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vt fontcvt: Use a hash to speed up glyph deduplication

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Walking a linked list of all glyphs to look for a duplicate is very slow
for large fonts (e.g., for CJK character sets).  In my test the runtime
for a sample 40000 character font went from just over 80 seconds on
average to just over 2 seconds.

Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Ed Maste 2014-06-04 03:02:49 +00:00
parent fe0a62f58d
commit 1b92a37c1c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=267035
1 changed files with 12 additions and 7 deletions
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19
tools/tools/vt/fontcvt/fontcvt.c
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@ -30,6 +30,8 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/fnv_hash.h>
#include <sys/endian.h>
#include <sys/param.h>
#include <sys/queue.h>
@ -49,11 +51,14 @@ static unsigned int width = 8, wbytes, height = 16;
struct glyph {
TAILQ_ENTRY(glyph) g_list;
SLIST_ENTRY(glyph) g_hash;
uint8_t *g_data;
unsigned int g_index;
};
#define FONTCVT_NHASH 4096
TAILQ_HEAD(glyph_list, glyph);
static SLIST_HEAD(, glyph) glyph_hash[FONTCVT_NHASH];
static struct glyph_list glyphs[VFNT_MAPS] = {
TAILQ_HEAD_INITIALIZER(glyphs[0]),
TAILQ_HEAD_INITIALIZER(glyphs[1]),
@ -147,17 +152,16 @@ static struct glyph *
add_glyph(const uint8_t *bytes, unsigned int map_idx, int fallback)
{
struct glyph *gl;
unsigned int i;
int hash;
glyph_total++;
glyph_count[map_idx]++;
for (i = 0; i < VFNT_MAPS; i++) {
TAILQ_FOREACH(gl, &glyphs[i], g_list) {
if (memcmp(gl->g_data, bytes, wbytes * height) == 0) {
glyph_dupe++;
return (gl);
}
hash = fnv_32_buf(bytes, wbytes * height, FNV1_32_INIT) % FONTCVT_NHASH;
SLIST_FOREACH(gl, &glyph_hash[hash], g_hash) {
if (memcmp(gl->g_data, bytes, wbytes * height) == 0) {
glyph_dupe++;
return (gl);
}
}
@ -168,6 +172,7 @@ add_glyph(const uint8_t *bytes, unsigned int map_idx, int fallback)
TAILQ_INSERT_HEAD(&glyphs[map_idx], gl, g_list);
else
TAILQ_INSERT_TAIL(&glyphs[map_idx], gl, g_list);
SLIST_INSERT_HEAD(&glyph_hash[hash], gl, g_hash);
glyph_unique++;
return (gl);