[kvm-unit-tests PATCH v2 10/23] lib/printf: Add support for printing wide strings

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This change adds support for wide strings (u16*) to printf()
variants. This feature is used by a future change.

Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
---
 lib/printf.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/lib/printf.c b/lib/printf.c
index 724befa..14a3fed 100644
--- a/lib/printf.c
+++ b/lib/printf.c
@@ -57,6 +57,102 @@ static void print_str(pstream_t *p, const char *s, strprops_t props)
     }
 }
 
+/*
+ * Adapted from drivers/firmware/efi/libstub/vsprintf.c
+ */
+static u32 utf16_to_utf32(const u16 **s16)
+{
+    u16 c0, c1;
+
+    c0 = *(*s16)++;
+    /* not a surrogate */
+    if ((c0 & 0xf800) != 0xd800)
+	return c0;
+    /* invalid: low surrogate instead of high */
+    if (c0 & 0x0400)
+	return 0xfffd;
+    c1 = **s16;
+    /* invalid: missing low surrogate */
+    if ((c1 & 0xfc00) != 0xdc00)
+	return 0xfffd;
+    /* valid surrogate pair */
+    ++(*s16);
+    return (0x10000 - (0xd800 << 10) - 0xdc00) + (c0 << 10) + c1;
+}
+
+/*
+ * Adapted from drivers/firmware/efi/libstub/vsprintf.c
+ */
+static size_t utf16s_utf8nlen(const u16 *s16, size_t maxlen)
+{
+    size_t len, clen;
+
+    for (len = 0; len < maxlen && *s16; len += clen) {
+	u16 c0 = *s16++;
+
+	/* First, get the length for a BMP character */
+	clen = 1 + (c0 >= 0x80) + (c0 >= 0x800);
+	if (len + clen > maxlen)
+	    break;
+	/*
+	 * If this is a high surrogate, and we're already at maxlen, we
+	 * can't include the character if it's a valid surrogate pair.
+	 * Avoid accessing one extra word just to check if it's valid
+	 * or not.
+	 */
+	if ((c0 & 0xfc00) == 0xd800) {
+	    if (len + clen == maxlen)
+		break;
+	    if ((*s16 & 0xfc00) == 0xdc00) {
+		++s16;
+		++clen;
+	    }
+	}
+    }
+
+    return len;
+}
+
+/*
+ * Adapted from drivers/firmware/efi/libstub/vsprintf.c
+ */
+static void print_wstring(pstream_t *p, const u16 *s, strprops_t props)
+{
+    const u16 *ws = (const u16 *)s;
+    size_t pos = 0, size = p->remain + 1, len = utf16s_utf8nlen(ws, props.precision);
+
+    while (len-- > 0) {
+	u32 c32 = utf16_to_utf32(&ws);
+	u8 *s8;
+	size_t clen;
+
+	if (c32 < 0x80) {
+	    addchar(p, c32);
+	    continue;
+	}
+
+	/* Number of trailing octets */
+	clen = 1 + (c32 >= 0x800) + (c32 >= 0x10000);
+
+	len -= clen;
+	s8 = (u8 *)(p->buffer - p->added + pos);
+
+	/* Avoid writing partial character */
+	addchar(p, '\0');
+	pos += clen;
+	if (pos >= size)
+	    continue;
+
+	/* Set high bits of leading octet */
+	*s8 = (0xf00 >> 1) >> clen;
+	/* Write trailing octets in reverse order */
+	for (s8 += clen; clen; --clen, c32 >>= 6)
+	    *s8-- = 0x80 | (c32 & 0x3f);
+	/* Set low bits of leading octet */
+	*s8 |= c32;
+    }
+}
+
 static char digits[16] = "0123456789abcdef";
 
 static void print_int(pstream_t *ps, long long n, int base, strprops_t props)
@@ -302,7 +398,10 @@ int vsnprintf(char *buf, int size, const char *fmt, va_list va)
 	    print_unsigned(&s, (unsigned long)va_arg(args, void *), 16, props);
 	    break;
 	case 's':
-	    print_str(&s, va_arg(args, const char *), props);
+	    if (nlong)
+		print_wstring(&s, va_arg(args, const u16 *), props);
+	    else
+		print_str(&s, va_arg(args, const char *), props);
 	    break;
 	default:
 	    addchar(&s, f);
-- 
2.25.1




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