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/* Like std::ofstream but without being incredibly slow. Backed by a raw fd.
* Does not support many data types. Currently, it's targeted at writing ARPA
* files quickly.
*/
#ifndef UTIL_FAKE_OFSTREAM_H
#define UTIL_FAKE_OFSTREAM_H
#include "util/double-conversion/double-conversion.h"
#include "util/double-conversion/utils.h"
#include "util/file.hh"
#include "util/scoped.hh"
#include "util/string_piece.hh"
#define BOOST_LEXICAL_CAST_ASSUME_C_LOCALE
#include <boost/lexical_cast.hpp>
namespace util {
class FakeOFStream {
public:
static const std::size_t kOutBuf = 1048576;
// Does not take ownership of out.
// Allows default constructor, but must call SetFD.
explicit FakeOFStream(int out = -1)
: buf_(util::MallocOrThrow(kOutBuf)),
builder_(static_cast<char*>(buf_.get()), kOutBuf),
// Mostly the default but with inf instead. And no flags.
convert_(double_conversion::DoubleToStringConverter::NO_FLAGS, "inf", "NaN", 'e', -6, 21, 6, 0),
fd_(out) {}
~FakeOFStream() {
if (buf_.get()) Flush();
}
void SetFD(int to) {
if (builder_.position()) Flush();
fd_ = to;
}
FakeOFStream &operator<<(float value) {
// Odd, but this is the largest number found in the comments.
EnsureRemaining(double_conversion::DoubleToStringConverter::kMaxPrecisionDigits + 8);
convert_.ToShortestSingle(value, &builder_);
return *this;
}
FakeOFStream &operator<<(double value) {
EnsureRemaining(double_conversion::DoubleToStringConverter::kMaxPrecisionDigits + 8);
convert_.ToShortest(value, &builder_);
return *this;
}
FakeOFStream &operator<<(StringPiece str) {
if (str.size() > kOutBuf) {
Flush();
util::WriteOrThrow(fd_, str.data(), str.size());
} else {
EnsureRemaining(str.size());
builder_.AddSubstring(str.data(), str.size());
}
return *this;
}
// Inefficient! TODO: more efficient implementation
FakeOFStream &operator<<(unsigned value) {
return *this << boost::lexical_cast<std::string>(value);
}
FakeOFStream &operator<<(char c) {
EnsureRemaining(1);
builder_.AddCharacter(c);
return *this;
}
// Note this does not sync.
void Flush() {
util::WriteOrThrow(fd_, buf_.get(), builder_.position());
builder_.Reset();
}
// Not necessary, but does assure the data is cleared.
void Finish() {
Flush();
// It will segfault trying to null terminate otherwise.
builder_.Finalize();
buf_.reset();
util::FSyncOrThrow(fd_);
}
private:
void EnsureRemaining(std::size_t amount) {
if (static_cast<std::size_t>(builder_.size() - builder_.position()) <= amount) {
Flush();
}
}
util::scoped_malloc buf_;
double_conversion::StringBuilder builder_;
double_conversion::DoubleToStringConverter convert_;
int fd_;
};
} // namespace
#endif
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