Re: [PATCH 1/6] t0021/rot13-filter: refactor packet reading functions

[Christian Couder]

On Sun, Oct 22, 2017 at 2:58 AM, Junio C Hamano  wrote:
> Christian Couder  writes:
>
>> To make it possible in a following commit to move packet
>> reading and writing functions into a Packet.pm module,
>> let's refactor these functions, so they don't handle
>> printing debug output and exiting.
>>
>> Signed-off-by: Christian Couder 
>> ---
>>  t/t0021/rot13-filter.pl | 12 
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/t/t0021/rot13-filter.pl b/t/t0021/rot13-filter.pl
>> index ad685d92f8..e4495a52f3 100644
>> --- a/t/t0021/rot13-filter.pl
>> +++ b/t/t0021/rot13-filter.pl
>> @@ -60,8 +60,7 @@ sub packet_bin_read {
>>   my $bytes_read = read STDIN, $buffer, 4;
>>   if ( $bytes_read == 0 ) {
>>   # EOF - Git stopped talking to us!
>> - print $debug "STOP\n";
>> - exit();
>> + return ( -1, "" );
>>   }
>>   elsif ( $bytes_read != 4 ) {
>>   die "invalid packet: '$buffer'";
>> @@ -85,7 +84,7 @@ sub packet_bin_read {
>>
>>  sub packet_txt_read {
>>   my ( $res, $buf ) = packet_bin_read();
>> - unless ( $buf eq '' or $buf =~ s/\n$// ) {
>> + unless ( $res == -1 or $buf eq '' or $buf =~ s/\n$// ) {
>>   die "A non-binary line MUST be terminated by an LF.";
>>   }
>>   return ( $res, $buf );
>> @@ -131,7 +130,12 @@ print $debug "init handshake complete\n";
>>  $debug->flush();
>>
>>  while (1) {
>> - my ( $command ) = packet_txt_read() =~ /^command=(.+)$/;
>> + my ( $res, $command ) = packet_txt_read();
>> + if ( $res == -1 ) {
>> + print $debug "STOP\n";
>> + exit();
>> + }
>> + $command =~ s/^command=//;
>>   print $debug "IN: $command";
>>   $debug->flush();
>
> This was not an issue in the old code which died upon unexpected EOF
> inside the lowest-level helper packet_bin_read(), but now you have
> one call to packet_bin_read() and many calls to packet_txt_read()
> whose return value is not checked for this new condition you are
> allowing packet_bin_read() to return.  This step taken alone is a
> regression---let's see how the remainder of the series updates the
> callers to compensate.

Yeah, in the new version I will send really soon now, I have made a
number of changes to check the return value for the EOF condition.

> I initially thought that it may be more Perl-ish to return undef or
> string instead of returning a 2-element list, but this code needs to
> distinguish three conditions (i.e. a normal string that is 0 or more
> bytes long, a flush, and an EOF), so that is not sufficient.  Perl
> experts on the list still may be able to suggest a better way than
> the current one to do so, but that is outside the scope of this
> refactoring.

Yeah I can't think of a better way either.

Thanks.

Re: [PATCH 1/6] t0021/rot13-filter: refactor packet reading functions

[Junio C Hamano]

Christian Couder  writes:

