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comment karsten's bug2196 patch a little

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This commit is contained in:
Nick Mathewson 2010-11-29 15:27:54 -05:00
parent 4fed43ab2e
commit a8a8e08220
1 changed files with 28 additions and 2 deletions
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30
src/or/rephist.c
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@ -1994,7 +1994,7 @@ rep_hist_exit_stats_term(void)
tor_free(exit_streams);
}
/** Helper: compare two ints. */
/** Helper for qsort: compare two ints. */
static int
_compare_int(const void *x, const void *y) {
return (*(int*)x - *(int*)y);
@ -2021,7 +2021,31 @@ rep_hist_format_exit_stats(time_t now)
return NULL; /* Not initialized. */
/* Go through all ports to find the n ports that saw most written and
* read bytes. */
* read bytes.
*
* Invariant: at the end of the loop for iteration i,
* total_read is the sum of all exit_bytes_read[0..i]
* total_written is the sum of all exit_bytes_written[0..i]
* total_stream is the sum of all exit_streams[0..i]
*
* top_elements = MAX(EXIT_STATS_TOP_N_PORTS,
* #{j | 0 <= j <= i && volume(i) > 0})
*
* For all 0 <= j < top_elements,
* top_bytes[j] > 0
* 0 <= top_ports[j] <= 65535
* top_bytes[j] = volume(top_ports[j])
*
* There is no j in 0..i and k in 0..top_elements such that:
* volume(j) > top_bytes[k] AND j is not in top_ports[0..top_elements]
*
* There is no j!=cur_min_idx in 0..top_elements such that:
* top_bytes[j] < top_bytes[cur_min_idx]
*
* where volume(x) == exit_bytes_read[x]+exit_bytes_written[x]
*
* Worst case: O(EXIT_STATS_NUM_PORTS * EXIT_STATS_TOP_N_PORTS)
*/
for (i = 1; i < EXIT_STATS_NUM_PORTS; i++) {
total_read += exit_bytes_read[i];
total_written += exit_bytes_written[i];
@ -2054,6 +2078,8 @@ rep_hist_format_exit_stats(time_t now)
other_read = total_read;
other_written = total_written;
other_streams = total_streams;
/* Sort the ports; this puts them out of sync with top_bytes, but we
* won't be using top_bytes again anyway */
qsort(top_ports, top_elements, sizeof(int), _compare_int);
for (j = 0; j < top_elements; j++) {
cur_port = top_ports[j];