initial commit: pulser

diff --git a/pulser.c b/pulser.c
new file mode 100644 (file)
index 0000000..fc48c22
--- /dev/null
+++ b/pulser.c
@@ -0,0 +1,91 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <jh.h>
+#include <unistd.h>
+#include <time.h>
+#include <assert.h>
+
+time_t real_seconds(void) {
+  struct timespec t;
+  int s = clock_gettime(CLOCK_REALTIME, &t);
+  assert(s==0);
+  return t.tv_sec;
+}
+
+/* Subtract the `struct timeval' values X and Y,
+   storing the result in RESULT.
+   Return 1 if the difference is negative, otherwise 0. */
+int timeval_subtract (struct timeval *result, struct timeval *x, struct timeval *y) {
+  /* Perform the carry for the later subtraction by updating y. */
+  if (x->tv_usec < y->tv_usec) {
+    int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
+    y->tv_usec -= 1000000 * nsec;
+    y->tv_sec += nsec;
+  }
+  if (x->tv_usec - y->tv_usec > 1000000) {
+    int nsec = (x->tv_usec - y->tv_usec) / 1000000;
+    y->tv_usec += 1000000 * nsec;
+    y->tv_sec -= nsec;
+  }
+
+  /* Compute the time remaining to wait.
+     tv_usec is certainly positive. */
+  result->tv_sec = x->tv_sec - y->tv_sec;
+  result->tv_usec = x->tv_usec - y->tv_usec;
+
+  /* Return 1 if result is negative. */
+  return x->tv_sec < y->tv_sec;
+}
+
+void sleep_until(time_t dst_sec) {
+  struct timespec dst;
+  dst.tv_sec = dst_sec;
+  dst.tv_nsec = 0;
+  while (clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &dst, NULL)) /* nothing */;
+}
+
+time_t round_up(time_t t, int align) {
+  t = t - 1; /* counter bad +t for aligned things in last step */
+  t = t - t%align; /* round down to align */
+  t = t + align; /* add alignment to make it a round up */
+  return t;
+}
+
+void handle_connection(int s) {
+  dup2(s, 1);
+  dup2(s, 0);
+
+  char line_in[100];
+  if (!fgets(line_in, 100, stdin)) return;
+  char *p = line_in + strlen("GET /");
+
+  setbuf(stdout, NULL);
+  printf("HTTP/1.1 200 OK\r\nContent-Type: text/html; charset=utf-8\r\n\r\n<!--");
+
+  char *spaaaace = malloc(1024*64);
+  memset(spaaaace, ' ', 1024*64);
+  spaaaace[0] = 'A';
+
+  time_t t = round_up(real_seconds(), 4);
+  while (1) {
+    if (*p != '0' && *p != '1') return;
+    if (*p == '1') t+=2;
+    sleep_until(t);
+    if (fwrite(spaaaace, 1024, 64, stdout) <= 0) return;
+    t += (*p == '1') ? 2 : 4;
+    p++;
+  }
+}
+
+int main(void) {
+  int s = netopen_server(NULL, "4422", JH_TCP_HINTS);
+  while (1) {
+    int s_ = accept(s, NULL, NULL);
+    pid_t p = fork();
+    if (p == 0) {
+      handle_connection(s_);
+      return 0;
+    }
+    close(s_);
+  }
+}