zap/src/mem/utf8dec.c


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/*
	Copyright 2022 Gabriel Jensen.
	This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
	If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/

#include <zap/priv.h>

#include <zap/mem.h>

void zap_utf8dec(zap_chr8 const * const _in,zap_chr20 * const _out) {
	zap_chr8 const * in  = _in;
	zap_chr20 *      out = _out;
	for (;;++out) {
		zap_chr8 const oct = *in;
		if (oct >= 0xF0u) { /* Four octets. */
			zap_chr20 chr =  ((zap_chr20)oct ^ 0xF0u) << 0x12u;
			++in;
			chr           += ((zap_chr20)*in ^ 0x80u) << 0xCu;
			++in;
			chr           += ((zap_chr20)*in ^ 0x80u) << 0x6u;
			++in;
			chr           +=  (zap_chr20)*in ^ 0x80u;
			++in;
			*out = chr;
			continue;
		}
		if (oct >= 0xE0u) { /* Three octets. */
			zap_chr20 chr =  ((zap_chr20)oct ^ 0xE0u) << 0xCu;
			++in;
			chr           += ((zap_chr20)*in ^ 0x80u) << 0x6u;
			++in;
			chr           +=  (zap_chr20)*in ^ 0x80u;
			++in;
			*out = chr;
			continue;
		}
		if (oct >= 0xC0u) { /* Two octets. */
			zap_chr20 chr =  ((zap_chr20)oct ^ 0xC0u) << 0x6u;
			++in;
			          chr +=  (zap_chr20)*in ^ 0x80u;
			++in;
			*out = chr;
			continue;
		}
		/* One octet. */
		*out = oct;
		++in;
		sus_unlikely (oct == 0x0u) {break;}
	}
}