blob: ccf17da20b28821c998030cb55e0736c1d1f13d7 [file] [log] [blame]
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "spdy/core/hpack/hpack_encoder.h"
#include <algorithm>
#include <limits>
#include <utility>
#include "http2/hpack/huffman/hpack_huffman_encoder.h"
#include "common/platform/api/quiche_bug_tracker.h"
#include "common/platform/api/quiche_logging.h"
#include "spdy/core/hpack/hpack_constants.h"
#include "spdy/core/hpack/hpack_header_table.h"
#include "spdy/core/hpack/hpack_output_stream.h"
namespace spdy {
class HpackEncoder::RepresentationIterator {
public:
// |pseudo_headers| and |regular_headers| must outlive the iterator.
RepresentationIterator(const Representations& pseudo_headers,
const Representations& regular_headers)
: pseudo_begin_(pseudo_headers.begin()),
pseudo_end_(pseudo_headers.end()),
regular_begin_(regular_headers.begin()),
regular_end_(regular_headers.end()) {}
// |headers| must outlive the iterator.
explicit RepresentationIterator(const Representations& headers)
: pseudo_begin_(headers.begin()),
pseudo_end_(headers.end()),
regular_begin_(headers.end()),
regular_end_(headers.end()) {}
bool HasNext() {
return pseudo_begin_ != pseudo_end_ || regular_begin_ != regular_end_;
}
const Representation Next() {
if (pseudo_begin_ != pseudo_end_) {
return *pseudo_begin_++;
} else {
return *regular_begin_++;
}
}
private:
Representations::const_iterator pseudo_begin_;
Representations::const_iterator pseudo_end_;
Representations::const_iterator regular_begin_;
Representations::const_iterator regular_end_;
};
namespace {
// The default header listener.
void NoOpListener(absl::string_view /*name*/, absl::string_view /*value*/) {}
// The default HPACK indexing policy.
bool DefaultPolicy(absl::string_view name, absl::string_view /* value */) {
if (name.empty()) {
return false;
}
// :authority is always present and rarely changes, and has moderate
// length, therefore it makes a lot of sense to index (insert in the
// dynamic table).
if (name[0] == kPseudoHeaderPrefix) {
return name == ":authority";
}
return true;
}
} // namespace
HpackEncoder::HpackEncoder()
: output_stream_(),
min_table_size_setting_received_(std::numeric_limits<size_t>::max()),
listener_(NoOpListener),
should_index_(DefaultPolicy),
enable_compression_(true),
should_emit_table_size_(false) {}
HpackEncoder::~HpackEncoder() = default;
bool HpackEncoder::EncodeHeaderSet(const SpdyHeaderBlock& header_set,
std::string* output) {
// Separate header set into pseudo-headers and regular headers.
Representations pseudo_headers;
Representations regular_headers;
bool found_cookie = false;
for (const auto& header : header_set) {
if (!found_cookie && header.first == "cookie") {
// Note that there can only be one "cookie" header, because header_set is
// a map.
found_cookie = true;
CookieToCrumbs(header, &regular_headers);
} else if (!header.first.empty() &&
header.first[0] == kPseudoHeaderPrefix) {
DecomposeRepresentation(header, &pseudo_headers);
} else {
DecomposeRepresentation(header, &regular_headers);
}
}
{
RepresentationIterator iter(pseudo_headers, regular_headers);
EncodeRepresentations(&iter, output);
}
return true;
}
void HpackEncoder::ApplyHeaderTableSizeSetting(size_t size_setting) {
if (size_setting == header_table_.settings_size_bound()) {
return;
}
if (size_setting < header_table_.settings_size_bound()) {
min_table_size_setting_received_ =
std::min(size_setting, min_table_size_setting_received_);
}
header_table_.SetSettingsHeaderTableSize(size_setting);
should_emit_table_size_ = true;
}
void HpackEncoder::EncodeRepresentations(RepresentationIterator* iter,
std::string* output) {
MaybeEmitTableSize();
while (iter->HasNext()) {
const auto header = iter->Next();
listener_(header.first, header.second);
if (enable_compression_) {
size_t index =
header_table_.GetByNameAndValue(header.first, header.second);
if (index != kHpackEntryNotFound) {
EmitIndex(index);
} else if (should_index_(header.first, header.second)) {
EmitIndexedLiteral(header);
