T,
+    buf: &mut B,
+    ctx: DecodeContext,
+    mut merge: M,
+) -> Result<(), DecodeError>
+where
+    M: FnMut(&mut T, &mut B, DecodeContext) -> Result<(), DecodeError>,
+    B: Buf,
+{
+    let len = decode_varint(buf)?;
+    let remaining = buf.remaining();
+    if len > remaining as u64 {
+        return Err(DecodeError::new("buffer underflow"));
+    }
+
+    let limit = remaining - len as usize;
+    while buf.remaining() > limit {
+        merge(value, buf, ctx.clone())?;
+    }
+
+    if buf.remaining() != limit {
+        return Err(DecodeError::new("delimited length exceeded"));
+    }
+    Ok(())
+}
+
+pub fn skip_field<B>(
+    wire_type: WireType,
+    tag: u32,
+    buf: &mut B,
+    ctx: DecodeContext,
+) -> Result<(), DecodeError>
+where
+    B: Buf,
+{
+    ctx.limit_reached()?;
+    let len = match wire_type {
+        WireType::Varint => decode_varint(buf).map(|_| 0)?,
+        WireType::ThirtyTwoBit => 4,
+        WireType::SixtyFourBit => 8,
+        WireType::LengthDelimited => decode_varint(buf)?,
+        WireType::StartGroup => loop {
+            let (inner_tag, inner_wire_type) = decode_key(buf)?;
+            match inner_wire_type {
+                WireType::EndGroup => {
+                    if inner_tag != tag {
+                        return Err(DecodeError::new("unexpected end group tag"));
+                    }
+                    break 0;
+                }
+                _ => skip_field(inner_wire_type, inner_tag, buf, ctx.enter_recursion())?,
+            }
+        },
+        WireType::EndGroup => return Err(DecodeError::new("unexpected end group tag")),
+    };
+
+    if len > buf.remaining() as u64 {
+        return Err(DecodeError::new("buffer underflow"));
+    }
+
+    buf.advance(len as usize);
+    Ok(())
+}
+
+/// Helper macro which emits an `encode_repeated` function for the type.
+macro_rules! encode_repeated {
+    ($ty:ty) => {
+        pub fn encode_repeated<B>(tag: u32, values: &[$ty], buf: &mut B)
+        where
+            B: BufMut,
+        {
+            for value in values {
+                encode(tag, value, buf);
+            }
+        }
+    };
+}
+
+/// Helper macro which emits a `merge_repeated` function for the numeric type.
+macro_rules! merge_repeated_numeric {
+    ($ty:ty,
+     $wire_type:expr,
+     $merge:ident,
+     $merge_repeated:ident) => {
+        pub fn $merge_repeated<B>(
+            wire_type: WireType,
+            values: &mut Vec<$ty>,
+            buf: &mut B,
+            ctx: DecodeContext,
+        ) -> Result<(), DecodeError>
+        where
+            B: Buf,
+        {
+            if wire_type == WireType::LengthDelimited {
+                // Packed.
+                merge_loop(values, buf, ctx, |values, buf, ctx| {
+                    let mut value = Default::default();
+                    $merge($wire_type, &mut value, buf, ctx)?;
+                    values.push(value);
+                    Ok(())
+                })
+            } else {
+                // Unpacked.
+                check_wire_type($wire_type, wire_type)?;
+                let mut value = Default::default();
+                $merge(wire_type, &mut value, buf, ctx)?;
+                values.push(value);
+                Ok(())
+            }
+        }
+    };
+}
+
+/// Macro which emits a module containing a set of encoding functions for a
+/// variable width numeric type.
+macro_rules! varint {
+    ($ty:ty,
+     $proto_ty:ident) => (
+        varint!($ty,
+                $proto_ty,
+                to_uint64(value) { *value as u64 },
+                from_uint64(value) { value as $ty });
+    );
+
+    ($ty:ty,
+     $proto_ty:ident,
+     to_uint64($to_uint64_value:ident) $to_uint64:expr,
+     from_uint64($from_uint64_value:ident) $from_uint64:expr) => (
+
+         pub mod $proto_ty {
+            use crate::encoding::*;
+
+            pub fn encode<B>(tag: u32, $to_uint64_value: &$ty, buf: &mut B) where B: BufMut {
+                encode_key(tag, WireType::Varint, buf);
+                encode_varint($to_uint64, buf);
+            }
+
+            pub fn merge<B>(wire_type: WireType, value: &mut $ty, buf: &mut B, _ctx: DecodeContext) -> Result<(), DecodeError> where B: Buf {
+                check_wire_type(WireType::Varint, wire_type)?;
+                let $from_uint64_value = decode_varint(buf)?;
+                *value = $from_uint64;
+                Ok(())
+            }
+
+            encode_repeated!($ty);
+
+            pub fn encode_packed<B>(tag: u32, values: &[$ty], buf: &mut B) where B: BufMut {
+                if values.is_empty() { return; }
+
+                encode_key(tag, WireType::LengthDelimited, buf);
+                let len: usize = values.iter().map(|$to_uint64_value| {
+                    encoded_len_varint($to_uint64)
+                }).sum();
+                encode_varint(len as u64, buf);
+
+                for $to_uint64_value in values {
+                    encode_varint($to_uint64, buf);
+                }
+            }
+
+            merge_repeated_numeric!($ty, WireType::Varint, merge, merge_repeated);
+
+            #[inline]
+            pub fn encoded_len(tag: u32, $to_uint64_value: &$ty) -> usize {
+                key_len(tag) + encoded_len_varint($to_uint64)
+            }
+
+            #[inline]
+            pub fn encoded_len_repeated(tag: u32, values: &[$ty]) -> usize {
+                key_len(tag) * values.len() + values.iter().map(|$to_uint64_value| {
+                    encoded_len_varint($to_uint64)
+                }).sum::<usize>()
+            }
+
+            #[inline]
+            pub fn encoded_len_packed(tag: u32, values: &[$ty]) -> usize {
+                if values.is_empty() {
+                    0
+                } else {
+                    let len = values.iter()
+                                    .map(|$to_uint64_value| encoded_len_varint($to_uint64))
+                                    .sum::<usize>();
+                    key_len(tag) + encoded_len_varint(len as u64) + len
+                }
+            }
+
+            #[cfg(test)]
+            mod test {
+                use proptest::prelude::*;
+
+                use crate::encoding::$proto_ty::*;
+                use crate::encoding::test::{
+                    check_collection_type,
+                    check_type,
+                };
+
+                proptest! {
+                    #[test]
+                    fn check(value: $ty, tag in MIN_TAG..=MAX_TAG) {
+                        check_type(value, tag, WireType::Varint,
+                                   encode, merge, encoded_len)?;
+                    }
+                    #[test]
+                    fn check_repeated(value: Vec<$ty>, tag in MIN_TAG..=MAX_TAG) {
+                        check_collection_type(value, tag, WireType::Varint,
+                                              encode_repeated, merge_repeated,
+                                              encoded_len_repeated)?;
+                    }
+                    #[test]
+                    fn check_packed(value: Vec<$ty>, tag in MIN_TAG..=MAX_TAG) {
+                        check_type(value, tag, WireType::LengthDelimited,
+                                   encode_packed, merge_repeated,
+                                   encoded_len_packed)?;
+                    }
+                }
+            }
+         }
+
+    );
+}
+varint!(bool, bool,
+        to_uint64(value) if *value { 1u64 } else { 0u64 },
+        from_uint64(value) value != 0);
+varint!(i32, int32);
+varint!(i64, int64);
+varint!(u32, uint32);
+varint!(u64, uint64);
+varint!(i32, sint32,
+to_uint64(value) {
+    ((value << 1) ^ (value >> 31)) as u32 as u64
+},
+from_uint64(value) {
+    let value = value as u32;
+    ((value >> 1) as i32) ^ (-((value & 1) as i32))
+});
+varint!(i64, sint64,
+to_uint64(value) {
+    ((value << 1) ^ (value >> 63)) as u64
+},
+from_uint64(value) {
+    ((value >> 1) as i64) ^ (-((value & 1) as i64))
+});
+
+/// Macro which emits a module containing a set of encoding functions for a
+/// fixed width numeric type.
