Convert src/core/jbig2.js to use standard classes

*Please note:* Ignoring whitespace-only changes is probably necessary in order to review this.

src/core/jbig2.js

@@ -24,35 +24,33 @@ class Jbig2Error extends BaseException {
   }
 }
 
-const Jbig2Image = (function Jbig2ImageClosure() {
 // Utility data structures
-  function ContextCache() {}
+class ContextCache {
-
-  ContextCache.prototype = {
   getContexts(id) {
     if (id in this) {
       return this[id];
     }
     return (this[id] = new Int8Array(1 << 16));
-    },
+  }
-  };
+}
 
-  function DecodingContext(data, start, end) {
+class DecodingContext {
+  constructor(data, start, end) {
     this.data = data;
     this.start = start;
     this.end = end;
   }
 
-  DecodingContext.prototype = {
   get decoder() {
     const decoder = new ArithmeticDecoder(this.data, this.start, this.end);
     return shadow(this, "decoder", decoder);
-    },
+  }
+
   get contextCache() {
     const cache = new ContextCache();
     return shadow(this, "contextCache", cache);
-    },
+  }
-  };
+}
 
 // Annex A. Arithmetic Integer Decoding Procedure
 // A.2 Procedure for decoding values
@@ -64,8 +62,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
     let v = 0;
     for (let i = 0; i < length; i++) {
       const bit = decoder.readBit(contexts, prev);
-        prev =
+      prev = prev < 256 ? (prev << 1) | bit : (((prev << 1) | bit) & 511) | 256;
-          prev < 256 ? (prev << 1) | bit : (((prev << 1) | bit) & 511) | 256;
       v = (v << 1) | bit;
     }
     return v >>> 0;
@@ -555,12 +552,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       for (k = 0; k < referenceTemplateLength; k++) {
         i0 = i + referenceTemplateY[k] - offsetY;
         j0 = j + referenceTemplateX[k] - offsetX;
-          if (
+        if (i0 < 0 || i0 >= referenceHeight || j0 < 0 || j0 >= referenceWidth) {
-            i0 < 0 ||
-            i0 >= referenceHeight ||
-            j0 < 0 ||
-            j0 >= referenceWidth
-          ) {
           contextLabel <<= 1; // out of bound pixel
         } else {
           contextLabel = (contextLabel << 1) | referenceBitmap[i0][j0];
@@ -626,11 +618,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       let bitmap;
       if (refinement) {
         // 6.5.8.2 Refinement/aggregate-coded symbol bitmap
-          const numberOfInstances = decodeInteger(
+        const numberOfInstances = decodeInteger(contextCache, "IAAI", decoder);
-            contextCache,
-            "IAAI",
-            decoder
-          );
         if (numberOfInstances > 1) {
           bitmap = decodeTextRegion(
             huffman,
@@ -654,11 +642,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
             huffmanInput
           );
         } else {
-            const symbolId = decodeIAID(
+          const symbolId = decodeIAID(contextCache, decoder, symbolCodeLength);
-              contextCache,
-              decoder,
-              symbolCodeLength
-            );
           const rdx = decodeInteger(contextCache, "IARDX", decoder); // 6.4.11.3
           const rdy = decodeInteger(contextCache, "IARDY", decoder); // 6.4.11.4
           const symbol =
@@ -1021,9 +1005,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
   }
   if (combinationOperator !== 0) {
     throw new Jbig2Error(
-        "operator " +
+      `operator "${combinationOperator}" is not supported in halftone region`
-          combinationOperator +
-          " is not supported in halftone region"
     );
   }
 
@@ -1564,10 +1546,8 @@ const Jbig2Image = (function Jbig2ImageClosure() {
   return { imgData, width, height };
 }
 
