[sfnt] Cache offset and size to bitmap data table.

This commit avoids `EBDT' and friends being looked up again and
again while loading a single embedded bitmap.

* include/freetype/internal/tttypes.h (TT_FaceRec)
[TT_CONFIG_OPTION_EMBEDDED_BITMAPS]: New fields `ebdt_start' and
`ebdt_size'.

* src/sfnt/ttsbit.c (tt_sbit_decoder_init): Move table lookup to ...
(tt_face_load_sbit): ... this function; also store the table size
and offset.

ChangeLog

@@ -1,3 +1,18 @@
+2016-08-26  Werner Lemberg  <wl@gnu.org>
+
+	[sfnt] Cache offset and size to bitmap data table.
+
+	This commit avoids `EBDT' and friends being looked up again and
+	again while loading a single embedded bitmap.
+
+	* include/freetype/internal/tttypes.h (TT_FaceRec)
+	[TT_CONFIG_OPTION_EMBEDDED_BITMAPS]: New fields `ebdt_start' and
+	`ebdt_size'.
+
+	* src/sfnt/ttsbit.c (tt_sbit_decoder_init): Move table lookup to ...
+	(tt_face_load_sbit): ... this function; also store the table size
+	and offset.
+
 2016-08-26  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	* src/smooth/ftgrays.c (gray_raster_render): Minor tweaks.

include/freetype/internal/tttypes.h

@@ -1393,6 +1393,12 @@ FT_BEGIN_HEADER
     FT_Bool               sph_compatibility_mode;
 #endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
+#ifdef TT_CONFIG_OPTION_EMBEDDED_BITMAPS
+    /* since 2.7 */
+    FT_ULong              ebdt_start;  /* either `CBDT', `EBDT', or `bdat' */
+    FT_ULong              ebdt_size;
+#endif
+
   } TT_FaceRec;
 
 

src/sfnt/ttsbit.c

@@ -197,6 +197,27 @@
     if ( !error )
       FT_TRACE3(( "sbit_num_strikes: %u\n", face->sbit_num_strikes ));
 
+    face->ebdt_start = 0;
+    face->ebdt_size  = 0;
+
+    if ( face->sbit_table_type != TT_SBIT_TABLE_TYPE_NONE )
+    {
+      FT_ULong  ebdt_size;
+
+
+      error = face->goto_table( face, TTAG_CBDT, stream, &ebdt_size );
+      if ( error )
+        error = face->goto_table( face, TTAG_EBDT, stream, &ebdt_size );
+      if ( error )
+        error = face->goto_table( face, TTAG_bdat, stream, &ebdt_size );
+
+      if ( !error )
+      {
+        face->ebdt_start = FT_STREAM_POS();
+        face->ebdt_size  = ebdt_size;
+      }
+    }
+
     return FT_Err_Ok;
 
   Exit:
@@ -424,17 +445,13 @@
                         FT_ULong             strike_index,
                         TT_SBit_MetricsRec*  metrics )
   {
-    FT_Error   error;
+    FT_Error   error  = FT_ERR( Table_Missing );
     FT_Stream  stream = face->root.stream;
-    FT_ULong   ebdt_size;
 
 
-    error = face->goto_table( face, TTAG_CBDT, stream, &ebdt_size );
-    if ( error )
-      error = face->goto_table( face, TTAG_EBDT, stream, &ebdt_size );
-    if ( error )
-      error = face->goto_table( face, TTAG_bdat, stream, &ebdt_size );
-    if ( error )
+    if ( !face->ebdt_size )
+      goto Exit;
+    if ( FT_STREAM_SEEK( face->ebdt_start ) )
       goto Exit;
 
     decoder->face    = face;
@@ -445,8 +462,8 @@
     decoder->metrics_loaded   = 0;
     decoder->bitmap_allocated = 0;
 
-    decoder->ebdt_start = FT_STREAM_POS();
-    decoder->ebdt_size  = ebdt_size;
+    decoder->ebdt_start = face->ebdt_start;
+    decoder->ebdt_size  = face->ebdt_size;
 
     decoder->eblc_base  = face->sbit_table;
     decoder->eblc_limit = face->sbit_table + face->sbit_table_size;