+macro_rules! fixed_width {
+    ($ty:ty,
+     $width:expr,
+     $wire_type:expr,
+     $proto_ty:ident,
+     $put:ident,
+     $get:ident) => {
+        pub mod $proto_ty {
+            use crate::encoding::*;
+
+            pub fn encode<B>(tag: u32, value: &$ty, buf: &mut B)
+            where
+                B: BufMut,
+            {
+                encode_key(tag, $wire_type, buf);
+                buf.$put(*value);
+            }
+
+            pub fn merge<B>(
+                wire_type: WireType,
+                value: &mut $ty,
+                buf: &mut B,
+                _ctx: DecodeContext,
+            ) -> Result<(), DecodeError>
+            where
+                B: Buf,
+            {
+                check_wire_type($wire_type, wire_type)?;
+                if buf.remaining() < $width {
+                    return Err(DecodeError::new("buffer underflow"));
+                }
+                *value = buf.$get();
+                Ok(())
+            }
+
+            encode_repeated!($ty);
+
+            pub fn encode_packed<B>(tag: u32, values: &[$ty], buf: &mut B)
+            where
+                B: BufMut,
+            {
+                if values.is_empty() {
+                    return;
+                }
+
+                encode_key(tag, WireType::LengthDelimited, buf);
+                let len = values.len() as u64 * $width;
+                encode_varint(len as u64, buf);
+
+                for value in values {
+                    buf.$put(*value);
+                }
+            }
+
+            merge_repeated_numeric!($ty, $wire_type, merge, merge_repeated);
+
+            #[inline]
+            pub fn encoded_len(tag: u32, _: &$ty) -> usize {
+                key_len(tag) + $width
+            }
+
+            #[inline]
+            pub fn encoded_len_repeated(tag: u32, values: &[$ty]) -> usize {
+                (key_len(tag) + $width) * values.len()
+            }
+
+            #[inline]
+            pub fn encoded_len_packed(tag: u32, values: &[$ty]) -> usize {
+                if values.is_empty() {
+                    0
+                } else {
+                    let len = $width * values.len();
+                    key_len(tag) + encoded_len_varint(len as u64) + len
+                }
+            }
+
+            #[cfg(test)]
+            mod test {
+                use proptest::prelude::*;
+
+                use super::super::test::{check_collection_type, check_type};
+                use super::*;
+
+                proptest! {
+                    #[test]
+                    fn check(value: $ty, tag in MIN_TAG..=MAX_TAG) {
+                        check_type(value, tag, $wire_type,
+                                   encode, merge, encoded_len)?;
+                    }
+                    #[test]
+                    fn check_repeated(value: Vec<$ty>, tag in MIN_TAG..=MAX_TAG) {
+                        check_collection_type(value, tag, $wire_type,
+                                              encode_repeated, merge_repeated,
+                                              encoded_len_repeated)?;
+                    }
+                    #[test]
+                    fn check_packed(value: Vec<$ty>, tag in MIN_TAG..=MAX_TAG) {
+                        check_type(value, tag, WireType::LengthDelimited,
+                                   encode_packed, merge_repeated,
+                                   encoded_len_packed)?;
+                    }
+                }
+            }
+        }
+    };
+}
+fixed_width!(
+    f32,
+    4,
+    WireType::ThirtyTwoBit,
+    float,
+    put_f32_le,
+    get_f32_le
+);
+fixed_width!(
+    f64,
+    8,
+    WireType::SixtyFourBit,
+    double,
+    put_f64_le,
+    get_f64_le
+);
+fixed_width!(
+    u32,
+    4,
+    WireType::ThirtyTwoBit,
+    fixed32,
+    put_u32_le,
+    get_u32_le
+);
+fixed_width!(
+    u64,
+    8,
+    WireType::SixtyFourBit,
+    fixed64,
+    put_u64_le,
+    get_u64_le
+);
+fixed_width!(
+    i32,
+    4,
+    WireType::ThirtyTwoBit,
+    sfixed32,
+    put_i32_le,
+    get_i32_le
+);
+fixed_width!(
+    i64,
+    8,
+    WireType::SixtyFourBit,
+    sfixed64,
+    put_i64_le,
+    get_i64_le
+);
+
+/// Macro which emits encoding functions for a length-delimited type.
+macro_rules! length_delimited {
+    ($ty:ty) => {
+        encode_repeated!($ty);
+
+        pub fn merge_repeated<B>(
+            wire_type: WireType,
+            values: &mut Vec<$ty>,
+            buf: &mut B,
+            ctx: DecodeContext,
+        ) -> Result<(), DecodeError>
+        where
+            B: Buf,
+        {
+            check_wire_type(WireType::LengthDelimited, wire_type)?;
+            let mut value = Default::default();
+            merge(wire_type, &mut value, buf, ctx)?;
+            values.push(value);
+            Ok(())
+        }
+
+        #[inline]
+        pub fn encoded_len(tag: u32, value: &$ty) -> usize {
+            key_len(tag) + encoded_len_varint(value.len() as u64) + value.len()
+        }
+
+        #[inline]
+        pub fn encoded_len_repeated(tag: u32, values: &[$ty]) -> usize {
+            key_len(tag) * values.len()
+                + values
+                    .iter()
+                    .map(|value| encoded_len_varint(value.len() as u64) + value.len())
+                    .sum::<usize>()
+        }
+    };
+}
+
+pub mod string {
+    use super::*;
+
+    pub fn encode<B>(tag: u32, value: &String, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        encode_key(tag, WireType::LengthDelimited, buf);
+        encode_varint(value.len() as u64, buf);
+        buf.put_slice(value.as_bytes());
+    }
+    pub fn merge<B>(
+        wire_type: WireType,
+        value: &mut String,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        // ## Unsafety
+        //
+        // `string::merge` reuses `bytes::merge`, with an additional check of utf-8
+        // well-formedness. If the utf-8 is not well-formed, or if any other error occurs, then the
+        // string is cleared, so as to avoid leaking a string field with invalid data.
+        //
+        // This implementation uses the unsafe `String::as_mut_vec` method instead of the safe
+        // alternative of temporarily swapping an empty `String` into the field, because it results
+        // in up to 10% better performance on the protobuf message decoding benchmarks.
+        //
+        // It's required when using `String::as_mut_vec` that invalid utf-8 data not be leaked into
+        // the backing `String`. To enforce this, even in the event of a panic in `bytes::merge` or
+        // in the buf implementation, a drop guard is used.
+        unsafe {
+            struct DropGuard<'a>(&'a mut Vec<u8>);
+            impl<'a> Drop for DropGuard<'a> {
+                #[inline]
+                fn drop(&mut self) {
+                    self.0.clear();
+                }
+            }
+
+            let drop_guard = DropGuard(value.as_mut_vec());
+            bytes::merge(wire_type, drop_guard.0, buf, ctx)?;
+            match str::from_utf8(drop_guard.0) {
+                Ok(_) => {
+                    // Success; do not clear the bytes.
