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/**
* Copyright (c) 2013, Ford Motor Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following
* disclaimer in the documentation and/or other materials provided with the
* distribution.
*
* Neither the name of the Ford Motor Company nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SRC_COMPONENTS_UTILS_INCLUDE_UTILS_BITSTREAM_H_
#define SRC_COMPONENTS_UTILS_INCLUDE_UTILS_BITSTREAM_H_
#include "stdint.h"
#include <climits>
#include <cstring>
#include <string>
#include <vector>
#include "utils/macro.h"
namespace utils {
// Big endian input bitstream class
// Tool to read and parse incoming data in a recursive way
// Has sublte similarity to standard stream classes in a way
// it handles stream parsing errors:
// If error while parsing stream occurs, whole stream is marked as
// "bad" and all subsequent parsing is stopped.
class BitStream {
public:
BitStream(uint8_t* bytes, size_t bytes_count);
~BitStream();
// Mark stream as badly-formed.
// Should be called by Extract* family of procedures if they decide
// that stream is invalid
void MarkBad() { bad_ = true; }
// Predicates to check whether there were errors while parsing
// Stream is good when it is created
bool IsGood() { return !bad_; }
bool IsBad() { return bad_; }
operator bool() { return IsGood(); }
private:
// These two functions are used for internal stream checks only
// Stream parser procedures must not define their logic depending on
// amount of data left in particular bit stream
// Amount of full bytes left in stream
size_t FullBytesLeft();
// Amount of total bits left in stream
size_t BitsLeft();
// These stream extractors are helpers for direct friend extractors
// of this class.
// Extract single value, amount of bits read from stream depends on T size
// If there is not enough data in the stream, stream is marked bad
template<typename T>
void Extract(T& val);
// Read single value, amount of bits read from stream is signaled by |bits|
// parameter. T must be wide enough to hold this amount of bits.
// If there is not enough data in the stream, stream is marked bad
template<typename T>
void ExtractBits(T& val, size_t bits);
// Extract |length| bytes from the stream. Stream read position
// must be byte aligned when it is called, stream is marked bad otherwise.
// If there is not enough data in the stream, it is marked bad.
void ExtractBytes(void* buffer, size_t length);
private:
const uint8_t* bytes_;
const size_t bytes_count_;
size_t byte_offset_;
size_t bit_offset_;
bool bad_;
private:
friend void Extract(BitStream*, uint8_t*);
friend void Extract(BitStream*, uint8_t*, size_t);
friend void Extract(BitStream*, uint32_t*);
friend void Extract(BitStream*, uint32_t*, size_t);
friend void Extract(BitStream*, std::string*, size_t);
friend void Extract(BitStream*, std::vector<uint8_t>*, size_t);
};
// Extract single byte from stream
// If there is not enough data in the stream it is marked bad.
void Extract(BitStream* bs, uint8_t* val);
// Extract defined amount of |bits| from stream and store them
// in a byte size |val|. Hence |bits| must be less than 8.
void Extract(BitStream* bs, uint8_t* val, size_t bits);
// Extract 32 bit word from stream.
// If there is not enough data in the stream it is marked bad.
void Extract(BitStream* bs, uint32_t* val);
// Extract up to 32 |bits| from stream and store them in a |val|
// If there is not enough data in the stream it is marked bad.
void Extract(BitStream* bs, uint32_t* val, size_t bits);
// Extract |length| bytes from stream and store them to the
// string |str|. If stream is too short it is marked bad.
// String must not contain zero bytes.
void Extract(BitStream* bs, std::string* str, size_t length);
// Extract |length| bytes from stream and store them to the
// vector |data|. If stream is too short it is marked bad.
void Extract(BitStream* bs, std::vector<uint8_t>* data, size_t length);
// Template member definitions
template<typename T>
void BitStream::Extract(T& val) {
// Slow but simple implementation
// It's a space for bit stream reading optimization
ExtractBits(val, sizeof(val) * CHAR_BIT);
}
template<typename T>
void BitStream::ExtractBits(T& val, size_t bits) {
DCHECK(sizeof(val) * CHAR_BIT >= bits);
if (IsGood()) {
if (bits > BitsLeft()) {
MarkBad();
return;
}
val = T(); // Clear value
for (size_t i = 0; i < bits; ++i) {
size_t next_bit_number = CHAR_BIT - 1 - bit_offset_;
uint8_t nextbit = (bytes_[byte_offset_] >> next_bit_number) & 1;
val = (val << 1) | nextbit;
++bit_offset_;
if (bit_offset_ == CHAR_BIT) {
++byte_offset_;
bit_offset_ = 0;
}
}
}
}
} // namespace utils
#endif // SRC_COMPONENTS_UTILS_INCLUDE_UTILS_BITSTREAM_H_
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