From 3f4ca11498028756ebde239ae469c0f88e5d3ecc Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 8 Jan 2019 18:29:36 +0100
Subject: [PATCH] fileio: add 'dir_fd' parameter to read_full_file_full()

Let's introduce an "at" version of read_full_file().

(cherry picked from commit f6be4db4530b7cfea191227c141343a4fb10d4c6)

Signed-off-by: Guorui Yu <GuoRui.Yu@linux.alibaba.com>
---
 src/basic/fileio.c | 84 +++++++++++++++++++++++++++++++++++++++++++---
 src/basic/fileio.h |  5 +--
 2 files changed, 83 insertions(+), 6 deletions(-)

diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index 833c55b030..d7da834a74 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -501,15 +501,91 @@ finalize:
         return r;
 }
 
-int read_full_file_full(const char *filename, ReadFullFileFlags flags, char **contents, size_t *size) {
+static int mode_to_flags(const char *mode) {
+        const char *p;
+        int flags;
+
+        if ((p = startswith(mode, "r+")))
+                flags = O_RDWR;
+        else if ((p = startswith(mode, "r")))
+                flags = O_RDONLY;
+        else if ((p = startswith(mode, "w+")))
+                flags = O_RDWR|O_CREAT|O_TRUNC;
+        else if ((p = startswith(mode, "w")))
+                flags = O_WRONLY|O_CREAT|O_TRUNC;
+        else if ((p = startswith(mode, "a+")))
+                flags = O_RDWR|O_CREAT|O_APPEND;
+        else if ((p = startswith(mode, "a")))
+                flags = O_WRONLY|O_CREAT|O_APPEND;
+        else
+                return -EINVAL;
+
+        for (; *p != 0; p++) {
+
+                switch (*p) {
+
+                case 'e':
+                        flags |= O_CLOEXEC;
+                        break;
+
+                case 'x':
+                        flags |= O_EXCL;
+                        break;
+
+                case 'm':
+                        /* ignore this here, fdopen() might care later though */
+                        break;
+
+                case 'c': /* not sure what to do about this one */
+                default:
+                        return -EINVAL;
+                }
+        }
+
+        return flags;
+}
+
+static int xfopenat(int dir_fd, const char *path, const char *mode, int flags, FILE **ret) {
+        FILE *f;
+
+        /* A combination of fopen() with openat() */
+
+        if (dir_fd == AT_FDCWD && flags == 0) {
+                f = fopen(path, mode);
+                if (!f)
+                        return -errno;
+        } else {
+                int fd, mode_flags;
+
+                mode_flags = mode_to_flags(mode);
+                if (mode_flags < 0)
+                        return mode_flags;
+
+                fd = openat(dir_fd, path, mode_flags | flags);
+                if (fd < 0)
+                        return -errno;
+
+                f = fdopen(fd, mode);
+                if (!f) {
+                        safe_close(fd);
+                        return -errno;
+                }
+        }
+
+        *ret = f;
+        return 0;
+}
+
+int read_full_file_full(int dir_fd, const char *filename, ReadFullFileFlags flags, char **contents, size_t *size) {
         _cleanup_fclose_ FILE *f = NULL;
+        int r;
 
         assert(filename);
         assert(contents);
 
-        f = fopen(filename, "re");
-        if (!f)
-                return -errno;
+        r = xfopenat(dir_fd, filename, "re", 0, &f);
+        if (r < 0)
+                return r;
 
         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 
diff --git a/src/basic/fileio.h b/src/basic/fileio.h
index be10ac77b6..916ddc5e47 100644
--- a/src/basic/fileio.h
+++ b/src/basic/fileio.h
@@ -6,6 +6,7 @@
 #include <stddef.h>
 #include <stdio.h>
 #include <sys/stat.h>
+#include <sys/fcntl.h>
 #include <sys/types.h>
 
 #include "macro.h"
@@ -42,9 +43,9 @@ static inline int write_string_file(const char *fn, const char *line, WriteStrin
 int write_string_filef(const char *fn, WriteStringFileFlags flags, const char *format, ...) _printf_(3, 4);
 
 int read_one_line_file(const char *filename, char **line);
-int read_full_file_full(const char *filename, ReadFullFileFlags flags, char **contents, size_t *size);
+int read_full_file_full(int dir_fd, const char *filename, ReadFullFileFlags flags, char **contents, size_t *size);
 static inline int read_full_file(const char *filename, char **contents, size_t *size) {
-        return read_full_file_full(filename, 0, contents, size);
+        return read_full_file_full(AT_FDCWD, filename, 0, contents, size);
 }
 int read_full_stream_full(FILE *f, const char *filename, ReadFullFileFlags flags, char **contents, size_t *size);
 static inline int read_full_stream(FILE *f, char **contents, size_t *size) {
-- 
2.39.1