+                    mem::forget(drop_guard);
+                    Ok(())
+                }
+                Err(_) => Err(DecodeError::new(
+                    "invalid string value: data is not UTF-8 encoded",
+                )),
+            }
+        }
+    }
+
+    length_delimited!(String);
+
+    #[cfg(test)]
+    mod test {
+        use proptest::prelude::*;
+
+        use super::super::test::{check_collection_type, check_type};
+        use super::*;
+
+        proptest! {
+            #[test]
+            fn check(value: String, tag in MIN_TAG..=MAX_TAG) {
+                super::test::check_type(value, tag, WireType::LengthDelimited,
+                                        encode, merge, encoded_len)?;
+            }
+            #[test]
+            fn check_repeated(value: Vec<String>, tag in MIN_TAG..=MAX_TAG) {
+                super::test::check_collection_type(value, tag, WireType::LengthDelimited,
+                                                   encode_repeated, merge_repeated,
+                                                   encoded_len_repeated)?;
+            }
+        }
+    }
+}
+
+pub trait BytesAdapter: sealed::BytesAdapter {}
+
+mod sealed {
+    use super::{Buf, BufMut};
+
+    pub trait BytesAdapter: Default + Sized + 'static {
+        fn len(&self) -> usize;
+
+        /// Replace contents of this buffer with the contents of another buffer.
+        fn replace_with<B>(&mut self, buf: B)
+        where
+            B: Buf;
+
+        /// Appends this buffer to the (contents of) other buffer.
+        fn append_to<B>(&self, buf: &mut B)
+        where
+            B: BufMut;
+
+        fn is_empty(&self) -> bool {
+            self.len() == 0
+        }
+    }
+}
+
+impl BytesAdapter for Bytes {}
+
+impl sealed::BytesAdapter for Bytes {
+    fn len(&self) -> usize {
+        Buf::remaining(self)
+    }
+
+    fn replace_with<B>(&mut self, mut buf: B)
+    where
+        B: Buf,
+    {
+        *self = buf.copy_to_bytes(buf.remaining());
+    }
+
+    fn append_to<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        buf.put(self.clone())
+    }
+}
+
+impl BytesAdapter for Vec<u8> {}
+
+impl sealed::BytesAdapter for Vec<u8> {
+    fn len(&self) -> usize {
+        Vec::len(self)
+    }
+
+    fn replace_with<B>(&mut self, buf: B)
+    where
+        B: Buf,
+    {
+        self.clear();
+        self.reserve(buf.remaining());
+        self.put(buf);
+    }
+
+    fn append_to<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        buf.put(self.as_slice())
+    }
+}
+
+pub mod bytes {
+    use super::*;
+
+    pub fn encode<A, B>(tag: u32, value: &A, buf: &mut B)
+    where
+        A: BytesAdapter,
+        B: BufMut,
+    {
+        encode_key(tag, WireType::LengthDelimited, buf);
+        encode_varint(value.len() as u64, buf);
+        value.append_to(buf);
+    }
+
+    pub fn merge<A, B>(
+        wire_type: WireType,
+        value: &mut A,
+        buf: &mut B,
+        _ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        A: BytesAdapter,
+        B: Buf,
+    {
+        check_wire_type(WireType::LengthDelimited, wire_type)?;
+        let len = decode_varint(buf)?;
+        if len > buf.remaining() as u64 {
+            return Err(DecodeError::new("buffer underflow"));
+        }
+        let len = len as usize;
+
+        // Clear the existing value. This follows from the following rule in the encoding guide[1]:
+        //
+        // > Normally, an encoded message would never have more than one instance of a non-repeated
+        // > field. However, parsers are expected to handle the case in which they do. For numeric
+        // > types and strings, if the same field appears multiple times, the parser accepts the
+        // > last value it sees.
+        //
+        // [1]: https://developers.google.com/protocol-buffers/docs/encoding#optional
+        value.replace_with(buf.copy_to_bytes(len));
+        Ok(())
+    }
+
+    length_delimited!(impl BytesAdapter);
+
+    #[cfg(test)]
+    mod test {
+        use proptest::prelude::*;
+
+        use super::super::test::{check_collection_type, check_type};
+        use super::*;
+
+        proptest! {
+            #[test]
+            fn check_vec(value: Vec<u8>, tag in MIN_TAG..=MAX_TAG) {
+                super::test::check_type::<Vec<u8>, Vec<u8>>(value, tag, WireType::LengthDelimited,
+                                                            encode, merge, encoded_len)?;
+            }
+
+            #[test]
+            fn check_bytes(value: Vec<u8>, tag in MIN_TAG..=MAX_TAG) {
+                let value = Bytes::from(value);
+                super::test::check_type::<Bytes, Bytes>(value, tag, WireType::LengthDelimited,
+                                                        encode, merge, encoded_len)?;
+            }
+
+            #[test]
+            fn check_repeated_vec(value: Vec<Vec<u8>>, tag in MIN_TAG..=MAX_TAG) {
+                super::test::check_collection_type(value, tag, WireType::LengthDelimited,
+                                                   encode_repeated, merge_repeated,
+                                                   encoded_len_repeated)?;
+            }
+
+            #[test]
+            fn check_repeated_bytes(value: Vec<Vec<u8>>, tag in MIN_TAG..=MAX_TAG) {
+                let value = value.into_iter().map(Bytes::from).collect();
+                super::test::check_collection_type(value, tag, WireType::LengthDelimited,
+                                                   encode_repeated, merge_repeated,
+                                                   encoded_len_repeated)?;
+            }
+        }
+    }
+}
+
+pub mod message {
+    use super::*;
+
+    pub fn encode<M, B>(tag: u32, msg: &M, buf: &mut B)
+    where
+        M: Message,
+        B: BufMut,
+    {
+        encode_key(tag, WireType::LengthDelimited, buf);
+        encode_varint(msg.encoded_len() as u64, buf);
+        msg.encode_raw(buf);
+    }
+
+    pub fn merge<M, B>(
+        wire_type: WireType,
+        msg: &mut M,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        M: Message,
+        B: Buf,
+    {
+        check_wire_type(WireType::LengthDelimited, wire_type)?;
+        ctx.limit_reached()?;
+        merge_loop(
+            msg,
+            buf,
+            ctx.enter_recursion(),
+            |msg: &mut M, buf: &mut B, ctx| {
+                let (tag, wire_type) = decode_key(buf)?;
+                msg.merge_field(tag, wire_type, buf, ctx)
+            },
+        )
+    }
+
+    pub fn encode_repeated<M, B>(tag: u32, messages: &[M], buf: &mut B)
+    where
+        M: Message,
+        B: BufMut,
+    {
+        for msg in messages {
+            encode(tag, msg, buf);
+        }
+    }
+
+    pub fn merge_repeated<M, B>(
+        wire_type: WireType,
+        messages: &mut Vec<M>,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        M: Message + Default,
+        B: Buf,
+    {
+        check_wire_type(WireType::LengthDelimited, wire_type)?;
+        let mut msg = M::default();
+        merge(WireType::LengthDelimited, &mut msg, buf, ctx)?;
+        messages.push(msg);
+        Ok(())
+    }
+
+    #[inline]
+    pub fn encoded_len<M>(tag: u32, msg: &M) -> usize
+    where
+        M: Message,
+    {
+        let len = msg.encoded_len();
+        key_len(tag) + encoded_len_varint(len as u64) + len
+    }
+
+    #[inline]
+    pub fn encoded_len_repeated<M>(tag: u32, messages: &[M]) -> usize
+    where
+        M: Message,
+    {
+        key_len(tag) * messages.len()
+            + messages
+                .iter()
