rtmp: Do not misuse memcmp

CC: libav-stable@libav.org
(cherry picked from commit 5718e3487ba3b26aba341070be0b6b0b4de45ea3)
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Conflicts:
	libavformat/rtmpproto.c

1 files changed, 33 insertions, 0 deletions

diff --git a/libavformat/rtmppkt.c b/libavformat/rtmppkt.c
index 3af56270d2..ace77297c6 100644
--- a/libavformat/rtmppkt.c
+++ b/libavformat/rtmppkt.c
@@ -525,3 +525,36 @@ void ff_rtmp_packet_dump(void *ctx, RTMPPacket *p)
         av_log(ctx, AV_LOG_DEBUG, "\n");
     }
 }
+
+int ff_amf_match_string(const uint8_t *data, int size, const char *str)
+{
+    int len = strlen(str);
+    int amf_len, type;
+
+    if (size < 1)
+        return 0;
+
+    type = *data++;
+
+    if (type != AMF_DATA_TYPE_LONG_STRING &&
+        type != AMF_DATA_TYPE_STRING)
+        return 0;
+
+    if (type == AMF_DATA_TYPE_LONG_STRING) {
+        if ((size -= 4 + 1) < 0)
+            return 0;
+        amf_len = bytestream_get_be32(&data);
+    } else {
+        if ((size -= 2 + 1) < 0)
+            return 0;
+        amf_len = bytestream_get_be16(&data);
+    }
+
+    if (amf_len > size)
+        return 0;
+
+    if (amf_len != len)
+        return 0;
+
+    return !memcmp(data, str, len);
+}