[FFmpeg-devel] [PATCH 1/3] avcodec/avpacket: add av_packet_resize()

[James Almer]

This function acts as a replacement for both av_grow_packet() and
av_shrink_packet(), the latter which is now deprecated and will be removed as
it does not correctly handle non-writable packets.

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavcodec/avpacket.c | 19 +++++++++++++++----
 libavcodec/packet.h   | 16 ++++++++++++++++
 libavcodec/version.h  |  3 +++
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 32cb71fcf0..7d0dbadbed 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -100,6 +100,7 @@ int av_new_packet(AVPacket *pkt, int size)
     return 0;
 }
 
+#if FF_API_SHRINK_PACKET
 void av_shrink_packet(AVPacket *pkt, int size)
 {
     if (pkt->size <= size)
@@ -107,16 +108,26 @@ void av_shrink_packet(AVPacket *pkt, int size)
     pkt->size = size;
     memset(pkt->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 }
+#endif
 
 int av_grow_packet(AVPacket *pkt, int grow_by)
 {
-    int new_size;
     av_assert0((unsigned)pkt->size <= INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE);
     if ((unsigned)grow_by >
         INT_MAX - (pkt->size + AV_INPUT_BUFFER_PADDING_SIZE))
         return AVERROR(ENOMEM);
 
-    new_size = pkt->size + grow_by + AV_INPUT_BUFFER_PADDING_SIZE;
+    return av_packet_resize(pkt, pkt->size + grow_by);
+}
+
+int av_packet_resize(AVPacket *pkt, int size)
+{
+    int new_size;
+
+    if (size < 0 || size > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE)
+        return AVERROR(EINVAL);
+
+    new_size = size + AV_INPUT_BUFFER_PADDING_SIZE;
     if (pkt->buf) {
         size_t data_offset;
         uint8_t *old_data = pkt->data;
@@ -143,10 +154,10 @@ int av_grow_packet(AVPacket *pkt, int grow_by)
         if (!pkt->buf)
             return AVERROR(ENOMEM);
         if (pkt->size > 0)
-            memcpy(pkt->buf->data, pkt->data, pkt->size);
+            memcpy(pkt->buf->data, pkt->data, FFMIN(pkt->size, size));
         pkt->data = pkt->buf->data;
     }
-    pkt->size += grow_by;
+    pkt->size = size;
     memset(pkt->data + pkt->size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
     return 0;
diff --git a/libavcodec/packet.h b/libavcodec/packet.h
index 3d9013d783..1720d973f5 100644
--- a/libavcodec/packet.h
+++ b/libavcodec/packet.h
@@ -484,13 +484,29 @@ void av_init_packet(AVPacket *pkt);
  */
 int av_new_packet(AVPacket *pkt, int size);
 
+#if FF_API_SHRINK_PACKET
 /**
  * Reduce packet size, correctly zeroing padding
  *
  * @param pkt packet
  * @param size new size
+ *
+ * @deprecated Use av_packet_resize
  */
+attribute_deprecated
 void av_shrink_packet(AVPacket *pkt, int size);
+#endif
+
+/**
+ * Resize the payload of a packet, correctly zeroing padding and avoiding data
+ * copy if possible.
+ *
+ * @param pkt packet
+ * @param size new size
+ *
+ * @return 0 on success, a negative AVERROR on error
+ */
+int av_packet_resize(AVPacket *pkt, int size);
 
 /**
  * Increase packet size, correctly zeroing padding
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 3124ec8061..6c362b43e2 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -162,5 +162,8 @@
 #ifndef FF_API_GET_FRAME_CLASS
 #define FF_API_GET_FRAME_CLASS     (LIBAVCODEC_VERSION_MAJOR < 60)
 #endif
+#ifndef FF_API_SHRINK_PACKET
+#define FF_API_SHRINK_PACKET       (LIBAVCODEC_VERSION_MAJOR < 60)
+#endif
 
 #endif /* AVCODEC_VERSION_H */
-- 
2.30.2