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[bdf, pfr, psnames] Accelarate charmap searches.

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The binary searches within charmaps can be accelerated because they
often contain dense continuous blocks of character codes. Within such
blocks, you can predict matches based on misses.  This method has been
deployed in `bdf` since 0f122fef34; we only refactor it there.  We now
use it in `pfr` and `psnames`, which speeds up the unicode charmap
access by about 50% in PFR and Type 1 fonts.

* src/bdf/bdfdrivr.c (bdf_cmap_char_{index,next}): Refactor.
* src/pfr/pfrcmap.c (pfr_cmap_char_{index,next}): Predict `mid` based
on the mismatch distance.
* src/psnames/psmodule.c (ps_unicodes_char_{index,next}): Ditto.
This commit is contained in:
Alexei Podtelezhnikov 2022-11-06 13:12:47 -05:00
parent ae4eb996ab
commit 6139f2b647
3 changed files with 45 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
src/bdf/bdfdrivr.c
View File

@ -92,24 +92,18 @@ THE SOFTWARE.
{
BDF_CMap cmap = (BDF_CMap)bdfcmap;
BDF_encoding_el* encodings = cmap->encodings;
FT_ULong min, max, mid; /* num_encodings */
FT_UShort result = 0; /* encodings->glyph */
FT_ULong min = 0;
FT_ULong max = cmap->num_encodings;
FT_ULong mid = ( min + max ) >> 1;
min = 0;
max = cmap->num_encodings;
mid = ( min + max ) >> 1;
while ( min < max )
{
FT_ULong code;
FT_ULong code = encodings[mid].enc;
if ( mid >= max || mid < min )
mid = ( min + max ) >> 1;
code = encodings[mid].enc;
if ( charcode == code )
{
/* increase glyph index by 1 -- */
@ -123,8 +117,10 @@ THE SOFTWARE.
else
min = mid + 1;
/* prediction in a continuous block */
/* reasonable prediction in a continuous block */
mid += charcode - code;
if ( mid >= max || mid < min )
mid = ( min + max ) >> 1;
}
return result;
@ -137,25 +133,19 @@ THE SOFTWARE.
{
BDF_CMap cmap = (BDF_CMap)bdfcmap;
BDF_encoding_el* encodings = cmap->encodings;
FT_ULong min, max, mid; /* num_encodings */
FT_UShort result = 0; /* encodings->glyph */
FT_ULong charcode = *acharcode + 1;
FT_ULong min = 0;
FT_ULong max = cmap->num_encodings;
FT_ULong mid = ( min + max ) >> 1;
min = 0;
max = cmap->num_encodings;
mid = ( min + max ) >> 1;
while ( min < max )
{
FT_ULong code; /* same as BDF_encoding_el.enc */
FT_ULong code = encodings[mid].enc;
if ( mid >= max || mid < min )
mid = ( min + max ) >> 1;
code = encodings[mid].enc;
if ( charcode == code )
{
/* increase glyph index by 1 -- */
@ -171,6 +161,8 @@ THE SOFTWARE.
/* prediction in a continuous block */
mid += charcode - code;
if ( mid >= max || mid < min )
mid = ( min + max ) >> 1;
}
charcode = 0;

24
src/pfr/pfrcmap.c
View File

@ -69,17 +69,14 @@
pfr_cmap_char_index( PFR_CMap cmap,
FT_UInt32 char_code )
{
FT_UInt min = 0;
FT_UInt max = cmap->num_chars;
FT_UInt min = 0;
FT_UInt max = cmap->num_chars;
FT_UInt mid = min + ( max - min ) / 2;
PFR_Char gchar;
while ( min < max )
{
PFR_Char gchar;
FT_UInt mid;
mid = min + ( max - min ) / 2;
gchar = cmap->chars + mid;
if ( gchar->char_code == char_code )
@ -89,6 +86,11 @@
min = mid + 1;
else
max = mid;
/* reasonable prediction in a continuous block */
mid += char_code - gchar->char_code;
if ( mid >= max || mid < min )
mid = min + ( max - min ) / 2;
}
return 0;
}
@ -106,13 +108,12 @@
{
FT_UInt min = 0;
FT_UInt max = cmap->num_chars;
FT_UInt mid;
FT_UInt mid = min + ( max - min ) / 2;
PFR_Char gchar;
while ( min < max )
{
mid = min + ( ( max - min ) >> 1 );
gchar = cmap->chars + mid;
if ( gchar->char_code == char_code )
@ -132,6 +133,11 @@
min = mid + 1;
else
max = mid;
/* reasonable prediction in a continuous block */
mid += char_code - gchar->char_code;
if ( mid >= max || mid < min )
mid = min + ( max - min ) / 2;
}
/* we didn't find it, but we have a pair just above it */

31
src/psnames/psmodule.c
View File

@ -412,21 +412,18 @@
ps_unicodes_char_index( PS_Unicodes table,
FT_UInt32 unicode )
{
PS_UniMap *min, *max, *mid, *result = NULL;
PS_UniMap *result = NULL;
PS_UniMap *min = table->maps;
PS_UniMap *max = min + table->num_maps;
PS_UniMap *mid = min + ( ( max - min ) >> 1 );
/* Perform a binary search on the table. */
min = table->maps;
max = min + table->num_maps - 1;
while ( min <= max )
while ( min < max )
{
FT_UInt32 base_glyph;
mid = min + ( ( max - min ) >> 1 );
if ( mid->unicode == unicode )
{
result = mid;
@ -438,13 +435,15 @@
if ( base_glyph == unicode )
result = mid; /* remember match but continue search for base glyph */
if ( min == max )
break;
if ( base_glyph < unicode )
min = mid + 1;
else
max = mid - 1;
max = mid;
/* reasonable prediction in a continuous block */
mid += unicode - base_glyph;
if ( mid >= max || mid < min )
mid = min + ( ( max - min ) >> 1 );
}
if ( result )
@ -465,14 +464,13 @@
{
FT_UInt min = 0;
FT_UInt max = table->num_maps;
FT_UInt mid;
FT_UInt mid = min + ( ( max - min ) >> 1 );
PS_UniMap* map;
FT_UInt32 base_glyph;
while ( min < max )
{
mid = min + ( ( max - min ) >> 1 );
map = table->maps + mid;
if ( map->unicode == char_code )
@ -490,6 +488,11 @@
min = mid + 1;
else
max = mid;
/* reasonable prediction in a continuous block */
mid += char_code - base_glyph;
if ( mid >= max || mid < min )
mid = min + ( max - min ) / 2;
}
if ( result )