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text_rendering/cache.c

@@ -0,0 +1,106 @@
+#define _POSIX_C_SOURCE 200809l
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "hash.h"
+#include "font.h"
+#include "util.h"
+
+
+static struct hm_ref *hash_table;
+static struct font_glyph cache_array[CACHE_SIZE] = {0};
+
+// bitmap size is aligned to word
+#define _BSIZE ((CACHE_SIZE+0x3f)&(~0x3f))
+static uint64_t bitmap[_BSIZE] = {0};
+
+// bitmap operations
+#define B_RESET() memset(bitmap, 0, _BSIZE*sizeof(uint64_t))
+#define B_SET(x)  bitmap[(x)/_BSIZE] |= 1<<((x)%_BSIZE)
+#define B_TEST(x) (bitmap[(x)/_BSIZE]&(1<<((x)%_BSIZE)))
+
+// reset the bitmap every n cycles
+#define NCYCLES (CACHE_SIZE/2)
+static int cycles = 0;
+
+
+static inline void set_bit(unsigned int x)
+{
+//	printf("cycles: %d, set: %d\n", cycles, x);
+	cycles = (cycles+1)%NCYCLES;
+	if (!cycles) B_RESET();
+	B_SET(x);
+}
+
+
+void cache_init(void)
+{
+	hash_table = hm_create(CACHE_SIZE);
+}
+
+
+void cache_destroy(void)
+{
+	hm_destroy(hash_table);
+}
+
+
+struct font_glyph * cache_get(unsigned int code)
+{
+	struct hm_entry *r = hm_search(hash_table, code);
+
+	// miss
+	if (!r)
+		return NULL;
+
+	// hit
+	set_bit((struct font_glyph *)(r->data)-cache_array);
+	return (struct font_glyph *)(r->data);
+}
+
+
+int cache_insert(struct font_glyph *g)
+{
+	struct font_glyph *spot = NULL;
+	uint32_t x = 0;
+	// find an open spot in the cache
+	// TODO: use __builtin_clz to speed this up
+	for (; x < CACHE_SIZE; x++) {
+//		printf("test: %d\n", x);
+		if (!B_TEST(x))
+			break;
+	}
+
+	// allocation in cache failed
+	if (B_TEST(x))
+		return -1;
+
+	set_bit(x);
+	spot = &cache_array[x];
+	*spot = *g;
+
+/*
+	for (int i = 0; i < _BSIZE; i++) {
+		//print_byte(bitmap[i]);
+		//print_byte(bitmap[i]>>8);
+		//print_byte(bitmap[i]>>16);
+		//print_byte(bitmap[i]>>24);
+		//print_byte(bitmap[i]>>32);
+		//print_byte(bitmap[i]>>40);
+		//print_byte(bitmap[i]>>48);
+		//print_byte(bitmap[i]>>56);
+		printf("%lx", bitmap[i]);
+	}
+	printf("\n");
+*/
+
+	struct hm_entry e = { .code  = g->codepoint, .data = spot};
+	if (!hm_insert(hash_table, &e))
+		return -1;
+
+	return 0;
+}

text_rendering/cache.h

@@ -0,0 +1,10 @@
+#ifndef _CACHE_H
+#define _CACHE_H
+
+void cache_init(void);
+void cache_destroy(void);
+struct font_glyph * cache_get(unsigned int code);
+int cache_insert(struct font_glyph *g);
+
+
+#endif

text_rendering/font.c

@@ -0,0 +1,66 @@
+#define _POSIX_C_SOURCE 200809l
+#define STB_TRUETYPE_IMPLEMENTATION
+#define STBTT_STATIC
+
+#include <grapheme.h>
+
+#include "stb_truetype.h"
+#include "util.h"
+#include "font.h"
+
+
+#define UTF8(c) (c&0x80)
+
+
+// Generates a cached atlas of font glyphs encoded usign a signed distance field
+// https://www.youtube.com/watch?v=1b5hIMqz_wM
+// https://github.com/pjako/msdf_c
+// this way the texture atlas for the font will be bigger but we save up the space
+// needed for rendering the font in multiple sizes
+
+
+struct font_atlas {
+	unsigned int glyphs, width, height;
+	unsigned char *atlas;
+	unsigned int glyph_max_w, glyph_max_h;
+
+	struct {
+		stbtt_fontinfo info;
+		float scale;
+	} stb;
+	int file_size;
+	unsigned char *file;
+};
+
+
+// loads a font into memory, storing all the ASCII characters in the atlas
+int load_font(struct font_atlas *atlas, const char *path, int height)
+{
+	if (!atlas || !path)
+		return -1;
+
+	dump_file(path, &(atlas->file), &(atlas->file_size));
+
+	stbtt_InitFont(&(atlas->stb.info), atlas->file, 0);
+	atlas->stb.scale = stbtt_ScaleForPixelHeight(&(atlas->stb.info), height);
+	int ascent, descent, linegap, baseline;
+	int x0,y0,x1,y1;
+	stbtt_GetFontVMetrics(&(atlas->stb.info), &ascent, &descent, &linegap);
+	stbtt_GetFontBoundingBox(&(atlas->stb.info), &x0, &y0, &x1, &y1);
+
+	baseline = atlas->stb.scale * -y0;
+	atlas->glyph_max_w = (atlas->stb.scale*x1) - (atlas->stb.scale*x0);
+	atlas->glyph_max_h = (baseline+atlas->stb.scale*y1) - (baseline+atlas->stb.scale*y0);
+
+	atlas->atlas = emalloc(atlas->glyph_max_w*atlas->glyph_max_h*CACHE_SIZE);
+
+	return 0;
+}
+
+
+int free_font(struct font_atlas *atlas)
+{
+	efree(atlas->atlas);
+	efree(atlas->file);
+	return 0;
+}