+                .map(Message::encoded_len)
+                .map(|len| len + encoded_len_varint(len as u64))
+                .sum::<usize>()
+    }
+}
+
+pub mod group {
+    use super::*;
+
+    pub fn encode<M, B>(tag: u32, msg: &M, buf: &mut B)
+    where
+        M: Message,
+        B: BufMut,
+    {
+        encode_key(tag, WireType::StartGroup, buf);
+        msg.encode_raw(buf);
+        encode_key(tag, WireType::EndGroup, buf);
+    }
+
+    pub fn merge<M, B>(
+        tag: u32,
+        wire_type: WireType,
+        msg: &mut M,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        M: Message,
+        B: Buf,
+    {
+        check_wire_type(WireType::StartGroup, wire_type)?;
+
+        ctx.limit_reached()?;
+        loop {
+            let (field_tag, field_wire_type) = decode_key(buf)?;
+            if field_wire_type == WireType::EndGroup {
+                if field_tag != tag {
+                    return Err(DecodeError::new("unexpected end group tag"));
+                }
+                return Ok(());
+            }
+
+            M::merge_field(msg, field_tag, field_wire_type, buf, ctx.enter_recursion())?;
+        }
+    }
+
+    pub fn encode_repeated<M, B>(tag: u32, messages: &[M], buf: &mut B)
+    where
+        M: Message,
+        B: BufMut,
+    {
+        for msg in messages {
+            encode(tag, msg, buf);
+        }
+    }
+
+    pub fn merge_repeated<M, B>(
+        tag: u32,
+        wire_type: WireType,
+        messages: &mut Vec<M>,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        M: Message + Default,
+        B: Buf,
+    {
+        check_wire_type(WireType::StartGroup, wire_type)?;
+        let mut msg = M::default();
+        merge(tag, WireType::StartGroup, &mut msg, buf, ctx)?;
+        messages.push(msg);
+        Ok(())
+    }
+
+    #[inline]
+    pub fn encoded_len<M>(tag: u32, msg: &M) -> usize
+    where
+        M: Message,
+    {
+        2 * key_len(tag) + msg.encoded_len()
+    }
+
+    #[inline]
+    pub fn encoded_len_repeated<M>(tag: u32, messages: &[M]) -> usize
+    where
+        M: Message,
+    {
+        2 * key_len(tag) * messages.len() + messages.iter().map(Message::encoded_len).sum::<usize>()
+    }
+}
+
+/// Rust doesn't have a `Map` trait, so macros are currently the best way to be
+/// generic over `HashMap` and `BTreeMap`.
+macro_rules! map {
+    ($map_ty:ident) => {
+        use crate::encoding::*;
+        use core::hash::Hash;
+
+        /// Generic protobuf map encode function.
+        pub fn encode<K, V, B, KE, KL, VE, VL>(
+            key_encode: KE,
+            key_encoded_len: KL,
+            val_encode: VE,
+            val_encoded_len: VL,
+            tag: u32,
+            values: &$map_ty<K, V>,
+            buf: &mut B,
+        ) where
+            K: Default + Eq + Hash + Ord,
+            V: Default + PartialEq,
+            B: BufMut,
+            KE: Fn(u32, &K, &mut B),
+            KL: Fn(u32, &K) -> usize,
+            VE: Fn(u32, &V, &mut B),
+            VL: Fn(u32, &V) -> usize,
+        {
+            encode_with_default(
+                key_encode,
+                key_encoded_len,
+                val_encode,
+                val_encoded_len,
+                &V::default(),
+                tag,
+                values,
+                buf,
+            )
+        }
+
+        /// Generic protobuf map merge function.
+        pub fn merge<K, V, B, KM, VM>(
+            key_merge: KM,
+            val_merge: VM,
+            values: &mut $map_ty<K, V>,
+            buf: &mut B,
+            ctx: DecodeContext,
+        ) -> Result<(), DecodeError>
+        where
+            K: Default + Eq + Hash + Ord,
+            V: Default,
+            B: Buf,
+            KM: Fn(WireType, &mut K, &mut B, DecodeContext) -> Result<(), DecodeError>,
+            VM: Fn(WireType, &mut V, &mut B, DecodeContext) -> Result<(), DecodeError>,
+        {
+            merge_with_default(key_merge, val_merge, V::default(), values, buf, ctx)
+        }
+
+        /// Generic protobuf map encode function.
+        pub fn encoded_len<K, V, KL, VL>(
+            key_encoded_len: KL,
+            val_encoded_len: VL,
+            tag: u32,
+            values: &$map_ty<K, V>,
+        ) -> usize
+        where
+            K: Default + Eq + Hash + Ord,
+            V: Default + PartialEq,
+            KL: Fn(u32, &K) -> usize,
+            VL: Fn(u32, &V) -> usize,
+        {
+            encoded_len_with_default(key_encoded_len, val_encoded_len, &V::default(), tag, values)
+        }
+
+        /// Generic protobuf map encode function with an overriden value default.
+        ///
+        /// This is necessary because enumeration values can have a default value other
+        /// than 0 in proto2.
+        pub fn encode_with_default<K, V, B, KE, KL, VE, VL>(
+            key_encode: KE,
+            key_encoded_len: KL,
+            val_encode: VE,
+            val_encoded_len: VL,
+            val_default: &V,
+            tag: u32,
+            values: &$map_ty<K, V>,
+            buf: &mut B,
+        ) where
+            K: Default + Eq + Hash + Ord,
+            V: PartialEq,
+            B: BufMut,
+            KE: Fn(u32, &K, &mut B),
+            KL: Fn(u32, &K) -> usize,
+            VE: Fn(u32, &V, &mut B),
+            VL: Fn(u32, &V) -> usize,
+        {
+            for (key, val) in values.iter() {
+                let skip_key = key == &K::default();
+                let skip_val = val == val_default;
+
+                let len = (if skip_key { 0 } else { key_encoded_len(1, key) })
+                    + (if skip_val { 0 } else { val_encoded_len(2, val) });
+
+                encode_key(tag, WireType::LengthDelimited, buf);
+                encode_varint(len as u64, buf);
+                if !skip_key {
+                    key_encode(1, key, buf);
+                }
+                if !skip_val {
+                    val_encode(2, val, buf);
+                }
+            }
+        }
+
+        /// Generic protobuf map merge function with an overriden value default.
+        ///
+        /// This is necessary because enumeration values can have a default value other
+        /// than 0 in proto2.
+        pub fn merge_with_default<K, V, B, KM, VM>(
+            key_merge: KM,
+            val_merge: VM,
+            val_default: V,
+            values: &mut $map_ty<K, V>,
+            buf: &mut B,
+            ctx: DecodeContext,
+        ) -> Result<(), DecodeError>
+        where
+            K: Default + Eq + Hash + Ord,
+            B: Buf,
+            KM: Fn(WireType, &mut K, &mut B, DecodeContext) -> Result<(), DecodeError>,
+            VM: Fn(WireType, &mut V, &mut B, DecodeContext) -> Result<(), DecodeError>,
+        {
+            let mut key = Default::default();
+            let mut val = val_default;
+            ctx.limit_reached()?;
+            merge_loop(
+                &mut (&mut key, &mut val),
+                buf,
+                ctx.enter_recursion(),
+                |&mut (ref mut key, ref mut val), buf, ctx| {
+                    let (tag, wire_type) = decode_key(buf)?;
+                    match tag {
+                        1 => key_merge(wire_type, key, buf, ctx),
+                        2 => val_merge(wire_type, val, buf, ctx),
+                        _ => skip_field(wire_type, tag, buf, ctx),
+                    }
+                },
+            )?;
+            values.insert(key, val);
+
+            Ok(())
+        }
+
+        /// Generic protobuf map encode function with an overriden value default.
