Fix for 687337 Zerodivide in cie_cache_mult

Fix for 687337 Zerodivide in cie_cache_mult.

DETAILS:

The direct cause of the problem, and also the reason that we
have not seen this problem in real world files is that the
050-01.ps test file contains the following color rendering
dictionary.

/RenderDict2
12 dict begin
  /BlackPoint [ 0 0 0 ] def
  /ColorRenderingType 1 def
  /EncodeABC [ {} {} {} ] def
  /EncodeLMN [ {} {} {} ] def
  /MatrixABC [ 0 0 0  0 0 0  0 0 0 ] def
  /MatrixLMN [ 0 0 0  0 0 0  0 0 0 ] def
  /RangeABC [ 0 1  0 1  0 1 ] def
  /RangeLMN [ 0 1  0 1  0 1 ] def
  /RangePQR [ 0 1  0 1  0 1 ] def
  /TransformPQR [ {} {} {} ] def
  /WhitePoint [ 1 1 1 ] def

Note:  The matrices full of zeroes do not represent real
world data.  The zero matrices will result in all output
component values being zero no matter what the inputs.

Using this data, Ghostscript uses the given ranges and
matrices to calculate values for DomainABC and DomainLMN.
The results are [0, 0] for each domain.  The domain values
are later used to calculate a scaling factors which is
also 0.  Calculations, which use one of these values as
a divisor, then generate a divide by zero exception.

One option to fix this problem would be to check for zero
before doing any calculations with the scaling factors.
However another and simpler option is to check for the zero
factors when they are crated and set the value to a value
which will not cause the divide problem.  Note:  Even though
we are using a dummy factor (1.0), the zero matrices still
result in zero output values from the calculations.


Index: src/gscie.c
===================================================================
RCS file: /cvs/ghostscript/gs/src/gscie.c,v
retrieving revision 1.14
diff -u -r1.14 gscie.c
--- a/src/gscie.c       4 Dec 2003 12:35:35 -0000       1.14
+++ b/src/gscie.c       12 Mar 2004 07:21:25 -0000
@@ -821,7 +821,13 @@
 #else
     pcache->base = A - delta / 2;      /* so lookup will round */
 #endif
-    pcache->factor = (delta == 0 ? 0 : N / R);
+    /*
+     * If size of the domain is zero, then use 1.0 as the scaling
+     * factor.  This prevents divide by zero errors in later calculations.
+     * This should only occurs with zero matrices.  It does occur with
+     * Genoa test file 050-01.ps.
+     */
+    pcache->factor = (delta == 0.0 ? 1.0 : N / R);
     if_debug4('c', "[c]cache %s 0x%lx base=%g, factor=%g\n",
              (const char *)cname, (ulong) pcache,
              pcache->base, pcache->factor);