Use uthash for the sprite position cache

kitty/glyph-cache.c

@@ -0,0 +1,67 @@
+/*
+ * glyph-cache.c
+ * Copyright (C) 2021 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#include "glyph-cache.h"
+#include "uthash.h"
+
+
+#undef uthash_fatal
+#define uthash_fatal(msg) fatal(msg)
+
+
+typedef struct SpritePosItem {
+    SpritePositionHead
+    UT_hash_handle hh;
+    glyph_index key[];
+} SpritePosItem;
+
+static glyph_index *scratch = NULL;
+static unsigned scratch_sz = 0;
+
+
+void
+free_glyph_cache_global_resources(void) {
+    free(scratch);
+    scratch = NULL; scratch_sz = 0;
+}
+
+
+static inline unsigned
+key_size_for_glyph_count(unsigned count) { return count + 2; }
+
+
+SpritePosition*
+find_or_create_sprite_position(SpritePosition **head_, glyph_index *glyphs, glyph_index count, glyph_index ligature_index, bool *created) {
+    SpritePosItem **head = (SpritePosItem**)head_, *p;
+    const unsigned key_sz = key_size_for_glyph_count(count);
+    if (key_sz > scratch_sz) {
+        scratch = realloc(scratch, key_sz + 16);
+        if (!scratch) return NULL;
+        scratch_sz = key_sz + 16;
+    }
+    const unsigned key_sz_bytes = key_sz * sizeof(glyph_index);
+    scratch[0] = count; scratch[1] = ligature_index;
+    memcpy(scratch + 2, glyphs, count * sizeof(glyph_index));
+    HASH_FIND(hh, *head, scratch, key_sz_bytes, p);
+    if (p) { *created = false; return (SpritePosition*)p; }
+
+    p = calloc(1, sizeof(SpritePosItem) + key_sz_bytes);
+    if (!p) return NULL;
+    memcpy(p->key, scratch, key_sz_bytes);
+    HASH_ADD(hh, *head, key, key_sz_bytes, p);
+    *created = true;
+    return (SpritePosition*)p;
+}
+
+void
+free_sprite_position_hash_table(SpritePosition **head_) {
+    SpritePosItem **head = (SpritePosItem**)head_, *s, *tmp;
+    HASH_ITER(hh, *head, s, tmp) {
+        HASH_DEL(*head, s);
+        free(s);
+    }
+}