lavu: add a new API for reference-counted data buffers.

libavutil/buffer.c

@@ -0,0 +1,194 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include "atomic.h"
+#include "buffer_internal.h"
+#include "common.h"
+#include "mem.h"
+
+AVBufferRef *av_buffer_create(uint8_t *data, int size,
+                              void (*free)(void *opaque, uint8_t *data),
+                              void *opaque, int flags)
+{
+    AVBufferRef *ref = NULL;
+    AVBuffer    *buf = NULL;
+
+    buf = av_mallocz(sizeof(*buf));
+    if (!buf)
+        return NULL;
+
+    buf->data     = data;
+    buf->size     = size;
+    buf->free     = free ? free : av_buffer_default_free;
+    buf->opaque   = opaque;
+    buf->refcount = 1;
+
+    if (flags & AV_BUFFER_FLAG_READONLY)
+        buf->flags |= BUFFER_FLAG_READONLY;
+
+    ref = av_mallocz(sizeof(*ref));
+    if (!ref) {
+        av_freep(&buf);
+        return NULL;
+    }
+
+    ref->buffer = buf;
+    ref->data   = data;
+    ref->size   = size;
+
+    return ref;
+}
+
+void av_buffer_default_free(void *opaque, uint8_t *data)
+{
+    av_free(data);
+}
+
+AVBufferRef *av_buffer_alloc(int size)
+{
+    AVBufferRef *ret = NULL;
+    uint8_t    *data = NULL;
+
+    data = av_malloc(size);
+    if (!data)
+        return NULL;
+
+    ret = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
+    if (!ret)
+        av_freep(&data);
+
+    return ret;
+}
+
+AVBufferRef *av_buffer_allocz(int size)
+{
+    AVBufferRef *ret = av_buffer_alloc(size);
+    if (!ret)
+        return NULL;
+
+    memset(ret->data, 0, size);
+    return ret;
+}
+
+AVBufferRef *av_buffer_ref(AVBufferRef *buf)
+{
+    AVBufferRef *ret = av_mallocz(sizeof(*ret));
+
+    if (!ret)
+        return NULL;
+
+    *ret = *buf;
+
+    avpriv_atomic_int_add_and_fetch(&buf->buffer->refcount, 1);
+
+    return ret;
+}
+
+void av_buffer_unref(AVBufferRef **buf)
+{
+    AVBuffer *b;
+
+    if (!buf || !*buf)
+        return;
+    b = (*buf)->buffer;
+    av_freep(buf);
+
+    if (!avpriv_atomic_int_add_and_fetch(&b->refcount, -1)) {
+        b->free(b->opaque, b->data);
+        av_freep(&b);
+    }
+}
+
+int av_buffer_is_writable(const AVBufferRef *buf)
+{
+    if (buf->buffer->flags & AV_BUFFER_FLAG_READONLY)
+        return 0;
+
+    return avpriv_atomic_int_add_and_fetch(&buf->buffer->refcount, 0) == 1;
+}
+
+int av_buffer_make_writable(AVBufferRef **pbuf)
+{
+    AVBufferRef *newbuf, *buf = *pbuf;
+
+    if (av_buffer_is_writable(buf))
+        return 0;
+
+    newbuf = av_buffer_alloc(buf->size);
+    if (!newbuf)
+        return AVERROR(ENOMEM);
+
+    memcpy(newbuf->data, buf->data, buf->size);
+    av_buffer_unref(pbuf);
+    *pbuf = newbuf;
+
+    return 0;
+}
+
+int av_buffer_realloc(AVBufferRef **pbuf, int size)
+{
+    AVBufferRef *buf = *pbuf;
+    uint8_t *tmp;
+
+    if (!buf) {
+        /* allocate a new buffer with av_realloc(), so it will be reallocatable
+         * later */
+        uint8_t *data = av_realloc(NULL, size);
+        if (!data)
+            return AVERROR(ENOMEM);
+
+        buf = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
+        if (!buf) {
+            av_freep(&data);
+            return AVERROR(ENOMEM);
+        }
+
+        buf->buffer->flags |= BUFFER_FLAG_REALLOCATABLE;
+        *pbuf = buf;
+
+        return 0;
+    } else if (buf->size == size)
+        return 0;
+
+    if (!(buf->buffer->flags & BUFFER_FLAG_REALLOCATABLE) ||
+        !av_buffer_is_writable(buf)) {
+        /* cannot realloc, allocate a new reallocable buffer and copy data */
+        AVBufferRef *new = NULL;
+
+        av_buffer_realloc(&new, size);
+        if (!new)
+            return AVERROR(ENOMEM);
+
+        memcpy(new->data, buf->data, FFMIN(size, buf->size));
+
+        av_buffer_unref(pbuf);
+        *pbuf = new;
+        return 0;
+    }
+
+    tmp = av_realloc(buf->buffer->data, size);
+    if (!tmp)
+        return AVERROR(ENOMEM);
+
+    buf->buffer->data = buf->data = tmp;
+    buf->buffer->size = buf->size = size;
+    return 0;
+}