101 lines
2.6 KiB
C++
101 lines
2.6 KiB
C++
|
/*
|
||
|
|
* Copyright (C) 2018 The Android Open Source Project
|
||
|
|
*
|
||
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
||
|
|
* you may not use this file except in compliance with the License.
|
||
|
|
* You may obtain a copy of the License at
|
||
|
|
*
|
||
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
*
|
||
|
|
* Unless required by applicable law or agreed to in writing, software
|
||
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
||
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
* See the License for the specific language governing permissions and
|
||
|
|
* limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "leb128.h"
|
||
|
|
|
||
|
|
#include <inttypes.h>
|
||
|
|
#include <limits.h>
|
||
|
|
|
||
|
|
#include <berberis/base/checks.h>
|
||
|
|
|
||
|
|
namespace nogrod {
|
||
|
|
|
||
|
|
Leb128Decoder::Leb128Decoder(const uint8_t* buffer, size_t size) : buffer_(buffer), size_(size) {}
|
||
|
|
|
||
|
|
// Returns number of bytes it took do decode the value, 0 if decode has failed.
|
||
|
|
size_t Leb128Decoder::Decode(size_t offset, uint64_t* result) const {
|
||
|
|
return DecodeLeb128(buffer_ + offset, size_ - offset, result);
|
||
|
|
}
|
||
|
|
|
||
|
|
size_t DecodeLeb128(const uint8_t* buf, uint64_t buf_size, uint64_t* result) {
|
||
|
|
uint64_t value = 0;
|
||
|
|
size_t shift = 0;
|
||
|
|
size_t size = 0;
|
||
|
|
|
||
|
|
uint8_t byte;
|
||
|
|
|
||
|
|
do {
|
||
|
|
if (size >= buf_size) {
|
||
|
|
FATAL("leb128: ran out of bounds while reading value at offset=%zd (buf_size=%" PRId64 ")",
|
||
|
|
size,
|
||
|
|
buf_size);
|
||
|
|
}
|
||
|
|
|
||
|
|
if (shift >= CHAR_BIT * sizeof(uint64_t)) {
|
||
|
|
FATAL("leb128: the value at offset %zd is too big (does not fit into uint64_t), shift=%zd",
|
||
|
|
size,
|
||
|
|
shift);
|
||
|
|
}
|
||
|
|
|
||
|
|
byte = buf[size++];
|
||
|
|
|
||
|
|
value += static_cast<uint64_t>(byte & 0x7f) << shift;
|
||
|
|
|
||
|
|
shift += 7;
|
||
|
|
} while ((byte & 0x80) != 0);
|
||
|
|
|
||
|
|
*result = value;
|
||
|
|
return size;
|
||
|
|
}
|
||
|
|
|
||
|
|
size_t DecodeSleb128(const uint8_t* buf, uint64_t buf_size, int64_t* result) {
|
||
|
|
uint64_t value = 0;
|
||
|
|
size_t shift = 0;
|
||
|
|
size_t size = 0;
|
||
|
|
|
||
|
|
uint8_t byte;
|
||
|
|
|
||
|
|
do {
|
||
|
|
if (size >= buf_size) {
|
||
|
|
FATAL("sleb128: ran out of bounds while reading value at offset=%zd (buf_size=%" PRId64 ")",
|
||
|
|
size,
|
||
|
|
buf_size);
|
||
|
|
}
|
||
|
|
|
||
|
|
if (shift >= CHAR_BIT * sizeof(uint64_t)) {
|
||
|
|
FATAL("sleb128: the value at offset %zd is too big (does not fit into uint64_t), shift=%zd",
|
||
|
|
size,
|
||
|
|
shift);
|
||
|
|
}
|
||
|
|
|
||
|
|
byte = buf[size++];
|
||
|
|
|
||
|
|
value += static_cast<uint64_t>(byte & 0x7f) << shift;
|
||
|
|
|
||
|
|
shift += 7;
|
||
|
|
} while ((byte & 0x80) != 0);
|
||
|
|
|
||
|
|
// sign extent is not applicable if shift is out of bounds of uint64_t
|
||
|
|
if (shift < (sizeof(uint64_t) * CHAR_BIT) && (byte & 0x40) != 0) {
|
||
|
|
value |= -(static_cast<uint64_t>(1) << shift);
|
||
|
|
}
|
||
|
|
|
||
|
|
memcpy(result, &value, sizeof(*result));
|
||
|
|
return size;
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace nogrod
|