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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;
+}