+        ///
+        /// This is necessary because enumeration values can have a default value other
+        /// than 0 in proto2.
+        pub fn encoded_len_with_default<K, V, KL, VL>(
+            key_encoded_len: KL,
+            val_encoded_len: VL,
+            val_default: &V,
+            tag: u32,
+            values: &$map_ty<K, V>,
+        ) -> usize
+        where
+            K: Default + Eq + Hash + Ord,
+            V: PartialEq,
+            KL: Fn(u32, &K) -> usize,
+            VL: Fn(u32, &V) -> usize,
+        {
+            key_len(tag) * values.len()
+                + values
+                    .iter()
+                    .map(|(key, val)| {
+                        let len = (if key == &K::default() {
+                            0
+                        } else {
+                            key_encoded_len(1, key)
+                        }) + (if val == val_default {
+                            0
+                        } else {
+                            val_encoded_len(2, val)
+                        });
+                        encoded_len_varint(len as u64) + len
+                    })
+                    .sum::<usize>()
+        }
+    };
+}
+
+#[cfg(feature = "std")]
+pub mod hash_map {
+    use std::collections::HashMap;
+    map!(HashMap);
+}
+
+pub mod btree_map {
+    map!(BTreeMap);
+}
+
+#[cfg(test)]
+mod test {
+    use alloc::string::ToString;
+    use core::borrow::Borrow;
+    use core::fmt::Debug;
+    use core::u64;
+
+    use ::bytes::{Bytes, BytesMut};
+    use proptest::{prelude::*, test_runner::TestCaseResult};
+
+    use crate::encoding::*;
+
+    pub fn check_type<T, B>(
+        value: T,
+        tag: u32,
+        wire_type: WireType,
+        encode: fn(u32, &B, &mut BytesMut),
+        merge: fn(WireType, &mut T, &mut Bytes, DecodeContext) -> Result<(), DecodeError>,
+        encoded_len: fn(u32, &B) -> usize,
+    ) -> TestCaseResult
+    where
+        T: Debug + Default + PartialEq + Borrow<B>,
+        B: ?Sized,
+    {
+        prop_assume!(MIN_TAG <= tag && tag <= MAX_TAG);
+
+        let expected_len = encoded_len(tag, value.borrow());
+
+        let mut buf = BytesMut::with_capacity(expected_len);
+        encode(tag, value.borrow(), &mut buf);
+
+        let mut buf = buf.freeze();
+
+        prop_assert_eq!(
+            buf.remaining(),
+            expected_len,
+            "encoded_len wrong; expected: {}, actual: {}",
+            expected_len,
+            buf.remaining()
+        );
+
+        if !buf.has_remaining() {
+            // Short circuit for empty packed values.
+            return Ok(());
+        }
+
+        let (decoded_tag, decoded_wire_type) =
+            decode_key(&mut buf).map_err(|error| TestCaseError::fail(error.to_string()))?;
+        prop_assert_eq!(
+            tag,
+            decoded_tag,
+            "decoded tag does not match; expected: {}, actual: {}",
+            tag,
+            decoded_tag
+        );
+
+        prop_assert_eq!(
+            wire_type,
+            decoded_wire_type,
+            "decoded wire type does not match; expected: {:?}, actual: {:?}",
+            wire_type,
+            decoded_wire_type,
+        );
+
+        match wire_type {
+            WireType::SixtyFourBit if buf.remaining() != 8 => Err(TestCaseError::fail(format!(
+                "64bit wire type illegal remaining: {}, tag: {}",
+                buf.remaining(),
+                tag
+            ))),
+            WireType::ThirtyTwoBit if buf.remaining() != 4 => Err(TestCaseError::fail(format!(
+                "32bit wire type illegal remaining: {}, tag: {}",
+                buf.remaining(),
+                tag
+            ))),
+            _ => Ok(()),
+        }?;
+
+        let mut roundtrip_value = T::default();
+        merge(
+            wire_type,
+            &mut roundtrip_value,
+            &mut buf,
+            DecodeContext::default(),
+        )
+        .map_err(|error| TestCaseError::fail(error.to_string()))?;
+
+        prop_assert!(
+            !buf.has_remaining(),
+            "expected buffer to be empty, remaining: {}",
+            buf.remaining()
+        );
+
+        prop_assert_eq!(value, roundtrip_value);
+
+        Ok(())
+    }
+
+    pub fn check_collection_type<T, B, E, M, L>(
+        value: T,
+        tag: u32,
+        wire_type: WireType,
+        encode: E,
+        mut merge: M,
+        encoded_len: L,
+    ) -> TestCaseResult
+    where
+        T: Debug + Default + PartialEq + Borrow<B>,
+        B: ?Sized,
+        E: FnOnce(u32, &B, &mut BytesMut),
+        M: FnMut(WireType, &mut T, &mut Bytes, DecodeContext) -> Result<(), DecodeError>,
+        L: FnOnce(u32, &B) -> usize,
+    {
+        prop_assume!(MIN_TAG <= tag && tag <= MAX_TAG);
+
+        let expected_len = encoded_len(tag, value.borrow());
+
+        let mut buf = BytesMut::with_capacity(expected_len);
+        encode(tag, value.borrow(), &mut buf);
+
+        let mut buf = buf.freeze();
+
+        prop_assert_eq!(
+            buf.remaining(),
+            expected_len,
+            "encoded_len wrong; expected: {}, actual: {}",
+            expected_len,
+            buf.remaining()
+        );
+
+        let mut roundtrip_value = Default::default();
+        while buf.has_remaining() {
+            let (decoded_tag, decoded_wire_type) =
+                decode_key(&mut buf).map_err(|error| TestCaseError::fail(error.to_string()))?;
+
+            prop_assert_eq!(
+                tag,
+                decoded_tag,
+                "decoded tag does not match; expected: {}, actual: {}",
+                tag,
+                decoded_tag
+            );
+
+            prop_assert_eq!(
+                wire_type,
+                decoded_wire_type,
+                "decoded wire type does not match; expected: {:?}, actual: {:?}",
+                wire_type,
+                decoded_wire_type
+            );
+
+            merge(
+                wire_type,
+                &mut roundtrip_value,
+                &mut buf,
+                DecodeContext::default(),
+            )
+            .map_err(|error| TestCaseError::fail(error.to_string()))?;
+        }
+
+        prop_assert_eq!(value, roundtrip_value);
+
+        Ok(())
+    }
+
+    #[test]
+    fn string_merge_invalid_utf8() {
+        let mut s = String::new();
+        let buf = b"\x02\x80\x80";
+
+        let r = string::merge(
+            WireType::LengthDelimited,
+            &mut s,
+            &mut &buf[..],
+            DecodeContext::default(),
+        );
+        r.expect_err("must be an error");
+        assert!(s.is_empty());
+    }
+
+    #[test]
+    fn varint() {
+        fn check(value: u64, mut encoded: &[u8]) {
+            // TODO(rust-lang/rust-clippy#5494)
+            #![allow(clippy::clone_double_ref)]
+
+            // Small buffer.
