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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/web_package/input_reader.h"
#include "base/strings/string_util.h"
namespace web_package {
absl::optional<uint8_t> InputReader::ReadByte() {
if (buf_.empty())
return absl::nullopt;
uint8_t byte = buf_[0];
Advance(1);
return byte;
}
absl::optional<base::span<const uint8_t>> InputReader::ReadBytes(size_t n) {
if (buf_.size() < n)
return absl::nullopt;
auto result = buf_.subspan(0, n);
Advance(n);
return result;
}
absl::optional<base::StringPiece> InputReader::ReadString(size_t n) {
auto bytes = ReadBytes(n);
if (!bytes)
return absl::nullopt;
base::StringPiece str(reinterpret_cast<const char*>(bytes->data()),
bytes->size());
if (!base::IsStringUTF8(str))
return absl::nullopt;
return str;
}
absl::optional<uint64_t> InputReader::ReadCBORHeader(CBORType expected_type) {
auto pair = ReadTypeAndArgument();
if (!pair || pair->first != expected_type)
return absl::nullopt;
return pair->second;
}
// https://datatracker.ietf.org/doc/html/rfc8949.html#section-3
absl::optional<std::pair<CBORType, uint64_t>>
InputReader::ReadTypeAndArgument() {
absl::optional<uint8_t> first_byte = ReadByte();
if (!first_byte)
return absl::nullopt;
CBORType type = static_cast<CBORType>((*first_byte & 0xE0) / 0x20);
uint8_t b = *first_byte & 0x1F;
if (b <= 23)
return std::make_pair(type, b);
if (b == 24) {
auto content = ReadByte();
if (!content || *content < 24)
return absl::nullopt;
return std::make_pair(type, *content);
}
if (b == 25) {
uint16_t content;
if (!ReadBigEndian(&content) || content >> 8 == 0)
return absl::nullopt;
return std::make_pair(type, content);
}
if (b == 26) {
uint32_t content;
if (!ReadBigEndian(&content) || content >> 16 == 0)
return absl::nullopt;
return std::make_pair(type, content);
}
if (b == 27) {
uint64_t content;
if (!ReadBigEndian(&content) || content >> 32 == 0)
return absl::nullopt;
return std::make_pair(type, content);
}
return absl::nullopt;
}
void InputReader::Advance(size_t n) {
DCHECK_LE(n, buf_.size());
buf_ = buf_.subspan(n);
current_offset_ += n;
}
} // namespace web_package
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