rocksdb/util/file_util.cc

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#include <string>
#include <algorithm>
#include "util/file_util.h"
#include "rocksdb/env.h"
#include "db/filename.h"
#include "util/file_reader_writer.h"
namespace rocksdb {
// Utility function to copy a file up to a specified length
Status CopyFile(Env* env, const std::string& source,
const std::string& destination, uint64_t size) {
const EnvOptions soptions;
Status s;
unique_ptr<SequentialFileReader> src_reader;
unique_ptr<WritableFileWriter> dest_writer;
{
unique_ptr<SequentialFile> srcfile;
s = env->NewSequentialFile(source, &srcfile, soptions);
unique_ptr<WritableFile> destfile;
if (s.ok()) {
s = env->NewWritableFile(destination, &destfile, soptions);
} else {
return s;
}
if (size == 0) {
// default argument means copy everything
if (s.ok()) {
s = env->GetFileSize(source, &size);
} else {
return s;
}
}
src_reader.reset(new SequentialFileReader(std::move(srcfile)));
dest_writer.reset(new WritableFileWriter(std::move(destfile), soptions));
}
char buffer[4096];
Slice slice;
while (size > 0) {
uint64_t bytes_to_read =
std::min(static_cast<uint64_t>(sizeof(buffer)), size);
if (s.ok()) {
s = src_reader->Read(bytes_to_read, &slice, buffer);
}
if (s.ok()) {
if (slice.size() == 0) {
return Status::Corruption("file too small");
}
s = dest_writer->Append(slice);
}
if (!s.ok()) {
return s;
}
size -= slice.size();
}
return Status::OK();
}
} // namespace rocksdb