first commit

build/node_modules/pngjs/lib/chunkstream.js

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+'use strict';
+
+
+var util = require('util');
+var Stream = require('stream');
+
+
+var ChunkStream = module.exports = function() {
+  Stream.call(this);
+
+  this._buffers = [];
+  this._buffered = 0;
+
+  this._reads = [];
+  this._paused = false;
+
+  this._encoding = 'utf8';
+  this.writable = true;
+};
+util.inherits(ChunkStream, Stream);
+
+
+ChunkStream.prototype.read = function(length, callback) {
+
+  this._reads.push({
+    length: Math.abs(length),  // if length < 0 then at most this length
+    allowLess: length < 0,
+    func: callback
+  });
+
+  process.nextTick(function() {
+    this._process();
+
+    // its paused and there is not enought data then ask for more
+    if (this._paused && this._reads.length > 0) {
+      this._paused = false;
+
+      this.emit('drain');
+    }
+  }.bind(this));
+};
+
+ChunkStream.prototype.write = function(data, encoding) {
+
+  if (!this.writable) {
+    this.emit('error', new Error('Stream not writable'));
+    return false;
+  }
+
+  var dataBuffer;
+  if (Buffer.isBuffer(data)) {
+    dataBuffer = data;
+  }
+  else {
+    dataBuffer = new Buffer(data, encoding || this._encoding);
+  }
+
+  this._buffers.push(dataBuffer);
+  this._buffered += dataBuffer.length;
+
+  this._process();
+
+  // ok if there are no more read requests
+  if (this._reads && this._reads.length === 0) {
+    this._paused = true;
+  }
+
+  return this.writable && !this._paused;
+};
+
+ChunkStream.prototype.end = function(data, encoding) {
+
+  if (data) {
+    this.write(data, encoding);
+  }
+
+  this.writable = false;
+
+  // already destroyed
+  if (!this._buffers) {
+    return;
+  }
+
+  // enqueue or handle end
+  if (this._buffers.length === 0) {
+    this._end();
+  }
+  else {
+    this._buffers.push(null);
+    this._process();
+  }
+};
+
+ChunkStream.prototype.destroySoon = ChunkStream.prototype.end;
+
+ChunkStream.prototype._end = function() {
+
+  if (this._reads.length > 0) {
+    this.emit('error',
+      new Error('There are some read requests waiting on finished stream')
+    );
+  }
+
+  this.destroy();
+};
+
+ChunkStream.prototype.destroy = function() {
+
+  if (!this._buffers) {
+    return;
+  }
+
+  this.writable = false;
+  this._reads = null;
+  this._buffers = null;
+
+  this.emit('close');
+};
+
+ChunkStream.prototype._processReadAllowingLess = function(read) {
+  // ok there is any data so that we can satisfy this request
+  this._reads.shift(); // == read
+
+  // first we need to peek into first buffer
+  var smallerBuf = this._buffers[0];
+
+  // ok there is more data than we need
+  if (smallerBuf.length > read.length) {
+
+    this._buffered -= read.length;
+    this._buffers[0] = smallerBuf.slice(read.length);
+
+    read.func.call(this, smallerBuf.slice(0, read.length));
+
+  }
+  else {
+    // ok this is less than maximum length so use it all
+    this._buffered -= smallerBuf.length;
+    this._buffers.shift(); // == smallerBuf
+
+    read.func.call(this, smallerBuf);
+  }
+};
+
+ChunkStream.prototype._processRead = function(read) {
+  this._reads.shift(); // == read
+
+  var pos = 0;
+  var count = 0;
+  var data = new Buffer(read.length);
+
+  // create buffer for all data
+  while (pos < read.length) {
+
+    var buf = this._buffers[count++];
+    var len = Math.min(buf.length, read.length - pos);
+
+    buf.copy(data, pos, 0, len);
+    pos += len;
+
+    // last buffer wasn't used all so just slice it and leave
+    if (len !== buf.length) {
+      this._buffers[--count] = buf.slice(len);
+    }
+  }
+
+  // remove all used buffers
+  if (count > 0) {
+    this._buffers.splice(0, count);
+  }
+
+  this._buffered -= read.length;
+
+  read.func.call(this, data);
+};
+
+ChunkStream.prototype._process = function() {
+
+  try {
+    // as long as there is any data and read requests
+    while (this._buffered > 0 && this._reads && this._reads.length > 0) {
+
+      var read = this._reads[0];
+
+      // read any data (but no more than length)
+      if (read.allowLess) {
+        this._processReadAllowingLess(read);
+
+      }
+      else if (this._buffered >= read.length) {
+        // ok we can meet some expectations
+
+        this._processRead(read);
+      }
+      else {
+        // not enought data to satisfy first request in queue
+        // so we need to wait for more
+        break;
+      }
+    }
+
+    if (this._buffers && this._buffers.length > 0 && this._buffers[0] === null) {
+      this._end();
+    }
+  }
+  catch (ex) {
+    this.emit('error', ex);
+  }
+};