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Parser.js
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Parser.js
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var MAX_PACKET_LENGTH = Math.pow(2, 24) - 1;
var MUL_32BIT = Math.pow(2, 32);
var PacketHeader = require('./PacketHeader');
var BigNumber = require('bignumber.js');
module.exports = Parser;
function Parser(options) {
options = options || {};
this._supportBigNumbers = options.config && options.config.supportBigNumbers;
this._buffer = new Buffer(0);
this._longPacketBuffers = [];
this._offset = 0;
this._packetEnd = null;
this._packetHeader = null;
this._packetOffset = null;
this._onError = options.onError || function(err) { throw err; };
this._onPacket = options.onPacket || function() {};
this._nextPacketNumber = 0;
this._encoding = 'utf-8';
this._paused = false;
}
Parser.prototype.write = function(buffer) {
this.append(buffer);
while (true) {
if (this._paused) {
return;
}
if (!this._packetHeader) {
if (this._bytesRemaining() < 4) {
break;
}
this._packetHeader = new PacketHeader(
this.parseUnsignedNumber(3),
this.parseUnsignedNumber(1)
);
if (this._packetHeader.number !== this._nextPacketNumber) {
var err = new Error(
'Packets out of order. Got: ' + this._packetHeader.number + ' ' +
'Expected: ' + this._nextPacketNumber
);
err.code = 'PROTOCOL_PACKETS_OUT_OF_ORDER';
err.fatal = true;
this._onError(err);
}
this.incrementPacketNumber();
}
if (this._bytesRemaining() < this._packetHeader.length) {
break;
}
this._packetEnd = this._offset + this._packetHeader.length;
this._packetOffset = this._offset;
if (this._packetHeader.length === MAX_PACKET_LENGTH) {
this._longPacketBuffers.push(this._buffer.slice(this._packetOffset, this._packetEnd));
this._advanceToNextPacket();
continue;
}
this._combineLongPacketBuffers();
// Try...finally to ensure exception safety. Unfortunately this is costing
// us up to ~10% performance in some benchmarks.
var hadException = true;
try {
this._onPacket(this._packetHeader);
hadException = false;
} catch (err) {
if (typeof err.code !== 'string' || err.code.substr(0, 7) !== 'PARSER_') {
// Rethrow unknown errors
throw err;
}
// Pass down parser errors
this._onError(err);
hadException = false;
} finally {
this._advanceToNextPacket();
// If we had an exception, the parser while loop will be broken out
// of after the finally block. So we need to make sure to re-enter it
// to continue parsing any bytes that may already have been received.
if (hadException) {
process.nextTick(this.write.bind(this));
}
}
}
};
Parser.prototype.append = function append(chunk) {
if (!chunk || chunk.length === 0) {
return;
}
var buffer = chunk;
var sliceEnd = this._buffer.length;
var sliceStart = this._packetOffset === null
? this._offset
: this._packetOffset;
var sliceLength = sliceEnd - sliceStart;
if (sliceLength !== 0) {
// Create a new Buffer
buffer = new Buffer(sliceLength + chunk.length);
// Copy data
this._buffer.copy(buffer, 0, sliceStart, sliceEnd);
chunk.copy(buffer, sliceLength);
}
// Adjust data-tracking pointers
this._buffer = buffer;
this._offset = this._offset - sliceStart;
this._packetEnd = this._packetEnd !== null
? this._packetEnd - sliceStart
: null;
this._packetOffset = this._packetOffset !== null
? this._packetOffset - sliceStart
: null;
};
Parser.prototype.pause = function() {
this._paused = true;
};
Parser.prototype.resume = function() {
this._paused = false;
// nextTick() to avoid entering write() multiple times within the same stack
// which would cause problems as write manipulates the state of the object.
process.nextTick(this.write.bind(this));
};
Parser.prototype.peak = function() {
return this._buffer[this._offset];
};
Parser.prototype.parseUnsignedNumber = function(bytes) {
if (bytes === 1) {
return this._buffer[this._offset++];
}
var buffer = this._buffer;
var offset = this._offset + bytes - 1;
var value = 0;
if (bytes > 4) {
var err = new Error('parseUnsignedNumber: Supports only up to 4 bytes');
err.offset = (this._offset - this._packetOffset - 1);
err.code = 'PARSER_UNSIGNED_TOO_LONG';
throw err;
}
while (offset >= this._offset) {
value = ((value << 8) | buffer[offset]) >>> 0;
offset--;
}
this._offset += bytes;
return value;
};
Parser.prototype.parseLengthCodedString = function() {
var length = this.parseLengthCodedNumber();
if (length === null) {
return null;
}
return this.parseString(length);
};
Parser.prototype.parseLengthCodedBuffer = function() {
var length = this.parseLengthCodedNumber();
if (length === null) {
return null;
}
return this.parseBuffer(length);
};
Parser.prototype.parseLengthCodedNumber = function parseLengthCodedNumber() {
if (this._offset >= this._buffer.length) {
var err = new Error('Parser: read past end');
err.offset = (this._offset - this._packetOffset);
err.code = 'PARSER_READ_PAST_END';
throw err;
}
var bits = this._buffer[this._offset++];
if (bits <= 250) {
return bits;
}
switch (bits) {
case 251:
return null;
case 252:
return this.parseUnsignedNumber(2);
case 253:
return this.parseUnsignedNumber(3);
case 254:
break;
default:
var err = new Error('Unexpected first byte' + (bits ? ': 0x' + bits.toString(16) : ''));
