rtmppkt: Add method to read an AMF string that is not prefixed by its type

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

libavformat/rtmppkt.c

@@ -102,13 +102,11 @@ int ff_amf_read_number(GetByteContext *bc, double *val)
     return 0;
 }
 
-int ff_amf_read_string(GetByteContext *bc, uint8_t *str,
+int ff_amf_get_string(GetByteContext *bc, uint8_t *str,
                       int strsize, int *length)
 {
     int stringlen = 0;
     int readsize;
-    if (bytestream2_get_byte(bc) != AMF_DATA_TYPE_STRING)
-        return AVERROR_INVALIDDATA;
     stringlen = bytestream2_get_be16(bc);
     if (stringlen + 1 > strsize)
         return AVERROR(EINVAL);
@@ -122,6 +120,14 @@ int ff_amf_read_string(GetByteContext *bc, uint8_t *str,
     return 0;
 }
 
+int ff_amf_read_string(GetByteContext *bc, uint8_t *str,
+                       int strsize, int *length)
+{
+    if (bytestream2_get_byte(bc) != AMF_DATA_TYPE_STRING)
+        return AVERROR_INVALIDDATA;
+    return ff_amf_get_string(bc, str, strsize, length);
+}
+
 int ff_amf_read_null(GetByteContext *bc)
 {
     if (bytestream2_get_byte(bc) != AMF_DATA_TYPE_NULL)

libavformat/rtmppkt.h

@@ -277,6 +277,23 @@ int ff_amf_read_bool(GetByteContext *gbc, int *val);
 */
 int ff_amf_read_number(GetByteContext *gbc, double *val);
 
+/**
+ * Get AMF string value.
+ *
+ * This function behaves the same as ff_amf_read_string except that
+ * it does not expect the AMF type prepended to the actual data.
+ * Appends a trailing null byte to output string in order to
+ * ease later parsing.
+ *
+ *@param[in,out] gbc     GetByteContext initialized with AMF-formatted data
+ *@param[out]    str     read string
+ *@param[in]     strsize buffer size available to store the read string
+ *@param[out]    length  read string length
+ *@return 0 on success or an AVERROR code on failure
+*/
+int ff_amf_get_string(GetByteContext *bc, uint8_t *str,
+                      int strsize, int *length);
+
 /**
  * Read AMF string value.
  *