text_rendering/font.h

@@ -0,0 +1,40 @@
+#ifndef _FONT_H
+#define _FONT_H
+
+#define CACHE_SIZE 512
+
+/* width and height of a glyph contain the kering advance
+ * (u,v)
+ *   +----------*---+ -
+ *   |   .ii.   |   | ^
+ *   |  @@@@@@. |<->| |
+ *   | V@Mio@@o |adv| |
+ *   | :i.  V@V |   | |
+ *   |   :oM@@M |   | |
+ *   | :@@@MM@M |   | |
+ *   | @@o  o@M |   | |
+ *   |:@@.  M@M |   | |
+ *   | @@@o@@@@ |   | |
+ *   | :M@@V:@@.|   | v
+ *   +----------*---+ -
+ *   |<------------->|
+ *           w
+ */
+struct font_glyph {
+	unsigned int codepoint;
+	unsigned int u, v, w, h;
+};
+
+
+struct font_atlas;
+
+int load_font(struct font_atlas *atlas, const char *path, int height);
+int free_font(struct font_atlas *atlas);
+
+void cache_init(void);
+void cache_destroy(void);
+struct font_glyph * cache_get(unsigned int code);
+int cache_insert(struct font_glyph *g);
+
+
+#endif

text_rendering/hash.c

@@ -0,0 +1,76 @@
+#define _POSIX_C_SOURCE 200809l
+#define _DEFAULT_SOURCE
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "hash.h"
+
+#define MAXSIZE 4096
+
+
+static unsigned int hash(unsigned int code)
+{
+	// identity map the ascii range
+	if (code < 128) return code;
+	return (uint32_t)((uint64_t)(code*2654435761)>>32);
+}
+
+
+struct hm_ref * hm_create(unsigned int size)
+{
+	if (!size || size > MAXSIZE)
+		return NULL;
+
+	// round to the greater power of two
+	size = 1<<__builtin_clz(size);
+
+	// FIXME: check for intger overflow here
+	struct hm_ref *h = malloc(sizeof(struct hm_ref)+sizeof(struct hm_entry)*size);
+	if (h) {
+		h->items = 0;
+		h->size  = size;
+		memset(h->bucket, 0, sizeof(struct hm_ref)*size);
+	}
+	return h;
+}
+
+
+void hm_destroy(struct hm_ref *hm)
+{
+	free(hm);
+}
+
+
+static struct hm_entry * lookup(struct hm_ref *hm, unsigned int code)
+{
+	// fast modulo operation for power-of-2 size
+	unsigned int mask = hm->size - 1;
+	unsigned int i = hash(code);
+	for (unsigned int j = 1; ; i += j++) {
+		if (!hm->bucket[i&mask].code || hm->bucket[i].code == code)
+			return &(hm->bucket[i&mask]);
+	}
+	return NULL;
+}
+
+
+struct hm_entry * hm_search(struct hm_ref *hm, unsigned int code)
+{
+	struct hm_entry *r = lookup(hm, code);
+	if (r) {
+		if (r->code == code)
+			return r;
+		return NULL;
+	}
+	return r;
+}
+
+
+struct hm_entry * hm_insert(struct hm_ref *hm, struct hm_entry *entry)
+{
+	struct hm_entry *r = lookup(hm, entry->code);
+	if (r) *r = *entry;
+	return r;
+}

text_rendering/hash.h

@@ -0,0 +1,21 @@
+#ifndef _HASH_H
+#define _HASH_H
+
+struct hm_entry {
+	unsigned long code;
+	void *data;
+};
+
+
+struct hm_ref {
+	unsigned int items, size;
+	struct hm_entry bucket[];
+};
+
+
+struct hm_ref * hm_create(unsigned int size);
+void hm_destroy(struct hm_ref *hm);
+struct hm_entry * hm_search(struct hm_ref *hm, unsigned int code);
+struct hm_entry * hm_insert(struct hm_ref *hm, struct hm_entry *entry);
+
+#endif

