From cccbd5aa139b8e0cac233f317cb3e7252daae0d9 Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Thu, 1 Aug 2019 16:03:59 +0200
Subject: Add ability to write_tar_header to embedd extended attributes
This commit patches the tar writer to generate a PAX header with SCHILY
xattr key/value pairs if requested.
The Schily format is used for two reasons:
- It is simple
- It is apparently more widely supported than the libarchive format
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
lib/tar/write_header.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 52 insertions(+), 1 deletion(-)
(limited to 'lib')
diff --git a/lib/tar/write_header.c b/lib/tar/write_header.c
index e4d4d38..d3a184a 100644
--- a/lib/tar/write_header.c
+++ b/lib/tar/write_header.c
@@ -112,13 +112,64 @@ static int write_gnu_header(int fd, const struct stat *orig,
return padd_file(fd, payload_len, 512);
}
+static size_t num_digits(size_t num)
+{
+ size_t i = 1;
+
+ while (num > 10) {
+ num /= 10;
+ ++i;
+ }
+
+ return i;
+}
+
+static int write_schily_xattr(int fd, const struct stat *orig,
+ const char *name, const tar_xattr_t *xattr)
+{
+ static const char *prefix = "SCHILY.xattr.";
+ size_t len, total_size = 0;
+ const tar_xattr_t *it;
+ struct stat sb;
+
+ for (it = xattr; it != NULL; it = it->next) {
+ len = strlen(prefix) + strlen(it->key) + strlen(it->value) + 2;
+
+ total_size += num_digits(len) + 1 + len;
+ }
+
+ sb = *orig;
+ sb.st_mode = S_IFREG | 0644;
+ sb.st_size = total_size;
+
+ if (write_header(fd, &sb, name, NULL, TAR_TYPE_PAX))
+ return -1;
+
+ for (it = xattr; it != NULL; it = it->next) {
+ len = strlen(prefix) + strlen(it->key) + strlen(it->value) + 2;
+ len += num_digits(len) + 1;
+
+ dprintf(fd, "%zu %s%s=%s\n", len, prefix, it->key, it->value);
+ }
+
+ return padd_file(fd, total_size, 512);
+}
+
int write_tar_header(int fd, const struct stat *sb, const char *name,
- const char *slink_target, unsigned int counter)
+ const char *slink_target, const tar_xattr_t *xattr,
+ unsigned int counter)
{
const char *reason;
char buffer[64];
int type;
+ if (xattr != NULL) {
+ sprintf(buffer, "pax/xattr%u", counter);
+
+ if (write_schily_xattr(fd, sb, buffer, xattr))
+ return -1;
+ }
+
if (!S_ISLNK(sb->st_mode))
slink_target = NULL;
--
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