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75 lines
2.3 KiB
C++
75 lines
2.3 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2012.
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This file is part of Sortix.
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Sortix is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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Sortix. If not, see <http://www.gnu.org/licenses/>.
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utf8.cpp
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Encodes UTF-32 strings in UTF-8.
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*******************************************************************************/
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#include <errno.h>
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#include <sortix/kernel/kernel.h>
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#include "utf8.h"
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namespace Sortix
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{
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namespace UTF8
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{
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unsigned Encode(uint32_t unicode, char* dest)
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{
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uint8_t* buf = (uint8_t*) dest;
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unsigned bytes = 1;
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unsigned bits = 7;
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if ( (1U<<7U) <= unicode ) { bytes = 2; bits = 11; }
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if ( (1U<<11U) <= unicode ) { bytes = 3; bits = 16; }
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if ( (1U<<16U) <= unicode ) { bytes = 4; bits = 21; }
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if ( (1U<<21U) <= unicode ) { bytes = 5; bits = 26; }
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if ( (1U<<26U) <= unicode ) { bytes = 6; bits = 31; }
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if ( (1U<<31U) <= unicode ) { errno = EINVAL; return 0; }
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uint8_t prefix;
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unsigned prefixavai;
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switch ( bytes )
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{
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case 1: prefixavai = 7; prefix = 0b0U << prefixavai; break;
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case 2: prefixavai = 5; prefix = 0b110U << prefixavai; break;
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case 3: prefixavai = 4; prefix = 0b1110U << prefixavai; break;
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case 4: prefixavai = 3; prefix = 0b11110U << prefixavai; break;
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case 5: prefixavai = 2; prefix = 0b111110U << prefixavai; break;
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case 6: prefixavai = 1; prefix = 0b1111110U << prefixavai; break;
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}
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// Put the first bits in the unused area of the prefix.
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prefix |= unicode >> (bits - prefixavai);
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*buf++ = prefix;
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unsigned bitsleft = bits - prefixavai;
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while ( bitsleft )
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{
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bitsleft -= 6;
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uint8_t elembits = (unicode>>bitsleft) & ((1U<<6U)-1U);
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uint8_t elem = (0b10U<<6U) | elembits;
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*buf++ = elem;
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}
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return bytes;
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}
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}
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}
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