Crude PDF stream implementation

Author: kkoopa

lib/canvas.js

@@ -16,6 +16,7 @@ var canvas = require('./bindings')
   , cairoVersion = canvas.cairoVersion
   , Context2d = require('./context2d')
   , PNGStream = require('./pngstream')
+  , PDFStream = require('./pdfstream')
   , JPEGStream = require('./jpegstream')
   , FontFace = canvas.FontFace
   , fs = require('fs')
@@ -70,6 +71,7 @@ if (canvas.freetypeVersion) {
 
 exports.Context2d = Context2d;
 exports.PNGStream = PNGStream;
+exports.PDFStream = PDFStream;
 exports.JPEGStream = JPEGStream;
 exports.Image = Image;
 exports.ImageData = canvas.ImageData;
@@ -161,6 +163,30 @@ Canvas.prototype.createSyncPNGStream = function(){
   return new PNGStream(this, true);
 };
 
+/**
+ * Create a `PDFStream` for `this` canvas.
+ *
+ * @return {PDFStream}
+ * @api public
+ */
+
+Canvas.prototype.pdfStream =
+Canvas.prototype.createPDFStream = function(){
+  return new PDFStream(this);
+};
+
+/**
+ * Create a synchronous `PDFStream` for `this` canvas.
+ *
+ * @return {PDFStream}
+ * @api public
+ */
+
+Canvas.prototype.syncPDFStream =
+Canvas.prototype.createSyncPDFStream = function(){
+  return new PDFStream(this, true);
+};
+
 /**
  * Create a `JPEGStream` for `this` canvas.
  *

lib/pdfstream.js

@@ -0,0 +1,59 @@
+'use strict';
+
+/*!
+ * Canvas - PDFStream
+ */
+
+/**
+ * Module dependencies.
+ */
+
+var Stream = require('stream').Stream;
+
+/**
+ * Initialize a `PDFStream` with the given `canvas`.
+ *
+ * "data" events are emitted with `Buffer` chunks, once complete the
+ * "end" event is emitted. The following example will stream to a file
+ * named "./my.pdf".
+ *
+ *     var out = fs.createWriteStream(__dirname + '/my.pdf')
+ *       , stream = canvas.createPDFStream();
+ *
+ *     stream.pipe(out);
+ *
+ * @param {Canvas} canvas
+ * @param {Boolean} sync
+ * @api public
+ */
+
+var PDFStream = module.exports = function PDFStream(canvas, sync) {
+  var self = this
+    , method = sync
+      ? 'streamPDFSync'
+      : 'streamPDF';
+  this.sync = sync;
+  this.canvas = canvas;
+  this.readable = true;
+  // TODO: implement async
+  if ('streamPDF' == method) method = 'streamPDFSync';
+  process.nextTick(function(){
+    canvas[method](function(err, chunk, len){
+      if (err) {
+        self.emit('error', err);
+        self.readable = false;
+      } else if (len) {
+        self.emit('data', chunk, len);
+      } else {
+        self.emit('end');
+        self.readable = false;
+      }
+    });
+  });
+};
+
+/**
+ * Inherit from `EventEmitter`.
+ */
+
+PDFStream.prototype.__proto__ = Stream.prototype;

src/Canvas.cc

@@ -40,6 +40,7 @@ Canvas::Initialize(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
   Local<ObjectTemplate> proto = ctor->PrototypeTemplate();
   Nan::SetPrototypeMethod(ctor, "toBuffer", ToBuffer);
   Nan::SetPrototypeMethod(ctor, "streamPNGSync", StreamPNGSync);
+  Nan::SetPrototypeMethod(ctor, "streamPDFSync", StreamPDFSync);
 #ifdef HAVE_JPEG
   Nan::SetPrototypeMethod(ctor, "streamJPEGSync", StreamJPEGSync);
 #endif
@@ -434,6 +435,84 @@ NAN_METHOD(Canvas::StreamPNGSync) {
   return;
 }
 
