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/*
* Dynamic patch
* Copyright (C) 2024 Nguyễn Gia Phong
*
* This file is part of taosc.
*
* Taosc is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Taosc 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with taosc. If not, see <https://www.gnu.org/licenses/>.
*/
#include "stdlib.c"
const char *taosc_predicate;
const void *taosc_destination;
/*
* Get an environment variable and parse as a number.
* Return 0 on error.
*/
uint64_t getenvull(const char *name)
{
const char *const s = getenv(name);
if (s == NULL)
return 0ULL;
errno = 0;
const uint64_t u = strtoull(s, NULL, 0);
if (errno)
return 0ULL;
return u;
}
void init(int argc, const char *const *argv, const char **envp)
{
environ = envp;
taosc_predicate = getenv("TAOSC_PREDICATE");
if (taosc_predicate == NULL)
taosc_predicate = "p0"; /* false */
taosc_destination = (void *) getenvull("TAOSC_DESTINATION");
}
/* Parse *p as an integer. */
int64_t scani(const char **p)
{
int64_t i = 0;
for (; **p >= '0' && **p <= '9'; ++*p)
i = i * 10 + **p - '0';
return i;
}
/* Parse and evaluate *ptr in a prefix Polish notation, recursively. */
int64_t eval(const char **ptr, const int64_t *env)
{
const char op = *(*ptr)++;
switch (op) {
case 'n': /* negative integer */
return -scani(ptr);
case 'p': /* positive integer */
return scani(ptr);
case 'v': /* variable look up */
return env[scani(ptr)];
}
const bool eq = **ptr == '=';
*ptr += eq;
const int64_t a = eval(ptr, env);
const int64_t b = eval(ptr, env);
switch (op) {
case '=':
return a == b;
case '!':
return a != b;
case '>':
return eq ? (a >= b) : (a > b);
case '<':
return eq ? (a <= b) : (a < b);
case '+':
return a + b;
case '-':
return a - b;
case '*':
return a * b;
case '/':
return a / b;
default:
__builtin_unreachable();
}
}
const void *dest(const struct STATE *state)
{
const char *tmp = taosc_predicate;
return eval(&tmp, (const int64_t *) state) ? NULL : taosc_destination;
}
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