PeerStreamer

/*

 * 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);

}