Add utility to turn a POSIX/PAX tar archive into a squashfs image

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 48 insertions, 0 deletions

diff --git a/tar/skip.c b/tar/skip.c
new file mode 100644
index 0000000..69208b2
--- /dev/null
+++ b/tar/skip.c
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "util.h"
+#include "tar.h"
+
+#include <stdio.h>
+
+static int skip_bytes(int fd, uint64_t size)
+{
+	unsigned char buffer[1024];
+	ssize_t ret;
+	size_t diff;
+
+	while (size != 0) {
+		diff = sizeof(buffer);
+		if (diff > size)
+			diff = size;
+
+		ret = read_retry(fd, buffer, diff);
+
+		if (ret < 0) {
+			perror("reading tar record data");
+			return -1;
+		}
+
+		if ((size_t)ret < diff) {
+			fputs("unexpected end of file\n", stderr);
+			return -1;
+		}
+
+		size -= diff;
+	}
+
+	return 0;
+}
+
+int skip_padding(int fd, uint64_t size)
+{
+	size_t tail = size % 512;
+
+	return tail ? skip_bytes(fd, 512 - tail) : 0;
+}
+
+int skip_entry(int fd, uint64_t size)
+{
+	size_t tail = size % 512;
+
+	return skip_bytes(fd, tail ? (size + 512 - tail) : size);
+}