Reranko05 commented on PR #50568:
URL: https://github.com/apache/arrow/pull/50568#issuecomment-5087279280
@kou Sure
`json_writer_internal.h`
```cpp
#pragma once
#include <cstdint>
#include <sstream>
#include <string>
#include <string_view>
#include "arrow/util/visibility.h"
namespace arrow::json {
class ARROW_EXPORT JsonWriter {
public:
JsonWriter() = default;
void StartObject();
void EndObject();
void StartArray();
void EndArray();
void Key(std::string_view key);
void String(std::string_view value);
void RawValue(std::string_view value);
void Bool(bool value);
void Int(int32_t value);
void Int64(int64_t value);
void Uint(uint32_t value);
void Uint64(uint64_t value);
void Double(double value);
void Null();
std::string_view GetString() const;
void Clear();
private:
void MaybeComma();
void WriteQuotedString(std::string_view value);
std::ostringstream output_;
mutable std::string output_cache_;
bool needs_comma_ = false;
};
} // namespace arrow::json
```
`json_writer_internal.cc`
```cpp
#include "arrow/json/json_writer_internal.h"
namespace arrow::json {
void JsonWriter::StartObject() {
MaybeComma();
output_ << '{';
needs_comma_ = false;
}
void JsonWriter::EndObject() {
output_ << '}';
needs_comma_ = true;
}
void JsonWriter::StartArray() {
MaybeComma();
output_ << '[';
needs_comma_ = false;
}
void JsonWriter::EndArray() {
output_ << ']';
needs_comma_ = true;
}
void JsonWriter::Key(std::string_view key) {
MaybeComma();
WriteQuotedString(key);
output_ << ':';
needs_comma_ = false;
}
void JsonWriter::String(std::string_view value) {
MaybeComma();
WriteQuotedString(value);
needs_comma_ = true;
}
void JsonWriter::RawValue(std::string_view value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Bool(bool value) {
MaybeComma();
output_ << (value ? "true" : "false");
needs_comma_ = true;
}
void JsonWriter::Int(int32_t value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Int64(int64_t value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Uint(uint32_t value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Uint64(uint64_t value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Double(double value) {
MaybeComma();
output_ << value;
needs_comma_ = true;
}
void JsonWriter::Null() {
MaybeComma();
output_ << "null";
needs_comma_ = true;
}
std::string_view JsonWriter::GetString() const {
output_cache_ = output_.str();
return output_cache_;
}
void JsonWriter::Clear() {
output_.str("");
output_.clear();
output_cache_.clear();
needs_comma_ = false;
}
void JsonWriter::MaybeComma() {
if (needs_comma_) {
output_ << ',';
}
}
void JsonWriter::WriteQuotedString(std::string_view value) {
output_ << '"';
for (char c : value) {
switch (c) {
case '"':
output_ << "\\\"";
break;
case '\\':
output_ << "\\\\";
break;
case '\b':
output_ << "\\b";
break;
case '\f':
output_ << "\\f";
break;
case '\n':
output_ << "\\n";
break;
case '\r':
output_ << "\\r";
break;
case '\t':
output_ << "\\t";
break;
default:
output_ << c;
break;
}
}
output_ << '"';
}
} // namespace arrow::json
```
Add temporary benchmark in `json_writer_internal_test.cc`
```cpp
#include <chrono>
#include <iostream>
```
```cpp
TEST(JsonWriter, BenchmarkSerialization) {
JsonWriter writer;
constexpr int kIterations = 1000000;
auto start = std::chrono::steady_clock::now();
for (int i = 0; i < kIterations; ++i) {
writer.Clear();
writer.StartObject();
writer.Key("id");
writer.Int(i);
writer.Key("name");
writer.String("Apache Arrow");
writer.Key("value");
writer.Double(3.1415926535);
writer.Key("valid");
writer.Bool(true);
writer.EndObject();
auto s = writer.GetString();
(void)s;
}
auto end = std::chrono::steady_clock::now();
auto ms =
std::chrono::duration_cast<std::chrono::milliseconds>(end - start)
.count();
std::cout << "Time: " << ms << " ms\n";
}
```
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