Change `src/core/jpg.js` to use the `error` utility function instead of `throw`ing

This allows us to remove the `try/catch` statements used in `src/core/stream.js` when parsing JPEG images.
As far as I can tell, the only reason for the current usage of plain `throw` is that `jpg.js` originally was external code. Given that this code now lives in our repo, this patch brings the JPEG code more in line with e.g. `src/core/jpx.js` and `src/core/jbig2.js`.

src/core/jpg.js

@@ -1,4 +1,3 @@
-
 /* Copyright 2014 Mozilla Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the 'License');
@@ -18,25 +17,27 @@
 
 (function (root, factory) {
   if (typeof define === 'function' && define.amd) {
-    define('pdfjs/core/jpg', ['exports'], factory);
+    define('pdfjs/core/jpg', ['exports', 'pdfjs/shared/util'], factory);
   } else if (typeof exports !== 'undefined') {
-    factory(exports);
+    factory(exports, require('../shared/util.js'));
   } else {
-    factory((root.pdfjsCoreJpg = {}));
+    factory((root.pdfjsCoreJpg = {}), root.pdfjsSharedUtil);
   }
-}(this, function (exports) {
+}(this, function (exports, sharedUtil) {
 
-/*
+var error = sharedUtil.error;
-This code was forked from https://github.com/notmasteryet/jpgjs. The original
-version was created by github user notmasteryet
 
-- The JPEG specification can be found in the ITU CCITT Recommendation T.81
+/**
- (www.w3.org/Graphics/JPEG/itu-t81.pdf)
+ * This code was forked from https://github.com/notmasteryet/jpgjs.
-- The JFIF specification can be found in the JPEG File Interchange Format
+ * The original version was created by GitHub user notmasteryet.
- (www.w3.org/Graphics/JPEG/jfif3.pdf)
+ *
-- The Adobe Application-Specific JPEG markers in the Supporting the DCT Filters
+ * - The JPEG specification can be found in the ITU CCITT Recommendation T.81
- in PostScript Level 2, Technical Note #5116
+ *   (www.w3.org/Graphics/JPEG/itu-t81.pdf)
- (partners.adobe.com/public/developer/en/ps/sdk/5116.DCT_Filter.pdf)
+ * - The JFIF specification can be found in the JPEG File Interchange Format
+ *   (www.w3.org/Graphics/JPEG/jfif3.pdf)
+ * - The Adobe Application-Specific JPEG markers in the
+ *   Supporting the DCT Filters in PostScript Level 2, Technical Note #5116
+ *   (partners.adobe.com/public/developer/en/ps/sdk/5116.DCT_Filter.pdf)
  */
 
 var JpegImage = (function jpegImage() {
@@ -123,8 +124,8 @@ var JpegImage = (function jpegImage() {
       if (bitsData === 0xFF) {
         var nextByte = data[offset++];
         if (nextByte) {
-          throw 'unexpected marker: ' +
+          error('JPEG error: unexpected marker ' +
-            ((bitsData << 8) | nextByte).toString(16);
+                ((bitsData << 8) | nextByte).toString(16));
         }
         // unstuff 0
       }
@@ -140,7 +141,7 @@ var JpegImage = (function jpegImage() {
           return node;
         }
         if (typeof node !== 'object') {
-          throw 'invalid huffman sequence';
+          error('JPEG error: invalid huffman sequence');
         }
       }
     }
@@ -247,7 +248,7 @@ var JpegImage = (function jpegImage() {
             }
           } else {
             if (s !== 1) {
-              throw 'invalid ACn encoding';
+              error('JPEG error: invalid ACn encoding');
             }
             successiveACNextValue = receiveAndExtend(s);
             successiveACState = r ? 2 : 3;
@@ -363,7 +364,7 @@ var JpegImage = (function jpegImage() {
       bitsCount = 0;
       marker = (data[offset] << 8) | data[offset + 1];
       if (marker <= 0xFF00) {
-        throw 'marker was not found';
+        error('JPEG error: marker was not found');
       }
 
       if (marker >= 0xFFD0 && marker <= 0xFFD7) { // RSTx
@@ -388,7 +389,7 @@ var JpegImage = (function jpegImage() {
     var t;
 
     if (!qt) {
-      throw 'missing required Quantization Table.';
+      error('JPEG error: missing required Quantization Table.');
     }
 
     // inverse DCT on rows
@@ -630,7 +631,7 @@ var JpegImage = (function jpegImage() {
       var huffmanTablesAC = [], huffmanTablesDC = [];
       var fileMarker = readUint16();
       if (fileMarker !== 0xFFD8) { // SOI (Start of Image)
-        throw 'SOI not found';
+        error('JPEG error: SOI not found');
       }
 
       fileMarker = readUint16();
@@ -705,7 +706,7 @@ var JpegImage = (function jpegImage() {
                   tableData[z] = readUint16();
                 }
               } else {
-                throw 'DQT: invalid table spec';
+                error('JPEG error: DQT - invalid table spec');
               }
               quantizationTables[quantizationTableSpec & 15] = tableData;
             }
@@ -715,7 +716,7 @@ var JpegImage = (function jpegImage() {
           case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
           case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT)
             if (frame) {
-              throw 'Only single frame JPEGs supported';
+              error('JPEG error: Only single frame JPEGs supported');
             }
             readUint16(); // skip data length
             frame = {};
@@ -815,7 +816,7 @@ var JpegImage = (function jpegImage() {
               offset -= 3;
               break;
             }
-            throw 'unknown JPEG marker ' + fileMarker.toString(16);
+            error('JPEG error: unknown marker ' + fileMarker.toString(16));
         }
         fileMarker = readUint16();
       }
@@ -1028,7 +1029,7 @@ var JpegImage = (function jpegImage() {
 
     getData: function getData(width, height, forceRGBoutput) {
       if (this.numComponents > 4) {
-        throw 'Unsupported color mode';
+        error('JPEG error: Unsupported color mode');
       }
       // type of data: Uint8Array(width * height * numComponents)
       var data = this._getLinearizedBlockData(width, height);

src/core/stream.js

@@ -922,10 +922,9 @@ var JpegStream = (function JpegStreamClosure() {
     if (this.bufferLength) {
       return;
     }
-    try {
     var jpegImage = new JpegImage();
 
-      // checking if values needs to be transformed before conversion
+    // Checking if values need to be transformed before conversion.
     if (this.forceRGB && this.dict && isArray(this.dict.get('Decode'))) {
       var decodeArr = this.dict.getArray('Decode');
       var bitsPerComponent = this.dict.get('BitsPerComponent') || 8;
@@ -951,9 +950,6 @@ var JpegStream = (function JpegStreamClosure() {
     this.buffer = data;
     this.bufferLength = data.length;
     this.eof = true;
-    } catch (e) {
-      error('JPEG error: ' + e);
-    }
   };
 
   JpegStream.prototype.getBytes = function JpegStream_getBytes(length) {