> To make it possible in a following commit to move packet
> reading and writing functions into a Packet.pm module,
> let's refactor these functions, so they don't handle
> printing debug output and exiting.
>
> Signed-off-by: Christian Couder 
> ---
>  t/t0021/rot13-filter.pl | 12 
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/t/t0021/rot13-filter.pl b/t/t0021/rot13-filter.pl
> index ad685d92f8..e4495a52f3 100644
> --- a/t/t0021/rot13-filter.pl
> +++ b/t/t0021/rot13-filter.pl
> @@ -60,8 +60,7 @@ sub packet_bin_read {
>   my $bytes_read = read STDIN, $buffer, 4;
>   if ( $bytes_read == 0 ) {
>   # EOF - Git stopped talking to us!
> - print $debug "STOP\n";
> - exit();
> + return ( -1, "" );
>   }
>   elsif ( $bytes_read != 4 ) {
>   die "invalid packet: '$buffer'";
> @@ -85,7 +84,7 @@ sub packet_bin_read {
>  
>  sub packet_txt_read {
>   my ( $res, $buf ) = packet_bin_read();
> - unless ( $buf eq '' or $buf =~ s/\n$// ) {
> + unless ( $res == -1 or $buf eq '' or $buf =~ s/\n$// ) {
>   die "A non-binary line MUST be terminated by an LF.";
>   }
>   return ( $res, $buf );
> @@ -131,7 +130,12 @@ print $debug "init handshake complete\n";
>  $debug->flush();
>  
>  while (1) {
> - my ( $command ) = packet_txt_read() =~ /^command=(.+)$/;
> + my ( $res, $command ) = packet_txt_read();
> + if ( $res == -1 ) {
> + print $debug "STOP\n";
> + exit();
> + }
> + $command =~ s/^command=//;
>   print $debug "IN: $command";
>   $debug->flush();

This was not an issue in the old code which died upon unexpected EOF
inside the lowest-level helper packet_bin_read(), but now you have
one call to packet_bin_read() and many calls to packet_txt_read()
whose return value is not checked for this new condition you are
allowing packet_bin_read() to return.  This step taken alone is a
regression---let's see how the remainder of the series updates the
callers to compensate.

I initially thought that it may be more Perl-ish to return undef or
string instead of returning a 2-element list, but this code needs to
distinguish three conditions (i.e. a normal string that is 0 or more
bytes long, a flush, and an EOF), so that is not sufficient.  Perl
experts on the list still may be able to suggest a better way than
the current one to do so, but that is outside the scope of this
refactoring.

Thanks for starting to work on this.

Re: [PATCH 1/6] t0021/rot13-filter: refactor packet reading functions

[Stefan Beller]

On Thu, Oct 19, 2017 at 5:30 AM, Christian Couder
 wrote:
> To make it possible in a following commit to move packet
> reading and writing functions into a Packet.pm module,
> let's refactor these functions, so they don't handle
> printing debug output and exiting.
>
> Signed-off-by: Christian Couder 
> ---

It looks good to me, though I am no perl expert by far.

[PATCH 1/6] t0021/rot13-filter: refactor packet reading functions

[Christian Couder]

To make it possible in a following commit to move packet
reading and writing functions into a Packet.pm module,
let's refactor these functions, so they don't handle
printing debug output and exiting.

Signed-off-by: Christian Couder 
---
 t/t0021/rot13-filter.pl | 12 
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/t/t0021/rot13-filter.pl b/t/t0021/rot13-filter.pl
index ad685d92f8..e4495a52f3 100644
--- a/t/t0021/rot13-filter.pl
+++ b/t/t0021/rot13-filter.pl
@@ -60,8 +60,7 @@ sub packet_bin_read {
my $bytes_read = read STDIN, $buffer, 4;
if ( $bytes_read == 0 ) {
# EOF - Git stopped talking to us!
-   print $debug "STOP\n";
-   exit();
+   return ( -1, "" );
}
elsif ( $bytes_read != 4 ) {
die "invalid packet: '$buffer'";
@@ -85,7 +84,7 @@ sub packet_bin_read {
 
 sub packet_txt_read {
my ( $res, $buf ) = packet_bin_read();
-   unless ( $buf eq '' or $buf =~ s/\n$// ) {
+   unless ( $res == -1 or $buf eq '' or $buf =~ s/\n$// ) {
die "A non-binary line MUST be terminated by an LF.";
}
return ( $res, $buf );
@@ -131,7 +130,12 @@ print $debug "init handshake complete\n";
 $debug->flush();
 
 while (1) {
-   my ( $command ) = packet_txt_read() =~ /^command=(.+)$/;
+   my ( $res, $command ) = packet_txt_read();
+   if ( $res == -1 ) {
+   print $debug "STOP\n";
+   exit();
+   }
+   $command =~ s/^command=//;
print $debug "IN: $command";
$debug->flush();
 
-- 
2.15.0.rc1.106.g7e97f58a41