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use super::table::{Index, Table};
use super::{huffman, Header};
use bytes::{BufMut, BytesMut};
use http::header::{HeaderName, HeaderValue};
#[derive(Debug)]
pub struct Encoder {
table: Table,
size_update: Option<SizeUpdate>,
}
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
enum SizeUpdate {
One(usize),
Two(usize, usize), // min, max
}
impl Encoder {
pub fn new(max_size: usize, capacity: usize) -> Encoder {
Encoder {
table: Table::new(max_size, capacity),
size_update: None,
}
}
/// Queues a max size update.
///
/// The next call to `encode` will include a dynamic size update frame.
pub fn update_max_size(&mut self, val: usize) {
match self.size_update {
Some(SizeUpdate::One(old)) => {
if val > old {
if old > self.table.max_size() {
self.size_update = Some(SizeUpdate::One(val));
} else {
self.size_update = Some(SizeUpdate::Two(old, val));
}
} else {
self.size_update = Some(SizeUpdate::One(val));
}
}
Some(SizeUpdate::Two(min, _)) => {
if val < min {
self.size_update = Some(SizeUpdate::One(val));
} else {
self.size_update = Some(SizeUpdate::Two(min, val));
}
}
None => {
if val != self.table.max_size() {
// Don't bother writing a frame if the value already matches
// the table's max size.
self.size_update = Some(SizeUpdate::One(val));
}
}
}
}
/// Encode a set of headers into the provide buffer
pub fn encode<I>(&mut self, headers: I, dst: &mut BytesMut)
where
I: IntoIterator<Item = Header<Option<HeaderName>>>,
{
let span = tracing::trace_span!("hpack::encode");
let _e = span.enter();
self.encode_size_updates(dst);
let mut last_index = None;
for header in headers {
match header.reify() {
// The header has an associated name. In which case, try to
// index it in the table.
Ok(header) => {
let index = self.table.index(header);
self.encode_header(&index, dst);
last_index = Some(index);
}
// The header does not have an associated name. This means that
// the name is the same as the previously yielded header. In
// which case, we skip table lookup and just use the same index
// as the previous entry.
Err(value) => {
self.encode_header_without_name(
last_index.as_ref().unwrap_or_else(|| {
panic!("encoding header without name, but no previous index to use for name");
}),
&value,
dst,
);
}
}
}
}
fn encode_size_updates(&mut self, dst: &mut BytesMut) {
match self.size_update.take() {
Some(SizeUpdate::One(val)) => {
self.table.resize(val);
encode_size_update(val, dst);
}
Some(SizeUpdate::Two(min, max)) => {
self.table.resize(min);
self.table.resize(max);
encode_size_update(min, dst);
encode_size_update(max, dst);
}
None => {}
}
}
fn encode_header(&mut self, index: &Index, dst: &mut BytesMut) {
match *index {
Index::Indexed(idx, _) => {
encode_int(idx, 7, 0x80, dst);
}
Index::Name(idx, _) => {
let header = self.table.resolve(index);
encode_not_indexed(idx, header.value_slice(), header.is_sensitive(), dst);
}
Index::Inserted(_) => {
let header = self.table.resolve(index);
assert!(!header.is_sensitive());
dst.put_u8(0b0100_0000);
encode_str(header.name().as_slice(), dst);
encode_str(header.value_slice(), dst);
}
Index::InsertedValue(idx, _) => {
let header = self.table.resolve(index);
assert!(!header.is_sensitive());
encode_int(idx, 6, 0b0100_0000, dst);
encode_str(header.value_slice(), dst);
}
Index::NotIndexed(_) => {
let header = self.table.resolve(index);
encode_not_indexed2(
header.name().as_slice(),
header.value_slice(),
header.is_sensitive(),
dst,
);
}
}
}
fn encode_header_without_name(
&mut self,
last: &Index,
value: &HeaderValue,
dst: &mut BytesMut,
) {
match *last {
Index::Indexed(..)
| Index::Name(..)
| Index::Inserted(..)
