Use strong hash (SHA1) for glyphs

Using a cryptographically strong hash means that comparing the
hash alone is sufficient for determining glyph equality (no need
to compare the glyph bits directly). This will allow us to replace
system-memory copies of the glyph bits, (which we've only been
holding onto for comparisons), with Pixmaps.

1 files changed, 40 insertions, 44 deletions

diff --git a/render/glyph.c b/render/glyph.c
index 1204c3b79..7dbdda2d9 100644
--- a/render/glyph.c
+++ b/render/glyph.c
@@ -26,6 +26,8 @@
 #include <dix-config.h>
 #endif
 
+#include <openssl/sha.h>
+
 #include "misc.h"
 #include "scrnintstr.h"
 #include "os.h"
@@ -412,7 +414,10 @@ _GlyphSetSetNewPrivate (GlyphSetPtr glyphSet, int n, pointer ptr)
 }
 
 GlyphRefPtr
-FindGlyphRef (GlyphHashPtr hash, CARD32 signature, Bool match, GlyphPtr compare)
+FindGlyphRef (GlyphHashPtr	hash,
+	      CARD32		signature,
+	      Bool		match,
+	      unsigned char	sha1[20])
 {
     CARD32	elt, step, s;
     GlyphPtr	glyph;
@@ -443,7 +448,7 @@ FindGlyphRef (GlyphHashPtr hash, CARD32 signature, Bool match, GlyphPtr compare)
 	}
 	else if (s == signature &&
 		 (!match || 
-		  memcmp (&compare->info, &glyph->info, compare->size) == 0))
+		  memcmp (glyph->sha1, sha1, 20) == 0))
 	{
 	    break;
 	}
@@ -460,54 +465,42 @@ FindGlyphRef (GlyphHashPtr hash, CARD32 signature, Bool match, GlyphPtr compare)
     return gr;
 }
 
-CARD32
-HashGlyphInfoAndBits (xGlyphInfo *gi, CARD8 *data, unsigned int size)
+int
+HashGlyph (xGlyphInfo    *gi,
+	   CARD8	 *bits,
+	   unsigned long size,
+	   unsigned char sha1[20])
 {
-    CARD32  *bits;
-    CARD32  hash;
-    int	    n;
+    SHA_CTX ctx;
+    int success;
 
-    hash = 0;
+    success = SHA1_Init (&ctx);
+    if (! success)
+	return BadAlloc;
 
-    bits = (CARD32 *) gi;
-    n = sizeof (xGlyphInfo) / sizeof (CARD32);
-    while (n--)
-	hash ^= *bits++;
+    success = SHA1_Update (&ctx, gi, sizeof (xGlyphInfo));
+    if (! success)
+	return BadAlloc;
 
-    bits = (CARD32 *) data;
-    n = size / sizeof (CARD32);
-    while (n--)
-	hash ^= *bits++;
+    success = SHA1_Update (&ctx, bits, size);
+    if (! success)
+	return BadAlloc;
 
-    return hash;
-}
+    success = SHA1_Final (sha1, &ctx);
+    if (! success)
+	return BadAlloc;
 
-CARD32
-HashGlyph (GlyphPtr glyph)
-{
-    return HashGlyphInfoAndBits (&glyph->info,
-				 (CARD8 *) (&glyph->info + 1),
-				 glyph->size - sizeof (xGlyphInfo));
+    return Success;
 }
 
 GlyphPtr
-FindGlyphByHash (CARD32	    hash,
-		 xGlyphInfo *gi,
-		 CARD8	    *bits,
-		 int	    format)
+FindGlyphByHash (unsigned char sha1[20], int format)
 {
     GlyphRefPtr gr;
-    GlyphPtr template;
-
-    /* XXX: Should handle out-of-memory here */
-    template = AllocateGlyph (gi, format);
-    memcpy ((CARD8 *) (template + 1), bits,
-	    template->size - sizeof (xGlyphInfo));
+    CARD32 signature = *(CARD32 *) sha1;
 
     gr = FindGlyphRef (&globalGlyphs[format],
-		       hash, TRUE, template);
-
-    xfree (template);
+		       signature, TRUE, sha1);
 
     if (gr->glyph && gr->glyph != DeletedGlyph)
 	return gr->glyph;
@@ -553,6 +546,7 @@ FreeGlyph (GlyphPtr glyph, int format)
 	GlyphRefPtr      gr;
 	int	         i;
 	int	         first;
+	CARD32		 signature;
 
 	first = -1;
 	for (i = 0; i < globalGlyphs[format].hashSet->size; i++)
@@ -563,8 +557,9 @@ FreeGlyph (GlyphPtr glyph, int format)
 		first = i;
 	    }
 
-	gr = FindGlyphRef (&globalGlyphs[format],
-			   HashGlyph (glyph), TRUE, glyph);
+	signature = *(CARD32 *) glyph->sha1;
+	gr = FindGlyphRef (&globalGlyphs[format], signature,
+			   TRUE, glyph->sha1);
 	if (gr - globalGlyphs[format].table != first)
 	    DuplicateRef (glyph, "Found wrong one");
 	if (gr->glyph && gr->glyph != DeletedGlyph)
@@ -591,12 +586,13 @@ void
 AddGlyph (GlyphSetPtr glyphSet, GlyphPtr glyph, Glyph id)
 {
     GlyphRefPtr	    gr;
-    CARD32	    hash;
+    CARD32	    signature;
 
     CheckDuplicates (&globalGlyphs[glyphSet->fdepth], "AddGlyph top global");
     /* Locate existing matching glyph */
-    hash = HashGlyph (glyph);
-    gr = FindGlyphRef (&globalGlyphs[glyphSet->fdepth], hash, TRUE, glyph);
+    signature = *(CARD32 *) glyph->sha1;
+    gr = FindGlyphRef (&globalGlyphs[glyphSet->fdepth], signature,
+		       TRUE, glyph->sha1);
     if (gr->glyph && gr->glyph != DeletedGlyph && gr->glyph != glyph)
     {
 	PictureScreenPtr ps;
@@ -616,7 +612,7 @@ AddGlyph (GlyphSetPtr glyphSet, GlyphPtr glyph, Glyph id)
     else if (gr->glyph != glyph)
     {
 	gr->glyph = glyph;
-	gr->signature = hash;
+	gr->signature = signature;
 	globalGlyphs[glyphSet->fdepth].tableEntries++;
     }
     
@@ -753,7 +749,7 @@ ResizeGlyphHash (GlyphHashPtr hash, CARD32 change, Bool global)
 	    if (glyph && glyph != DeletedGlyph)
 	    {
 		s = hash->table[i].signature;
-		gr = FindGlyphRef (&newHash, s, global, glyph);
+		gr = FindGlyphRef (&newHash, s, global, glyph->sha1);
 		gr->signature = s;
 		gr->glyph = glyph;
 		++newHash.tableEntries;