pkt-line: extern packet_length()

In a future commit, we will be manually processing packets and we will
need to access the length header. In order to simplify this, extern
packet_length() so that the logic can be reused.

Change the function parameter from `const char *linelen` to
`const char lenbuf_hex[4]`. Even though these two types behave
identically as function parameters, use the array notation to
semantically indicate exactly what this function is expecting as an
argument. Also, rename it from linelen to lenbuf_hex as the former
sounds like it should be an integral type which is misleading.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/pkt-line.h b/pkt-line.h
index fef3a0d..a72af91 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -75,6 +75,15 @@ int packet_read(int fd, char **src_buffer, size_t *src_len, char
 		*buffer, unsigned size, int options);
 
 /*
+ * Convert a four hex digit packet line length header into its numeric
+ * representation.
+ *
+ * If lenbuf_hex contains non-hex characters, return -1. Otherwise, return the
+ * numeric value of the length header.
+ */
+int packet_length(const char lenbuf_hex[4]);
+
+/*
  * Read a packetized line into a buffer like the 'packet_read()' function but
  * returns an 'enum packet_read_status' which indicates the status of the read.
  * The number of bytes read will be assigned to *pktlen if the status of the