Fix skipping over 4B varlena padding bytes

4B varlenas can start with NUL bytes on big endian, so the old coding
would eat too many bytes. Instead, handle the 1B cases first and then
compute the correct number of padding bytes instead of looking at the
byte values.

Author: Christoph Berg <[email protected]>

Author: df7cb

decode.c

@@ -1078,17 +1078,6 @@ extract_data(const char *buffer, unsigned int buff_size, unsigned int *out_size,
 	int			padding = 0;
 	int			result	= 0;
 
-	/* Skip padding bytes. */
-	while (*buffer == 0x00)
-	{
-		if (buff_size == 0)
-			return -1;
-
-		buff_size--;
-		buffer++;
-		padding++;
-	}
-
 	if (VARATT_IS_1B_E(buffer))
 	{
 		/*
@@ -1153,6 +1142,11 @@ extract_data(const char *buffer, unsigned int buff_size, unsigned int *out_size,
 		return result;
 	}
 
+	/* Skip padding bytes. */
+	padding = (char *)INTALIGN(buffer) - buffer;
+	buffer += padding;
+	buff_size -= padding;
+
 	if (VARATT_IS_4B_U(buffer) && buff_size >= 4)
 	{
 		/*