posix: device_io: implement fdopen()

Implement fdopen(), as required by the POSIX_DEVICE_IO Option
Group.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

lib/os/fdtable.c

@@ -403,6 +403,17 @@ int zvfs_close(int fd)
 	return res;
 }
 
+FILE *zvfs_fdopen(int fd, const char *mode)
+{
+	ARG_UNUSED(mode);
+
+	if (_check_fd(fd) < 0) {
+		return NULL;
+	}
+
+	return (FILE *)&fdtable[fd];
+}
+
 int zvfs_fstat(int fd, struct stat *buf)
 {
 	if (_check_fd(fd) < 0) {

lib/posix/options/device_io.c

@@ -5,6 +5,7 @@
  */
 
 #include <stddef.h>
+#include <stdio.h>
 #include <stdint.h>
 
 #include <zephyr/posix/poll.h>
@@ -13,6 +14,7 @@
 
 /* prototypes for external, not-yet-public, functions in fdtable.c or fs.c */
 int zvfs_close(int fd);
+FILE *zvfs_fdopen(int fd, const char *mode);
 int zvfs_open(const char *name, int flags);
 ssize_t zvfs_read(int fd, void *buf, size_t sz, size_t *from_offset);
 ssize_t zvfs_write(int fd, const void *buf, size_t sz, size_t *from_offset);
@@ -45,6 +47,11 @@ int close(int fd)
 FUNC_ALIAS(close, _close, int);
 #endif
 
+FILE *fdopen(int fd, const char *mode)
+{
+	return zvfs_fdopen(fd, mode);
+}
+
 int open(const char *name, int flags, ...)
 {
 	/* FIXME: necessarily need to check for O_CREAT and unpack ... if set */