From a32b211d2089089072dd236880704c1c5b37a0fe Mon Sep 17 00:00:00 2001
From: Alessandro Mauri <alemauri001@gmail.com>
Date: Sat, 11 Feb 2023 10:46:46 +0100
Subject: [PATCH] cache

---
 cache/cache.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 cache/cache.c

diff --git a/cache/cache.c b/cache/cache.c
new file mode 100644
index 0000000..0ab3ba3
--- /dev/null
+++ b/cache/cache.c
@@ -0,0 +1,73 @@
+#define _POSIX_C_SOURCE 200809l
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <search.h>
+
+#define CACHE_SIZE 512
+
+static struct hsearch_data hash_table;
+struct data {
+	unsigned int glyph;
+	unsigned int w, h, u, v;
+};
+static struct data 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;
+
+
+void cache_init()
+{
+	hcreate_r(CACHE_SIZE, &hash_table);
+}
+
+
+void cache_destroy()
+{
+	hdestroy_r(&hash_table);
+}
+
+
+// d->glyph already contains the right glyph 
+struct data * cache_get(uint32_t glyph)
+{
+	static char gstr[5] = {0};
+	static ENTRY e, *r;
+	memcpy(gstr, &glyph, 4);
+	e.data = gstr;
+	hsearch_r(e, FIND, &r, &hash_table);
+	
+	// miss
+	if (!r)
+		return NULL;
+	
+	// hit
+	cycles = (cycles+1)%NCYCLES;
+	if (!cycles) B_RESET();
+	B_SET((struct data *)(r->data)-cache_array);
+	return (struct data *)(r->data);
+}
+
+
+int cache_insert(struct data *d)
+{
+	struct data *spot = NULL;
+	uint32_t x = 0;
+	for (; x < CACHE_SIZE; x++)
+		if (!B_TEST(x))
+			break;
+}