125 lines
4.7 KiB
C
125 lines
4.7 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/calls/calls.h"
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#include "libc/str/thompike.h"
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#include "libc/sysv/errfuns.h"
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/**
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* Reads single keystroke or control sequence from character device.
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*
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* When reading ANSI UTF-8 text streams, characters and control codes
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* are oftentimes encoded as multi-byte sequences. This function knows
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* how long each sequence is, so that each read consumes a single thing
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* from the underlying file descriptor, e.g.
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*
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* "a" ALFA
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* "\316\261" ALPHA
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* "\033[A" CURSOR UP
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* "\033[38;5;202m" ORANGERED
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* "\eOP" PF1
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*
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* This routine generalizes to ascii, utf-8, chorded modifier keys,
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* function keys, color codes, c0/c1 control codes, cursor movement,
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* mouse movement, etc.
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*
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* Userspace buffering isn't required, since ANSI escape sequences and
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* UTF-8 are decoded without peeking. Noncanonical overlong encodings
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* can cause the stream to go out of sync. This function recovers such
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* events by ignoring continuation bytes at the beginning of each read.
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*
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* String control sequences, e.g. "\e_hello\e\\" currently are not
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* tokenized as a single read. Lastly note, this function has limited
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* support for UNICODE representations of C0/C1 control codes, e.g.
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*
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* "\000" NUL
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* "\300\200" NUL
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* "\302\233A" CURSOR UP
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*
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* @param buf is guaranteed to receive a NUL terminator if size>0
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* @return number of bytes read (helps differentiate "\0" vs. "")
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* @see examples/ttyinfo.c
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* @see ANSI X3.64-1979
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* @see ISO/IEC 6429
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* @see FIPS-86
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* @see ECMA-48
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*/
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ssize_t readansi(int fd, char *buf, size_t size) {
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int i, j;
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uint8_t c;
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enum { kAscii, kUtf8, kEsc, kCsi, kSs } t;
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if (size) buf[0] = 0;
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for (j = i = 0, t = kAscii;;) {
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if (i + 2 >= size) return enomem();
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if (read(fd, &c, 1) != 1) return -1;
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buf[i++] = c;
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buf[i] = 0;
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switch (t) {
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case kAscii:
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if (c < 0200) {
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if (c == '\e') {
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t = kEsc;
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} else {
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return i;
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}
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} else if (c >= 0300) {
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t = kUtf8;
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j = ThomPikeLen(c) - 1;
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}
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break;
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case kUtf8:
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if (!--j) return i;
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break;
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case kEsc:
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switch (c) {
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case '[':
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t = kCsi;
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break;
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case 'N':
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case 'O':
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t = kSs;
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break;
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case 0x20 ... 0x2F:
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break;
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default:
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return i;
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}
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break;
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case kCsi:
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switch (c) {
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case ':':
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case ';':
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case '<':
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case '=':
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case '>':
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case '?':
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case '0' ... '9':
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break;
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default:
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return i;
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}
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break;
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case kSs:
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return i;
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default:
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unreachable;
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}
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}
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}
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