+            let mut buf = Vec::with_capacity(1);
+            encode_varint(value, &mut buf);
+            assert_eq!(buf, encoded);
+
+            // Large buffer.
+            let mut buf = Vec::with_capacity(100);
+            encode_varint(value, &mut buf);
+            assert_eq!(buf, encoded);
+
+            assert_eq!(encoded_len_varint(value), encoded.len());
+
+            let roundtrip_value = decode_varint(&mut encoded.clone()).expect("decoding failed");
+            assert_eq!(value, roundtrip_value);
+
+            let roundtrip_value = decode_varint_slow(&mut encoded).expect("slow decoding failed");
+            assert_eq!(value, roundtrip_value);
+        }
+
+        check(2u64.pow(0) - 1, &[0x00]);
+        check(2u64.pow(0), &[0x01]);
+
+        check(2u64.pow(7) - 1, &[0x7F]);
+        check(2u64.pow(7), &[0x80, 0x01]);
+        check(300, &[0xAC, 0x02]);
+
+        check(2u64.pow(14) - 1, &[0xFF, 0x7F]);
+        check(2u64.pow(14), &[0x80, 0x80, 0x01]);
+
+        check(2u64.pow(21) - 1, &[0xFF, 0xFF, 0x7F]);
+        check(2u64.pow(21), &[0x80, 0x80, 0x80, 0x01]);
+
+        check(2u64.pow(28) - 1, &[0xFF, 0xFF, 0xFF, 0x7F]);
+        check(2u64.pow(28), &[0x80, 0x80, 0x80, 0x80, 0x01]);
+
+        check(2u64.pow(35) - 1, &[0xFF, 0xFF, 0xFF, 0xFF, 0x7F]);
+        check(2u64.pow(35), &[0x80, 0x80, 0x80, 0x80, 0x80, 0x01]);
+
+        check(2u64.pow(42) - 1, &[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]);
+        check(2u64.pow(42), &[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x01]);
+
+        check(
+            2u64.pow(49) - 1,
+            &[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F],
+        );
+        check(
+            2u64.pow(49),
+            &[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x01],
+        );
+
+        check(
+            2u64.pow(56) - 1,
+            &[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F],
+        );
+        check(
+            2u64.pow(56),
+            &[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x01],
+        );
+
+        check(
+            2u64.pow(63) - 1,
+            &[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F],
+        );
+        check(
+            2u64.pow(63),
+            &[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x01],
+        );
+
+        check(
+            u64::MAX,
+            &[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x01],
+        );
+    }
+
+    /// This big bowl o' macro soup generates an encoding property test for each combination of map
+    /// type, scalar map key, and value type.
+    /// TODO: these tests take a long time to compile, can this be improved?
+    #[cfg(feature = "std")]
+    macro_rules! map_tests {
+        (keys: $keys:tt,
+         vals: $vals:tt) => {
+            mod hash_map {
+                map_tests!(@private HashMap, hash_map, $keys, $vals);
+            }
+            mod btree_map {
+                map_tests!(@private BTreeMap, btree_map, $keys, $vals);
+            }
+        };
+
+        (@private $map_type:ident,
+                  $mod_name:ident,
+                  [$(($key_ty:ty, $key_proto:ident)),*],
+                  $vals:tt) => {
+            $(
+                mod $key_proto {
+                    use std::collections::$map_type;
+
+                    use proptest::prelude::*;
+
+                    use crate::encoding::*;
+                    use crate::encoding::test::check_collection_type;
+
+                    map_tests!(@private $map_type, $mod_name, ($key_ty, $key_proto), $vals);
+                }
+            )*
+        };
+
+        (@private $map_type:ident,
+                  $mod_name:ident,
+                  ($key_ty:ty, $key_proto:ident),
+                  [$(($val_ty:ty, $val_proto:ident)),*]) => {
+            $(
+                proptest! {
+                    #[test]
+                    fn $val_proto(values: $map_type<$key_ty, $val_ty>, tag in MIN_TAG..=MAX_TAG) {
+                        check_collection_type(values, tag, WireType::LengthDelimited,
+                                              |tag, values, buf| {
+                                                  $mod_name::encode($key_proto::encode,
+                                                                    $key_proto::encoded_len,
+                                                                    $val_proto::encode,
+                                                                    $val_proto::encoded_len,
+                                                                    tag,
+                                                                    values,
+                                                                    buf)
+                                              },
+                                              |wire_type, values, buf, ctx| {
+                                                  check_wire_type(WireType::LengthDelimited, wire_type)?;
+                                                  $mod_name::merge($key_proto::merge,
+                                                                   $val_proto::merge,
+                                                                   values,
+                                                                   buf,
+                                                                   ctx)
+                                              },
+                                              |tag, values| {
+                                                  $mod_name::encoded_len($key_proto::encoded_len,
+                                                                         $val_proto::encoded_len,
+                                                                         tag,
+                                                                         values)
+                                              })?;
+                    }
+                }
+             )*
+        };
+    }
+
+    #[cfg(feature = "std")]
+    map_tests!(keys: [
+        (i32, int32),
+        (i64, int64),
+        (u32, uint32),
+        (u64, uint64),
+        (i32, sint32),
+        (i64, sint64),
+        (u32, fixed32),
+        (u64, fixed64),
+        (i32, sfixed32),
+        (i64, sfixed64),
+        (bool, bool),
+        (String, string)
+    ],
+    vals: [
+        (f32, float),
+        (f64, double),
+        (i32, int32),
+        (i64, int64),
+        (u32, uint32),
+        (u64, uint64),
+        (i32, sint32),
+        (i64, sint64),
+        (u32, fixed32),
+        (u64, fixed64),
+        (i32, sfixed32),
+        (i64, sfixed64),
+        (bool, bool),
+        (String, string),
+        (Vec<u8>, bytes)
+    ]);
+}
diff --git a/third_party/rust/prost/src/error.rs b/third_party/rust/prost/src/error.rs
new file mode 100644
index 0000000000..fc098299c8
--- /dev/null
+++ b/third_party/rust/prost/src/error.rs
@@ -0,0 +1,131 @@
+//! Protobuf encoding and decoding errors.
+
+use alloc::borrow::Cow;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+
+use core::fmt;
+
+/// A Protobuf message decoding error.
+///
+/// `DecodeError` indicates that the input buffer does not caontain a valid
+/// Protobuf message. The error details should be considered 'best effort': in
+/// general it is not possible to exactly pinpoint why data is malformed.
+#[derive(Clone, PartialEq, Eq)]
+pub struct DecodeError {
+    inner: Box<Inner>,
+}
+
+#[derive(Clone, PartialEq, Eq)]
+struct Inner {
+    /// A 'best effort' root cause description.
+    description: Cow<'static, str>,
+    /// A stack of (message, field) name pairs, which identify the specific
+    /// message type and field where decoding failed. The stack contains an
+    /// entry per level of nesting.
+    stack: Vec<(&'static str, &'static str)>,
+}
+
+impl DecodeError {
+    /// Creates a new `DecodeError` with a 'best effort' root cause description.
+    ///
+    /// Meant to be used only by `Message` implementations.
+    #[doc(hidden)]
+    #[cold]
+    pub fn new(description: impl Into<Cow<'static, str>>) -> DecodeError {
+        DecodeError {
+            inner: Box::new(Inner {
+                description: description.into(),
+                stack: Vec::new(),
+            }),
+        }
+    }
+
+    /// Pushes a (message, field) name location pair on to the location stack.
