https://dsss.be/w/ 2026-05-08T03:31:01+00:00 https://dsss.be/w/ https://dsss.be/w/_media/wiki:dokuwiki.svg text/html 2009-08-13T16:49:12+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:getopt?rev=1250182152&do=diff #include <unistd.h> #include <stdio.h> #include <stdlib.h> int main (int argc, char** argv) { int o; int opt_a; char* opt_c; while ((o = getopt (argc, argv, "abc:")) != -1) { switch (o) { case 'a': opt_a = 1; break; case 'c': opt_c = optarg; break; default: usage(); } } argc -= optind; argv += optind; // throw away option arguments } text/html 2011-03-03T19:29:35+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:getting_mixed_c_and_assembler_output?rev=1299180575&do=diff At compile time (from here) $ gcc -g -Wa,"-ahl=mixed.lst" source_file.c After compile time: $ gcc -c -g -O2 source_file.c -o da.o $ objdump -S da.o text/html 2011-03-03T19:28:01+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:index?rev=1299180481&do=diff C/C++ code snippets * getopt * key-value pairs * timing * memmem - find substrings of raw memory (as opposed to null terminated strings) * Getting mixed C and assembler output #include <unistd.h> #include <stdio.h> #include <stdlib.h> #ifdef DEBUGMSG #define DEBUG printf #else #define DEBUG(...) #endif #define die(...) { fprintf(stderr, __VA_ARGS__); exit(1); } #define pdie(s) { perror(s); exit(1); } char parse_size(int64_t* v, char* s) { char suffix; if (sscanf(s,"%lld%c",v… text/html 2009-08-13T16:47:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:key-value_pairs?rev=1250182079&do=diff // takes a string and a delimiter. turns the first instance of the delimiter into a null and returns a pointer to the next character // if no delimiter found, returns null // basically, a cheap one-token tokenizer (without the mess of strtok) char* split2(char* str,char c) { char* p; for (p=str; *p; p++) { if ((*p)==c) { (*p)='\0'; return p+1; } } return NULL; } int main(int argc, char** argv) { if (argc==1) usage(); int i; for (i=1; i<argc; i++) { char* key; char* value; … text/html 2014-06-09T20:28:46+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:memmem?rev=1402345726&do=diff Here's an implementation of the GNU function memmem that appears to be much faster (2x) than the standard memmem included on my Debian system for my workload. #include <string.h> #include <stdint.h> // Implements the GNU function memmem much faster (2x) than the standard memmem included on my Debian system char* memmem(char* haystack, int hlen, char* needle, int nlen) { if (nlen > hlen) return 0; int i=0,j=0; switch(nlen) { // we have a few specialized compares for certain needle sizes ca… text/html 2009-08-13T16:49:34+00:00 Anonymous (anonymous@undisclosed.example.com) https://dsss.be/w/c:timing?rev=1250182174&do=diff char* timestamp() { static char buf[64]; struct tm t; time_t now = time(NULL); localtime_r(&now,&t); sprintf(buf,"%04d%02d%02d-%02d%02d%02d",t.tm_year+1900,t.tm_mon+1,t.tm_mday,t.tm_hour,t.tm_min,t.tm_sec); return buf; } /** * Returns the number of seconds since the epoch as a double-precision * float with microsecond resolution. * * @return Time since first call to this function */ double getCurrentTime() { double t; struct timeval tstr; if (gettimeofday(&tstr, NULL) < 0) {…