replace per-tick allocations in push_text with an arena/bump allocator

apps/scenery/scenes/title.c

@@ -37,13 +37,8 @@ static void title_tick(State *state) {
         },
         (Color) { 0, 0, 0, 255 }
     );
-    push_text(
-        text_str,
-        (Vec2){ 0, 0 },
-        text_h,
-        (Color) { 255, 255, 255, 255 },
-        font
-    );
+    push_text(text_str, (Vec2){ 0, 0 }, text_h, (Color) { 255, 255, 255, 255 }, font);
+
     free(text_str);
 }
 

src/rendering/twn_rendering.c

@@ -22,13 +22,7 @@ Matrix4 camera_look_at_matrix;
 
 
 void render_queue_clear(void) {
-    /* this doesn't even _deserve_ a TODO */
-    /* if you're gonna remove it, this is also being done in main.c */
-    for (size_t i = 0; i < arrlenu(ctx.render_queue_2d); ++i) {
-        if (ctx.render_queue_2d[i].type == PRIMITIVE_2D_TEXT) {
-            SDL_free(ctx.render_queue_2d[i].text.text);
-        }
-    }
+    text_cache_reset_arena(&ctx.text_cache);
     
     /* since i don't intend to free the queues, */
     /* it's faster and simpler to just "start over" */

src/rendering/twn_rendering_c.h

@@ -154,6 +154,8 @@ void text_cache_init(TextCache *cache);
 
 void text_cache_deinit(TextCache *cache);
 
+void text_cache_reset_arena(TextCache *cache);
+
 /* vertex buffer */
 
 VertexBuffer create_vertex_buffer(void);

src/rendering/twn_text.c

@@ -11,6 +11,88 @@
 #define ASCII_END 128
 #define NUM_DISPLAY_ASCII ((ASCII_END - ASCII_START) + 1)
 
+/* should be large enough that there's virtually never more than one block */
+#define STRING_ARENA_BLOCK_SIZE 512000
+
+
+typedef struct StringArenaBlock {
+    struct StringArenaBlock *next;
+    char *buffer;
+    size_t used;
+} StringArenaBlock;
+
+
+typedef struct StringArena {
+    StringArenaBlock *head;
+    StringArenaBlock *current_block;
+    char *ptr;
+} StringArena;
+
+static StringArena string_arena;
+
+
+static void string_arena_init(StringArena *arena) {
+    arena->head = cmalloc(sizeof *arena->head);
+    arena->current_block = arena->head;
+    arena->ptr = arena->current_block->buffer;
+
+    arena->current_block->next = NULL;
+    arena->current_block->buffer = cmalloc(STRING_ARENA_BLOCK_SIZE);
+    arena->current_block->used = 0;
+}
+
+
+static void string_arena_deinit(StringArena *arena) {
+    StringArenaBlock *p = arena->head;
+    while (p != NULL) {
+        StringArenaBlock *block = p;
+        p = block->next; /* need to keep this before freeing */
+
+        SDL_free(block->buffer);
+        SDL_free(block);
+    }
+}
+
+
+static void string_arena_reset(StringArena *arena) {
+    arena->current_block = arena->head;
+    arena->current_block->used = 0;
+    arena->ptr = arena->current_block->buffer;
+}
+
+
+static char *string_arena_alloc(StringArena *arena, size_t size) {
+    /* will never fit! */
+    if (size > STRING_ARENA_BLOCK_SIZE) {
+        /* is there a more graceful way to handle this without risking some sort of horror? */
+        CRY("String arena allocation failure", "Tried to allocate a size larger than the block size");
+        die_abruptly();
+    }
+
+    /* won't fit, we need a new block first */
+    if (arena->current_block->used + size > STRING_ARENA_BLOCK_SIZE) {
+        log_info("String arena block size exceeded, moving on to the next...");
+
+        /* only allocate if there wasn't one ready to go already */
+        if (arena->current_block->next == NULL) {
+            log_info("Allocating string arena block...");
+
+            arena->current_block->next = cmalloc(sizeof *arena->head);
+            arena->current_block->next->next = NULL;
+            arena->current_block->next->buffer = cmalloc(STRING_ARENA_BLOCK_SIZE);
+        }
+
+        arena->current_block = arena->current_block->next;
+        arena->current_block->used = 0;
+        arena->ptr = arena->current_block->buffer;
+    }
+
+    char *chunk = arena->ptr;
+    arena->ptr += size;
+    arena->current_block->used += size * (sizeof *arena->ptr);
+    return chunk;
+}
+
 
 static FontData *text_load_font_data(const char *path, int height_px) {
     FontData *font_data = ccalloc(1, sizeof *font_data);
@@ -146,6 +228,7 @@ void render_text(const TextPrimitive *text) {
 
 void text_cache_init(TextCache *cache) {
     arrsetlen(cache->data, 0);
+    string_arena_init(&string_arena);
 }
 
 
@@ -155,6 +238,13 @@ void text_cache_deinit(TextCache *cache) {
     }
 
     arrfree(cache->data);
+    string_arena_deinit(&string_arena);
+}
+
+
+void text_cache_reset_arena(TextCache *cache) {
+    (void)cache;
+    string_arena_reset(&string_arena);
 }
 
 
@@ -162,8 +252,9 @@ void push_text(char *string, Vec2 position, int height_px, Color color, const ch
     ensure_font_cache(font_path, height_px);
 
     /* the original string might not be around by the time it's used, so copy it */
-    /* TODO: arena */
-    char *dup_string = SDL_strdup(string);
+    size_t str_length = SDL_strlen(string) + 1;
+    char *dup_string = string_arena_alloc(&string_arena, str_length);
+    SDL_strlcpy(dup_string, string, str_length);
 
     TextPrimitive text = {
         .color = color,

src/twn_loop.c

@@ -372,18 +372,11 @@ static void clean_up(void) {
     */
 
     input_state_deinit(&ctx.game.input);    
-
-    /* if you're gonna remove this, it's also being done in rendering.c */
-    for (size_t i = 0; i < arrlenu(ctx.render_queue_2d); ++i) {
-        if (ctx.render_queue_2d[i].type == PRIMITIVE_2D_TEXT) {
-            SDL_free(ctx.render_queue_2d[i].text.text);
-        }
-    }
-    arrfree(ctx.render_queue_2d);
-
     text_cache_deinit(&ctx.text_cache);
     textures_cache_deinit(&ctx.texture_cache);
 
+    arrfree(ctx.render_queue_2d);
+
     PHYSFS_deinit();
     SDL_Quit();
 }