Merge branch 'ungetwc' into 'master'

Implementing ungetwc

See merge request redox-os/relibc!390

src/header/wchar/mod.rs

@@ -237,9 +237,24 @@ pub extern "C" fn swscanf(s: *const wchar_t, format: *const wchar_t, ap: va_list
     unimplemented!();
 }
 
-// #[no_mangle]
-pub extern "C" fn ungetwc(wc: wint_t, stream: *mut FILE) -> wint_t {
-    unimplemented!();
+/// Push wide character `wc` back onto `stream` so it'll be read next
+#[no_mangle]
+pub unsafe extern "C" fn ungetwc(wc: wint_t, stream: &mut FILE) -> wint_t {
+    if wc == WEOF {
+        return wc;
+    }
+    static mut INTERNAL: mbstate_t = mbstate_t;
+    let mut bytes: [c_char; MB_CUR_MAX as usize] = [0; MB_CUR_MAX as usize];
+
+    let amount = wcrtomb(bytes.as_mut_ptr(), wc as wchar_t, &mut INTERNAL);
+    if amount == usize::MAX {
+        return WEOF;
+    }
+    for i in 0..amount {
+        ungetc(bytes[i] as c_int, &mut *stream);
+    }
+    
+    wc
 }
 
 // #[no_mangle]

tests/Makefile

@@ -43,6 +43,7 @@ EXPECT_NAMES=\
 	stdio/printf_space_pad \
 	stdio/ungetc_ftell \
 	stdio/ungetc_multiple \
+	stdio/ungetwc \
 	stdio/fscanf_offby1 \
 	stdio/fscanf \
 	stdio/printf_neg_pad \

tests/wchar/ungetwc.c

@@ -0,0 +1,26 @@
+#include <wchar.h>
+#include <wctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+ 
+int main()
+{
+   FILE *stream;
+   wint_t wc;
+   wint_t wc2;
+
+   if (NULL == (stream = fopen("wchar/ungetwc.in", "r+")))
+      return 1;
+ 
+   while (WEOF != (wc = fgetwc(stream)) && iswdigit(wc)) {}
+ 
+   if (WEOF != wc)
+      ungetwc(wc, stream);
+   
+   wc2 = fgetwc(stream);
+   assert(WEOF != wc2);
+   assert(wc == wc2);
+   
+   return 0;
+}

tests/wchar/ungetwc.in

@@ -0,0 +1 @@
+123A