[FFmpeg-cvslog] avio: Add an internal function for reading without copying

[Ben Avison]

ffmpeg | branch: master | Ben Avison <bavison at riscosopen.org> | Wed Jul 31 23:46:08 2013 +0100| [daf1e0d3de03bd424016e2a7520e4e94ece5c0ac] | committer: Martin Storsjö

avio: Add an internal function for reading without copying

As long as there is enough contiguous data in the avio buffer,
just return a pointer to it instead of copying it to the caller
provided buffer.

Signed-off-by: Martin Storsjö <martin at martin.st>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=daf1e0d3de03bd424016e2a7520e4e94ece5c0ac
---

 libavformat/avio_internal.h |   17 +++++++++++++++++
 libavformat/aviobuf.c       |   12 ++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/libavformat/avio_internal.h b/libavformat/avio_internal.h
index 3da2fc8..4fa3adb 100644
--- a/libavformat/avio_internal.h
+++ b/libavformat/avio_internal.h
@@ -38,6 +38,23 @@ int ffio_init_context(AVIOContext *s,
 
 
 /**
+ * Read size bytes from AVIOContext, returning a pointer.
+ * Note that the data pointed at by the returned pointer is only
+ * valid until the next call that references the same IO context.
+ * @param s IO context
+ * @param buf pointer to buffer into which to assemble the requested
+ *    data if it is not available in contiguous addresses in the
+ *    underlying buffer
+ * @param size number of bytes requested
+ * @param data address at which to store pointer: this will be a
+ *    a direct pointer into the underlying buffer if the requested
+ *    number of bytes are available at contiguous addresses, otherwise
+ *    will be a copy of buf
+ * @return number of bytes read or AVERROR
+ */
+int ffio_read_indirect(AVIOContext *s, unsigned char *buf, int size, unsigned char **data);
+
+/**
  * Read size bytes from AVIOContext into buf.
  * This reads at most 1 packet. If that is not enough fewer bytes will be
  * returned.
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index bc89768..07aa880 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -490,6 +490,18 @@ int avio_read(AVIOContext *s, unsigned char *buf, int size)
     return size1 - size;
 }
 
+int ffio_read_indirect(AVIOContext *s, unsigned char *buf, int size, unsigned char **data)
+{
+    if (s->buf_end - s->buf_ptr >= size && !s->write_flag) {
+        *data = s->buf_ptr;
+        s->buf_ptr += size;
+        return size;
+    } else {
+        *data = buf;
+        return avio_read(s, buf, size);
+    }
+}
+
 int ffio_read_partial(AVIOContext *s, unsigned char *buf, int size)
 {
     int len;