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Reduce number of fwrite when writing pcap-ng EPB. 

According to callgrind with the patch dumping 3000 pakets the number of
calls to write_to_file is reduced from 11541 to 9000 reducing the number
of lr from 4 681 518 to 4 314 101.

If the buffer holding the packet was guaranteed to be padded to 32 bit
boundary the code could be simplified and if there was space "in front"
for the packet header it would be even better.

Change-Id: Ie991c05fa9d831ee4d703bd47b8123f2b1f83277
Reviewed-on: https://code.wireshark.org/review/20256
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
AndersBroman 2017-02-23 09:27:50 +01:00 committed by Anders Broman
parent d347a608c9
commit bd9afdddfe
1 changed files with 25 additions and 2 deletions
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27
writecap/pcapio.c
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@ -516,6 +516,9 @@ pcapng_write_enhanced_packet_block(FILE* pfile,
guint64 timestamp;
guint32 options_length;
const guint32 padding = 0;
guint8 buff[8];
guint8 i;
guint8 pad_len = 0;
block_total_length = (guint32)(sizeof(struct epb) +
ADD_PADDING(caplen) +
@ -543,8 +546,28 @@ pcapng_write_enhanced_packet_block(FILE* pfile,
return FALSE;
if (!write_to_file(pfile, pd, caplen, bytes_written, err))
return FALSE;
if (caplen % 4) {
if (!write_to_file(pfile, (const guint8*)&padding, 4 - caplen % 4, bytes_written, err))
/* Use more efficient write in case of no "extras" */
if(caplen % 4) {
pad_len = 4 - (caplen % 4);
}
if(!comment && flags == 0 && options_length==0){
/* Put padding in the buffer */
for (i = 0; i < pad_len; i++) {
buff[i] = 0;
}
/* Write the total length */
buff[i] = (block_total_length & 0x000000ff);
i++;
buff[i] = (block_total_length & 0x0000ff00) >> 8;
i++;
buff[i] = (block_total_length & 0x00ff0000) >> 16;
i++;
buff[i] = (block_total_length & 0xff000000) >> 24;
i++;
return write_to_file(pfile, (const guint8*)&buff, i, bytes_written, err);
}
if (pad_len) {
if (!write_to_file(pfile, (const guint8*)&padding, pad_len, bytes_written, err))
return FALSE;
}
if (!pcapng_write_string_option(pfile, OPT_COMMENT, comment,