| Index::InsertedValue(..) => {
let idx = self.table.resolve_idx(last);
encode_not_indexed(idx, value.as_ref(), value.is_sensitive(), dst);
}
Index::NotIndexed(_) => {
let last = self.table.resolve(last);
encode_not_indexed2(
last.name().as_slice(),
value.as_ref(),
value.is_sensitive(),
dst,
);
}
}
}
}
impl Default for Encoder {
fn default() -> Encoder {
Encoder::new(4096, 0)
}
}
fn encode_size_update(val: usize, dst: &mut BytesMut) {
encode_int(val, 5, 0b0010_0000, dst)
}
fn encode_not_indexed(name: usize, value: &[u8], sensitive: bool, dst: &mut BytesMut) {
if sensitive {
encode_int(name, 4, 0b10000, dst);
} else {
encode_int(name, 4, 0, dst);
}
encode_str(value, dst);
}
fn encode_not_indexed2(name: &[u8], value: &[u8], sensitive: bool, dst: &mut BytesMut) {
if sensitive {
dst.put_u8(0b10000);
} else {
dst.put_u8(0);
}
encode_str(name, dst);
encode_str(value, dst);
}
fn encode_str(val: &[u8], dst: &mut BytesMut) {
if !val.is_empty() {
let idx = position(dst);
// Push a placeholder byte for the length header
dst.put_u8(0);
// Encode with huffman
huffman::encode(val, dst);
let huff_len = position(dst) - (idx + 1);
if encode_int_one_byte(huff_len, 7) {
// Write the string head
dst[idx] = 0x80 | huff_len as u8;
} else {
// Write the head to a placeholder
const PLACEHOLDER_LEN: usize = 8;
let mut buf = [0u8; PLACEHOLDER_LEN];
let head_len = {
let mut head_dst = &mut buf[..];
encode_int(huff_len, 7, 0x80, &mut head_dst);
PLACEHOLDER_LEN - head_dst.remaining_mut()
};
// This is just done to reserve space in the destination
dst.put_slice(&buf[1..head_len]);
// Shift the header forward
for i in 0..huff_len {
let src_i = idx + 1 + (huff_len - (i + 1));
let dst_i = idx + head_len + (huff_len - (i + 1));
dst[dst_i] = dst[src_i];
}
// Copy in the head
for i in 0..head_len {
dst[idx + i] = buf[i];
}
}
} else {
// Write an empty string
dst.put_u8(0);
}
}
/// Encode an integer into the given destination buffer
fn encode_int<B: BufMut>(
mut value: usize, // The integer to encode
prefix_bits: usize, // The number of bits in the prefix
first_byte: u8, // The base upon which to start encoding the int
dst: &mut B,
) {
if encode_int_one_byte(value, prefix_bits) {
dst.put_u8(first_byte | value as u8);
return;
}
let low = (1 << prefix_bits) - 1;
value -= low;
dst.put_u8(first_byte | low as u8);
while value >= 128 {
dst.put_u8(0b1000_0000 | value as u8);
value >>= 7;
}
dst.put_u8(value as u8);
}
/// Returns true if the in the int can be fully encoded in the first byte.