text_rendering/main.c

@@ -0,0 +1,35 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <grapheme.h>
+
+#include "cache.h"
+#include "font.h"
+
+
+int main(void)
+{
+	cache_init();
+
+	struct font_glyph *g, b;
+	b.codepoint = 'a';
+	b.u = b.v = 10;
+	b.w = b.h = 20;
+
+	g = cache_get('a');
+	if (!g)	printf("no element\n");
+	g = cache_get(0xa3c0);
+	if (!g) printf("not present\n");
+
+	const char *s = "κόσμε ciao mamma @à``²`²aas³³²";
+	size_t ret, off;
+	uint_least32_t cp;
+	for (off = 0; (ret = grapheme_decode_utf8(s+off, SIZE_MAX, &cp)) > 0 && cp != 0; off += ret) {
+		printf("%.*s (%d) -> %d\n", (int)ret, s+off, (int)ret, cp);
+		b.codepoint = cp;
+		if (cache_insert(&b)) printf("failed insert %d\n", b.codepoint);
+		if ((g = cache_get(cp))) printf("got %d\n", g->codepoint);
+	}
+
+	cache_destroy();
+	return 0;
+}

text_rendering/util.c

@@ -0,0 +1,98 @@
+#define _POSIX_C_SOURCE 200809l
+
+#include <sys/mman.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <err.h>
+
+#include "util.h"
+
+
+const char *bit_rep[16] = {
+    [ 0] = "0000", [ 1] = "0001", [ 2] = "0010", [ 3] = "0011",
+    [ 4] = "0100", [ 5] = "0101", [ 6] = "0110", [ 7] = "0111",
+    [ 8] = "1000", [ 9] = "1001", [10] = "1010", [11] = "1011",
+    [12] = "1100", [13] = "1101", [14] = "1110", [15] = "1111",
+};
+
+
+
+void * emalloc(unsigned long int size)
+{
+	void *r = malloc(size);
+	if (!r)
+		err(EXIT_FAILURE, "malloc() of size %ld", size);
+	return r;
+}
+
+
+void * ecalloc(unsigned long int nmemb, unsigned long int size)
+{
+	void *r = calloc(nmemb, size);
+	if (!r)
+		err(EXIT_FAILURE, "calloc() of size %ld, nmemb %ld", size, nmemb);
+	return r;
+}
+
+
+void efree(void *ptr)
+{
+	if (ptr)
+		free(ptr);
+}
+
+
+void map_file(const unsigned char **str, int *size, const char *path)
+{
+	if (!path) {
+		errno = EINVAL;
+		err(EXIT_FAILURE, "NULL filename");
+	}
+	FILE *fp = fopen(path, "r");
+	if (!fp)
+		err(EXIT_FAILURE, "Cannot open file %s", path);
+	*size = lseek(fileno(fp), 0, SEEK_END);
+	if (*size == (off_t)-1)
+		err(EXIT_FAILURE, "lseek() failed");
+	*str = mmap(0, *size, PROT_READ, MAP_PRIVATE, fileno(fp), 0);
+	if (*str == (void*)-1)
+		err(EXIT_FAILURE, "mmap() failed");
+	if (fclose(fp))
+		err(EXIT_FAILURE, "Error closing file");
+}
+
+
+void dump_file(const char *path, unsigned char **buf, int *buf_len)
+{
+	if (!path) {
+		errno = EINVAL;
+		err(EXIT_FAILURE, "NULL filename");
+	}
+	if (!buf) {
+		errno = EINVAL;
+		err(EXIT_FAILURE, "No buffer specified");
+	}
+	if (!buf_len) {
+		errno = EINVAL;
+		err(EXIT_FAILURE, "Nowhere to store buffer size");
+	}
+	FILE *fp = fopen(path, "r");
+	if (!fp)
+		err(EXIT_FAILURE, "Cannot open file %s", path);
+	*buf_len = lseek(fileno(fp), 0, SEEK_END);
+	if (*buf_len == (off_t)-1)
+		err(EXIT_FAILURE, "lseek() failed");
+	*buf = emalloc(*buf_len);
+	*buf_len = fread(*buf, 1, *buf_len, fp);
+	if (fclose(fp))
+		err(EXIT_FAILURE, "Error closing file");
+}
+
+
+void print_byte(unsigned char byte)
+{
+	printf("%s%s", bit_rep[byte >> 4], bit_rep[byte & 0x0F]);
+}

text_rendering/util.h

@@ -0,0 +1,13 @@
+#ifndef _UTIL_H
+#define _UTIL_H
+
+void * emalloc(unsigned long int size);
+void * ecalloc(unsigned long int nmemb, unsigned long int size);
+void efree(void *ptr);
+
+void map_file(const unsigned char **str, int *size, const char *path);
+void dump_file(const char *path, unsigned char **buf, int *buf_len);
+
+void print_byte(unsigned char byte);
+
+#endif