Merge pull request #116 from edgar-bonet/stresstest-opts

* stresstest.c: separate -h and -v from the rest in usage
* stresstest.c: add option to set the random seed
* stresstest.c: add option to randomly output garbage
* stresstest.c: add option to randomly chunk the output
* stresstest.c: add option to set the sampling rate
* Let stresstest parse its command line

stresstest.c

@@ -6,20 +6,95 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <time.h>
 #include <unistd.h>
+#include <string.h>
 #include <math.h>
 
+const char help[] =
+    "Usage:\n"
+    "  stresstest [-2] [-c] [-g] [-r rate]\n"
+    "  stresstest -h\n"
+    "\n"
+    "  -h       print this help message and exit\n"
+    "  -2       output two waves\n"
+    "  -c       randomly chunk the output\n"
+    "  -g       occasionally output garbage\n"
+    "  -r rate  sample rate in samples/s (default: 100)\n"
+    "  -s seed  set random seed\n";
+
+const char optstring[] = "h2cgr:s:";
+
 int main(int argc, char *argv[]) {
-    (void) argv;
-    unsigned int n;
-
-    for(n=0;;n+=5) {
-        printf("%.1f\n", (sin(n*M_PI/180)*5)+5);
-        if(argc==2)
-            printf("%.1f\n", (cos(n*M_PI/180)*5)+5);
-        fflush(stdout);
-        usleep(10000);
+    char buffer[1024];
+    size_t buffer_pos = 0;
+    int opt;
+    bool two_waves = false;
+    bool chunked = false;
+    bool add_garbage = false;
+    double rate = 100;
+    unsigned int seed = time(NULL);
+
+    // Parse the command line.
+    while ((opt = getopt(argc, argv, optstring)) != -1) {
+        switch (opt) {
+            case 'h':
+                printf(help);
+                return EXIT_SUCCESS;
+            case '2':
+                two_waves = true;
+                break;
+            case 'c':
+                chunked = true;
+                break;
+            case 'g':
+                add_garbage = true;
+                break;
+            case 'r':
+                rate = atof(optarg);
+                break;
+            case 's':
+                seed = atoi(optarg);
+                break;
+            default:
+                fprintf(stderr, help);
+                return EXIT_FAILURE;
+        }
+    }
+    if (argc > optind) {
+        fprintf(stderr, help);
+        return EXIT_FAILURE;
+    }
+
+    const useconds_t delay = 1e6 / rate;
+    srand(seed);
+
+    for (unsigned int n=0; ; n+=5) {
+        buffer_pos += sprintf(buffer + buffer_pos, "%.1f\n", (sin(n*M_PI/180)*5)+5);
+        if (add_garbage && rand() <= RAND_MAX / 5)
+            buffer_pos += sprintf(buffer + buffer_pos, "garbage ");
+        if (two_waves) {
+            buffer_pos += sprintf(buffer + buffer_pos, "%.1f\n", (cos(n*M_PI/180)*5)+5);
+            if (add_garbage && rand() <= RAND_MAX / 5)
+                buffer_pos += sprintf(buffer + buffer_pos, "garbage ");
+        }
+        if (chunked) {
+            size_t send_pos = 0;
+            while (buffer_pos - send_pos >= 16) {
+                const size_t bytes_to_send = 1 + rand() % 16;  // 1..16
+                write(STDOUT_FILENO, buffer + send_pos, bytes_to_send);
+                usleep(50);  // let ttyplot read this before proceeding
+                send_pos += bytes_to_send;
+            }
+            if (send_pos > 0 && send_pos < buffer_pos)
+                memmove(buffer, buffer + send_pos, buffer_pos - send_pos);
+            buffer_pos -= send_pos;
+        } else {
+            write(STDOUT_FILENO, buffer, buffer_pos);
+            buffer_pos = 0;
+        }
+        usleep(delay);
     }
 
     return 0;