write mode: implemented generation of the cpio archive format.

1 files changed, 145 insertions, 0 deletions

diff --git a/src/meta/tpax_init_cpio_header.c b/src/meta/tpax_init_cpio_header.c
new file mode 100644
index 0000000..3de22f6
--- /dev/null
+++ b/src/meta/tpax_init_cpio_header.c
@@ -0,0 +1,145 @@
+/**************************************************************/
+/*  tpax: a topological pax implementation                    */
+/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
+/*  Released under GPLv2 and GPLv3; see COPYING.TPAX.         */
+/**************************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <sys/stat.h>
+
+#include <tpax/tpax.h>
+#include <tpax/tpax_specs.h>
+#include "tpax_driver_impl.h"
+
+#ifndef ssizeof
+#define ssizeof(x) (ssize_t)(sizeof(x))
+#endif
+
+#define TPAX_CPIO_PERM_MASK         \
+	( S_ISUID | S_ISGID          \
+	| S_IRUSR | S_IWUSR | S_IXUSR \
+	| S_IRGRP | S_IWGRP | S_IXGRP \
+	| S_IROTH | S_IWOTH | S_IXOTH )
+
+static void tpax_octal_write(char * ch, ssize_t len, uint64_t val)
+{
+	for (; len; ) {
+		ch[--len] = val % 8 + '0';
+		val /= 8;
+	}
+}
+
+int tpax_meta_init_cpio_header(
+	const char *                    path,
+	const struct stat *             st,
+	const char *                    linkname,
+	int                             cdev,
+	int                             cino,
+	int                             cnlink,
+	struct tpax_cpio_header *       chdr)
+{
+	size_t		fnsize;
+	size_t		lnklen;
+	size_t		stsize;
+	int64_t		stmtim;
+	uint32_t	typeflag;
+	uint32_t	permbits;
+	uint32_t	modebits;
+
+	/* filename size */
+	fnsize = strlen(path) + 1;
+
+	/* size & mtime validation */
+	stsize = S_ISREG(st->st_mode) ? st->st_size : 0;
+	stmtim = st->st_mtim.tv_sec;
+
+	if (stsize > 077777777777)
+		return -1;
+
+	if ((stmtim < 0) || (stmtim > 077777777777))
+		return -1;
+
+	/* linkname validation */
+	if (S_ISLNK(st->st_mode) && !linkname)
+		return -1;
+
+	lnklen = S_ISLNK(st->st_mode)
+		? strlen(linkname)
+		: 0;
+
+	/* typeflag validation */
+	if (S_ISREG(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISREG;
+	else if (S_ISLNK(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISLNK;
+	else if (S_ISDIR(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISDIR;
+	else if (S_ISCHR(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISCHR;
+	else if (S_ISBLK(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISBLK;
+	else if (S_ISFIFO(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISFIFO;
+	else if (S_ISSOCK(st->st_mode))
+		typeflag = TPAX_CPIO_FILEMODE_ISSOCK;
+	else
+		return -1;
+
+	/* permbits, modeflag */
+	permbits = st->st_mode & TPAX_CPIO_PERM_MASK;
+	modebits = permbits | typeflag;
+
+	/* one shot */
+	memset(chdr,0,sizeof(*chdr));
+
+	/* c_magic */
+	chdr->c_magic[0] = '0';
+	chdr->c_magic[1] = '7';
+	chdr->c_magic[2] = '0';
+	chdr->c_magic[3] = '7';
+	chdr->c_magic[4] = '0';
+	chdr->c_magic[5] = '7';
+
+	/* c_dev, c_ino */
+	tpax_octal_write(chdr->c_dev,ssizeof(chdr->c_dev),cdev);
+	tpax_octal_write(chdr->c_ino,ssizeof(chdr->c_ino),cino);
+
+	/* c_mode */
+	tpax_octal_write(chdr->c_mode,ssizeof(chdr->c_mode),modebits);
+
+	/* c_uid, c_gid */
+	if ((uint64_t)st->st_uid <= 0777777)
+		tpax_octal_write(chdr->c_uid,ssizeof(chdr->c_uid),st->st_uid);
+	else
+		tpax_octal_write(chdr->c_uid,ssizeof(chdr->c_uid),0);
+
+	if ((uint64_t)st->st_gid <= 0777777)
+		tpax_octal_write(chdr->c_gid,ssizeof(chdr->c_gid),st->st_gid);
+	else
+		tpax_octal_write(chdr->c_gid,ssizeof(chdr->c_gid),0);
+
+	/* c_nlink */
+	tpax_octal_write(chdr->c_nlink,ssizeof(chdr->c_nlink),cnlink);
+
+	/* c_rdev */
+	tpax_octal_write(chdr->c_rdev,ssizeof(chdr->c_rdev),st->st_rdev);
+
+	/* c_mtime */
+	tpax_octal_write(chdr->c_mtime,ssizeof(chdr->c_mtime),stmtim);
+
+	/* c_namesize */
+	tpax_octal_write(chdr->c_namesize,ssizeof(chdr->c_namesize),fnsize);
+
+	/* c_filesize */
+	tpax_octal_write(chdr->c_filesize,ssizeof(chdr->c_filesize),lnklen ? lnklen : stsize);
+
+	/* all done; c_name to be written along with c_filedata */
+	return 0;
+}