Merge pull request #4405 from nnethercote/avoid-re-reading-streams

Avoid unnecessary re-reading of streams

src/core/chunked_stream.js

@@ -187,6 +187,8 @@ var ChunkedStream = (function ChunkedStreamClosure() {
     },
 
     makeSubStream: function ChunkedStream_makeSubStream(start, length, dict) {
+      this.ensureRange(start, start + length);
+
       function ChunkedStreamSubstream() {}
       ChunkedStreamSubstream.prototype = Object.create(this);
       ChunkedStreamSubstream.prototype.getMissingChunks = function() {

src/core/parser.js

@@ -300,12 +300,10 @@ var Parser = (function ParserClosure() {
         return new LZWStream(stream, earlyChange);
       }
       if (name == 'DCTDecode' || name == 'DCT') {
-        var bytes = stream.getBytes(length);
-        return new JpegStream(bytes, stream.dict, this.xref);
+        return new JpegStream(stream, length, stream.dict, this.xref);
       }
       if (name == 'JPXDecode' || name == 'JPX') {
-        var bytes = stream.getBytes(length);
-        return new JpxStream(bytes, stream.dict);
+        return new JpxStream(stream, length, stream.dict);
       }
       if (name == 'ASCII85Decode' || name == 'A85') {
         return new Ascii85Stream(stream);
@@ -320,8 +318,7 @@ var Parser = (function ParserClosure() {
         return new RunLengthStream(stream);
       }
       if (name == 'JBIG2Decode') {
-        var bytes = stream.getBytes(length);
-        return new Jbig2Stream(bytes, stream.dict);
+        return new Jbig2Stream(stream, length, stream.dict);
       }
       warn('filter "' + name + '" not supported yet');
       return stream;

src/core/stream.js

@@ -14,8 +14,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* globals bytesToString, ColorSpace, Dict, EOF, error, info, Jbig2Image,
-           JpegImage, JpxImage, Lexer, Util, PDFJS, isArray, warn */
+/* globals bytesToString, ColorSpace, Dict, EOF, error, info, isArray,
+           Jbig2Image, JpegImage, JpxImage, Lexer, PDFJS, shadow, Util, warn */
 
 'use strict';
 
@@ -328,13 +328,12 @@ var FlateStream = (function FlateStreamClosure() {
     0x50003, 0x50013, 0x5000b, 0x5001b, 0x50007, 0x50017, 0x5000f, 0x00000
   ]), 5];
 
-  function FlateStream(stream) {
-    var bytes = stream.getBytes();
-    var bytesPos = 0;
+  function FlateStream(str) {
+    this.str = str;
+    this.dict = str.dict;
 
-    this.dict = stream.dict;
-    var cmf = bytes[bytesPos++];
-    var flg = bytes[bytesPos++];
+    var cmf = str.getByte();
+    var flg = str.getByte();
     if (cmf == -1 || flg == -1)
       error('Invalid header in flate stream: ' + cmf + ', ' + flg);
     if ((cmf & 0x0f) != 0x08)
@@ -344,9 +343,6 @@ var FlateStream = (function FlateStreamClosure() {
     if (flg & 0x20)
       error('FDICT bit set in flate stream: ' + cmf + ', ' + flg);
 
-    this.bytes = bytes;
-    this.bytesPos = bytesPos;
-
     this.codeSize = 0;
     this.codeBuf = 0;
 
@@ -356,37 +352,37 @@ var FlateStream = (function FlateStreamClosure() {
   FlateStream.prototype = Object.create(DecodeStream.prototype);
 
   FlateStream.prototype.getBits = function FlateStream_getBits(bits) {
+    var str = this.str;
     var codeSize = this.codeSize;
     var codeBuf = this.codeBuf;
-    var bytes = this.bytes;
-    var bytesPos = this.bytesPos;
 
     var b;
     while (codeSize < bits) {
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad encoding in flate stream');
+      }
       codeBuf |= b << codeSize;
       codeSize += 8;
     }
     b = codeBuf & ((1 << bits) - 1);
     this.codeBuf = codeBuf >> bits;
     this.codeSize = codeSize -= bits;
-    this.bytesPos = bytesPos;
+
     return b;
   };
 
   FlateStream.prototype.getCode = function FlateStream_getCode(table) {
+    var str = this.str;
     var codes = table[0];
     var maxLen = table[1];
     var codeSize = this.codeSize;
     var codeBuf = this.codeBuf;
-    var bytes = this.bytes;
-    var bytesPos = this.bytesPos;
 
     while (codeSize < maxLen) {
       var b;
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad encoding in flate stream');
+      }
       codeBuf |= (b << codeSize);
       codeSize += 8;
     }
@@ -397,7 +393,6 @@ var FlateStream = (function FlateStreamClosure() {
       error('Bad encoding in flate stream');
     this.codeBuf = (codeBuf >> codeLen);
     this.codeSize = (codeSize - codeLen);
-    this.bytesPos = bytesPos;
     return codeVal;
   };
 
