Make blend_render re-use buffer - thread-unsafe but more optimized

Author: JustAMan

src/SubtitleOctopus.cpp

@@ -24,7 +24,7 @@ typedef struct {
 
 buffer_t blend, blend_result;
 
-int buffer_resize(buffer_t *buf, int new_size, int keep_content) {
+void* buffer_resize(buffer_t *buf, int new_size, int keep_content) {
     if (buf->size >= new_size) {
         if (buf->size >= 1.3 * new_size) {
             // big reduction request
@@ -34,7 +34,7 @@ int buffer_resize(buffer_t *buf, int new_size, int keep_content) {
         }
         if (buf->lessen_counter < 30) {
             // not reducing the buffer yet
-            return 1;
+            return buf->buffer;
         }
     }
 
@@ -44,12 +44,12 @@ int buffer_resize(buffer_t *buf, int new_size, int keep_content) {
     } else {
         newbuf = malloc(new_size);
     }
-    if (!newbuf) return 0;
+    if (!newbuf) return NULL;
 
     buf->buffer = newbuf;
     buf->size = new_size;
     buf->lessen_counter = 0;
-    return 1;
+    return buf->buffer;
 }
 
 void buffer_init(buffer_t *buf) {
@@ -108,6 +108,8 @@ class SubtitleOctopus {
         resizeCanvas(frame_w, frame_h);
 
         reloadFonts();
+        buffer_init(&blend);
+        buffer_init(&blend_result);
     }
 
     /* TRACK */
@@ -143,7 +145,6 @@ class SubtitleOctopus {
         canvas_h = frame_h;
         canvas_w = frame_w;
     }
-
     ASS_Image* renderImage(double time, int* changed) {
         ASS_Image *img = ass_render_frame(ass_renderer, track, (int) (time * 1000), changed);
         return img;
@@ -154,8 +155,9 @@ class SubtitleOctopus {
         ass_free_track(track);
         ass_renderer_done(ass_renderer);
         ass_library_done(ass_library);
+        free(blend.buffer);
+        free(blend_result.buffer);
     }
-
     void reloadLibrary() {
         quitLibrary();
 
@@ -238,15 +240,15 @@ void* libassjs_render_blend(double tm, int force, int *changed, double *blend_ti
 
     // make float buffer for blending
     int width = max_x - min_x + 1, height = max_y - min_y + 1;
-    float* buf = (float*)malloc(sizeof(float) * width * height * 4);
+    float* buf = (float*)buffer_resize(&blend, sizeof(float) * width * height * 4, 0);
     if (buf == NULL) {
         printf("libass: error: cannot allocate buffer for blending");
         return NULL;
     }
-    unsigned char *result = (unsigned char*)malloc(sizeof(unsigned char) * width * height * 4);
+    unsigned char *result = (unsigned char*)buffer_resize(&blend_result,
+            sizeof(unsigned char) * width * height * 4, 0);
     if (result == NULL) {
         printf("libass: error: cannot allocate result for blending");
-        free(buf);
         return NULL;
     }
     memset(buf, 0, sizeof(float) * width * height * 4);
@@ -308,7 +310,6 @@ void* libassjs_render_blend(double tm, int force, int *changed, double *blend_ti
     }
 
     // return the thing
-    free(buf);
     *dest_x = min_x;
     *dest_y = min_y;
     *dest_width = width;

src/post-worker.js

@@ -209,7 +209,6 @@ self.blendRender = function (force) {
             var blendH = Module.getValue(self.blendH, 'i32');
             // make a copy, as we should free the memory so subsequent calls can utilize it
             var result = new Uint8Array(HEAPU8.subarray(renderResult, renderResult + blendW * blendH * 4));
-            Module._free(renderResult);
 
             canvases = [{w: blendW, h: blendH, x: blendX, y: blendY, buffer: result.buffer}];
             buffers = [result.buffer];