diff options
Diffstat (limited to 'slowbaud.c')
| -rw-r--r-- | slowbaud.c | 35 |
1 files changed, 24 insertions, 11 deletions
@@ -1,6 +1,12 @@ /* Simulate low bitrate serial connection, like a 1980s modem. Author: B. Watson. License: WTFPL. */ + +/* configurables: */ +#define FRACTIONAL_USEC +#define SHOW_CPU_TIME + + #include <stdio.h> #include <stdlib.h> #include <unistd.h> @@ -16,6 +22,7 @@ #include <signal.h> #include <time.h> #include <string.h> +#include <math.h> /* portability stuff only tested on Linux and OSX. Hope it's OK. */ #if defined(__FreeBSD__) || defined(HAVE_LIBUTIL_H) @@ -41,8 +48,6 @@ struct timeval tv; struct itimerval itv, itv_disarm; sigset_t sigmask; -#define FRACTIONAL_USEC - #ifdef FRACTIONAL_USEC #define FRAC_US_DENOM 100 int frac_us_num; @@ -115,9 +120,22 @@ void debug_stats(void) { double actual = ((double)outbytes * 10.0L) / elapsed_sec; double offby = 100.0L * (((double)bps / actual) - 1.0L); fprintf(stderr, - "outbytes %lu, elapsed_us %lu, tv_usec %lu, requested bps %d (%.2fms), " + "outbytes %lu, elapsed_us %lu, tv_usec %lu\nrequested bps %d (%.2fms), " "actual %.2f, accuracy %.2f%%\n", outbytes, elapsed_us, itv.it_value.tv_usec, bps, finterval, actual, 100.0 - offby); +#ifdef SHOW_CPU_TIME + { + struct timespec ts; + long end_cpu_us; + double cpu_pct; + + clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts); + end_cpu_us = ts.tv_sec * 1000000L + ts.tv_nsec / 1000L; + cpu_pct = (double)(end_cpu_us) / (double)(elapsed_us) * 100.0L; + fprintf(stderr, "CPU usage %luus, %.2f%%\n", end_cpu_us, cpu_pct); + } +#endif + } } @@ -290,18 +308,13 @@ int main(int argc, char **argv) { } /* if we used only integer math here, we couldn't support bps not - a multiple of 10 (e.g. 75 would be taken as 70). - We still have a rounding problem: 115200bps is 86.81ms/char, but - it gets rounded down to 86 here. Which would be around 116279bps, - or almost 1% too fast. We never reach 100% speed anyway, so the - loss from overhead actually offsets the extra bit of speed. - */ + a multiple of 10 (e.g. 75 would be taken as 70). */ interval = (unsigned long)(1000000.0L / ((double)bps / 10.0L)); #ifdef FRACTIONAL_USEC - frac_us_num = (double)FRAC_US_DENOM * ((1000000.0L / ((double)bps / 10.0L) - interval)); + frac_us_num = roundl((double)FRAC_US_DENOM * ((1000000.0L / ((double)bps / 10.0L) - interval))); if(debug) fprintf(stderr, "interval %ld + %d/%d us\n", interval, frac_us_num, FRAC_US_DENOM); - // srandom(NOW_USEC()); // don't think we should do this + srandom(NOW_USEC()); #else if(debug) fprintf(stderr, "interval %ld us\n", interval); #endif |