On Fri, May 06, 2022 at 09:55:52PM +0100, Nikos Nikoleris wrote:
> 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
>
Reviewed-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