fn encode_int_one_byte(value: usize, prefix_bits: usize) -> bool {
value < (1 << prefix_bits) - 1
}
fn position(buf: &BytesMut) -> usize {
buf.len()
}
#[cfg(test)]
mod test {
use super::*;
use crate::hpack::Header;
use http::*;
#[test]
fn test_encode_method_get() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![method("GET")]);
assert_eq!(*res, [0x80 | 2]);
assert_eq!(encoder.table.len(), 0);
}
#[test]
fn test_encode_method_post() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![method("POST")]);
assert_eq!(*res, [0x80 | 3]);
assert_eq!(encoder.table.len(), 0);
}
#[test]
fn test_encode_method_patch() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![method("PATCH")]);
assert_eq!(res[0], 0b01000000 | 2); // Incremental indexing w/ name pulled from table
assert_eq!(res[1], 0x80 | 5); // header value w/ huffman coding
assert_eq!("PATCH", huff_decode(&res[2..7]));
assert_eq!(encoder.table.len(), 1);
let res = encode(&mut encoder, vec![method("PATCH")]);
assert_eq!(1 << 7 | 62, res[0]);
assert_eq!(1, res.len());
}
#[test]
fn test_encode_indexed_name_literal_value() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![header("content-language", "foo")]);
assert_eq!(res[0], 0b01000000 | 27); // Indexed name
assert_eq!(res[1], 0x80 | 2); // header value w/ huffman coding
assert_eq!("foo", huff_decode(&res[2..4]));
// Same name, new value should still use incremental
let res = encode(&mut encoder, vec![header("content-language", "bar")]);
assert_eq!(res[0], 0b01000000 | 27); // Indexed name
assert_eq!(res[1], 0x80 | 3); // header value w/ huffman coding
assert_eq!("bar", huff_decode(&res[2..5]));
}
#[test]
fn test_repeated_headers_are_indexed() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![header("foo", "hello")]);
assert_eq!(&[0b01000000, 0x80 | 2], &res[0..2]);
assert_eq!("foo", huff_decode(&res[2..4]));
assert_eq!(0x80 | 4, res[4]);
assert_eq!("hello", huff_decode(&res[5..]));
assert_eq!(9, res.len());
assert_eq!(1, encoder.table.len());
let res = encode(&mut encoder, vec![header("foo", "hello")]);
assert_eq!([0x80 | 62], *res);
assert_eq!(encoder.table.len(), 1);
}
#[test]
fn test_evicting_headers() {
let mut encoder = Encoder::default();
// Fill the table
for i in 0..64 {
let key = format!("x-hello-world-{:02}", i);
let res = encode(&mut encoder, vec![header(&key, &key)]);
assert_eq!(&[0b01000000, 0x80 | 12], &res[0..2]);
assert_eq!(key, huff_decode(&res[2..14]));
assert_eq!(0x80 | 12, res[14]);
assert_eq!(key, huff_decode(&res[15..]));
assert_eq!(27, res.len());
// Make sure the header can be found...
let res = encode(&mut encoder, vec![header(&key, &key)]);
// Only check that it is found
assert_eq!(0x80, res[0] & 0x80);
}
assert_eq!(4096, encoder.table.size());
assert_eq!(64, encoder.table.len());
// Find existing headers
for i in 0..64 {
let key = format!("x-hello-world-{:02}", i);
let res = encode(&mut encoder, vec![header(&key, &key)]);
assert_eq!(0x80, res[0] & 0x80);
}
// Insert a new header
let key = "x-hello-world-64";
let res = encode(&mut encoder, vec![header(key, key)]);
assert_eq!(&[0b01000000, 0x80 | 12], &res[0..2]);
assert_eq!(key, huff_decode(&res[2..14]));
assert_eq!(0x80 | 12, res[14]);
assert_eq!(key, huff_decode(&res[15..]));
assert_eq!(27, res.len());
assert_eq!(64, encoder.table.len());
// Now try encoding entries that should exist in the table
for i in 1..65 {
let key = format!("x-hello-world-{:02}", i);
let res = encode(&mut encoder, vec![header(&key, &key)]);
assert_eq!(0x80 | (61 + (65 - i)), res[0]);
}
}
#[test]
fn test_large_headers_are_not_indexed() {
let mut encoder = Encoder::new(128, 0);
let key = "hello-world-hello-world-HELLO-zzz";
let res = encode(&mut encoder, vec![header(key, key)]);
assert_eq!(&[0, 0x80 | 25], &res[..2]);
