v

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module term
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// utf8_getchar returns an utf8 rune from standard input
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pub fn utf8_getchar() ?rune {
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	c := input_character()
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	if c == -1 {
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		return none
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	}
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	len := utf8_len(u8(~c))
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	if c < 0 {
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		return 0
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	} else if len == 0 {
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		return c
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	} else if len == 1 {
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		return -1
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	} else {
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		mut uc := c & ((1 << (7 - len)) - 1)
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		for i := 0; i + 1 < len; i++ {
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			c2 := input_character()
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			if c2 != -1 && (c2 >> 6) == 2 {
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				uc <<= 6
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				uc |= (c2 & 63)
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			} else if c2 == -1 {
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				return 0
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			} else {
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				return -1
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			}
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		}
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		return uc
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	}
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}
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// utf8_len calculates the length of a utf8 rune to read, according to its first byte
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pub fn utf8_len(c u8) int {
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	mut b := 0
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	mut x := c
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	if (x & 240) != 0 {
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		// 0xF0
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		x >>= 4
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	} else {
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		b += 4
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	}
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	if (x & 12) != 0 {
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		// 0x0C
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		x >>= 2
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	} else {
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		b += 2
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	}
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	if (x & 2) == 0 {
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		// 0x02
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		b++
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	}
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	return b
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}
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