2020-06-15 14:18:57 +00:00
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#ifndef COSMOPOLITAN_LIBC_STR_TPDECODECB_H_
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#define COSMOPOLITAN_LIBC_STR_TPDECODECB_H_
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2020-08-25 11:23:25 +00:00
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#include "libc/nexgen32e/bsr.h"
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2020-06-15 14:18:57 +00:00
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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/**
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* Generic Thompson-Pike Varint Decoder.
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* @return number of bytes successfully consumed or -1 w/ errno
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* @note synchronization is performed
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*/
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forceinline int tpdecodecb(wint_t *out, int first,
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int get(void *arg, uint32_t i), void *arg) {
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2020-08-25 11:23:25 +00:00
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uint32_t wc, cb, need, msb, j, i = 1;
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if (unlikely((wc = first) == -1)) return -1;
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while (unlikely((wc & 0b11000000) == 0b10000000)) {
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2020-06-15 14:18:57 +00:00
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if ((wc = get(arg, i++)) == -1) return -1;
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}
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2020-08-25 11:23:25 +00:00
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if (unlikely(!(0 <= wc && wc <= 0x7F))) {
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msb = wc < 252 ? bsr(~wc & 0xff) : 1;
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2020-06-15 14:18:57 +00:00
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need = 7 - msb;
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wc &= ((1u << msb) - 1) | 0b00000011;
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2020-08-25 11:23:25 +00:00
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for (j = 1; j < need; ++j) {
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2020-06-15 14:18:57 +00:00
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if ((cb = get(arg, i++)) == -1) return -1;
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if ((cb & 0b11000000) == 0b10000000) {
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wc = wc << 6 | (cb & 0b00111111);
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} else {
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if (out) *out = u'<EFBFBD>';
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return -1;
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}
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}
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}
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2020-08-25 11:23:25 +00:00
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if (likely(out)) *out = (wint_t)wc;
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2020-06-15 14:18:57 +00:00
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return i;
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}
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_STR_TPDECODECB_H_ */
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