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bnoordhuisbnoordhuis
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buffer: optimize Buffer.prototype.write(s, 'hex')
Move the implementation to C++ land. This is similar to commit 3f65916 but this time for the write() function and the Buffer(s, 'hex') constructor. Speeds up the benchmark below about 24x (2.6s vs 1:02m). var s = 'f'; for (var i = 0; i < 26; ++i) s += s; // 64 MB Buffer(s, 'hex');
1 parent 916aeba commit cd42f56

3 files changed

Lines changed: 68 additions & 30 deletions

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‎lib/buffer.js‎

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Original file line numberDiff line numberDiff line change
@@ -74,36 +74,6 @@ SlowBuffer.prototype.toString = function(encoding, start, end) {
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};
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SlowBuffer.prototype.hexWrite = function(string, offset, length) {
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offset = +offset || 0;
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var remaining = this.length - offset;
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if (!length) {
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length = remaining;
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} else {
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length = +length;
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if (length > remaining) {
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length = remaining;
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}
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}
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// must be an even number of digits
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var strLen = string.length;
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if (strLen % 2) {
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throw new TypeError('Invalid hex string');
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}
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if (length > strLen / 2) {
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length = strLen / 2;
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}
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for (var i = 0; i < length; i++) {
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var byte = parseInt(string.substr(i * 2, 2), 16);
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if (isNaN(byte)) throw new TypeError('Invalid hex string');
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this[offset + i] = byte;
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}
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SlowBuffer._charsWritten = i * 2;
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return i;
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};
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SlowBuffer.prototype.write = function(string, offset, length, encoding) {
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// Support both (string, offset, length, encoding)
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// and the legacy (string, encoding, offset, length)

‎src/node_buffer.cc‎

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Original file line numberDiff line numberDiff line change
@@ -545,6 +545,72 @@ Handle<Value> Buffer::Ucs2Write(const Arguments &args) {
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}
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inline unsigned hex2bin(char c) {
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if (c >= '0' && c <= '9') return c - '0';
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if (c >= 'A' && c <= 'F') return 10 + (c - 'A');
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if (c >= 'a' && c <= 'f') return 10 + (c - 'a');
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return static_cast<unsigned>(-1);
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}
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Handle<Value> Buffer::HexWrite(const Arguments& args) {
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HandleScope scope;
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Buffer* parent = ObjectWrap::Unwrap<Buffer>(args.This());
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if (args[0]->IsString() == false) {
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return ThrowTypeError("Argument must be a string");
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}
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Local<String> s = args[0].As<String>();
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if (s->Length() % 2 != 0) {
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return ThrowTypeError("Invalid hex string");
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}
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uint32_t start = args[1]->Uint32Value();
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uint32_t size = args[2]->Uint32Value();
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uint32_t end = start + size;
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if (start >= parent->length_) {
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Local<Integer> val = Integer::New(0, node_isolate);
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constructor_template->GetFunction()->Set(chars_written_sym, val);
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return scope.Close(val);
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}
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if (end < start || end > parent->length_) { // Overflow + bounds check.
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end = parent->length_;
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size = parent->length_ - start;
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}
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if (size == 0) {
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Local<Integer> val = Integer::New(0, node_isolate);
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constructor_template->GetFunction()->Set(chars_written_sym, val);
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return scope.Close(val);
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}
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char* dst = parent->data_ + start;
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String::AsciiValue string(s);
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const char* src = *string;
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uint32_t max = string.length() / 2;
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if (max > size) {
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max = size;
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}
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for (uint32_t i = 0; i < max; ++i) {
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unsigned a = hex2bin(src[i * 2 + 0]);
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unsigned b = hex2bin(src[i * 2 + 1]);
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if (!~a || !~b) return ThrowTypeError("Invalid hex string");
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dst[i] = a * 16 + b;
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}
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constructor_template->GetFunction()->Set(chars_written_sym,
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Integer::New(max * 2, node_isolate));
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return scope.Close(Integer::New(max, node_isolate));
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}
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// var charsWritten = buffer.asciiWrite(string, offset);
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Handle<Value> Buffer::AsciiWrite(const Arguments &args) {
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HandleScope scope;
@@ -950,6 +1016,7 @@ void Buffer::Initialize(Handle<Object> target) {
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "binaryWrite", Buffer::BinaryWrite);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "base64Write", Buffer::Base64Write);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "ucs2Write", Buffer::Ucs2Write);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "hexWrite", Buffer::HexWrite);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "readFloatLE", Buffer::ReadFloatLE);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "readFloatBE", Buffer::ReadFloatBE);
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NODE_SET_PROTOTYPE_METHOD(constructor_template, "readDoubleLE", Buffer::ReadDoubleLE);

‎src/node_buffer.h‎

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Original file line numberDiff line numberDiff line change
@@ -124,6 +124,7 @@ class NODE_EXTERN Buffer: public ObjectWrap {
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static v8::Handle<v8::Value> AsciiWrite(const v8::Arguments &args);
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static v8::Handle<v8::Value> Utf8Write(const v8::Arguments &args);
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static v8::Handle<v8::Value> Ucs2Write(const v8::Arguments &args);
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static v8::Handle<v8::Value> HexWrite(const v8::Arguments &args);
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static v8::Handle<v8::Value> ReadFloatLE(const v8::Arguments &args);
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static v8::Handle<v8::Value> ReadFloatBE(const v8::Arguments &args);
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static v8::Handle<v8::Value> ReadDoubleLE(const v8::Arguments &args);

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