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// Copyright 2008 Google Inc.
// Author: Lincoln Smith
//
// 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 <config.h>
#include "varint_bigendian.h"
#include <stdint.h> // int32_t, int64_t
#include <string.h> // memcpy
#include <string>
#include "logging.h"
#include "google/output_string.h"
namespace open_vcdiff {
template<> const int32_t VarintBE<int32_t>::kMaxVal = 0x7FFFFFFF;
template<> const int64_t VarintBE<int64_t>::kMaxVal = 0x7FFFFFFFFFFFFFFFULL;
// Reads a variable-length integer from **varint_ptr
// and returns it in a fixed-length representation. Increments
// *varint_ptr by the number of bytes read. Will not read
// past limit. Returns RESULT_ERROR if the value parsed
// does not fit in a non-negative signed integer, or if limit is NULL.
// Returns RESULT_END_OF_DATA if address_stream_end is reached
// before the whole integer can be decoded.
//
template <typename SignedIntegerType>
SignedIntegerType VarintBE<SignedIntegerType>::Parse(const char* limit,
const char** varint_ptr) {
if (!limit) {
return RESULT_ERROR;
}
SignedIntegerType result = 0;
for (const char* parse_ptr = *varint_ptr; parse_ptr < limit; ++parse_ptr) {
result += *parse_ptr & 0x7F;
if (!(*parse_ptr & 0x80)) {
*varint_ptr = parse_ptr + 1;
return result;
}
if (result > (kMaxVal >> 7)) {
// Shifting result by 7 bits would produce a number too large
// to be stored in a non-negative SignedIntegerType (an overflow.)
return RESULT_ERROR;
}
result = result << 7;
}
return RESULT_END_OF_DATA;
}
template <typename SignedIntegerType>
int VarintBE<SignedIntegerType>::EncodeInternal(SignedIntegerType v,
char* varint_buf) {
if (v < 0) {
LOG(DFATAL) << "Negative value " << v
<< " passed to VarintBE::EncodeInternal,"
" which requires non-negative argument" << LOG_ENDL;
return 0;
}
int length = 1;
char* buf_ptr = &varint_buf[kMaxBytes - 1];
*buf_ptr = static_cast<char>(v & 0x7F);
--buf_ptr;
v >>= 7;
while (v) {
*buf_ptr = static_cast<char>((v & 0x7F) | 0x80); // add continuation bit
--buf_ptr;
++length;
v >>= 7;
}
return length;
}
template <typename SignedIntegerType>
int VarintBE<SignedIntegerType>::Encode(SignedIntegerType v, char* ptr) {
char varint_buf[kMaxBytes];
const int length = EncodeInternal(v, varint_buf);
memcpy(ptr, &varint_buf[kMaxBytes - length], length);
return length;
}
template <typename SignedIntegerType>
void VarintBE<SignedIntegerType>::AppendToString(SignedIntegerType value,
string* s) {
char varint_buf[kMaxBytes];
const int length = EncodeInternal(value, varint_buf);
s->append(&varint_buf[kMaxBytes - length], length);
}
template <typename SignedIntegerType>
void VarintBE<SignedIntegerType>::AppendToOutputString(
SignedIntegerType value,
OutputStringInterface* output_string) {
char varint_buf[kMaxBytes];
const int length = EncodeInternal(value, varint_buf);
output_string->append(&varint_buf[kMaxBytes - length], length);
}
// Returns the encoding length of the specified value.
template <typename SignedIntegerType>
int VarintBE<SignedIntegerType>::Length(SignedIntegerType v) {
if (v < 0) {
LOG(DFATAL) << "Negative value " << v
<< " passed to VarintBE::Length,"
" which requires non-negative argument" << LOG_ENDL;
return 0;
}
int length = 0;
do {
v >>= 7;
++length;
} while (v);
return length;
}
template class VarintBE<int32_t>;
template class VarintBE<int64_t>;
} // namespace open_vcdiff
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