Struct FileEncoder

pub struct FileEncoder { /* private fields */ }

FileEncoder encodes data to file via fixed-size buffer.

There used to be a MemEncoder type that encoded all the data into a Vec. FileEncoder is better because its memory use is determined by the size of the buffer, rather than the full length of the encoded data, and because it doesn’t need to reallocate memory along the way.

Implementations

impl FileEncoder

pub fn new<P: AsRef<Path>>(path: P) -> Result<Self>

pub fn position(&self) -> usize

pub fn flush(&mut self)

pub fn file(&self) -> &File

pub fn path(&self) -> &Path

pub fn write_with<const N: usize>( &mut self, visitor: impl FnOnce(&mut [u8; N]) -> usize, )

Write up to N bytes to this encoder.

This function can be used to avoid the overhead of calling memcpy for writes that have runtime-variable length, but are small and have a small fixed upper bound.

This can be used to do in-place encoding as is done for leb128 (without this function we would need to write to a temporary buffer then memcpy into the encoder), and it can also be used to implement the varint scheme we use for rmeta and dep graph encoding, where we only want to encode the first few bytes of an integer. Copying in the whole integer then only advancing the encoder state for the few bytes we care about is more efficient than calling FileEncoder::write_all, because variable-size copies are always lowered to memcpy, which has overhead and contains a lot of logic we can bypass with this function. Note that common architectures support fixed-size writes up to 8 bytes with one instruction, so while this does in some sense do wasted work, we come out ahead.

pub fn write_array<const N: usize>(&mut self, buf: [u8; N])

Helper for calls where FileEncoder::write_with always writes the whole array.

pub fn finish(&mut self) -> FileEncodeResult

Trait Implementations

impl Drop for FileEncoder

fn drop(&mut self)

Executes the destructor for this type.

impl Encodable<FileEncoder> for [u8]

fn encode(&self, e: &mut FileEncoder)

impl Encodable<FileEncoder> for IntEncodedWithFixedSize

fn encode(&self, e: &mut FileEncoder)

impl Encoder for FileEncoder

fn emit_usize(&mut self, v: usize)

fn emit_u128(&mut self, v: u128)

fn emit_u64(&mut self, v: u64)

fn emit_u32(&mut self, v: u32)

fn emit_u16(&mut self, v: u16)

fn emit_u8(&mut self, v: u8)

fn emit_isize(&mut self, v: isize)

fn emit_i128(&mut self, v: i128)

fn emit_i64(&mut self, v: i64)

fn emit_i32(&mut self, v: i32)

fn emit_i16(&mut self, v: i16)

fn emit_raw_bytes(&mut self, s: &[u8])

fn emit_i8(&mut self, v: i8)

fn emit_bool(&mut self, v: bool)

fn emit_char(&mut self, v: char)

fn emit_str(&mut self, v: &str)