1 files changed, 69 insertions, 0 deletions
diff --git a/src/watcher.c b/src/watcher.c
new file mode 100644
index 0000000..71b6c52
--- /dev/null
+++ b/src/watcher.c
@@ -0,0 +1,69 @@
+#include "watcher.h"
+
+#include <errno.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "block.h"
+#include "util.h"
+
+static bool watcher_fd_is_readable(const watcher_fd* const watcher_fd) {
+    return (watcher_fd->revents & POLLIN) != 0;
+}
+
+int watcher_init(watcher* const watcher, const block* const blocks,
+                 const unsigned short block_count, const int signal_fd) {
+    if (signal_fd == -1) {
+        (void)fprintf(
+            stderr,
+            "error: invalid signal file descriptor passed to watcher\n");
+        return 1;
+    }
+
+    watcher_fd* const fd = &watcher->fds[SIGNAL_FD];
+    fd->fd = signal_fd;
+    fd->events = POLLIN;
+
+    for (unsigned short i = 0; i < block_count; ++i) {
+        const int block_fd = blocks[i].pipe[READ_END];
+        if (block_fd == -1) {
+            (void)fprintf(
+                stderr,
+                "error: invalid block file descriptors passed to watcher\n");
+            return 1;
+        }
+
+        watcher_fd* const fd = &watcher->fds[i];
+        fd->fd = block_fd;
+        fd->events = POLLIN;
+    }
+
+    return 0;
+}
+
+int watcher_poll(watcher* watcher, const int timeout_ms) {
+    int event_count = poll(watcher->fds, LEN(watcher->fds), timeout_ms);
+
+    // Don't return non-zero status for signal interruptions.
+    if (event_count == -1 && errno != EINTR) {
+        (void)fprintf(stderr, "error: watcher could not poll blocks\n");
+        return 1;
+    }
+
+    watcher->got_signal = watcher_fd_is_readable(&watcher->fds[SIGNAL_FD]);
+
+    watcher->active_block_count = event_count - (int)watcher->got_signal;
+    unsigned short i = 0;
+    unsigned short j = 0;
+    while (i < event_count && j < LEN(watcher->active_blocks)) {
+        if (watcher_fd_is_readable(&watcher->fds[j])) {
+            watcher->active_blocks[i] = j;
+            ++i;
+        }
+
+        ++j;
+    }
+
+    return 0;
+}