From 8dc63ddc326ec54709c580a400536fcc4ef62622 Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Mon, 19 Feb 2024 01:54:51 +0000
Subject: library api's: _util_ (utility helper interfaces) namespace overhaul.

---
 src/util/slbt_realpath.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 src/util/slbt_realpath.c

(limited to 'src/util/slbt_realpath.c')

diff --git a/src/util/slbt_realpath.c b/src/util/slbt_realpath.c
new file mode 100644
index 0000000..3929e04
--- /dev/null
+++ b/src/util/slbt_realpath.c
@@ -0,0 +1,101 @@
+/*******************************************************************/
+/*  slibtool: a skinny libtool implementation, written in C        */
+/*  Copyright (C) 2016--2024  SysDeer Technologies, LLC            */
+/*  Released under the Standard MIT License; see COPYING.SLIBTOOL. */
+/*******************************************************************/
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <slibtool/slibtool.h>
+
+#include "slibtool_driver_impl.h"
+#include "slibtool_readlink_impl.h"
+
+#ifdef HAVE_SYS_SYSCALL_H
+#include <sys/syscall.h>
+#endif
+
+#ifdef _MIDIPIX_ABI
+#include <sys/fs.h>
+#endif
+
+#ifndef ENOTSUP
+#define ENOTSUP EOPNOTSUPP
+#endif
+
+#ifdef SYS___realpathat
+extern long syscall(int, ...);
+#endif
+
+int slbt_util_realpath(
+	int             fdat,
+	const char *    path,
+	int             options,
+	char *          buf,
+	size_t          buflen)
+{
+	int             ret;
+	int             fd;
+	int             fdproc;
+	struct stat     st;
+	struct stat     stproc;
+	char    procfspath[36];
+
+	/* common validation */
+	if (!buf || (options & O_CREAT)) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/* framework-based wrapper */
+#ifdef _MIDIPIX_ABI
+	return __fs_rpath(fdat,path,options,buf,buflen);
+#endif
+
+#ifdef SYS___realpathat
+	return syscall(SYS___realpathat,fdat,path,buf,buflen,0);
+#endif
+
+	/* buflen */
+	if (buflen < PATH_MAX) {
+		errno = ENOBUFS;
+		return -1;
+	}
+
+	/* AT_FDCWD */
+	if (fdat == AT_FDCWD) {
+		return realpath(path,buf) ? 0 : -1;
+	}
+
+	/* /proc/self/fd */
+	if ((fd = openat(fdat,path,options,0)) < 0)
+		return -1;
+
+	sprintf(procfspath,"/proc/self/fd/%d",fd);
+
+	if (slbt_readlinkat(fdat,procfspath,buf,buflen)) {
+		close(fd);
+		return -1;
+	}
+
+	if ((fdproc = openat(AT_FDCWD,buf,options|O_NOFOLLOW,0)) < 0) {
+		close(fd);
+		errno = ELOOP;
+		return -1;
+	}
+
+	ret = fstat(fd,&st) || fstat(fdproc,&stproc);
+
+	close(fd);
+	close(fdproc);
+
+	if (ret || (st.st_dev != stproc.st_dev) || (st.st_ino != stproc.st_ino)) {
+		errno = ENOTSUP;
+		return -1;
+	}
+
+	return 0;
+}
-- 
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