} else {
EmitNonIndexedLiteral(header, enable_compression_);
}
} else {
EmitNonIndexedLiteral(header, enable_compression_);
}
}
output_stream_.TakeString(output);
}
void HpackEncoder::EmitIndex(size_t index) {
QUICHE_DVLOG(2) << "Emitting index " << index;
output_stream_.AppendPrefix(kIndexedOpcode);
output_stream_.AppendUint32(index);
}
void HpackEncoder::EmitIndexedLiteral(const Representation& representation) {
QUICHE_DVLOG(2) << "Emitting indexed literal: (" << representation.first
<< ", " << representation.second << ")";
output_stream_.AppendPrefix(kLiteralIncrementalIndexOpcode);
EmitLiteral(representation);
header_table_.TryAddEntry(representation.first, representation.second);
}
void HpackEncoder::EmitNonIndexedLiteral(const Representation& representation,
bool enable_compression) {
QUICHE_DVLOG(2) << "Emitting nonindexed literal: (" << representation.first
<< ", " << representation.second << ")";
output_stream_.AppendPrefix(kLiteralNoIndexOpcode);
size_t name_index = header_table_.GetByName(representation.first);
if (enable_compression && name_index != kHpackEntryNotFound) {
output_stream_.AppendUint32(name_index);
} else {
output_stream_.AppendUint32(0);
EmitString(representation.first);
}
EmitString(representation.second);
}
void HpackEncoder::EmitLiteral(const Representation& representation) {
size_t name_index = header_table_.GetByName(representation.first);
if (name_index != kHpackEntryNotFound) {
output_stream_.AppendUint32(name_index);
} else {
output_stream_.AppendUint32(0);
EmitString(representation.first);
}
EmitString(representation.second);
}
void HpackEncoder::EmitString(absl::string_view str) {
size_t encoded_size =
enable_compression_ ? http2::HuffmanSize(str) : str.size();
if (encoded_size < str.size()) {
QUICHE_DVLOG(2) << "Emitted Huffman-encoded string of length "
<< encoded_size;
output_stream_.AppendPrefix(kStringLiteralHuffmanEncoded);
output_stream_.AppendUint32(encoded_size);
http2::HuffmanEncodeFast(str, encoded_size, output_stream_.MutableString());
} else {
QUICHE_DVLOG(2) << "Emitted literal string of length " << str.size();
output_stream_.AppendPrefix(kStringLiteralIdentityEncoded);
output_stream_.AppendUint32(str.size());
output_stream_.AppendBytes(str);
}
}
void HpackEncoder::MaybeEmitTableSize() {
if (!should_emit_table_size_) {
return;
}
const size_t current_size = CurrentHeaderTableSizeSetting();
QUICHE_DVLOG(1) << "MaybeEmitTableSize current_size=" << current_size;
QUICHE_DVLOG(1) << "MaybeEmitTableSize min_table_size_setting_received_="
<< min_table_size_setting_received_;
if (min_table_size_setting_received_ < current_size) {
output_stream_.AppendPrefix(kHeaderTableSizeUpdateOpcode);
output_stream_.AppendUint32(min_table_size_setting_received_);
}
output_stream_.AppendPrefix(kHeaderTableSizeUpdateOpcode);
output_stream_.AppendUint32(current_size);
min_table_size_setting_received_ = std::numeric_limits<size_t>::max();
should_emit_table_size_ = false;
}
// static
void HpackEncoder::CookieToCrumbs(const Representation& cookie,
Representations* out) {
// See Section 8.1.2.5. "Compressing the Cookie Header Field" in the HTTP/2
// specification at https://tools.ietf.org/html/draft-ietf-httpbis-http2-14.
// Cookie values are split into individually-encoded HPACK representations.
absl::string_view cookie_value = cookie.second;
// Consume leading and trailing whitespace if present.
absl::string_view::size_type first = cookie_value.find_first_not_of(" \t");
absl::string_view::size_type last = cookie_value.find_last_not_of(" \t");
if (first == absl::string_view::npos) {
cookie_value = absl::string_view();
} else {
cookie_value = cookie_value.substr(first, (last - first) + 1);
}
for (size_t pos = 0;;) {
size_t end = cookie_value.find(";", pos);
if (end == absl::string_view::npos) {
out->push_back(std::make_pair(cookie.first, cookie_value.substr(pos)));
break;
}
out->push_back(
std::make_pair(cookie.first, cookie_value.substr(pos, end - pos)));
// Consume next space if present.
