cosmopolitan/libc/str/tpencode.ncabi.c

55 lines
2.8 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/str/internal.h"
#include "libc/str/tpenc.h"
#include "libc/str/tpencode.h"
/**
* Thompson-Pike Varint Encoder.
*
* Implementation Details: The header macro should ensure this function
* is only called for non-ASCII, or DCE'd entirely. In addition to that
* this function makes a promise to not clobber any registers but %rax.
*
* @param p is what ch gets encoded to
* @param size is the number of bytes available in buf
* @param ch is a 32-bit integer
* @param awesome mode enables numbers the IETF unilaterally banned
* @return number of bytes written
* @note this encoding was designed on a napkin in a new jersey diner
*/
unsigned(tpencode)(char *p, size_t size, wint_t wc, bool32 awesome) {
int i, j;
unsigned long w;
if ((0 <= wc && wc < 32) && awesome && size >= 2) {
p[0] = 0xc0;
p[1] = 0x80;
p[1] |= wc;
return 2;
}
i = 0;
w = tpenc(wc);
do {
if (!size--) break;
p[i++] = w & 0xff;
} while (w >>= 8);
return i;
}