assert_eq!(0, encoder.table.len());
assert_eq!(0, encoder.table.size());
}
#[test]
fn test_sensitive_headers_are_never_indexed() {
use http::header::HeaderValue;
let name = "my-password".parse().unwrap();
let mut value = HeaderValue::from_bytes(b"12345").unwrap();
value.set_sensitive(true);
let header = Header::Field {
name: Some(name),
value,
};
// Now, try to encode the sensitive header
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![header]);
assert_eq!(&[0b10000, 0x80 | 8], &res[..2]);
assert_eq!("my-password", huff_decode(&res[2..10]));
assert_eq!(0x80 | 4, res[10]);
assert_eq!("12345", huff_decode(&res[11..]));
// Now, try to encode a sensitive header w/ a name in the static table
let name = "authorization".parse().unwrap();
let mut value = HeaderValue::from_bytes(b"12345").unwrap();
value.set_sensitive(true);
let header = Header::Field {
name: Some(name),
value,
};
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![header]);
assert_eq!(&[0b11111, 8], &res[..2]);
assert_eq!(0x80 | 4, res[2]);
assert_eq!("12345", huff_decode(&res[3..]));
// Using the name component of a previously indexed header (without
// sensitive flag set)
let _ = encode(
&mut encoder,
vec![self::header("my-password", "not-so-secret")],
);
let name = "my-password".parse().unwrap();
let mut value = HeaderValue::from_bytes(b"12345").unwrap();
value.set_sensitive(true);
let header = Header::Field {
name: Some(name),
value,
};
let res = encode(&mut encoder, vec![header]);
assert_eq!(&[0b11111, 47], &res[..2]);
assert_eq!(0x80 | 4, res[2]);
assert_eq!("12345", huff_decode(&res[3..]));
}
#[test]
fn test_content_length_value_not_indexed() {
let mut encoder = Encoder::default();
let res = encode(&mut encoder, vec![header("content-length", "1234")]);
assert_eq!(&[15, 13, 0x80 | 3], &res[0..3]);
assert_eq!("1234", huff_decode(&res[3..]));
assert_eq!(6, res.len());
}
#[test]
fn test_encoding_headers_with_same_name() {
let mut encoder = Encoder::default();
let name = "hello";
// Encode first one
let _ = encode(&mut encoder, vec![header(name, "one")]);
// Encode second one
let res = encode(&mut encoder, vec![header(name, "two")]);
assert_eq!(&[0x40 | 62, 0x80 | 3], &res[0..2]);
assert_eq!("two", huff_decode(&res[2..]));
assert_eq!(5, res.len());
// Encode the first one again
let res = encode(&mut encoder, vec![header(name, "one")]);
assert_eq!(&[0x80 | 63], &res[..]);
// Now the second one
let res = encode(&mut encoder, vec![header(name, "two")]);
assert_eq!(&[0x80 | 62], &res[..]);
}
#[test]
fn test_evicting_headers_when_multiple_of_same_name_are_in_table() {
// The encoder only has space for 2 headers
let mut encoder = Encoder::new(76, 0);
let _ = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(1, encoder.table.len());
let _ = encode(&mut encoder, vec![header("bar", "foo")]);
assert_eq!(2, encoder.table.len());
// This will evict the first header, while still referencing the header
// name
let res = encode(&mut encoder, vec![header("foo", "baz")]);
assert_eq!(&[0x40 | 63, 0, 0x80 | 3], &res[..3]);
assert_eq!(2, encoder.table.len());
// Try adding the same header again
let res = encode(&mut encoder, vec![header("foo", "baz")]);
assert_eq!(&[0x80 | 62], &res[..]);
assert_eq!(2, encoder.table.len());
}
#[test]
fn test_max_size_zero() {
// Static table only
let mut encoder = Encoder::new(0, 0);
let res = encode(&mut encoder, vec![method("GET")]);
assert_eq!(*res, [0x80 | 2]);
assert_eq!(encoder.table.len(), 0);
let res = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(&[0, 0x80 | 2], &res[..2]);
assert_eq!("foo", huff_decode(&res[2..4]));
assert_eq!(0x80 | 3, res[4]);
assert_eq!("bar", huff_decode(&res[5..8]));
assert_eq!(0, encoder.table.len());
// Encode a custom value
