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// Copyright 2017 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.
#ifndef COMPONENTS_ZUCCHINI_PATCH_UTILS_H_
#define COMPONENTS_ZUCCHINI_PATCH_UTILS_H_
#include <stdint.h>
#include <iterator>
#include <type_traits>
#include "components/zucchini/image_utils.h"
#include "components/zucchini/version_info.h"
namespace zucchini {
// A Zucchini 'ensemble' patch is the concatenation of a patch header with a
// list of patch 'elements', each containing data for patching individual
// elements.
// Supported by MSVC, g++, and clang++. Ensures no gaps in packing.
#pragma pack(push, 1)
// Header for a Zucchini patch, found at the beginning of an ensemble patch.
struct PatchHeader {
// Magic signature at the beginning of a Zucchini patch file.
enum : uint32_t { kMagic = 'Z' | ('u' << 8) | ('c' << 16) | ('c' << 24) };
uint32_t magic = 0;
uint16_t major_version = kInvalidVersion;
uint16_t minor_version = kInvalidVersion;
uint32_t old_size = 0;
uint32_t old_crc = 0;
uint32_t new_size = 0;
uint32_t new_crc = 0;
};
// Sanity check.
static_assert(sizeof(PatchHeader) == 24, "PatchHeader must be 24 bytes");
// Header for a patch element, found at the beginning of every patch element.
struct PatchElementHeader {
uint32_t old_offset;
uint32_t old_length;
uint32_t new_offset;
uint32_t new_length;
uint32_t exe_type; // ExecutableType.
uint16_t version = kInvalidVersion;
};
// Sanity check.
static_assert(sizeof(PatchElementHeader) == 22,
"PatchElementHeader must be 22 bytes");
#pragma pack(pop)
// Descibes a raw FIX operation.
struct RawDeltaUnit {
offset_t copy_offset; // Offset in copy regions.
int8_t diff; // Bytewise difference.
};
// A Zucchini patch contains data streams encoded using varint format to reduce
// uncompressed size.
// Writes |value| as a varint in |dst| and returns an iterator pointing beyond
// the written region. |dst| is assumed to hold enough space. Typically, this
// will write to a vector using back insertion, e.g.:
// EncodeVarUInt(value, std::back_inserter(vector));
template <class T, class It>
It EncodeVarUInt(T value, It dst) {
static_assert(std::is_unsigned<T>::value, "Value type must be unsigned");
while (value >= 0x80) {
*dst++ = static_cast<uint8_t>(value) | 0x80;
value >>= 7;
}
*dst++ = static_cast<uint8_t>(value);
return dst;
}
// Same as EncodeVarUInt(), but for signed values.
template <class T, class It>
It EncodeVarInt(T value, It dst) {
static_assert(std::is_signed<T>::value, "Value type must be signed");
using unsigned_value_type = typename std::make_unsigned<T>::type;
if (value < 0)
return EncodeVarUInt((unsigned_value_type(~value) << 1) | 1, dst);
else
return EncodeVarUInt(unsigned_value_type(value) << 1, dst);
}
// Tries to read a varint unsigned integer from |[first, last)|. If
// succesful, writes result into |value| and returns the number of bytes
// read from |[first, last)|. Otherwise returns 0.
template <class T, class It>
typename std::iterator_traits<It>::difference_type DecodeVarUInt(It first,
It last,
T* value) {
static_assert(std::is_unsigned<T>::value, "Value type must be unsigned");
uint8_t sh = 0;
T val = 0;
for (auto it = first; it != last;) {
val |= T(*it & 0x7F) << sh;
if (*(it++) < 0x80) {
*value = val;
return it - first;
}
sh += 7;
if (sh >= sizeof(T) * 8) // Overflow!
return 0;
}
return 0;
}
// Same as DecodeVarUInt(), but for signed values.
template <class T, class It>
typename std::iterator_traits<It>::difference_type DecodeVarInt(It first,
It last,
T* value) {
static_assert(std::is_signed<T>::value, "Value type must be signed");
typename std::make_unsigned<T>::type tmp = 0;
auto res = DecodeVarUInt(first, last, &tmp);
if (res) {
if (tmp & 1)
*value = ~static_cast<T>(tmp >> 1);
else
*value = static_cast<T>(tmp >> 1);
}
return res;
}
} // namespace zucchini
#endif // COMPONENTS_ZUCCHINI_PATCH_UTILS_H_
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