2015-09-29 18:58:02 +03:00
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/* Like std::ofstream but without being incredibly slow. Backed by a raw fd.
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* Supports most of the built-in types except for long double.
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*/
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#ifndef UTIL_FILE_STREAM_H
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#define UTIL_FILE_STREAM_H
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#include "util/fake_ostream.hh"
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#include "util/file.hh"
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#include "util/scoped.hh"
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#include <cassert>
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#include <cstring>
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#include <stdint.h>
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namespace util {
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class FileStream : public FakeOStream<FileStream> {
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public:
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FileStream(int out = -1, std::size_t buffer_size = 8192)
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: buf_(util::MallocOrThrow(std::max<std::size_t>(buffer_size, kToStringMaxBytes))),
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current_(static_cast<char*>(buf_.get())),
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end_(current_ + std::max<std::size_t>(buffer_size, kToStringMaxBytes)),
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fd_(out) {}
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~FileStream() {
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flush();
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}
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void SetFD(int to) {
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flush();
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fd_ = to;
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}
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FileStream &flush() {
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if (current_ != buf_.get()) {
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util::WriteOrThrow(fd_, buf_.get(), current_ - (char*)buf_.get());
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current_ = static_cast<char*>(buf_.get());
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}
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return *this;
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}
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// For writes of arbitrary size.
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FileStream &write(const void *data, std::size_t length) {
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if (UTIL_LIKELY(current_ + length <= end_)) {
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std::memcpy(current_, data, length);
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current_ += length;
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return *this;
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}
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flush();
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if (current_ + length <= end_) {
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std::memcpy(current_, data, length);
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current_ += length;
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} else {
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util::WriteOrThrow(fd_, data, length);
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}
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return *this;
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}
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FileStream &seekp(uint64_t to) {
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2016-01-22 00:31:25 +03:00
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flush();
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2015-09-29 18:58:02 +03:00
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util::SeekOrThrow(fd_, to);
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return *this;
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}
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protected:
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friend class FakeOStream<FileStream>;
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// For writes directly to buffer guaranteed to have amount < buffer size.
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char *Ensure(std::size_t amount) {
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if (UTIL_UNLIKELY(current_ + amount > end_)) {
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flush();
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assert(current_ + amount <= end_);
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}
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return current_;
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}
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void AdvanceTo(char *to) {
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current_ = to;
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assert(current_ <= end_);
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}
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private:
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util::scoped_malloc buf_;
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char *current_, *end_;
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int fd_;
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};
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} // namespace
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#endif
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