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/*
* simple arithmetic expression evaluator
*
* Copyright (c) 2002 Michael Niedermayer <michaelni@gmx.at>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
/**
* @file eval.c
* simple arithmetic expression evaluator.
*
* see http://joe.hotchkiss.com/programming/eval/eval.html
*/
#include "avcodec.h"
#include "mpegvideo.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#ifndef NAN
#define NAN 0
#endif
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
typedef struct Parser{
int stack_index;
char *s;
double *const_value;
const char **const_name; // NULL terminated
double (**func1)(void *, double a); // NULL terminated
const char **func1_name; // NULL terminated
double (**func2)(void *, double a, double b); // NULL terminated
char **func2_name; // NULL terminated
void *opaque;
} Parser;
static double evalExpression(Parser *p);
static int strmatch(const char *s, const char *prefix){
int i;
for(i=0; prefix[i]; i++){
if(prefix[i] != s[i]) return 0;
}
return 1;
}
static double evalPrimary(Parser *p){
double d, d2=NAN;
char *next= p->s;
int i;
/* number */
d= strtod(p->s, &next);
if(next != p->s){
p->s= next;
return d;
}
/* named constants */
for(i=0; p->const_name && p->const_name[i]; i++){
if(strmatch(p->s, p->const_name[i])){
p->s+= strlen(p->const_name[i]);
return p->const_value[i];
}
}
p->s= strchr(p->s, '(');
if(p->s==NULL){
av_log(NULL, AV_LOG_ERROR, "Parser: missing ( in \"%s\"\n", next);
return NAN;
}
p->s++; // "("
d= evalExpression(p);
if(p->s[0]== ','){
p->s++; // ","
d2= evalExpression(p);
}
if(p->s[0] != ')'){
av_log(NULL, AV_LOG_ERROR, "Parser: missing ) in \"%s\"\n", next);
return NAN;
}
p->s++; // ")"
if( strmatch(next, "sinh" ) ) d= sinh(d);
else if( strmatch(next, "cosh" ) ) d= cosh(d);
else if( strmatch(next, "tanh" ) ) d= tanh(d);
else if( strmatch(next, "sin" ) ) d= sin(d);
else if( strmatch(next, "cos" ) ) d= cos(d);
else if( strmatch(next, "tan" ) ) d= tan(d);
else if( strmatch(next, "exp" ) ) d= exp(d);
else if( strmatch(next, "log" ) ) d= log(d);
else if( strmatch(next, "squish") ) d= 1/(1+exp(4*d));
else if( strmatch(next, "gauss" ) ) d= exp(-d*d/2)/sqrt(2*M_PI);
else if( strmatch(next, "abs" ) ) d= fabs(d);
else if( strmatch(next, "max" ) ) d= d > d2 ? d : d2;
else if( strmatch(next, "min" ) ) d= d < d2 ? d : d2;
else if( strmatch(next, "gt" ) ) d= d > d2 ? 1.0 : 0.0;
else if( strmatch(next, "gte" ) ) d= d >= d2 ? 1.0 : 0.0;
else if( strmatch(next, "lt" ) ) d= d > d2 ? 0.0 : 1.0;
else if( strmatch(next, "lte" ) ) d= d >= d2 ? 0.0 : 1.0;
else if( strmatch(next, "eq" ) ) d= d == d2 ? 1.0 : 0.0;
else if( strmatch(next, "(" ) ) d= d;
// else if( strmatch(next, "l1" ) ) d= 1 + d2*(d - 1);
// else if( strmatch(next, "sq01" ) ) d= (d >= 0.0 && d <=1.0) ? 1.0 : 0.0;
else{
for(i=0; p->func1_name && p->func1_name[i]; i++){
if(strmatch(next, p->func1_name[i])){
return p->func1[i](p->opaque, d);
}
}
for(i=0; p->func2_name && p->func2_name[i]; i++){
if(strmatch(next, p->func2_name[i])){
return p->func2[i](p->opaque, d, d2);
}
}
av_log(NULL, AV_LOG_ERROR, "Parser: unknown function in \"%s\"\n", next);
return NAN;
}
return d;
}
static double evalPow(Parser *p){
int sign= (*p->s == '+') - (*p->s == '-');
p->s += sign&1;
return (sign|1) * evalPrimary(p);
}
static double evalFactor(Parser *p){
double ret= evalPow(p);
while(p->s[0]=='^'){
p->s++;
ret= pow(ret, evalPow(p));
}
return ret;
}
static double evalTerm(Parser *p){
double ret= evalFactor(p);
while(p->s[0]=='*' || p->s[0]=='/'){
if(*p->s++ == '*') ret*= evalFactor(p);
else ret/= evalFactor(p);
}
return ret;
}
static double evalExpression(Parser *p){
double ret= 0;
if(p->stack_index <= 0) //protect against stack overflows
return NAN;
p->stack_index--;
do{
ret += evalTerm(p);
}while(*p->s == '+' || *p->s == '-');
p->stack_index++;
return ret;
}
double ff_eval(char *s, double *const_value, const char **const_name,
double (**func1)(void *, double), const char **func1_name,
double (**func2)(void *, double, double), char **func2_name,
void *opaque){
Parser p;
p.stack_index=100;
p.s= s;
p.const_value= const_value;
p.const_name = const_name;
p.func1 = func1;
p.func1_name = func1_name;
p.func2 = func2;
p.func2_name = func2_name;
p.opaque = opaque;
return evalExpression(&p);
}
#ifdef TEST
#undef printf
static double const_values[]={
M_PI,
M_E,
0
};
static const char *const_names[]={
"PI",
"E",
0
};
main(){
int i;
printf("%f == 12.7\n", ff_eval("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL));
for(i=0; i<1050; i++){
START_TIMER
ff_eval("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL);
STOP_TIMER("ff_eval")
}
}
#endif
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