ank/framed-rs
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Added a big comment about serialization buffer size.

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Alex Helfet 2017-12-24 22:40:31 +00:00
parent 396c9246d8
commit c1a850f1f1
1 changed files with 23 additions and 1 deletions
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24
src/typed.rs
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@ -43,6 +43,29 @@ impl<W: Write, T: Serialize> Sender<W, T> {
///
/// See also: [`send`](#method.send)
pub fn queue(&mut self, v: &T) -> Result<usize> {
// This uses a dynamically allocated buffer.
//
// I couldn't get a no_std version to compile with a stack-allocated
// buffer as [0u8; size_of::<T>()] due to compiler errors like:
// ```
// error[E0401]: can't use type parameters from outer function; try using a local type parameter instead
// --> src/typed.rs:46:39
// |
// 46 | const _sbl: usize = size_of::<T>();
// | ^ use of type variable from outer function
// ```
// I think this may require const generics
// (rust-lang tracking issue:
// https://github.com/rust-lang/rust/issues/44580).
//
// When I need to write a no_std version I see a few easy options:
// 1. Caller supplies a reference to a buffer, we can assert! that
// it's long enough. Annoying to use.
// 2. Choose a reasonable length buffer and assert it's long enough.
// Won't work for large enough structs, may consume an inappropriate
// amount of memory for embedded use.
// 3. Provide overloads for 1 and 2. For most cases the fixed size
// buffer will be fine, and if not you can provide your own.
let mut ser_buf = vec![0u8; size_of::<T>()];
let ser_len = ssmarshal::serialize(&mut ser_buf, v)?;
@ -50,7 +73,6 @@ impl<W: Write, T: Serialize> Sender<W, T> {
#[cfg(feature = "trace")] {
println!("framed: Serialized = {:?}", ser);
}
super::encode_to_writer(&ser, &mut self.w)
}