Buffer refactor and buffer bug fixes

src/SubtitleOctopus.cpp

@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
+#include <cstdint>
 #include "../lib/libass/libass/ass.h"
 
 #include "libass.cpp"
@@ -19,50 +20,66 @@
 
 int log_level = 3;
 
-typedef struct {
+class ReusableBuffer2D {
+private:
     void *buffer;
-    int size;
+    size_t size;
     int lessen_counter;
-} buffer_t;
-
-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
-            buf->lessen_counter++;
-        } else {
-            buf->lessen_counter = 0;
-        }
-        if (buf->lessen_counter < 10) {
-            // not reducing the buffer yet
-            return buf->buffer;
-        }
-    }
 
-    void *newbuf;
-    if (keep_content) {
-        newbuf = realloc(buf->buffer, new_size);
-    } else {
-        newbuf = malloc(new_size);
+public:
+    ReusableBuffer2D(): buffer(NULL), size(0), lessen_counter(0) {}
+
+    ~ReusableBuffer2D() {
+        free(buffer);
     }
-    if (!newbuf) return NULL;
 
-    if (!keep_content) free(buf->buffer);
-    buf->buffer = newbuf;
-    buf->size = new_size;
-    buf->lessen_counter = 0;
-    return buf->buffer;
-}
+    void clear() {
+        free(buffer);
+        buffer = NULL;
+        size = 0;
+        lessen_counter = 0;
+    }
 
-void buffer_init(buffer_t *buf) {
-    buf->buffer = NULL;
-    buf->size = -1;
-    buf->lessen_counter = 0;
-}
+    /*
+     * Request a raw pointer to a buffer being able to hold at least
+     * x times y values of size member_size.
+     * If zero is set to true, the requested region will be zero-initialised.
+     * On failure NULL is returned.
+     * The pointer is valid during the lifetime of the ReusableBuffer
+     * object until the next call to get_rawbuf or clear.
+     */
+    void *get_rawbuf(size_t x, size_t y, size_t member_size, bool zero) {
+        if (x > SIZE_MAX / member_size / y)
+            return NULL;
+
+        size_t new_size = x * y * member_size;
+        if (!new_size) new_size = 1;
+        if (size >= new_size) {
+            if (size >= 1.3 * new_size) {
+                // big reduction request
+                lessen_counter++;
+            } else {
+                lessen_counter = 0;
+            }
+            if (lessen_counter < 10) {
+                // not reducing the buffer yet
+                if (zero)
+                    memset(buffer, 0, new_size);
+                return buffer;
+            }
+        }
 
-void buffer_free(buffer_t *buf) {
-    free(buf->buffer);
-}
+        free(buffer);
+        buffer = malloc(new_size);
+        if (buffer) {
+            size = new_size;
+            memset(buffer, 0, size);
+        } else
+            size = 0;
+        lessen_counter = 0;
+        return buffer;
+    }
+};
 
 void msg_callback(int level, const char *fmt, va_list va, void *data) {
     if (level > log_level) // 6 for verbose
@@ -131,7 +148,7 @@ class SubtitleOctopus {
         resizeCanvas(frame_w, frame_h);
 
         reloadFonts();
-        buffer_init(&m_blend);
+        m_blend.clear();
     }
 
     /* TRACK */
@@ -177,7 +194,7 @@ class SubtitleOctopus {
         ass_free_track(track);
         ass_renderer_done(ass_renderer);
         ass_library_done(ass_library);
-        buffer_free(&m_blend);
+        m_blend.clear();
     }
     void reloadLibrary() {
         quitLibrary();
@@ -268,12 +285,11 @@ class SubtitleOctopus {
         }
 
         // make float buffer for blending
-        float* buf = (float*)buffer_resize(&m_blend, sizeof(float) * width * height * 4, 0);
+        float* buf = (float*)m_blend.get_rawbuf(width, height, sizeof(float) * 4, true);
         if (buf == NULL) {
             fprintf(stderr, "jso: cannot allocate buffer for blending\n");
             return &m_blendResult;
         }
-        memset(buf, 0, sizeof(float) * width * height * 4);
 
         // blend things in
         for (cur = img; cur != NULL; cur = cur->next) {
@@ -348,7 +364,7 @@ class SubtitleOctopus {
     }
 
 private:
-    buffer_t m_blend;
+    ReusableBuffer2D m_blend;
     RenderBlendResult m_blendResult;
 };