+/*
+ * Canvas::StreamPDF FreeCallback
+ */
+
+void stream_pdf_free(char *, void *) {}
+
+/*
+ * Canvas::StreamPDF callback.
+ */
+
+static cairo_status_t
+streamPDF(void *c, const uint8_t *data, unsigned len) {
+  Nan::HandleScope scope;
+  closure_t *closure = static_cast<closure_t *>(c);
+  Local<Object> buf = Nan::NewBuffer(const_cast<char *>(reinterpret_cast<const char *>(data)), len, stream_pdf_free, 0).ToLocalChecked();
+  Local<Value> argv[3] = {
+      Nan::Null()
+    , buf
+    , Nan::New<Number>(len) };
+  Nan::MakeCallback(Nan::GetCurrentContext()->Global(), closure->fn, 3, argv);
+  return CAIRO_STATUS_SUCCESS;
+}
+
+
+cairo_status_t canvas_write_to_pdf_stream(cairo_surface_t *surface, cairo_write_func_t write_func, void *closure) {
+  closure_t *pdf_closure = static_cast<closure_t *>(closure);
+  size_t whole_chunks = pdf_closure->len / PAGE_SIZE;
+  size_t remainder = pdf_closure->len - whole_chunks * PAGE_SIZE;
+
+  for (size_t i = 0; i < whole_chunks; ++i) {
+    write_func(pdf_closure, &pdf_closure->data[i * PAGE_SIZE], PAGE_SIZE);
+  }
+
+  if (remainder) {
+    write_func(pdf_closure, &pdf_closure->data[whole_chunks * PAGE_SIZE], remainder);
+  }
+
+  return CAIRO_STATUS_SUCCESS;
+}
+
+/*
+ * Stream PDF data synchronously.
+ */
+
+NAN_METHOD(Canvas::StreamPDFSync) {
+  if (!info[0]->IsFunction())
+    return Nan::ThrowTypeError("callback function required");
+
+  Canvas *canvas = Nan::ObjectWrap::Unwrap<Canvas>(info.Holder());
+
+  if (!canvas->isPDF())
+    return Nan::ThrowTypeError("wrong canvas type");
+
+  cairo_surface_finish(canvas->surface());
+
+  closure_t closure;
+  closure.data = static_cast<closure_t *>(canvas->closure())->data;
+  closure.len = static_cast<closure_t *>(canvas->closure())->len;
+  closure.fn = info[0].As<Function>();
+
+  Nan::TryCatch try_catch;
+
+  cairo_status_t status = canvas_write_to_pdf_stream(canvas->surface(), streamPDF, &closure);
+
+  if (try_catch.HasCaught()) {
+    try_catch.ReThrow();
+  } else if (status) {
+    Local<Value> error = Canvas::Error(status);
+    Nan::Call(closure.fn, Nan::GetCurrentContext()->Global(), 1, &error);
+  } else {
+    Local<Value> argv[3] = {
+        Nan::Null()
+      , Nan::Null()
+      , Nan::New<Uint32>(0) };
+    Nan::Call(closure.fn, Nan::GetCurrentContext()->Global(), 3, argv);
+  }
+}
+
 /*
  * Stream JPEG data synchronously.
  */

src/Canvas.h

@@ -62,6 +62,7 @@ class Canvas: public Nan::ObjectWrap {
     static NAN_SETTER(SetWidth);
     static NAN_SETTER(SetHeight);
     static NAN_METHOD(StreamPNGSync);
+    static NAN_METHOD(StreamPDFSync);
     static NAN_METHOD(StreamJPEGSync);
     static Local<Value> Error(cairo_status_t status);
 #if NODE_VERSION_AT_LEAST(0, 6, 0)

test/canvas.test.js

@@ -802,6 +802,24 @@ describe('Canvas', function () {
     });
   });
 
+  it('Canvas#createSyncPDFStream()', function (done) {
+    var canvas = new Canvas(20, 20, 'pdf');
+    var stream = canvas.createSyncPDFStream();
+    var firstChunk = true;
+    stream.on('data', function (chunk) {
+      if (firstChunk) {
+        firstChunk = false;
+        assert.equal('PDF', chunk.slice(1, 4).toString());
+      }
+    });
+    stream.on('end', function () {
+      done();
+    });
+    stream.on('error', function (err) {
+      done(err);
+    });
+  });
+
   it('Canvas#jpegStream()', function (done) {
     var canvas = new Canvas(640, 480);
     var stream = canvas.jpegStream();