openpilot is an open source driver assistance system. openpilot performs the functions of Automated Lane Centering and Adaptive Cruise Control for over 200 supported car makes and models.
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#include "system/loggerd/zstd_writer.h"
#include <cassert>
#include "common/util.h"
// Constructor: Initializes compression stream and opens file
ZstdFileWriter::ZstdFileWriter(const std::string& filename, int compression_level) {
// Create the compression stream
cstream_ = ZSTD_createCStream();
assert(cstream_);
size_t initResult = ZSTD_initCStream(cstream_, compression_level);
assert(!ZSTD_isError(initResult));
input_cache_capacity_ = ZSTD_CStreamInSize();
input_cache_.reserve(input_cache_capacity_);
output_buffer_.resize(ZSTD_CStreamOutSize());
file_ = util::safe_fopen(filename.c_str(), "wb");
assert(file_ != nullptr);
}
// Destructor: Finalizes compression and closes file
ZstdFileWriter::~ZstdFileWriter() {
flushCache(true);
util::safe_fflush(file_);
int err = fclose(file_);
assert(err == 0);
ZSTD_freeCStream(cstream_);
}
// Compresses and writes data to file
void ZstdFileWriter::write(void* data, size_t size) {
// Add data to the input cache
input_cache_.insert(input_cache_.end(), (uint8_t*)data, (uint8_t*)data + size);
// If the cache is full, compress and write to the file
if (input_cache_.size() >= input_cache_capacity_) {
flushCache(false);
}
}
// Compress and flush the input cache to the file
void ZstdFileWriter::flushCache(bool last_chunk) {
ZSTD_inBuffer input = {input_cache_.data(), input_cache_.size(), 0};
ZSTD_EndDirective mode = !last_chunk ? ZSTD_e_continue : ZSTD_e_end;
int finished = 0;
do {
ZSTD_outBuffer output = {output_buffer_.data(), output_buffer_.size(), 0};
size_t remaining = ZSTD_compressStream2(cstream_, &output, &input, mode);
assert(!ZSTD_isError(remaining));
size_t written = util::safe_fwrite(output_buffer_.data(), 1, output.pos, file_);
assert(written == output.pos);
finished = last_chunk ? (remaining == 0) : (input.pos == input.size);
} while (!finished);
input_cache_.clear(); // Clear cache after compression
}