+    ///
+    /// Meant to be used only by `Message` implementations.
+    #[doc(hidden)]
+    pub fn push(&mut self, message: &'static str, field: &'static str) {
+        self.inner.stack.push((message, field));
+    }
+}
+
+impl fmt::Debug for DecodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("DecodeError")
+            .field("description", &self.inner.description)
+            .field("stack", &self.inner.stack)
+            .finish()
+    }
+}
+
+impl fmt::Display for DecodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("failed to decode Protobuf message: ")?;
+        for &(message, field) in &self.inner.stack {
+            write!(f, "{}.{}: ", message, field)?;
+        }
+        f.write_str(&self.inner.description)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for DecodeError {}
+
+#[cfg(feature = "std")]
+impl From<DecodeError> for std::io::Error {
+    fn from(error: DecodeError) -> std::io::Error {
+        std::io::Error::new(std::io::ErrorKind::InvalidData, error)
+    }
+}
+
+/// A Protobuf message encoding error.
+///
+/// `EncodeError` always indicates that a message failed to encode because the
+/// provided buffer had insufficient capacity. Message encoding is otherwise
+/// infallible.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct EncodeError {
+    required: usize,
+    remaining: usize,
+}
+
+impl EncodeError {
+    /// Creates a new `EncodeError`.
+    pub(crate) fn new(required: usize, remaining: usize) -> EncodeError {
+        EncodeError {
+            required,
+            remaining,
+        }
+    }
+
+    /// Returns the required buffer capacity to encode the message.
+    pub fn required_capacity(&self) -> usize {
+        self.required
+    }
+
+    /// Returns the remaining length in the provided buffer at the time of encoding.
+    pub fn remaining(&self) -> usize {
+        self.remaining
+    }
+}
+
+impl fmt::Display for EncodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "failed to encode Protobuf messsage; insufficient buffer capacity (required: {}, remaining: {})",
+            self.required, self.remaining
+        )
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for EncodeError {}
+
+#[cfg(feature = "std")]
+impl From<EncodeError> for std::io::Error {
+    fn from(error: EncodeError) -> std::io::Error {
+        std::io::Error::new(std::io::ErrorKind::InvalidInput, error)
+    }
+}
diff --git a/third_party/rust/prost/src/lib.rs b/third_party/rust/prost/src/lib.rs
new file mode 100644
index 0000000000..9d4069e76e
--- /dev/null
+++ b/third_party/rust/prost/src/lib.rs
@@ -0,0 +1,93 @@
+#![doc(html_root_url = "https://docs.rs/prost/0.8.0")]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+// Re-export the alloc crate for use within derived code.
+#[doc(hidden)]
+pub extern crate alloc;
+
+// Re-export the bytes crate for use within derived code.
+#[doc(hidden)]
+pub use bytes;
+
+mod error;
+mod message;
+mod types;
+
+#[doc(hidden)]
+pub mod encoding;
+
+pub use crate::error::{DecodeError, EncodeError};
+pub use crate::message::Message;
+
+use bytes::{Buf, BufMut};
+
+use crate::encoding::{decode_varint, encode_varint, encoded_len_varint};
+
+// See `encoding::DecodeContext` for more info.
+// 100 is the default recursion limit in the C++ implementation.
+#[cfg(not(feature = "no-recursion-limit"))]
+const RECURSION_LIMIT: u32 = 100;
+
+/// Encodes a length delimiter to the buffer.
+///
+/// See [Message.encode_length_delimited] for more info.
+///
+/// An error will be returned if the buffer does not have sufficient capacity to encode the
+/// delimiter.
+pub fn encode_length_delimiter<B>(length: usize, buf: &mut B) -> Result<(), EncodeError>
+where
+    B: BufMut,
+{
+    let length = length as u64;
+    let required = encoded_len_varint(length);
+    let remaining = buf.remaining_mut();
+    if required > remaining {
+        return Err(EncodeError::new(required, remaining));
+    }
+    encode_varint(length, buf);
+    Ok(())
+}
+
+/// Returns the encoded length of a length delimiter.
+///
+/// Applications may use this method to ensure sufficient buffer capacity before calling
+/// `encode_length_delimiter`. The returned size will be between 1 and 10, inclusive.
+pub fn length_delimiter_len(length: usize) -> usize {
+    encoded_len_varint(length as u64)
+}
+
+/// Decodes a length delimiter from the buffer.
+///
+/// This method allows the length delimiter to be decoded independently of the message, when the
+/// message is encoded with [Message.encode_length_delimited].
+///
+/// An error may be returned in two cases:
+///
+///  * If the supplied buffer contains fewer than 10 bytes, then an error indicates that more
+///    input is required to decode the full delimiter.
+///  * If the supplied buffer contains more than 10 bytes, then the buffer contains an invalid
+///    delimiter, and typically the buffer should be considered corrupt.
+pub fn decode_length_delimiter<B>(mut buf: B) -> Result<usize, DecodeError>
+where
+    B: Buf,
+{
+    let length = decode_varint(&mut buf)?;
+    if length > usize::max_value() as u64 {
+        return Err(DecodeError::new(
+            "length delimiter exceeds maximum usize value",
+        ));
+    }
+    Ok(length as usize)
+}
+
+// Re-export #[derive(Message, Enumeration, Oneof)].
+// Based on serde's equivalent re-export [1], but enabled by default.
+//
+// [1]: https://github.com/serde-rs/serde/blob/v1.0.89/serde/src/lib.rs#L245-L256
+#[cfg(feature = "prost-derive")]
+#[allow(unused_imports)]
+#[macro_use]
+extern crate prost_derive;
+#[cfg(feature = "prost-derive")]
+#[doc(hidden)]
+pub use prost_derive::*;
diff --git a/third_party/rust/prost/src/message.rs b/third_party/rust/prost/src/message.rs
new file mode 100644
index 0000000000..112c7b89f1
--- /dev/null
+++ b/third_party/rust/prost/src/message.rs
@@ -0,0 +1,200 @@
+use alloc::boxed::Box;
+use core::fmt::Debug;
+use core::usize;
+
+use bytes::{Buf, BufMut};
+
+use crate::encoding::{
+    decode_key, encode_varint, encoded_len_varint, message, DecodeContext, WireType,
+};
+use crate::DecodeError;
+use crate::EncodeError;
+
+/// A Protocol Buffers message.
+pub trait Message: Debug + Send + Sync {
+    /// Encodes the message to a buffer.
+    ///
+    /// This method will panic if the buffer has insufficient capacity.
+    ///
+    /// Meant to be used only by `Message` implementations.
+    #[doc(hidden)]
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+        Self: Sized;
+
+    /// Decodes a field from a buffer, and merges it into `self`.
+    ///
+    /// Meant to be used only by `Message` implementations.
+    #[doc(hidden)]
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+        Self: Sized;
+
+    /// Returns the encoded length of the message without a length delimiter.
+    fn encoded_len(&self) -> usize;
+
+    /// Encodes the message to a buffer.
+    ///
+    /// An error will be returned if the buffer does not have sufficient capacity.
+    fn encode<B>(&self, buf: &mut B) -> Result<(), EncodeError>
+    where
+        B: BufMut,
+        Self: Sized,
+    {
+        let required = self.encoded_len();
+        let remaining = buf.remaining_mut();
+        if required > buf.remaining_mut() {
+            return Err(EncodeError::new(required, remaining));
+        }
+
+        self.encode_raw(buf);
+        Ok(())
+    }
+
+    #[cfg(feature = "std")]
+    /// Encodes the message to a newly allocated buffer.
