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55 lines
3 KiB
C
55 lines
3 KiB
C
/*-*- 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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#include "libc/str/internal.h"
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#include "libc/str/str.h"
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/**
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* Thompson-Pike Varint Encoder.
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*
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* Implementation Details: The header macro should ensure this function
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* is only called for non-ASCII, or DCE'd entirely. In addition to that
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* this function makes a promise to not clobber any registers but %rax.
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*
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* @param buf is what ch gets encoded to
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* @param size is the number of bytes available in buf
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* @param ch is a 32-bit integer
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* @param awesome mode enables numbers the IETF unilaterally banned
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* @return number of bytes written
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* @note this encoding was designed on a napkin in a new jersey diner
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*/
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unsigned(tpencode)(char *buf, size_t size, wint_t ch, bool32 awesome) {
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unsigned char *p = (unsigned char *)buf;
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if ((0 <= ch && ch < 32) && awesome && size >= 2) {
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p[0] = 0xc0;
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p[1] = 0x80 | (unsigned char)ch;
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return 2;
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}
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struct TpEncode op = UseTpDecoderRing(ch);
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size_t i = op.len;
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if (op.len <= size) {
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for (;;) {
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p[--i] = (unsigned char)(0b10000000 | (ch & 0b00111111));
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if (!i) break;
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ch >>= 6;
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}
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p[0] = op.mark | (unsigned char)ch;
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}
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return op.len;
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}
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