From 9ca35be2ab917dc88bcf5716ccf6cde20e709191 Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Sat, 26 Dec 2020 00:45:51 +0000
Subject: helper api: added slbt_realpath().

---
 include/slibtool/slibtool.h |  1 +
 project/common.mk           |  1 +
 src/helper/slbt_realpath.c  | 89 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 src/helper/slbt_realpath.c

diff --git a/include/slibtool/slibtool.h b/include/slibtool/slibtool.h
index de49275..ee70c79 100644
--- a/include/slibtool/slibtool.h
+++ b/include/slibtool/slibtool.h
@@ -300,6 +300,7 @@ slbt_api int  slbt_archive_import       (const struct slbt_driver_ctx *, struct
 slbt_api int  slbt_copy_file            (const struct slbt_driver_ctx *, struct slbt_exec_ctx *,
                                          char * src, char * dst);
 slbt_api int  slbt_dump_machine         (const char * compiler, char * machine, size_t bufsize);
+slbt_api int  slbt_realpath             (int, const char *, int, char *, size_t);
 
 /* utility api */
 slbt_api int  slbt_main                 (char **, char **,
diff --git a/project/common.mk b/project/common.mk
index e08e900..cd653bc 100644
--- a/project/common.mk
+++ b/project/common.mk
@@ -4,6 +4,7 @@ API_SRCS = \
 	src/helper/slbt_archive_import.c \
 	src/helper/slbt_copy_file.c \
 	src/helper/slbt_dump_machine.c \
+	src/helper/slbt_realpath.c \
 	src/logic/slbt_exec_compile.c \
 	src/logic/slbt_exec_ctx.c \
 	src/logic/slbt_exec_execute.c \
diff --git a/src/helper/slbt_realpath.c b/src/helper/slbt_realpath.c
new file mode 100644
index 0000000..4c7446e
--- /dev/null
+++ b/src/helper/slbt_realpath.c
@@ -0,0 +1,89 @@
+
+/*******************************************************************/
+/*  slibtool: a skinny libtool implementation, written in C        */
+/*  Copyright (C) 2016--2020  Z. Gilboa                            */
+/*  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_readlink_impl.h"
+
+#ifdef _MIDIPIX_ABI
+#include <sys/fs.h>
+#endif
+
+#ifndef ENOTSUP
+#define ENOTSUP EOPNOTSUPP
+#endif
+
+int slbt_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
+
+	/* 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_readlink(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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