Reference: http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130325/077133.html

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@178581 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 99 insertions, 26 deletions

diff --git a/src/support/win32/support.cpp b/src/support/win32/support.cpp
index 2139a3f85..75f639191 100644
--- a/src/support/win32/support.cpp
+++ b/src/support/win32/support.cpp
@@ -45,35 +45,108 @@ int vasprintf( char **sptr, const char *__restrict fmt, va_list ap )
     return count;
 }
 
-// FIXME: use wcrtomb and avoid copy
-// use mbsrtowcs which is available, first copy first nwc elements of src
+// Returns >= 0: the number of wide characters found in the multi byte sequence src (of src_size_bytes),
+// that fit in the buffer dst (of max_dest_chars elements size). The count returned excludes the null terminator.
+// When dst is NULL, no characters are copied and no "out" parameters are updated.
+// Returns (size_t) -1: an incomplete sequence encountered.
+// Leaves *src pointing the next character to convert or NULL if a null character was converted from *src.
 size_t mbsnrtowcs( wchar_t *__restrict dst, const char **__restrict src,
-                   size_t nmc, size_t len, mbstate_t *__restrict ps )
+                   size_t src_size_bytes, size_t max_dest_chars, mbstate_t *__restrict ps )
 {
-    char* local_src = new char[nmc+1];
-    char* nmcsrc = local_src;
-    strncpy( nmcsrc, *src, nmc );
-    nmcsrc[nmc] = '\0';
-    const size_t result = mbsrtowcs( dst, const_cast<const char **>(&nmcsrc), len, ps );
-    // propagate error
-    if( nmcsrc == NULL )
-        *src = NULL;
-    delete[] local_src;
-    return result;
+    const size_t terminated_sequence = static_cast<size_t>(0);
+    //const size_t invalid_sequence = static_cast<size_t>(-1);
+    const size_t incomplete_sequence = static_cast< size_t>(-2);
+
+    size_t dest_converted = 0;
+    size_t source_converted = 0;
+    size_t source_remaining = src_size_bytes;
+    size_t result = 0;
+    bool have_result = false;
+
+    while ( source_remaining ) {
+        if ( dst && dest_converted >= max_dest_chars )
+            break;
+        // Converts one multi byte character.
+        // if result > 0, it's the size in bytes of that character.
+        // othewise if result is zero it indicates the null character has been found.
+        // otherwise it's an error and errno may be set.
+        size_t char_size = mbrtowc( dst ? dst + dest_converted : NULL, *src + source_converted, source_remaining, ps );
+        // Don't do anything to change errno from here on.
+        if ( char_size > 0 ) {
+            source_remaining -= char_size;
+            source_converted += char_size;
+            ++dest_converted;
+            continue;
+        }
+        result = char_size;
+        have_result = true;
+        break;
+    }
+    if ( dst ) {
+        if ( have_result && result == terminated_sequence )
+            *src = NULL;
+        else
+            *src += source_converted;
+    }
+    if ( have_result && result != terminated_sequence && result != incomplete_sequence )
+        return static_cast<size_t>(-1);
+
+    return dest_converted;
 }
-// FIXME: use wcrtomb and avoid copy
-// use wcsrtombs which is available, first copy first nwc elements of src
+
+// Converts max_source_chars from the wide character buffer pointer to by *src,
+// into the multi byte character sequence buffer stored at dst which must be dst_size_bytes bytes in size.
+// Returns >= 0: the number of bytes in the sequence sequence converted frome *src, excluding the null terminator.
+// Returns size_t(-1) if an error occurs, also sets errno.
+// If dst is NULL dst_size_bytes is ignored and no bytes are copied to dst and no "out" parameters are updated.
 size_t wcsnrtombs( char *__restrict dst, const wchar_t **__restrict src,
-                   size_t nwc, size_t len, mbstate_t *__restrict ps )
+                   size_t max_source_chars, size_t dst_size_bytes, mbstate_t *__restrict ps )
 {
-    wchar_t* local_src = new wchar_t[nwc];
-    wchar_t* nwcsrc = local_src;
-    wcsncpy(nwcsrc, *src, nwc);
-    nwcsrc[nwc] = '\0';
-    const size_t result = wcsrtombs( dst, const_cast<const wchar_t **>(&nwcsrc), len, ps );
-    // propogate error
-    if( nwcsrc == NULL )
-        *src = NULL;
-    delete[] nwcsrc;
-    return result;
+    //const size_t invalid_sequence = static_cast<size_t>(-1);
+
+    size_t source_converted = 0;
+    size_t dest_converted = 0;
+    size_t dest_remaining = dst_size_bytes;
+    size_t char_size = 0;
+    const errno_t no_error = ( errno_t) 0;
+    errno_t result = ( errno_t ) 0;
+    bool have_result = false;
+    bool terminator_found = false;
+
+    while ( source_converted != max_source_chars ) {
+        if ( ! dest_remaining )
+            break;
+        wchar_t c = (*src)[source_converted];
+        if ( dst )
+            result = wcrtomb_s( &char_size, dst + dest_converted, dest_remaining, c, ps);
+        else
+            result = wcrtomb_s( &char_size, NULL, 0, c, ps); 
+        // If result is zero there is no error and char_size contains the size of the multi-byte-sequence converted.
+        // Otherwise result indicates an errno type error.
+        if ( result == no_error ) {
+            if ( c == L'\0' ) {
+                terminator_found = true;
+                break;
+            }
+            ++source_converted;
+            if ( dst )
+                dest_remaining -= char_size;
+            dest_converted += char_size;
+            continue;
+        }
+        have_result = true;
+        break;
+    }
+    if ( dst ) {
+        if ( terminator_found )
+            *src = NULL;
+        else
+            *src = *src + source_converted;
+    }
+    if ( have_result && result != no_error ) {
+        errno = result;
+        return static_cast<size_t>(-1);
+    }
+
+    return dest_converted;
 }