1 // Copyright 2012 Google Inc. All Rights Reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "build_log.h"
16
17 #include <algorithm>
18
19 #include <stdlib.h>
20 #include <time.h>
21
22 using namespace std;
23
random(int low,int high)24 int random(int low, int high) {
25 return int(low + (rand() / double(RAND_MAX)) * (high - low) + 0.5);
26 }
27
RandomCommand(char ** s)28 void RandomCommand(char** s) {
29 int len = random(5, 100);
30 *s = new char[len+1];
31 for (int i = 0; i < len; ++i)
32 (*s)[i] = (char)random(32, 127);
33 (*s)[len] = '\0';
34 }
35
main()36 int main() {
37 const int N = 20 * 1000 * 1000;
38
39 // Leak these, else 10% of the runtime is spent destroying strings.
40 char** commands = new char*[N];
41 pair<uint64_t, int>* hashes = new pair<uint64_t, int>[N];
42
43 srand((int)time(NULL));
44
45 for (int i = 0; i < N; ++i) {
46 RandomCommand(&commands[i]);
47 hashes[i] = make_pair(BuildLog::LogEntry::HashCommand(commands[i]), i);
48 }
49
50 sort(hashes, hashes + N);
51
52 int collision_count = 0;
53 for (int i = 1; i < N; ++i) {
54 if (hashes[i - 1].first == hashes[i].first) {
55 if (strcmp(commands[hashes[i - 1].second],
56 commands[hashes[i].second]) != 0) {
57 printf("collision!\n string 1: '%s'\n string 2: '%s'\n",
58 commands[hashes[i - 1].second],
59 commands[hashes[i].second]);
60 collision_count++;
61 }
62 }
63 }
64 printf("\n\n%d collisions after %d runs\n", collision_count, N);
65 }
66