[SDK:CRT] Implement vswprintf()

SDK/CRT/STDIO/wprintf.c

@@ -0,0 +1,92 @@
+/*++
+
+Copyright (c) 2024, Quinn Stephens.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   printf.c
+
+Abstract:
+
+   Provides wide formatted string printing routines.
+
+--*/
+
+#include <wchar.h>
+
+static
+size_t
+print_hex (
+    wchar_t *wcs,
+    size_t maxlen,
+    unsigned int num
+    )
+
+{
+    wchar_t *dest;
+    size_t n;
+    int shift;
+    unsigned int x;
+
+    dest = wcs;
+    n = 0;
+    shift = 28;
+    while (n < maxlen && shift >= 0) {
+        x = (num >> shift) & 0xf;
+        if (x >= 0xa) {
+            *dest = 'a' + (x - 0xa);
+        } else {
+            *dest = '0' + x;
+        }
+
+        dest++;
+        n++;
+        shift -= 4;
+    }
+
+    return n;
+}
+
+int
+vswprintf (
+    wchar_t *wcs,
+    size_t maxlen,
+    const wchar_t *format,
+    va_list args
+    )
+
+{
+    wchar_t *dest;
+    size_t n, size;
+
+    dest = wcs;
+    n = 0;
+    while (n < maxlen && *format != '\0') {
+        if (*format != '%') {
+            *dest++ = *format++;
+            n++;
+            continue;
+        }
+
+        format++;
+        switch (*format) {
+        case 'x':
+            size = print_hex(dest, maxlen - n, va_arg(args, unsigned int));
+            n += size;
+            dest += size;
+            format++;
+            break;
+        case '\0':
+            break;
+        case '%':
+        default:
+            *dest++ = *format++;
+            n++;
+            break;
+        }
+    }
+
+    wcs[n] = '\0';
+    return (int)n;
+}

SDK/INC/CRT/wchar.h

@@ -22,6 +22,7 @@ Abstract:
 extern "C" {
 #endif
 
+#include <stdarg.h>
 #include <string.h>
 
 size_t wcslen(const wchar_t *str);
@@ -35,6 +36,8 @@ wchar_t *wmemset(wchar_t *dest, wchar_t c, size_t count);
 wchar_t *wmemcpy(wchar_t *dest, const wchar_t *src, size_t count);
 wchar_t *wmemmove(wchar_t *dest, const wchar_t *src, size_t count);
 
+int vswprintf(wchar_t *wcs, size_t maxlen, const wchar_t *format, va_list args);
+
 #ifdef __cplusplus
 }
 #endif