Struct Writer 

pub struct Writer<'a> { /* private fields */ }

A cursor that writes ABI values into a byte slice.

The writer never grows its buffer. A caller that does not know how big a record will be should size the buffer with Writer::position on a dry run, or just use a buffer big enough for the largest record the ABI allows.

Implementations

impl Writer<'_>

pub fn record( &mut self, tag: Tag, version: u16, body: impl FnOnce(&mut Self) -> Result<()>, ) -> Result<()>

Writes a record, filling in its length once the body has been written.

Errors

Returns Error::BufferFull if the buffer runs out, Error::LengthOverflow if the body is longer than a u32 can describe, or whatever the body itself returns.

impl<'a> Writer<'a>

pub fn new(buf: &'a mut [u8]) -> Self

Starts writing at the beginning of buf.

pub const fn position(&self) -> usize

How many bytes have been written.

pub const fn remaining(&self) -> usize

How much room is left.

pub fn written(&self) -> &[u8]

Everything written so far.

pub fn u8(&mut self, v: u8) -> Result<()>

Writes one byte.

Errors

Returns Error::BufferFull if there is no room.

pub fn u16(&mut self, v: u16) -> Result<()>

Writes a little-endian u16.

Errors

Returns Error::BufferFull if there is no room.

pub fn u32(&mut self, v: u32) -> Result<()>

Writes a little-endian u32.

Errors

Returns Error::BufferFull if there is no room.

pub fn u64(&mut self, v: u64) -> Result<()>

Writes a little-endian u64.

Errors

Returns Error::BufferFull if there is no room.

pub fn raw(&mut self, v: &[u8]) -> Result<()>

Writes bytes with no length prefix and no padding.

Errors

Returns Error::BufferFull if there is no room.

pub fn align(&mut self) -> Result<()>

Writes zeroes up to the next alignment boundary.

Errors

Returns Error::BufferFull if there is no room.

pub fn var_bytes(&mut self, v: &[u8]) -> Result<()>

Writes a length-prefixed byte string and pads it out.

Errors

Returns Error::BufferFull if there is no room, or Error::LengthOverflow if the slice is longer than a u32 can describe.

pub fn var_str(&mut self, v: &str) -> Result<()>

Writes a length-prefixed string.

Errors

Returns the same errors as Writer::var_bytes.

pub fn patch_u32(&mut self, at: usize, v: u32) -> Result<()>

Overwrites a u32 that was already written, at absolute offset at.

This exists so a record can reserve its length field, write its payload, and then fill the length in once it is known.

Errors

Returns Error::BufferFull if at is not inside what has been written.

Trait Implementations

impl<'a> Debug for Writer<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.