144 lines
4.1 KiB
C
144 lines
4.1 KiB
C
/**
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* @file Utf8Decoder.h
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* @author Ambroz Bizjak <ambrop7@gmail.com>
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*
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* @section LICENSE
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef BADVPN_UTF8DECODER_H
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#define BADVPN_UTF8DECODER_H
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#include <stdint.h>
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#include <misc/debug.h>
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/**
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* Decodes UTF-8 data into Unicode characters.
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*/
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typedef struct {
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int bytes;
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int pos;
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uint32_t ch;
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} Utf8Decoder;
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/**
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* Initializes the UTF-8 decoder.
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*
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* @param o the object
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*/
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static void Utf8Decoder_Init (Utf8Decoder *o);
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/**
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* Inputs a byte to the decoder.
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*
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* @param o the object
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* @param b byte to input
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* @param out_ch will receive a Unicode character if this function returns 1.
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* If written, the character will be in the range 0 - 0x10FFFF,
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* excluding the surrogate range 0xD800 - 0xDFFF.
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* @return 1 if a Unicode character has been written to *out_ch, 0 if not
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*/
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static int Utf8Decoder_Input (Utf8Decoder *o, uint8_t b, uint32_t *out_ch);
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void Utf8Decoder_Init (Utf8Decoder *o)
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{
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o->bytes = 0;
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}
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int Utf8Decoder_Input (Utf8Decoder *o, uint8_t b, uint32_t *out_ch)
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{
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// one-byte character
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if ((b & 128) == 0) {
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o->bytes = 0;
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*out_ch = b;
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return 1;
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}
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// start of two-byte character
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if ((b & 224) == 192) {
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o->bytes = 2;
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o->pos = 1;
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o->ch = (uint32_t)(b & 31) << 6;
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return 0;
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}
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// start of three-byte character
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if ((b & 240) == 224) {
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o->bytes = 3;
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o->pos = 1;
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o->ch = (uint32_t)(b & 15) << 12;
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return 0;
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}
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// start of four-byte character
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if ((b & 248) == 240) {
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o->bytes = 4;
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o->pos = 1;
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o->ch = (uint32_t)(b & 7) << 18;
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return 0;
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}
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// continuation of multi-byte character
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if ((b & 192) == 128 && o->bytes > 0) {
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ASSERT(o->bytes <= 4)
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ASSERT(o->pos > 0)
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ASSERT(o->pos < o->bytes)
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// add bits from this byte
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o->ch |= (uint32_t)(b & 63) << (6 * (o->bytes - o->pos - 1));
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// end of multi-byte character?
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if (o->pos == o->bytes - 1) {
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// reset state
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o->bytes = 0;
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// don't report out-of-range characters
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if (o->ch > UINT32_C(0x10FFFF)) {
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return 0;
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}
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// don't report surrogates
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if (o->ch >= UINT32_C(0xD800) && o->ch <= UINT32_C(0xDFFF)) {
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return 0;
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}
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*out_ch = o->ch;
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return 1;
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}
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// increment byte index
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o->pos++;
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return 0;
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}
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// error, reset state
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o->bytes = 0;
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return 0;
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}
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#endif
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