-  function SimpleSegmentVisitor() {}
+class SimpleSegmentVisitor {
-
+  onPageInformation(info) {
-  SimpleSegmentVisitor.prototype = {
-    onPageInformation: function SimpleSegmentVisitor_onPageInformation(info) {
     this.currentPageInfo = info;
     const rowSize = (info.width + 7) >> 3;
     const buffer = new Uint8ClampedArray(rowSize * info.height);
@@ -1579,8 +1559,9 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       }
     }
     this.buffer = buffer;
-    },
+  }
-    drawBitmap: function SimpleSegmentVisitor_drawBitmap(regionInfo, bitmap) {
+
+  drawBitmap(regionInfo, bitmap) {
     const pageInfo = this.currentPageInfo;
     const width = regionInfo.width,
       height = regionInfo.height;
@@ -1632,13 +1613,9 @@ const Jbig2Image = (function Jbig2ImageClosure() {
           `operator ${combinationOperator} is not supported`
         );
     }
-    },
+  }
-    onImmediateGenericRegion: function SimpleSegmentVisitor_onImmediateGenericRegion(
+
-      region,
+  onImmediateGenericRegion(region, data, start, end) {
-      data,
-      start,
-      end
-    ) {
     const regionInfo = region.info;
     const decodingContext = new DecodingContext(data, start, end);
     const bitmap = decodeBitmap(
@@ -1652,11 +1629,13 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       decodingContext
     );
     this.drawBitmap(regionInfo, bitmap);
-    },
+  }
-    onImmediateLosslessGenericRegion: function SimpleSegmentVisitor_onImmediateLosslessGenericRegion() {
+
+  onImmediateLosslessGenericRegion() {
     this.onImmediateGenericRegion.apply(this, arguments);
-    },
+  }
-    onSymbolDictionary: function SimpleSegmentVisitor_onSymbolDictionary(
+
+  onSymbolDictionary(
     dictionary,
     currentSegment,
     referredSegments,
@@ -1705,14 +1684,9 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       decodingContext,
       huffmanInput
     );
-    },
+  }
-    onImmediateTextRegion: function SimpleSegmentVisitor_onImmediateTextRegion(
+
-      region,
+  onImmediateTextRegion(region, referredSegments, data, start, end) {
-      referredSegments,
-      data,
-      start,
-      end
-    ) {
     const regionInfo = region.info;
     let huffmanTables, huffmanInput;
 
@@ -1762,10 +1736,12 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       huffmanInput
     );
     this.drawBitmap(regionInfo, bitmap);
-    },
+  }
-    onImmediateLosslessTextRegion: function SimpleSegmentVisitor_onImmediateLosslessTextRegion() {
+
+  onImmediateLosslessTextRegion() {
     this.onImmediateTextRegion.apply(this, arguments);
-    },
+  }
+
   onPatternDictionary(dictionary, currentSegment, data, start, end) {
     let patterns = this.patterns;
     if (!patterns) {
@@ -1780,7 +1756,8 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       dictionary.template,
       decodingContext
     );
-    },
+  }
+
   onImmediateHalftoneRegion(region, referredSegments, data, start, end) {
     // HalftoneRegion refers to exactly one PatternDictionary.
     const patterns = this.patterns[referredSegments[0]];
@@ -1804,20 +1781,23 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       decodingContext
     );
     this.drawBitmap(regionInfo, bitmap);
-    },
+  }
+
   onImmediateLosslessHalftoneRegion() {
     this.onImmediateHalftoneRegion.apply(this, arguments);
-    },
+  }
+
   onTables(currentSegment, data, start, end) {
     let customTables = this.customTables;
     if (!customTables) {
       this.customTables = customTables = {};
     }
     customTables[currentSegment] = decodeTablesSegment(data, start, end);
-    },
+  }
-  };
+}
 
-  function HuffmanLine(lineData) {
+class HuffmanLine {
+  constructor(lineData) {
     if (lineData.length === 2) {
       // OOB line.
       this.isOOB = true;
@@ -1837,8 +1817,10 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       this.isLowerRange = lineData[4] === "lower";
     }
   }
+}
 
-  function HuffmanTreeNode(line) {
+class HuffmanTreeNode {
+  constructor(line) {
     this.children = [];
     if (line) {
       // Leaf node
@@ -1853,7 +1835,6 @@ const Jbig2Image = (function Jbig2ImageClosure() {
     }
   }
 