pos = end + 1;
if (pos != cookie_value.size() && cookie_value[pos] == ' ') {
pos++;
}
}
}
// static
void HpackEncoder::DecomposeRepresentation(const Representation& header_field,
Representations* out) {
size_t pos = 0;
size_t end = 0;
while (end != absl::string_view::npos) {
end = header_field.second.find('\0', pos);
out->push_back(std::make_pair(
header_field.first,
header_field.second.substr(
pos, end == absl::string_view::npos ? end : end - pos)));
pos = end + 1;
}
}
// Iteratively encodes a SpdyHeaderBlock.
class HpackEncoder::Encoderator : public ProgressiveEncoder {
public:
Encoderator(const SpdyHeaderBlock& header_set, HpackEncoder* encoder);
Encoderator(const Representations& representations, HpackEncoder* encoder);
// Encoderator is neither copyable nor movable.
Encoderator(const Encoderator&) = delete;
Encoderator& operator=(const Encoderator&) = delete;
// Returns true iff more remains to encode.
bool HasNext() const override { return has_next_; }
// Encodes up to max_encoded_bytes of the current header block into the
// given output string.
void Next(size_t max_encoded_bytes, std::string* output) override;
private:
HpackEncoder* encoder_;
std::unique_ptr<RepresentationIterator> header_it_;
Representations pseudo_headers_;
Representations regular_headers_;
bool has_next_;
};
HpackEncoder::Encoderator::Encoderator(const SpdyHeaderBlock& header_set,
HpackEncoder* encoder)
: encoder_(encoder), has_next_(true) {
// Separate header set into pseudo-headers and regular headers.
bool found_cookie = false;
for (const auto& header : header_set) {
if (!found_cookie && header.first == "cookie") {
// Note that there can only be one "cookie" header, because header_set
// is a map.
found_cookie = true;
CookieToCrumbs(header, &regular_headers_);
} else if (!header.first.empty() &&
header.first[0] == kPseudoHeaderPrefix) {
DecomposeRepresentation(header, &pseudo_headers_);
} else {
DecomposeRepresentation(header, &regular_headers_);
}
}
header_it_ = std::make_unique<RepresentationIterator>(pseudo_headers_,
regular_headers_);
encoder_->MaybeEmitTableSize();
}
HpackEncoder::Encoderator::Encoderator(const Representations& representations,
HpackEncoder* encoder)
: encoder_(encoder), has_next_(true) {
for (const auto& header : representations) {
if (header.first == "cookie") {
CookieToCrumbs(header, &regular_headers_);
} else if (!header.first.empty() &&
header.first[0] == kPseudoHeaderPrefix) {
pseudo_headers_.push_back(header);
} else {
regular_headers_.push_back(header);
}
}
header_it_ = std::make_unique<RepresentationIterator>(pseudo_headers_,
regular_headers_);
encoder_->MaybeEmitTableSize();
}
void HpackEncoder::Encoderator::Next(size_t max_encoded_bytes,
std::string* output) {
QUICHE_BUG_IF(spdy_bug_61_1, !has_next_)
<< "Encoderator::Next called with nothing left to encode.";
const bool enable_compression = encoder_->enable_compression_;
// Encode up to max_encoded_bytes of headers.
while (header_it_->HasNext() &&
encoder_->output_stream_.size() <= max_encoded_bytes) {
const Representation header = header_it_->Next();
encoder_->listener_(header.first, header.second);
if (enable_compression) {
size_t index = encoder_->header_table_.GetByNameAndValue(header.first,
header.second);
if (index != kHpackEntryNotFound) {
encoder_->EmitIndex(index);
} else if (encoder_->should_index_(header.first, header.second)) {
encoder_->EmitIndexedLiteral(header);
} else {
encoder_->EmitNonIndexedLiteral(header, enable_compression);
}
} else {
encoder_->EmitNonIndexedLiteral(header, enable_compression);
}
}
has_next_ = encoder_->output_stream_.size() > max_encoded_bytes;
encoder_->output_stream_.BoundedTakeString(max_encoded_bytes, output);
}
std::unique_ptr<HpackEncoder::ProgressiveEncoder> HpackEncoder::EncodeHeaderSet(
const SpdyHeaderBlock& header_set) {
return std::make_unique<Encoderator>(header_set, this);
}
std::unique_ptr<HpackEncoder::ProgressiveEncoder>
HpackEncoder::EncodeRepresentations(const Representations& representations) {
return std::make_unique<Encoderator>(representations, this);
}
} // namespace spdy