let res = encode(&mut encoder, vec![header("transfer-encoding", "chunked")]);
assert_eq!(&[15, 42, 0x80 | 6], &res[..3]);
assert_eq!("chunked", huff_decode(&res[3..]));
}
#[test]
fn test_update_max_size_combos() {
let mut encoder = Encoder::default();
assert!(encoder.size_update.is_none());
assert_eq!(4096, encoder.table.max_size());
encoder.update_max_size(4096); // Default size
assert!(encoder.size_update.is_none());
encoder.update_max_size(0);
assert_eq!(Some(SizeUpdate::One(0)), encoder.size_update);
encoder.update_max_size(100);
assert_eq!(Some(SizeUpdate::Two(0, 100)), encoder.size_update);
let mut encoder = Encoder::default();
encoder.update_max_size(8000);
assert_eq!(Some(SizeUpdate::One(8000)), encoder.size_update);
encoder.update_max_size(100);
assert_eq!(Some(SizeUpdate::One(100)), encoder.size_update);
encoder.update_max_size(8000);
assert_eq!(Some(SizeUpdate::Two(100, 8000)), encoder.size_update);
encoder.update_max_size(4000);
assert_eq!(Some(SizeUpdate::Two(100, 4000)), encoder.size_update);
encoder.update_max_size(50);
assert_eq!(Some(SizeUpdate::One(50)), encoder.size_update);
}
#[test]
fn test_resizing_table() {
let mut encoder = Encoder::default();
// Add a header
let _ = encode(&mut encoder, vec![header("foo", "bar")]);
encoder.update_max_size(1);
assert_eq!(1, encoder.table.len());
let res = encode(&mut encoder, vec![method("GET")]);
assert_eq!(&[32 | 1, 0x80 | 2], &res[..]);
assert_eq!(0, encoder.table.len());
let res = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(0, res[0]);
encoder.update_max_size(100);
let res = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(&[32 | 31, 69, 64], &res[..3]);
encoder.update_max_size(0);
let res = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(&[32, 0], &res[..2]);
}
#[test]
fn test_decreasing_table_size_without_eviction() {
let mut encoder = Encoder::default();
// Add a header
let _ = encode(&mut encoder, vec![header("foo", "bar")]);
encoder.update_max_size(100);
assert_eq!(1, encoder.table.len());
let res = encode(&mut encoder, vec![header("foo", "bar")]);
assert_eq!(&[32 | 31, 69, 0x80 | 62], &res[..]);
}
#[test]
fn test_nameless_header() {
let mut encoder = Encoder::default();
let res = encode(
&mut encoder,
vec![
Header::Field {
name: Some("hello".parse().unwrap()),
value: HeaderValue::from_bytes(b"world").unwrap(),
},
Header::Field {
name: None,
value: HeaderValue::from_bytes(b"zomg").unwrap(),
},
],
);
assert_eq!(&[0x40, 0x80 | 4], &res[0..2]);
assert_eq!("hello", huff_decode(&res[2..6]));
assert_eq!(0x80 | 4, res[6]);
assert_eq!("world", huff_decode(&res[7..11]));
// Next is not indexed
assert_eq!(&[15, 47, 0x80 | 3], &res[11..14]);
assert_eq!("zomg", huff_decode(&res[14..]));
}
#[test]
fn test_large_size_update() {
let mut encoder = Encoder::default();
encoder.update_max_size(1912930560);
assert_eq!(Some(SizeUpdate::One(1912930560)), encoder.size_update);
let mut dst = BytesMut::with_capacity(6);
encoder.encode_size_updates(&mut dst);
assert_eq!([63, 225, 129, 148, 144, 7], &dst[..]);
}
#[test]
#[ignore]
fn test_evicted_overflow() {
// Not sure what the best way to do this is.
}
fn encode(e: &mut Encoder, hdrs: Vec<Header<Option<HeaderName>>>) -> BytesMut {
let mut dst = BytesMut::with_capacity(1024);
e.encode(&mut hdrs.into_iter(), &mut dst);
dst
}
fn method(s: &str) -> Header<Option<HeaderName>> {
Header::Method(Method::from_bytes(s.as_bytes()).unwrap())
}
fn header(name: &str, val: &str) -> Header<Option<HeaderName>> {
let name = HeaderName::from_bytes(name.as_bytes()).unwrap();
let value = HeaderValue::from_bytes(val.as_bytes()).unwrap();
Header::Field {
name: Some(name),
value,
}
}
fn huff_decode(src: &[u8]) -> BytesMut {
let mut buf = BytesMut::new();
huffman::decode(src, &mut buf).unwrap()
}
}