1 files changed, 95 insertions, 0 deletions
diff --git a/copier.c b/copier.c
new file mode 100644
index 0000000..231e515
--- /dev/null
+++ b/copier.c
@@ -0,0 +1,95 @@
+/* See LICENSE file for copyright and license details. */
+#include <sys/socket.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+
+static const char *argv0 = "editasroot/copier";
+
+
+static void
+copy_file(int destfd, const char *destfname, int srcfd, const char *srcfname)
+{
+	char buf[BUFSIZ];
+	ssize_t r, w, p;
+
+	for (;;) {
+		r = read(srcfd, buf, sizeof(buf));
+		if (r <= 0) {
+			if (!r)
+				break;
+			fprintf(stderr, "%s: read %s: %s", argv0, srcfname, strerror(errno));
+			exit(1);
+		}
+
+		for (p = 0; p < r; p += w) {
+			w = write(destfd, buf, (size_t)(r - p));
+			if (r <= 0) {
+				fprintf(stderr, "%s: write %s: %s", argv0, destfname, strerror(errno));
+				exit(1);
+			}
+		}
+	}
+}
+
+
+int
+main(int argc, char *argv[])
+{
+	int filefd, parentfd;
+	const char *path;
+	ssize_t r;
+	char b;
+
+	if (!argc)
+		exit(1);
+	argv0 = *argv++;
+	if (--argc != 2)
+		exit(1);
+
+	path = argv[0];
+	parentfd = atoi(argv[1]);
+
+	filefd = open(path, O_RDWR); /* O_RDWR establishes that we can indeed write to the file */
+	if (filefd < 0) {
+		fprintf(stderr, "%s: open %s O_RDWR: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+	copy_file(parentfd, "<socket to parent>", filefd, path);
+	if (close(filefd)) {
+		fprintf(stderr, "%s: read %s: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+	if (shutdown(parentfd, SHUT_WR)) {
+		fprintf(stderr, "%s: shutdown <socket to parent> SHUT_WR: %s\n", argv0, strerror(errno));
+		exit(1);
+	}
+
+	r = read(parentfd, &b, 1);
+	if (r != 1) {
+		if (r)
+			fprintf(stderr, "%s: read %s: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+
+	filefd = open(path, O_WRONLY | O_TRUNC);
+	if (filefd < 0) {
+		fprintf(stderr, "%s: open %s O_WRONLY|O_TRUNC: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+	copy_file(filefd, path, parentfd, "<socket to parent>");
+	if (close(filefd)) {
+		fprintf(stderr, "%s: write %s: %s\n", argv0, path, strerror(errno));
+		exit(1);
+	}
+	if (close(parentfd)) {
+		fprintf(stderr, "%s: read <socket to parent>: %s\n", argv0, strerror(errno));
+		exit(1);
+	}
+
+	return 0;
+}