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lexer.c
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lexer.c
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/* Copyright (C) 2021 by Alexandru-Sergiu Marton
This file contains code derived from the source of the "Crafting
Interpreters" book, Copyright (c) 2015 Robert Nystrom, originally
licensed under the MIT license:
> Permission is hereby granted, free of charge, to any person obtaining a copy
> of this software and associated documentation files (the "Software"), to
> deal in the Software without restriction, including without limitation the
> rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> sell copies of the Software, and to permit persons to whom the Software is
> furnished to do so, subject to the following conditions:
>
> The above copyright notice and this permission notice shall be included in
> all copies or substantial portions of the Software.
>
> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> IN THE SOFTWARE.
This file is part of shell243.
shell243 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, either version 3 of the License, or
(at your option) any later version.
shell243 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 shell243. If not, see <https://www.gnu.org/licenses/>.
*/
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <ctype.h>
#include "lexer.h"
stream stm;
typedef enum { Q_SINGLE, Q_DOUBLE, Q_BACKSLASH, Q_NONE } quote_type;
static token
make_token (token_type type)
{
return (token) { .type = type, .start = stm.start, .length = stm.current - stm.start };
}
static token
error_token (const char *msg)
{
return (token) { .type = TOK_ERR, .start = msg, .length = strlen (msg) };
}
static bool
is_at_end ()
{
return *stm.current == '\0';
}
static char
advance ()
{
stm.current++;
return stm.current[-1];
}
static bool
match (char expected)
{
if (is_at_end ())
return false;
if (*stm.current != expected)
return false;
stm.current++;
return true;
}
static char
peek ()
{
return *stm.current;
}
static token
word (quote_type qtype)
{
int quote_offset = 0;
bool can_be_ionum = true;
char c = peek ();
while (!is_at_end ())
{
if (qtype == Q_NONE
&& (c == '|' || c == '&' || c == '<' || c == '>' || c == ';'
|| isspace (c)))
break;
if (c == '\\' && qtype == Q_NONE)
qtype = Q_BACKSLASH, quote_offset = stm.current - stm.start;
else if (c == '\'' && qtype == Q_NONE)
qtype = Q_SINGLE, quote_offset = stm.current - stm.start;
else if (c == '"' && qtype == Q_NONE)
qtype = Q_DOUBLE, quote_offset = stm.current - stm.start;
else if (qtype == Q_BACKSLASH)
{
qtype = Q_NONE;
memmove (stm.current - 1, stm.current, strlen (stm.current) + 1);
--stm.current;
}
else if ((c == '\'' && qtype == Q_SINGLE)
|| (c == '"' && qtype == Q_DOUBLE))
{
qtype = Q_NONE;
// Since this means we found both opening and closing
// quotes, we can safely shift our input two chars leftward.
memmove (stm.start + quote_offset, stm.start + quote_offset + 1,
strlen (stm.start + quote_offset + 1) + 1);
--stm.current;
memmove (stm.current, stm.current + 1,
strlen (stm.current + 1) + 1);
--stm.current;
}
if (can_be_ionum && !isdigit (c))
can_be_ionum = false;
advance ();
c = peek ();
}
if (qtype != Q_NONE && is_at_end ())
return error_token ("Reached EOF before closing quote.");
if (can_be_ionum && (c == '<' || c == '>'))
return make_token (TOK_IONUM);
return make_token (TOK_WORD);
}
static void
skip_whitespace ()
{
while (!is_at_end () && isspace (peek ()))
advance ();
}
void
init_lexer (char *cmd)
{
stm = (stream) { .start = cmd, .current = cmd };
}
token
next_token ()
{
stm.start = stm.current;
if (is_at_end ())
return make_token (TOK_EOF);
char c = advance ();
switch (c)
{
case ';':
return make_token (TOK_SEMI);
case '|':
if (match ('|'))
return make_token (TOK_OR);
return make_token (TOK_PIPE);
case '&':
if (match ('&'))
return make_token (TOK_AND);
return make_token (TOK_AMP);
case '<':
if (match ('<'))
return make_token (TOK_DLT);
return make_token (TOK_LT);
case '>':
if (match ('>'))
return make_token (TOK_DGT);
return make_token (TOK_GT);
case '\'':
return word (Q_SINGLE);
case '"':
return word (Q_DOUBLE);
case '\\':
return word (Q_BACKSLASH);
default:
if (isspace (c))
{
skip_whitespace ();
return next_token ();
}
return word (Q_NONE);
}
return error_token ("Unexpected character.");
}