libs/libc/wchar: add ungetwc implementation

Signed-off-by: guoshichao <guoshichao@xiaomi.com>

include/wchar.h

@@ -166,7 +166,8 @@ wint_t            putwchar(wchar_t);
 wint_t            putwchar_unlocked(wchar_t);
 int               swprintf(FAR wchar_t *, size_t, FAR const wchar_t *, ...);
 int               swscanf(FAR const wchar_t *, FAR const wchar_t *, ...);
-wint_t            ungetwc(wint_t, FILE *);
+wint_t            ungetwc(wint_t, FAR FILE *);
+wint_t            ungetwc_unlocked(wint_t, FAR FILE *);
 int               vfwprintf(FILE *, FAR const wchar_t *, va_list);
 int               vfwscanf(FILE *, FAR const wchar_t *, va_list);
 int               vwprintf(FAR const wchar_t *, va_list);

libs/libc/libc.csv

@@ -332,6 +332,8 @@
 "ub16sqr","fixedmath.h","!defined(CONFIG_HAVE_LONG_LONG)","ub16_t","ub16_t"
 "uname","sys/utsname.h","","int","FAR struct utsname *"
 "ungetc","stdio.h","defined(CONFIG_FILE_STREAM)","int","int","FAR FILE *"
+"ungetwc","wchar.h","defined(CONFIG_FILE_STREAM)","wint_t","wint_t","FAR FILE *"
+"ungetwc_unlocked","wchar.h","defined(CONFIG_FILE_STREAM)","wint_t","wint_t","FAR FILE *"
 "usleep","unistd.h","","int","useconds_t"
 "vasprintf","stdio.h","","int","FAR char **","FAR const IPTR char *","va_list"
 "versionsort","dirent.h","","int","FAR const struct dirent **","FAR const struct dirent **"

libs/libc/stdio/CMakeLists.txt

@@ -107,7 +107,8 @@ if(CONFIG_FILE_STREAM)
     lib_fopencookie.c
     lib_fmemopen.c
     lib_fgetwc.c
-    lib_getwc.c)
+    lib_getwc.c
+    lib_ungetwc.c)
 endif()
 
 target_sources(c PRIVATE ${SRCS})

libs/libc/stdio/Make.defs

@@ -49,7 +49,7 @@ CSRCS += lib_scanf.c lib_vscanf.c lib_fscanf.c lib_vfscanf.c lib_tmpfile.c
 CSRCS += lib_setbuf.c lib_setvbuf.c lib_libfilelock.c lib_libgetstreams.c
 CSRCS += lib_setbuffer.c lib_fputwc.c lib_putwc.c lib_fputws.c
 CSRCS += lib_fopencookie.c lib_fmemopen.c lib_open_memstream.c lib_fgetwc.c
-CSRCS += lib_getwc.c
+CSRCS += lib_getwc.c lib_ungetwc.c
 endif
 
 # Add the stdio directory to the build

libs/libc/stdio/lib_ungetwc.c

@@ -0,0 +1,125 @@
+/****************************************************************************
+ * libs/libc/stdio/lib_ungetwc.c
+ *
+ * Copyright © 2005-2014 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <wchar.h>
+#include <limits.h>
+#include <ctype.h>
+#include <fcntl.h>
+#include <string.h>
+
+#ifdef CONFIG_FILE_STREAM
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: ungetwc_unlocked
+ *
+ * Description:
+ *   Put a wide character back to the stream without lock the stream
+ *
+ * Input Parameters:
+ *   wc - the wide character to be put back
+ *   f - the file stream to put the wide character back to
+ *
+ * Returned Value:
+ *   Return the wide character that put back to the stream on success,
+ *   return WEOF on failed, and keep the given stream remains unchanged.
+ *
+ ****************************************************************************/
+
+wint_t ungetwc_unlocked(wint_t wc, FAR FILE *f)
+{
+  char mbc[MB_LEN_MAX];
+  int l = 1;
+
+  /* Stream must be open for read access */
+
+  if ((f->fs_oflags & O_RDOK) == 0)
+    {
+      return WEOF;
+    }
+
+  /* Try conversion early so we can fail without locking if invalid */
+
+  if ((l = wctomb(mbc, wc)) < 0)
+    {
+      return WEOF;
+    }
+
+#if CONFIG_NUNGET_CHARS > 0
+  if (f->fs_nungotten + l <= CONFIG_NUNGET_CHARS)
+    {
+      memcpy(f->fs_ungotten + f->fs_nungotten, mbc, l);
+      f->fs_nungotten += l;
+      return wc;
+    }
+  else
+#endif
+    {
+      return WEOF;
+    }
+}
+
+/****************************************************************************
+ * Name: ungetwc
+ *
+ * Description:
+ *   Put a wide character back to the stream
+ *
+ * Input Parameters:
+ *   wc - the wide character that need to put back to the stream
+ *   f - pointer to a FILE object that identifies an input stream
+ *
+ * Returned Value:
+ *   Return the wide character that put back to the stream on success,
+ *   return WEOF on failed, and keep the given stream remains unchanged.
+ *
+ ****************************************************************************/
+
+wint_t ungetwc(wint_t wc, FAR FILE *f)
+{
+  wint_t ret;
+
+  /* Verify that a non-NULL stream was provided and wc is not WEOF */
+
+  if (!f || wc == WEOF)
+    {
+      return WEOF;
+    }
+
+  flockfile(f);
+  ret = ungetwc_unlocked(wc, f);
+  funlockfile(f);
+  return ret;
+}
+
+#endif /* CONFIG_FILE_STREAM */