+    fn encode_to_vec(&self) -> Vec<u8>
+    where
+        Self: Sized,
+    {
+        let mut buf = Vec::with_capacity(self.encoded_len());
+
+        self.encode_raw(&mut buf);
+        buf
+    }
+
+    /// Encodes the message with a length-delimiter to a buffer.
+    ///
+    /// An error will be returned if the buffer does not have sufficient capacity.
+    fn encode_length_delimited<B>(&self, buf: &mut B) -> Result<(), EncodeError>
+    where
+        B: BufMut,
+        Self: Sized,
+    {
+        let len = self.encoded_len();
+        let required = len + encoded_len_varint(len as u64);
+        let remaining = buf.remaining_mut();
+        if required > remaining {
+            return Err(EncodeError::new(required, remaining));
+        }
+        encode_varint(len as u64, buf);
+        self.encode_raw(buf);
+        Ok(())
+    }
+
+    #[cfg(feature = "std")]
+    /// Encodes the message with a length-delimiter to a newly allocated buffer.
+    fn encode_length_delimited_to_vec(&self) -> Vec<u8>
+    where
+        Self: Sized,
+    {
+        let len = self.encoded_len();
+        let mut buf = Vec::with_capacity(len + encoded_len_varint(len as u64));
+
+        encode_varint(len as u64, &mut buf);
+        self.encode_raw(&mut buf);
+        buf
+    }
+
+    /// Decodes an instance of the message from a buffer.
+    ///
+    /// The entire buffer will be consumed.
+    fn decode<B>(mut buf: B) -> Result<Self, DecodeError>
+    where
+        B: Buf,
+        Self: Default,
+    {
+        let mut message = Self::default();
+        Self::merge(&mut message, &mut buf).map(|_| message)
+    }
+
+    /// Decodes a length-delimited instance of the message from the buffer.
+    fn decode_length_delimited<B>(buf: B) -> Result<Self, DecodeError>
+    where
+        B: Buf,
+        Self: Default,
+    {
+        let mut message = Self::default();
+        message.merge_length_delimited(buf)?;
+        Ok(message)
+    }
+
+    /// Decodes an instance of the message from a buffer, and merges it into `self`.
+    ///
+    /// The entire buffer will be consumed.
+    fn merge<B>(&mut self, mut buf: B) -> Result<(), DecodeError>
+    where
+        B: Buf,
+        Self: Sized,
+    {
+        let ctx = DecodeContext::default();
+        while buf.has_remaining() {
+            let (tag, wire_type) = decode_key(&mut buf)?;
+            self.merge_field(tag, wire_type, &mut buf, ctx.clone())?;
+        }
+        Ok(())
+    }
+
+    /// Decodes a length-delimited instance of the message from buffer, and
+    /// merges it into `self`.
+    fn merge_length_delimited<B>(&mut self, mut buf: B) -> Result<(), DecodeError>
+    where
+        B: Buf,
+        Self: Sized,
+    {
+        message::merge(
+            WireType::LengthDelimited,
+            self,
+            &mut buf,
+            DecodeContext::default(),
+        )
+    }
+
+    /// Clears the message, resetting all fields to their default.
+    fn clear(&mut self);
+}
+
+impl<M> Message for Box<M>
+where
+    M: Message,
+{
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        (**self).encode_raw(buf)
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        (**self).merge_field(tag, wire_type, buf, ctx)
+    }
+    fn encoded_len(&self) -> usize {
+        (**self).encoded_len()
+    }
+    fn clear(&mut self) {
+        (**self).clear()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const _MESSAGE_IS_OBJECT_SAFE: Option<&dyn Message> = None;
+}
diff --git a/third_party/rust/prost/src/types.rs b/third_party/rust/prost/src/types.rs
new file mode 100644
index 0000000000..864a2adda1
--- /dev/null
+++ b/third_party/rust/prost/src/types.rs
@@ -0,0 +1,424 @@
+//! Protocol Buffers well-known wrapper types.
+//!
+//! This module provides implementations of `Message` for Rust standard library types which
+//! correspond to a Protobuf well-known wrapper type. The remaining well-known types are defined in
+//! the `prost-types` crate in order to avoid a cyclic dependency between `prost` and
+//! `prost-build`.
+
+use alloc::string::String;
+use alloc::vec::Vec;
+
+use ::bytes::{Buf, BufMut, Bytes};
+
+use crate::{
+    encoding::{
+        bool, bytes, double, float, int32, int64, skip_field, string, uint32, uint64,
+        DecodeContext, WireType,
+    },
+    DecodeError, Message,
+};
+
+/// `google.protobuf.BoolValue`
+impl Message for bool {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self {
+            bool::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            bool::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self {
+            2
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = false;
+    }
+}
+
+/// `google.protobuf.UInt32Value`
+impl Message for u32 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0 {
+            uint32::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            uint32::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0 {
+            uint32::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0;
+    }
+}
+
+/// `google.protobuf.UInt64Value`
+impl Message for u64 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0 {
+            uint64::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            uint64::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0 {
+            uint64::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0;
+    }
+}
+
+/// `google.protobuf.Int32Value`
+impl Message for i32 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0 {
+            int32::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            int32::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0 {
+            int32::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0;
+    }
+}
+
+/// `google.protobuf.Int64Value`
+impl Message for i64 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0 {
+            int64::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            int64::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0 {
+            int64::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0;
+    }
+}
+
+/// `google.protobuf.FloatValue`
+impl Message for f32 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0.0 {
+            float::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            float::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0.0 {
+            float::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0.0;
+    }
+}
+
+/// `google.protobuf.DoubleValue`
+impl Message for f64 {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if *self != 0.0 {
+            double::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            double::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if *self != 0.0 {
+            double::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        *self = 0.0;
+    }
+}
+
+/// `google.protobuf.StringValue`
+impl Message for String {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if !self.is_empty() {
+            string::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            string::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if !self.is_empty() {
+            string::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        self.clear();
+    }
+}
+
+/// `google.protobuf.BytesValue`
+impl Message for Vec<u8> {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if !self.is_empty() {
+            bytes::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            bytes::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if !self.is_empty() {
+            bytes::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        self.clear();
+    }
+}
+
+/// `google.protobuf.BytesValue`
+impl Message for Bytes {
+    fn encode_raw<B>(&self, buf: &mut B)
+    where
+        B: BufMut,
+    {
+        if !self.is_empty() {
+            bytes::encode(1, self, buf)
+        }
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        if tag == 1 {
+            bytes::merge(wire_type, self, buf, ctx)
+        } else {
+            skip_field(wire_type, tag, buf, ctx)
+        }
+    }
+    fn encoded_len(&self) -> usize {
+        if !self.is_empty() {
+            bytes::encoded_len(1, self)
+        } else {
+            0
+        }
+    }
+    fn clear(&mut self) {
+        self.clear();
+    }
+}
+
+/// `google.protobuf.Empty`
+impl Message for () {
+    fn encode_raw<B>(&self, _buf: &mut B)
+    where
+        B: BufMut,
+    {
+    }
+    fn merge_field<B>(
+        &mut self,
+        tag: u32,
+        wire_type: WireType,
+        buf: &mut B,
+        ctx: DecodeContext,
+    ) -> Result<(), DecodeError>
+    where
+        B: Buf,
+    {
+        skip_field(wire_type, tag, buf, ctx)
+    }
+    fn encoded_len(&self) -> usize {
+        0
+    }
+    fn clear(&mut self) {}
+}