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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef PROFILEJSONWRITER_H
#define PROFILEJSONWRITER_H
#include <ostream>
#include <string>
#include <string.h>
#include "mozilla/JSONWriter.h"
#include "mozilla/UniquePtr.h"
class SpliceableChunkedJSONWriter;
// On average, profile JSONs are large enough such that we want to avoid
// reallocating its buffer when expanding. Additionally, the contents of the
// profile are not accessed until the profile is entirely written. For these
// reasons we use a chunked writer that keeps an array of chunks, which is
// concatenated together after writing is finished.
class ChunkedJSONWriteFunc : public mozilla::JSONWriteFunc
{
public:
friend class SpliceableJSONWriter;
ChunkedJSONWriteFunc() {
AllocChunk(kChunkSize);
}
bool IsEmpty() const {
MOZ_ASSERT_IF(!mChunkPtr, !mChunkEnd &&
mChunkList.length() == 0 &&
mChunkLengths.length() == 0);
return !mChunkPtr;
}
void Write(const char* aStr) override;
mozilla::UniquePtr<char[]> CopyData() const;
void Take(ChunkedJSONWriteFunc&& aOther);
private:
void AllocChunk(size_t aChunkSize);
static const size_t kChunkSize = 4096 * 512;
// Pointer for writing inside the current chunk.
//
// The current chunk is always at the back of mChunkList, i.e.,
// mChunkList.back() <= mChunkPtr <= mChunkEnd.
char* mChunkPtr;
// Pointer to the end of the current chunk.
//
// The current chunk is always at the back of mChunkList, i.e.,
// mChunkEnd >= mChunkList.back() + mChunkLengths.back().
char* mChunkEnd;
// List of chunks and their lengths.
//
// For all i, the length of the string in mChunkList[i] is
// mChunkLengths[i].
mozilla::Vector<mozilla::UniquePtr<char[]>> mChunkList;
mozilla::Vector<size_t> mChunkLengths;
};
struct OStreamJSONWriteFunc : public mozilla::JSONWriteFunc
{
explicit OStreamJSONWriteFunc(std::ostream& aStream)
: mStream(aStream)
{ }
void Write(const char* aStr) override {
mStream << aStr;
}
std::ostream& mStream;
};
class SpliceableJSONWriter : public mozilla::JSONWriter
{
public:
explicit SpliceableJSONWriter(mozilla::UniquePtr<mozilla::JSONWriteFunc> aWriter)
: JSONWriter(mozilla::Move(aWriter))
{ }
void StartBareList(CollectionStyle aStyle = SingleLineStyle) {
StartCollection(nullptr, "", aStyle);
}
void EndBareList() {
EndCollection("");
}
void NullElements(uint32_t aCount) {
for (uint32_t i = 0; i < aCount; i++) {
NullElement();
}
}
void Splice(const ChunkedJSONWriteFunc* aFunc);
void Splice(const char* aStr);
// Takes the chunks from aFunc and write them. If move is not possible
// (e.g., using OStreamJSONWriteFunc), aFunc's chunks are copied and its
// storage cleared.
virtual void TakeAndSplice(ChunkedJSONWriteFunc* aFunc);
};
class SpliceableChunkedJSONWriter : public SpliceableJSONWriter
{
public:
explicit SpliceableChunkedJSONWriter()
: SpliceableJSONWriter(mozilla::MakeUnique<ChunkedJSONWriteFunc>())
{ }
ChunkedJSONWriteFunc* WriteFunc() const {
return static_cast<ChunkedJSONWriteFunc*>(JSONWriter::WriteFunc());
}
// Adopts the chunks from aFunc without copying.
virtual void TakeAndSplice(ChunkedJSONWriteFunc* aFunc) override;
};
#endif // PROFILEJSONWRITER_H
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