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// Copyright (C) 2019, Cloudflare, Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
use super::Result;
use crate::h3::NameValue;
use super::INDEXED;
use super::LITERAL;
use super::LITERAL_WITH_NAME_REF;
/// A QPACK encoder.
#[derive(Default)]
pub struct Encoder {}
impl Encoder {
/// Creates a new QPACK encoder.
pub fn new() -> Encoder {
Encoder::default()
}
/// Encodes a list of headers into a QPACK header block.
pub fn encode<T: NameValue>(
&mut self, headers: &[T], out: &mut [u8],
) -> Result<usize> {
let mut b = octets::OctetsMut::with_slice(out);
// Required Insert Count.
encode_int(0, 0, 8, &mut b)?;
// Base.
encode_int(0, 0, 7, &mut b)?;
for h in headers {
match lookup_static(h) {
Some((idx, true)) => {
const STATIC: u8 = 0x40;
// Encode as statically indexed.
encode_int(idx, INDEXED | STATIC, 6, &mut b)?;
},
Some((idx, false)) => {
const STATIC: u8 = 0x10;
// Encode value as literal with static name reference.
encode_int(idx, LITERAL_WITH_NAME_REF | STATIC, 4, &mut b)?;
encode_str(h.value(), 7, &mut b)?;
},
None => {
// Encode as fully literal.
let name_len =
super::huffman::encode_output_length(h.name(), true)?;
encode_int(name_len as u64, LITERAL | 0x08, 3, &mut b)?;
super::huffman::encode(h.name(), &mut b, true)?;
encode_str(h.value(), 7, &mut b)?;
},
};
}
Ok(b.off())
}
}
fn lookup_static<T: NameValue>(h: &T) -> Option<(u64, bool)> {
let mut name_match = None;
for (i, e) in super::static_table::STATIC_TABLE.iter().enumerate() {
// Match header name first.
if h.name().len() == e.0.len() && h.name().eq_ignore_ascii_case(e.0) {
// No header value to match, return early.
if e.1.is_empty() {
return Some((i as u64, false));
}
// Match header value.
if h.value().len() == e.1.len() && h.value() == e.1 {
return Some((i as u64, true));
}
// Remember name-only match for later, but keep searching.
name_match = Some((i as u64, false));
}
}
name_match
}
fn encode_int(
mut v: u64, first: u8, prefix: usize, b: &mut octets::OctetsMut,
) -> Result<()> {
let mask = 2u64.pow(prefix as u32) - 1;
// Encode I on N bits.
if v < mask {
b.put_u8(first | v as u8)?;
return Ok(());
}
// Encode (2^N - 1) on N bits.
b.put_u8(first | mask as u8)?;
v -= mask;
while v >= 128 {
// Encode (I % 128 + 128) on 8 bits.
b.put_u8((v % 128 + 128) as u8)?;
v >>= 7;
}
// Encode I on 8 bits.
b.put_u8(v as u8)?;
Ok(())
}
fn encode_str(v: &[u8], prefix: usize, b: &mut octets::OctetsMut) -> Result<()> {
let len = super::huffman::encode_output_length(v, false)?;
encode_int(len as u64, 0x80, prefix, b)?;
super::huffman::encode(v, b, false)?;
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn encode_int1() {
let expected = [0b01010];
let mut encoded = [0; 1];
let mut b = octets::OctetsMut::with_slice(&mut encoded);
assert!(encode_int(10, 0, 5, &mut b).is_ok());
assert_eq!(expected, encoded);
}
#[test]
fn encode_int2() {
let expected = [0b11111, 0b10011010, 0b00001010];
let mut encoded = [0; 3];
let mut b = octets::OctetsMut::with_slice(&mut encoded);
assert!(encode_int(1337, 0, 5, &mut b).is_ok());
assert_eq!(expected, encoded);
}
#[test]
fn encode_int3() {
let expected = [0b101010];
let mut encoded = [0; 1];
let mut b = octets::OctetsMut::with_slice(&mut encoded);
assert!(encode_int(42, 0, 8, &mut b).is_ok());
assert_eq!(expected, encoded);
}
}
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