err.offset = (this._offset - this._packetOffset - 1);
err.code = 'PARSER_BAD_LENGTH_BYTE';
throw err;
}
var low = this.parseUnsignedNumber(4);
var high = this.parseUnsignedNumber(4);
var value;
if (high >>> 21) {
value = (new BigNumber(low)).plus((new BigNumber(MUL_32BIT)).times(high)).toString();
if (this._supportBigNumbers) {
return value;
}
var err = new Error(
'parseLengthCodedNumber: JS precision range exceeded, ' +
'number is >= 53 bit: "' + value + '"'
);
err.offset = (this._offset - this._packetOffset - 8);
err.code = 'PARSER_JS_PRECISION_RANGE_EXCEEDED';
throw err;
}
value = low + (MUL_32BIT * high);
return value;
};
Parser.prototype.parseFiller = function(length) {
return this.parseBuffer(length);
};
Parser.prototype.parseNullTerminatedBuffer = function() {
var end = this._nullByteOffset();
var value = this._buffer.slice(this._offset, end);
this._offset = end + 1;
return value;
};
Parser.prototype.parseNullTerminatedString = function() {
var end = this._nullByteOffset();
var value = this._buffer.toString(this._encoding, this._offset, end);
this._offset = end + 1;
return value;
};
Parser.prototype._nullByteOffset = function() {
var offset = this._offset;
while (this._buffer[offset] !== 0x00) {
offset++;
if (offset >= this._buffer.length) {
var err = new Error('Offset of null terminated string not found.');
err.offset = (this._offset - this._packetOffset);
err.code = 'PARSER_MISSING_NULL_BYTE';
throw err;
}
}
return offset;
};
Parser.prototype.parsePacketTerminatedString = function() {
var length = this._packetEnd - this._offset;
return this.parseString(length);
};
Parser.prototype.parseBuffer = function(length) {
var response = new Buffer(length);
this._buffer.copy(response, 0, this._offset, this._offset + length);
this._offset += length;
return response;
};
Parser.prototype.parseString = function(length) {
var offset = this._offset;
var end = offset + length;
var value = this._buffer.toString(this._encoding, offset, end);
this._offset = end;
return value;
};
Parser.prototype.parseGeometryValue = function() {
var buffer = this.parseLengthCodedBuffer();
var offset = 4;
if (buffer === null || !buffer.length) {
return null;
}
function parseGeometry() {
var result = null;
var byteOrder = buffer.readUInt8(offset); offset += 1;
var wkbType = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
switch(wkbType) {
case 1: // WKBPoint
var x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
var y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
result = {x: x, y: y};
break;
case 2: // WKBLineString
var numPoints = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
result = [];
for(var i=numPoints;i>0;i--) {
var x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
var y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
result.push({x: x, y: y});
}
break;
case 3: // WKBPolygon
var numRings = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
result = [];
for(var i=numRings;i>0;i--) {
var numPoints = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
var line = [];
for(var j=numPoints;j>0;j--) {
var x = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
var y = byteOrder? buffer.readDoubleLE(offset) : buffer.readDoubleBE(offset); offset += 8;
line.push({x: x, y: y});
}
result.push(line);
}
break;
case 4: // WKBMultiPoint
case 5: // WKBMultiLineString
case 6: // WKBMultiPolygon
case 7: // WKBGeometryCollection
var num = byteOrder? buffer.readUInt32LE(offset) : buffer.readUInt32BE(offset); offset += 4;
var result = [];
for(var i=num;i>0;i--) {
result.push(parseGeometry());
}
break;
}
return result;
}
return parseGeometry();
};
Parser.prototype.reachedPacketEnd = function() {
return this._offset === this._packetEnd;
};
Parser.prototype._bytesRemaining = function() {
return this._buffer.length - this._offset;
};
Parser.prototype.incrementPacketNumber = function() {
var currentPacketNumber = this._nextPacketNumber;
this._nextPacketNumber = (this._nextPacketNumber + 1) % 256;
return currentPacketNumber;
};
Parser.prototype.resetPacketNumber = function() {
this._nextPacketNumber = 0;
};
Parser.prototype.packetLength = function() {
return this._longPacketBuffers.reduce(function(length, buffer) {
return length + buffer.length;
}, this._packetHeader.length);
};
Parser.prototype._combineLongPacketBuffers = function() {
if (!this._longPacketBuffers.length) {
return;
}
var trailingPacketBytes = this._buffer.length - this._packetEnd;
var length = this._longPacketBuffers.reduce(function(length, buffer) {
return length + buffer.length;
}, this._bytesRemaining());
var combinedBuffer = new Buffer(length);
var offset = this._longPacketBuffers.reduce(function(offset, buffer) {
buffer.copy(combinedBuffer, offset);
return offset + buffer.length;
}, 0);
this._buffer.copy(combinedBuffer, offset, this._offset);
this._buffer = combinedBuffer;
this._longPacketBuffers = [];
this._offset = 0;
this._packetEnd = this._buffer.length - trailingPacketBytes;
this._packetOffset = 0;
};
Parser.prototype._advanceToNextPacket = function() {
this._offset = this._packetEnd;
this._packetHeader = null;
this._packetEnd = null;
this._packetOffset = null;
};