[kvm-unit-tests PATCH v3 13/27] lib/printf: Add support for printing wide strings

Nikos Nikoleris
2022-06-30T10:04:12Z

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@arm.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
---
lib/printf.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/lib/printf.c b/lib/printf.c
index d600199..27041bb 100644
--- a/lib/printf.c
+++ b/lib/printf.c
@@ -58,6 +58,102 @@ 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)
@@ -305,7 +401,10 @@ morefmt:
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