use o3::buffer::{ByteSink, Owned, Shared};
pub struct Wire;
impl Wire {
pub const fn decimal_len(mut n: usize) -> usize {
let mut len = 1;
while n >= 10 {
n /= 10;
len += 1;
}
len
}
pub fn write_dec(n: usize, buf: &mut [u8]) -> usize {
let len = Self::decimal_len(n);
let mut n = n;
let mut i = len;
loop {
i -= 1;
buf[i] = b'0' + (n % 10) as u8;
n /= 10;
if i == 0 {
return len;
}
}
}
pub fn write_hex(n: usize, buf: &mut [u8; 16]) -> usize {
if n == 0 {
buf[0] = b'0';
return 1;
}
let mut i = 16;
let mut val = n;
while val > 0 {
i -= 1;
buf[i] = b"0123456789abcdef"[val & 0xf];
val >>= 4;
}
buf.copy_within(i..16, 0);
16 - i
}
pub fn chunk_prefix(size: usize) -> ([u8; 18], usize) {
let mut hex = [0u8; 16];
let hex_len = Self::write_hex(size, &mut hex);
let mut out = [0u8; 18];
out[..hex_len].copy_from_slice(&hex[..hex_len]);
out[hex_len] = b'\r';
out[hex_len + 1] = b'\n';
(out, hex_len + 2)
}
pub fn chunk_frame(body: Shared) -> Shared {
let (prefix, prefix_len) = Self::chunk_prefix(body.len());
let capacity = prefix_len + body.len() + 2;
match Owned::try_build_exact(capacity, |out| {
out.write_slices([&prefix[..prefix_len], &body, b"\r\n"])
}) {
Ok(out) => out.freeze(),
Err(_) => {
let mut out = Vec::with_capacity(capacity);
match out.write_slices([&prefix[..prefix_len], &body, b"\r\n"]) {
Ok(()) => Shared::from(out),
Err(error) => match error {},
}
}
}
}
}
#[cfg(test)]
mod tests {
use super::Wire;
#[test]
fn decimal_writer_matches_usize_display() {
for value in [0, 1, 9, 10, 99, 100, 999, 1_000, usize::MAX] {
let expected = value.to_string();
let mut out = [0u8; 20];
let written = Wire::write_dec(value, &mut out);
assert_eq!(written, Wire::decimal_len(value));
assert_eq!(&out[..written], expected.as_bytes());
}
}
}