Re: [PATCH v6 1/8] pkt-line: add packet_read_line_gently()

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Sorry if you get this twice, somehow Thunderbird converted my response to HTML


On 4/24/2017 10:19 PM, Junio C Hamano wrote:
Ben Peart <peartben@xxxxxxxxx> writes:

On 4/24/2017 12:21 AM, Junio C Hamano wrote:
Ben Peart <peartben@xxxxxxxxx> writes:

+{
+	int len = packet_read(fd, NULL, NULL,
+			      packet_buffer, sizeof(packet_buffer),
+			      PACKET_READ_CHOMP_NEWLINE|PACKET_READ_GENTLE_ON_EOF);
+	if (dst_len)
+		*dst_len = len;
+	if (dst_line)
+		*dst_line = (len > 0) ? packet_buffer : NULL;
I have the same doubt as above for len == 0 case.
packet_read() returns -1 when PACKET_READ_GENTLE_ON_EOF is passed and
it hits truncated output from the remote process.
I know, but that is irrelevant to my question, which is about
CHOMP_NEWLINE.  I didn't even ask "why a negative len treated
specially?"  My question is about the case where len == 0.  Your
patch treats len==0 just like len==-1, i.e. an error, but I do not
know if that is correct, hence my question.  We both know len < 0
is an error and you do not need to waste time elaborating on it.



The packet_read_line() function returns NULL when len == 0 and PACKET_READ_CHOMP_NEWLINE is passed so I wrote the similar packet_read_line_gently() function to behave the same.

How about I update the comment in the function header to make this more clear:

diff --git a/pkt-line.h b/pkt-line.h
index 7c278a158b..b2965869ad 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -78,9 +78,10 @@ char *packet_read_line(int fd, int *size);
* Convenience wrapper for packet_read that sets the PACKET_READ_GENTLE_ON_EOF * and CHOMP_NEWLINE options. The return value specifies the number of bytes * read into the buffer or -1 on truncated input. If the *dst_line parameter - * is not NULL it will return NULL for a flush packet and otherwise points to - * a static buffer (that may be overwritten by subsequent calls). If the size
- * parameter is not NULL, the length of the packet is written to it.
+ * is not NULL it will return NULL for a flush packet or when the number of
+ * bytes copied is zero and otherwise points to a static buffer (that may be
+ * overwritten by subsequent calls). If the size parameter is not NULL, the
+ * length of the packet is written to it.
  */
 int packet_read_line_gently(int fd, int *size, char **dst_line);




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