Files opened with O_TMPFILE have no name, so read_file can't be used
with them. Therefore add a read_fd function, which slurps all a file's
contents into a buffer.
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
v1 -> v2:
- Justify why the buffer is three bytes longer than the file's content
(Yann)
- Check for malloc failure (Yann)
- Don't close file descriptor on failure as it's opened outside
the function
- set errno to indicate why the function failed
- use fstat and pread_full (Sascha)
---
include/libfile.h | 2 ++
lib/libfile.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 52 insertions(+)
diff --git a/include/libfile.h b/include/libfile.h
index a353ccfa9ea9..423e7ffec5b7 100644
--- a/include/libfile.h
+++ b/include/libfile.h
@@ -12,6 +12,8 @@ char *read_file_line(const char *fmt, ...);
void *read_file(const char *filename, size_t *size);
+void *read_fd(int fd, size_t *size);
+
int read_file_2(const char *filename, size_t *size, void **outbuf,
loff_t max_size);
diff --git a/lib/libfile.c b/lib/libfile.c
index e53ba08415a2..72a2fc79c721 100644
--- a/lib/libfile.c
+++ b/lib/libfile.c
@@ -306,6 +306,56 @@ void *read_file(const char *filename, size_t *size)
}
EXPORT_SYMBOL(read_file);
+/**
+ * read_fd - read from a file descriptor to an allocated buffer
+ * @filename: The file descriptor to read
+ * @size: After successful return contains the size of the file
+ *
+ * This function reads a file descriptor from offset 0 until EOF to an
+ * allocated buffer.
+ *
+ * Return: On success, returns a nul-terminated buffer with the file's
+ * contents that should be deallocated with free().
+ * On error, NULL is returned and errno is set to an error code.
+ */
+void *read_fd(int fd, size_t *out_size)
+{
+ struct stat st;
+ ssize_t ret;
+ void *buf;
+
+ ret = fstat(fd, &st);
+ if (ret < 0)
+ return NULL;
+
+ if (st.st_size == FILE_SIZE_STREAM) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ /* For user convenience, we always nul-terminate the buffer in
+ * case it contains a string. As we don't want to assume the string
+ * to be either an array of char or wchar_t, we just unconditionally
+ * add 2 bytes as terminator. As the two byte terminator needs to be
+ * aligned, we just make it three bytes
+ */
+ buf = malloc(st.st_size + 3);
+ if (!buf)
+ return NULL;
+
+ ret = pread_full(fd, buf, st.st_size, 0);
+ if (ret < 0) {
+ free(buf);
+ return NULL;
+ }
+
+ memset(buf + st.st_size, '\0', 3);
+ *out_size = st.st_size;
+
+ return buf;
+}
+EXPORT_SYMBOL(read_fd);
+
/**
* write_file - write a buffer to a file
* @filename: The filename to write
--
2.39.2
