Add generic proto writing method

1 files changed, 58 insertions, 0 deletions

diff --git a/proto.c b/proto.c
new file mode 100644
index 0000000..f1d2bc3
--- /dev/null
+++ b/proto.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2023 Mikhail Burakov. This file is part of streamer.
+ *
+ * streamer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * streamer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with streamer.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "proto.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+#include "toolbox/utils.h"
+
+#define UNCONST(x) ((void*)(uintptr_t)(x))
+
+static bool DrainBuffers(int fd, struct iovec* iovec, int count) {
+  for (;;) {
+    ssize_t result = writev(fd, iovec, count);
+    if (result < 0) {
+      if (errno == EINTR) continue;
+      LOG("Failed to write (%s)", strerror(errno));
+      return false;
+    }
+    for (int i = 0; i < count; i++) {
+      size_t delta = MIN((size_t)result, iovec[i].iov_len);
+      iovec[i].iov_base = (uint8_t*)iovec[i].iov_base + delta;
+      iovec[i].iov_len -= delta;
+      result -= delta;
+    }
+    if (!result) return true;
+  }
+}
+
+bool WriteProto(int fd, const struct Proto* proto, const void* data) {
+  struct iovec iovec[] = {
+      {.iov_base = UNCONST(proto), .iov_len = sizeof(struct Proto)},
+      {.iov_base = UNCONST(data), .iov_len = proto->size},
+  };
+  if (!DrainBuffers(fd, iovec, LENGTH(iovec))) {
+    LOG("Failed to drain buffers");
+    return false;
+  }
+  return true;
+}