@@ -441,6 +436,7 @@ var FlateStream = (function FlateStreamClosure() {
   };
 
   FlateStream.prototype.readBlock = function FlateStream_readBlock() {
+    var str = this.str;
     // read block header
     var hdr = this.getBits(3);
     if (hdr & 1)
@@ -448,21 +444,23 @@ var FlateStream = (function FlateStreamClosure() {
     hdr >>= 1;
 
     if (hdr === 0) { // uncompressed block
-      var bytes = this.bytes;
-      var bytesPos = this.bytesPos;
       var b;
 
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad block header in flate stream');
+      }
       var blockLen = b;
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad block header in flate stream');
+      }
       blockLen |= (b << 8);
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad block header in flate stream');
+      }
       var check = b;
-      if (typeof (b = bytes[bytesPos++]) == 'undefined')
+      if ((b = str.getByte()) === -1) {
         error('Bad block header in flate stream');
+      }
       check |= (b << 8);
       if (check != (~blockLen & 0xffff) &&
           (blockLen !== 0 || check !== 0)) {
@@ -478,19 +476,18 @@ var FlateStream = (function FlateStreamClosure() {
       var end = bufferLength + blockLen;
       this.bufferLength = end;
       if (blockLen === 0) {
-        if (typeof bytes[bytesPos] == 'undefined') {
+        if (str.peekBytes(1).length === 0) {
           this.eof = true;
         }
       } else {
         for (var n = bufferLength; n < end; ++n) {
-          if (typeof (b = bytes[bytesPos++]) == 'undefined') {
+          if ((b = str.getByte()) === -1) {
             this.eof = true;
             break;
           }
           buffer[n] = b;
         }
       }
-      this.bytesPos = bytesPos;
       return;
     }
 
@@ -777,17 +774,25 @@ var PredictorStream = (function PredictorStreamClosure() {
  * DecodeStreams.
  */
 var JpegStream = (function JpegStreamClosure() {
-  function JpegStream(bytes, dict, xref) {
+  function JpegStream(stream, length, dict, xref) {
     // TODO: per poppler, some images may have 'junk' before that
     // need to be removed
+    this.stream = stream;
+    this.length = length;
     this.dict = dict;
-    this.bytes = bytes;
 
     DecodeStream.call(this);
   }
 
   JpegStream.prototype = Object.create(DecodeStream.prototype);
 
+  Object.defineProperty(JpegStream.prototype, 'bytes', {
+    get: function JpegStream_bytes() {
+      return shadow(this, 'bytes', this.stream.getBytes(this.length));
+    },
+    configurable: true
+  });
+
   JpegStream.prototype.ensureBuffer = function JpegStream_ensureBuffer(req) {
     if (this.bufferLength)
       return;
@@ -836,15 +841,23 @@ var JpegStream = (function JpegStreamClosure() {
  * the stream behaves like all the other DecodeStreams.
  */
 var JpxStream = (function JpxStreamClosure() {
-  function JpxStream(bytes, dict) {
+  function JpxStream(stream, length, dict) {
+    this.stream = stream;
+    this.length = length;
     this.dict = dict;
-    this.bytes = bytes;
 
     DecodeStream.call(this);
   }
 
   JpxStream.prototype = Object.create(DecodeStream.prototype);
 
+  Object.defineProperty(JpxStream.prototype, 'bytes', {
+    get: function JpxStream_bytes() {
+      return shadow(this, 'bytes', this.stream.getBytes(this.length));
+    },
+    configurable: true
+  });
+
   JpxStream.prototype.ensureBuffer = function JpxStream_ensureBuffer(req) {
     if (this.bufferLength)
       return;
@@ -935,15 +948,23 @@ var JpxStream = (function JpxStreamClosure() {
  * the stream behaves like all the other DecodeStreams.
  */
 var Jbig2Stream = (function Jbig2StreamClosure() {
-  function Jbig2Stream(bytes, dict) {
+  function Jbig2Stream(stream, length, dict) {
+    this.stream = stream;
+    this.length = length;
     this.dict = dict;
-    this.bytes = bytes;
 
     DecodeStream.call(this);
   }
 
   Jbig2Stream.prototype = Object.create(DecodeStream.prototype);
 
+  Object.defineProperty(Jbig2Stream.prototype, 'bytes', {
+    get: function Jbig2Stream_bytes() {
+      return shadow(this, 'bytes', this.stream.getBytes(this.length));
+    },
+    configurable: true
+  });
+
   Jbig2Stream.prototype.ensureBuffer = function Jbig2Stream_ensureBuffer(req) {
     if (this.bufferLength)
       return;