/* * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 #define STACK_SIZE 100 typedef struct Parser{ double stack[STACK_SIZE]; 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 void evalExpression(Parser *p); static void push(Parser *p, double d){ if(p->stack_index+1>= STACK_SIZE){ fprintf(stderr, "stack overflow in the parser\n"); return; } p->stack[ p->stack_index++ ]= d; //printf("push %f\n", d); fflush(stdout); } static double pop(Parser *p){ if(p->stack_index<=0){ fprintf(stderr, "stack underflow in the parser\n"); return NAN; } //printf("pop\n"); fflush(stdout); return p->stack[ --p->stack_index ]; } 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 void evalPrimary(Parser *p){ double d, d2=NAN; char *next= p->s; int i; /* number */ d= strtod(p->s, &next); if(next != p->s){ push(p, d); p->s= next; return; } /* named constants */ for(i=0; p->const_name[i]; i++){ if(strmatch(p->s, p->const_name[i])){ push(p, p->const_value[i]); p->s+= strlen(p->const_name[i]); return; } } p->s= strchr(p->s, '('); if(p->s==NULL){ fprintf(stderr, "Parser: missing ( in \"%s\"\n", next); return; } p->s++; // "(" evalExpression(p); d= pop(p); p->s++; // ")" or "," if(p->s[-1]== ','){ evalExpression(p); d2= pop(p); 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, "lt" ) ) d= d > d2 ? 0.0 : 1.0; else if( strmatch(next, "eq" ) ) d= d == d2 ? 1.0 : 0.0; // 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{ int error=1; for(i=0; p->func1_name && p->func1_name[i]; i++){ if(strmatch(next, p->func1_name[i])){ d= p->func1[i](p->opaque, d); error=0; break; } } for(i=0; p->func2_name && p->func2_name[i]; i++){ if(strmatch(next, p->func2_name[i])){ d= p->func2[i](p->opaque, d, d2); error=0; break; } } if(error){ fprintf(stderr, "Parser: unknown function in \"%s\"\n", next); return; } } if(p->s[-1]!= ')'){ fprintf(stderr, "Parser: missing ) in \"%s\"\n", next); return; } push(p, d); } static void evalPow(Parser *p){ int neg= 0; if(p->s[0]=='+') p->s++; if(p->s[0]=='-'){ neg= 1; p->s++; } if(p->s[0]=='('){ p->s++;; evalExpression(p); if(p->s[0]!=')') fprintf(stderr, "Parser: missing )\n"); p->s++; }else{ evalPrimary(p); } if(neg) push(p, -pop(p)); } static void evalFactor(Parser *p){ evalPow(p); while(p->s[0]=='^'){ double d; p->s++; evalPow(p); d= pop(p); push(p, pow(pop(p), d)); } } static void evalTerm(Parser *p){ evalFactor(p); while(p->s[0]=='*' || p->s[0]=='/'){ int inv= p->s[0]=='/'; double d; p->s++; evalFactor(p); d= pop(p); if(inv) d= 1.0/d; push(p, d * pop(p)); } } static void evalExpression(Parser *p){ evalTerm(p); while(p->s[0]=='+' || p->s[0]=='-'){ int sign= p->s[0]=='-'; double d; p->s++; evalTerm(p); d= pop(p); if(sign) d= -d; push(p, d + pop(p)); } } 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=0; 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; evalExpression(&p); return pop(&p); }