On 02/15/16 12:12, Matt Fleming wrote:
> (Cc'ing Laszlo and linux-efi)
>
> On Fri, 12 Feb, at 11:13:33PM, Jason Andryuk wrote:
>> The comparisons should be >= since 0x800 and 0x80 require an additional bit
>> to store.
>>
>> For the 3 byte case, the existing shift would drop off 2 more bits than
>> intended.
>>
>> For the 2 byte case, there should be 5 bits bits in byte 1, and 6 bits in
>> byte 2.
>>
>> Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
>> ---
>>
>> Tested in user space, but not in the kernel. Conversions now match
>> python's unicode conversions.
>>
>> lib/ucs2_string.c | 14 +++++++-------
>> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> Thanks Jason. Peter, Laszlo, any comments?
>
>> diff --git a/lib/ucs2_string.c b/lib/ucs2_string.c
>> index 17dd74e..f0b323a 100644
>> --- a/lib/ucs2_string.c
>> +++ b/lib/ucs2_string.c
>> @@ -59,9 +59,9 @@ ucs2_utf8size(const ucs2_char_t *src)
>> for (i = 0; i < ucs2_strlen(src); i++) {
>> u16 c = src[i];
>>
>> - if (c > 0x800)
>> + if (c >= 0x800)
>> j += 3;
>> - else if (c > 0x80)
>> + else if (c >= 0x80)
>> j += 2;
>> else
>> j += 1;
This change looks justified, from the table at
https://en.wikipedia.org/wiki/UTF-8#Description
>> @@ -88,19 +88,19 @@ ucs2_as_utf8(u8 *dest, const ucs2_char_t *src, unsigned long maxlength)
>> for (i = 0; maxlength && i < limit; i++) {
>> u16 c = src[i];
>>
>> - if (c > 0x800) {
>> + if (c >= 0x800) {
>> if (maxlength < 3)
>> break;
>> maxlength -= 3;
>> dest[j++] = 0xe0 | (c & 0xf000) >> 12;
Okay, so byte #1 consumes the most significant 4 bits
>> - dest[j++] = 0x80 | (c & 0x0fc0) >> 8;
>> + dest[j++] = 0x80 | (c & 0x0fc0) >> 6;
Byte #2 is supposed to consume 6 more bits:
1234 56
00001111 11000000 binary
0 f c 0 hex -> mask is okay
Indeed the shift count should be 6.
>> dest[j++] = 0x80 | (c & 0x003f);
>> - } else if (c > 0x80) {
>> + } else if (c >= 0x80) {
>> if (maxlength < 2)
>> break;
>> maxlength -= 2;
>> - dest[j++] = 0xc0 | (c & 0xfe0) >> 5;
>> - dest[j++] = 0x80 | (c & 0x01f);
>> + dest[j++] = 0xc0 | (c & 0x7c0) >> 6;
Byte #1 is supposed to consume the 5 most significant bits, from the 11
bits that the code point has:
00000111 11111111 -- bin
0 7 f f -- hex -- all it can have
123 45
00000111 11000000 -- bin
0 7 c 0 -- hex -- mask is okay
Shift count of 6 looks okay.
>> + dest[j++] = 0x80 | (c & 0x03f);
Byte #2 is supposed to consume the remaining 6 bits:
123456
00000000 00111111 -- bin
0 0 3 f -- hex - mask is okay
Maybe if we could write the mask as 0x3f, instead of 0x03f.
Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>
>> } else {
>> maxlength -= 1;
>> dest[j++] = c & 0x7f;
>> --
>> 2.4.3
>>
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