-  HuffmanTreeNode.prototype = {
   buildTree(line, shift) {
     const bit = (line.prefixCode >> shift) & 1;
     if (shift <= 0) {
@@ -1867,7 +1848,8 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       }
       node.buildTree(line, shift - 1);
     }
-    },
+  }
+
   decodeNode(reader) {
     if (this.isLeaf) {
       if (this.isOOB) {
@@ -1881,10 +1863,11 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       throw new Jbig2Error("invalid Huffman data");
     }
     return node.decodeNode(reader);
-    },
+  }
-  };
+}
 
-  function HuffmanTable(lines, prefixCodesDone) {
+class HuffmanTable {
+  constructor(lines, prefixCodesDone) {
     if (!prefixCodesDone) {
       this.assignPrefixCodes(lines);
     }
@@ -1898,10 +1881,10 @@ const Jbig2Image = (function Jbig2ImageClosure() {
     }
   }
 
-  HuffmanTable.prototype = {
   decode(reader) {
     return this.rootNode.decodeNode(reader);
-    },
+  }
+
   assignPrefixCodes(lines) {
     // Annex B.3 Assigning the prefix codes.
     const linesLength = lines.length;
@@ -1935,8 +1918,8 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       }
       currentLength++;
     }
-    },
+  }
-  };
+}
 
 function decodeTablesSegment(data, start, end) {
   // Decodes a Tables segment, i.e., a custom Huffman table.
@@ -1965,9 +1948,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
 
   // Lower range table line
   prefixLength = reader.readBits(prefixSizeBits);
-    lines.push(
+  lines.push(new HuffmanLine([lowestValue - 1, prefixLength, 32, 0, "lower"]));
-      new HuffmanLine([lowestValue - 1, prefixLength, 32, 0, "lower"])
-    );
 
   // Upper range table line
   prefixLength = reader.readBits(prefixSizeBits);
@@ -2248,7 +2229,8 @@ const Jbig2Image = (function Jbig2ImageClosure() {
   return table;
 }
 
-  function Reader(data, start, end) {
+class Reader {
+  constructor(data, start, end) {
     this.data = data;
     this.start = start;
     this.end = end;
@@ -2257,7 +2239,6 @@ const Jbig2Image = (function Jbig2ImageClosure() {
     this.currentByte = 0;
   }
 
-  Reader.prototype = {
   readBit() {
     if (this.shift < 0) {
       if (this.position >= this.end) {
@@ -2269,7 +2250,7 @@ const Jbig2Image = (function Jbig2ImageClosure() {
     const bit = (this.currentByte >> this.shift) & 1;
     this.shift--;
     return bit;
-    },
+  }
 
   readBits(numBits) {
     let result = 0,
@@ -2278,19 +2259,19 @@ const Jbig2Image = (function Jbig2ImageClosure() {
       result |= this.readBit() << i;
     }
     return result;
-    },
+  }
 
   byteAlign() {
     this.shift = -1;
-    },
+  }
 
   next() {
     if (this.position >= this.end) {
       return -1;
     }
     return this.data[this.position++];
-    },
+  }
-  };
+}
 
 function getCustomHuffmanTable(index, referredTo, customTables) {
   // Returns a Tables segment that has been earlier decoded.
@@ -2571,23 +2552,17 @@ const Jbig2Image = (function Jbig2ImageClosure() {
   return bitmap;
 }
 
-  // eslint-disable-next-line no-shadow
+class Jbig2Image {
-  function Jbig2Image() {}
-
-  Jbig2Image.prototype = {
   parseChunks(chunks) {
     return parseJbig2Chunks(chunks);
-    },
+  }
 
   parse(data) {
     const { imgData, width, height } = parseJbig2(data);
     this.width = width;
     this.height = height;
     return imgData;
-    },
+  }
-  };
+}
-
-  return Jbig2Image;
-})();
 
 export { Jbig2Image };