RE: [PATCH v1 1/4] builtin/index-pack.c: change xwrite to write_in_full to allow large sizes.

[<rsbecker@nexbridge.com>]

On Monday, February 26, 2024 5:39 PM, Taylor Blau wrote:
>On Mon, Feb 26, 2024 at 05:05:35PM -0500, Randall S. Becker wrote:
>> From: "Randall S. Becker" <rsbecker@nexbridge.com>
>>
>> This change is required because some platforms do not support file
>> writes of arbitrary sizes (e.g, NonStop). xwrite ends up truncating
>> the output to the maximum single I/O size possible for the destination device.
>
>Hmm. I'm not sure I understand what NonStop's behavior is here...
>
>> diff --git a/builtin/index-pack.c b/builtin/index-pack.c index
>> a3a37bd215..f80b8d101a 100644
>> --- a/builtin/index-pack.c
>> +++ b/builtin/index-pack.c
>> @@ -1571,7 +1571,7 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
>>  		 * the last part of the input buffer to stdout.
>>  		 */
>>  		while (input_len) {
>> -			err = xwrite(1, input_buffer + input_offset, input_len);
>> +			err = write_in_full(1, input_buffer + input_offset, input_len);
>>  			if (err <= 0)
>>  				break;
>>  			input_len -= err;
>> --
>> 2.42.1
>
>The code above loops while input_len is non-zero, and correctly decrements it by the number of bytes written by xwrite() after each
>iteration.
>
>Assuming that xwrite()/write(2) works how I think it does on NonStop, I'm not sure I understand why this change is necessary.

NonStop has a limited SSIZE_MAX. xwrite only handles that much so anything beyond that gets dropped (not in the above code but in other builtins); hence the critical nature of getting this fix out. This particular change probably could be tightened up on a re-roll to just call write_in_full instead of the while loop. I can fix that for v2. The goal suggested by Phillip W was to change xwrite to write_in_full, so I guess I went a little too far.