Attachment 29194 Details for Bug 23025 – Correctly set the value of symCodeLen

[patch] Correctly set the value of symCodeLen

0001-Correctly-set-the-value-of-symCodeLen.patch (text/plain), 1.26 KB, created by David Benjamin on 2009-09-03 15:56:41 UTC

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Creator: David Benjamin

Created: 2009-09-03 15:56:41 UTC

Size: 1.26 KB

patch

obsolete

>From 222718b7e7b5e1f6082363c66f55bcf0738caa2e Mon Sep 17 00:00:00 2001
>From: David Benjamin <davidben@mit.edu>
>Date: Thu, 3 Sep 2009 18:50:08 -0400
>Subject: [PATCH] Correctly set the value of symCodeLen
>
>From 6.5.8.2.3, symCodeLen = ceil(log2(numInputSyms + numNewSyms)). The old
>code was taking 1+floor, which provides the wrong answer when they sum to a
>power of two.
>
>Signed-off-by: David Benjamin <davidben@mit.edu>
>---
> poppler/JBIG2Stream.cc |   13 ++++++++-----
> 1 files changed, 8 insertions(+), 5 deletions(-)
>
>diff --git a/poppler/JBIG2Stream.cc b/poppler/JBIG2Stream.cc
>index fec0e2d..97994bd 100644
>--- a/poppler/JBIG2Stream.cc
>+++ b/poppler/JBIG2Stream.cc
>@@ -1587,12 +1587,15 @@ GBool JBIG2Stream::readSymbolDictSeg(Guint segNum, Guint length,
>     goto eofError;
>   }
> 
>-  // compute symbol code length
>+  // compute symbol code length, per 6.5.8.2.3
>+  //  symCodeLen = ceil( log2( numInputSyms + numNewSyms ) )
>   symCodeLen = 1;
>-  i = (numInputSyms + numNewSyms) >> 1;
>-  while (i) {
>-    ++symCodeLen;
>-    i >>= 1;
>+  if (likely(numInputSyms + numNewSyms > 0)) { // don't fail too badly if the sum is 0
>+    i = (numInputSyms + numNewSyms - 1) >> 1;
>+    while (i) {
>+      ++symCodeLen;
>+      i >>= 1;
>+    }
>   }
> 
>   // get the input symbol bitmaps
>-- 
>1.6.0.4
>

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