[U-Boot] [PATCH 05/15] lib: vsprintf: correct printing of Unicode strings

[Heinrich Schuchardt]

On 08/26/2018 08:05 PM, Alexander Graf wrote:
> 
> 
> On 11.08.18 17:28, Heinrich Schuchardt wrote:
>> The width and precision of the printf() function refer to the number of
>> characters not to the number of bytes printed.
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> ---
>>  lib/vsprintf.c | 22 +++++++++++++---------
>>  1 file changed, 13 insertions(+), 9 deletions(-)
>>
>> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
>> index a07128ad96..b7eb9d5f5e 100644
>> --- a/lib/vsprintf.c
>> +++ b/lib/vsprintf.c
>> @@ -280,18 +280,22 @@ static char *string16(char *buf, char *end, u16 *s, int field_width,
>>  		int precision, int flags)
>>  {
>>  	u16 *str = s ? s : L"<NULL>";
>> -	int utf16_len = u16_strnlen(str, precision);
>> -	u8 utf8[utf16_len * MAX_UTF8_PER_UTF16];
>> -	int utf8_len, i;
>> -
>> -	utf8_len = utf16_to_utf8(utf8, str, utf16_len) - utf8;
>> +	ssize_t i, len = utf16_strnlen(str, precision);
>>  
>>  	if (!(flags & LEFT))
>> -		while (utf8_len < field_width--)
>> +		for (; len < field_width; --field_width)
>>  			ADDCH(buf, ' ');
>> -	for (i = 0; i < utf8_len; ++i)
>> -		ADDCH(buf, utf8[i]);
>> -	while (utf8_len < field_width--)
>> +	for (i = 0; i < len; ++i) {
>> +		s32 code = utf16_get((const u16 **)&str);
>> +
>> +		if (code < 0) {
>> +			code = '?';
>> +			if (*str)
>> +				++str;
>> +		}
>> +		utf8_put(code, &buf);
> 
> Can you introduce or reuse a strcpy() helper in charset.c for this? That
> way the compiler has the chance to inline utf16_get() and utf8_put() and
> make the function fast.

strcpy() works on bytes not on multi-byte utf-8 characters. So it is
unclear to me how I should make use of strcpy() here.

Of cause we could define utf8_put() and utf8_get() as inline function.
But that would increase code size. Is this what you would prefer? I
would guess that the serial interface is always the slowest part of text
output anyway.

Regards

Heinrich

> 
> 
> Alex
>