58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
/* vim: tabstop=4 shiftwidth=4 noexpandtab
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* This file is part of ToaruOS and is released under the terms
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* of the NCSA / University of Illinois License - see LICENSE.md
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* Copyright (C) 2018 K. Lange
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*
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* This is a simple implementation of a UTF-8 decoder with an
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* equivalent API to the older third-party (and much cooler...)
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* version that ToaruOS used to use. Keep feeding it bytes and
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* will eventually set *codep to a codepoint. Should also be able
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* to detect bad UTF-8.
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*/
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#include <stdint.h>
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#define UTF8_ACCEPT 0
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#define UTF8_REJECT 1
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/**
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* Conceptually similar to its predecessor, this implementation is much
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* less cool, as it uses three separate state tables and more shifts.
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*/
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static inline uint32_t decode(uint32_t* state, uint32_t* codep, uint32_t byte) {
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static int state_table[32] = {
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0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 0xxxxxxx */
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1,1,1,1,1,1,1,1, /* 10xxxxxx */
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2,2,2,2, /* 110xxxxx */
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3,3, /* 1110xxxx */
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4, /* 11110xxx */
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1 /* 11111xxx */
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};
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static int mask_bytes[32] = {
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0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,
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0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,0x7F,
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0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
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0x1F,0x1F,0x1F,0x1F,
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0x0F,0x0F,
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0x07,
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0x00
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};
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static int next[5] = {
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0,
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1,
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0,
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2,
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3
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};
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if (*state == UTF8_ACCEPT) {
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*codep = byte & mask_bytes[byte >> 3];
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*state = state_table[byte >> 3];
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} else if (*state > 0) {
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*codep = (byte & 0x3F) | (*codep << 6);
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*state = next[*state];
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}
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return *state;
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}
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