1  #include <stdio.h>
 2  #include <stdlib.h>
 3  
 4  #include <darwintest.h>
 5  #include <darwintest_perf.h>
 6  
 7  static void
 8  perf_fixed_size(size_t size_per_write)
 9  {
10  	dt_stat_time_t latency = dt_stat_time_create("write_latency",
11  			"adding %zu bytes to a memstream", size_per_write);
12  	dt_stat_set_variable_d(latency, "bytes", (double)size_per_write);
13  	char *src = calloc(1, size_per_write);
14  	T_QUIET; T_ASSERT_NOTNULL(src, "allocated source buffer");
15  
16  	while (!dt_stat_stable(latency)) {
17  		char *buf = NULL;
18  		size_t size = 0;
19  
20  		FILE *victim = open_memstream(&buf, &size);
21  		T_QUIET; T_WITH_ERRNO; T_ASSERT_NOTNULL(victim, "opened memstream");
22  
23  		T_STAT_MEASURE_BATCH(latency) {
24  			(void)fwrite(src, size_per_write, 1, victim);
25  		}
26  
27  		fclose(victim);
28  		T_QUIET; T_ASSERT_NOTNULL(buf, "buffer was set by open_memstream");
29  		T_QUIET; T_ASSERT_GE(size, size_per_write,
30  				"memstream added non-zero bytes");
31  
32  		free(buf);
33  	}
34  
35  	free(src);
36  	dt_stat_finalize(latency);
37  }
38  
39  T_DECL(perf_open_memstream, "measure the performance of open_memstream")
40  {
41  	size_t sizes[] = { 1, 8, 16, 64, 1024, 2048, 4096, 16 * 1024 };
42  	for (size_t i = 0; i < sizeof(sizes) / sizeof(sizes[0]); i++) {
43  		perf_fixed_size(sizes[i]);
44  	}
45  }