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/*
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 * Copyright (c) 2002-2006 Michael Niedermayer <michaelni@gmx.at>
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 * Copyright (c) 2006 Oded Shimon <ods15@ods15.dyndns.org>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file libavcodec/eval.c
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 * simple arithmetic expression evaluator.
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 *
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 * see http://joe.hotchkiss.com/programming/eval/eval.html
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 */
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#include "libavutil/avutil.h"
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#include "eval.h"
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typedef struct Parser{
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    int stack_index;
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    char *s;
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    const double *const_value;
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    const char * const *const_name;          // NULL terminated
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    double (**func1)(void *, double a); // NULL terminated
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    const char **func1_name;          // NULL terminated
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    double (**func2)(void *, double a, double b); // NULL terminated
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    const char **func2_name;          // NULL terminated
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    void *opaque;
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    const char **error;
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#define VARS 10
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    double var[VARS];
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} Parser;
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static const int8_t si_prefixes['z' - 'E' + 1]={
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    ['y'-'E']= -24,
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    ['z'-'E']= -21,
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    ['a'-'E']= -18,
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    ['f'-'E']= -15,
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    ['p'-'E']= -12,
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    ['n'-'E']= - 9,
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    ['u'-'E']= - 6,
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    ['m'-'E']= - 3,
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    ['c'-'E']= - 2,
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    ['d'-'E']= - 1,
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    ['h'-'E']=   2,
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    ['k'-'E']=   3,
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    ['K'-'E']=   3,
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    ['M'-'E']=   6,
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    ['G'-'E']=   9,
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    ['T'-'E']=  12,
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    ['P'-'E']=  15,
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    ['E'-'E']=  18,
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    ['Z'-'E']=  21,
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    ['Y'-'E']=  24,
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};
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double av_strtod(const char *numstr, char **tail) {
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    double d;
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    char *next;
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    d = strtod(numstr, &next);
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    /* if parsing succeeded, check for and interpret postfixes */
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    if (next!=numstr) {
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        if(*next >= 'E' && *next <= 'z'){
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            int e= si_prefixes[*next - 'E'];
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            if(e){
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                if(next[1] == 'i'){
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                    d*= pow( 2, e/0.3);
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                    next+=2;
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                }else{
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                    d*= pow(10, e);
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                    next++;
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                }
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            }
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        }
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        if(*next=='B') {
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            d*=8;
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            next++;
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        }
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    }
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    /* if requested, fill in tail with the position after the last parsed
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       character */
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    if (tail)
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        *tail = next;
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    return d;
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}
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static int strmatch(const char *s, const char *prefix){
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    int i;
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    for(i=0; prefix[i]; i++){
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        if(prefix[i] != s[i]) return 0;
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    }
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    return 1;
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}
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struct AVExpr {
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    enum {
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        e_value, e_const, e_func0, e_func1, e_func2,
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        e_squish, e_gauss, e_ld,
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        e_mod, e_max, e_min, e_eq, e_gt, e_gte,
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        e_pow, e_mul, e_div, e_add,
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        e_last, e_st, e_while,
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    } type;
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    double value; // is sign in other types
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    union {
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        int const_index;
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        double (*func0)(double);
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        double (*func1)(void *, double);
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        double (*func2)(void *, double, double);
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    } a;
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    struct AVExpr *param[2];
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};
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static double eval_expr(Parser * p, AVExpr * e) {
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    switch (e->type) {
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        case e_value:  return e->value;
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        case e_const:  return e->value * p->const_value[e->a.const_index];
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        case e_func0:  return e->value * e->a.func0(eval_expr(p, e->param[0]));
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        case e_func1:  return e->value * e->a.func1(p->opaque, eval_expr(p, e->param[0]));
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        case e_func2:  return e->value * e->a.func2(p->opaque, eval_expr(p, e->param[0]), eval_expr(p, e->param[1]));
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        case e_squish: return 1/(1+exp(4*eval_expr(p, e->param[0])));
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        case e_gauss: { double d = eval_expr(p, e->param[0]); return exp(-d*d/2)/sqrt(2*M_PI); }
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        case e_ld:     return e->value * p->var[av_clip(eval_expr(p, e->param[0]), 0, VARS-1)];
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        case e_while: {
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            double d = NAN;
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            while(eval_expr(p, e->param[0]))
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                d=eval_expr(p, e->param[1]);
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            return d;
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        }
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        default: {
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            double d = eval_expr(p, e->param[0]);
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            double d2 = eval_expr(p, e->param[1]);
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            switch (e->type) {
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                case e_mod: return e->value * (d - floor(d/d2)*d2);
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                case e_max: return e->value * (d >  d2 ?   d : d2);
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                case e_min: return e->value * (d <  d2 ?   d : d2);
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                case e_eq:  return e->value * (d == d2 ? 1.0 : 0.0);
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                case e_gt:  return e->value * (d >  d2 ? 1.0 : 0.0);
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                case e_gte: return e->value * (d >= d2 ? 1.0 : 0.0);
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                case e_pow: return e->value * pow(d, d2);
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                case e_mul: return e->value * (d * d2);
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                case e_div: return e->value * (d / d2);
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                case e_add: return e->value * (d + d2);
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                case e_last:return e->value * d2;
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                case e_st : return e->value * (p->var[av_clip(d, 0, VARS-1)]= d2);
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            }
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        }
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    }
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    return NAN;
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}
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static AVExpr * parse_expr(Parser *p);
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void ff_free_expr(AVExpr * e) {
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    if (!e) return;
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    ff_free_expr(e->param[0]);
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    ff_free_expr(e->param[1]);
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    av_freep(&e);
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}
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static AVExpr * parse_primary(Parser *p) {
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    AVExpr * d = av_mallocz(sizeof(AVExpr));
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    char *next= p->s;
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    int i;
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    if (!d)
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        return NULL;
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    /* number */
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    d->value = av_strtod(p->s, &next);
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    if(next != p->s){
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        d->type = e_value;
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        p->s= next;
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        return d;
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    }
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    d->value = 1;
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    /* named constants */
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    for(i=0; p->const_name && p->const_name[i]; i++){
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        if(strmatch(p->s, p->const_name[i])){
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            p->s+= strlen(p->const_name[i]);
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            d->type = e_const;
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            d->a.const_index = i;
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            return d;
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        }
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    }
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    p->s= strchr(p->s, '(');
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    if(p->s==NULL){
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        *p->error = "undefined constant or missing (";
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        p->s= next;
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        ff_free_expr(d);
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        return NULL;
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    }
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    p->s++; // "("
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    if (*next == '(') { // special case do-nothing
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        av_freep(&d);
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        d = parse_expr(p);
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        if(p->s[0] != ')'){
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            *p->error = "missing )";
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            ff_free_expr(d);
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            return NULL;
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        }
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        p->s++; // ")"
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        return d;
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    }
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    d->param[0] = parse_expr(p);
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    if(p->s[0]== ','){
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        p->s++; // ","
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        d->param[1] = parse_expr(p);
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    }
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    if(p->s[0] != ')'){
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        *p->error = "missing )";
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        ff_free_expr(d);
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        return NULL;
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    }
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    p->s++; // ")"
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    d->type = e_func0;
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         if( strmatch(next, "sinh"  ) ) d->a.func0 = sinh;
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    else if( strmatch(next, "cosh"  ) ) d->a.func0 = cosh;
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    else if( strmatch(next, "tanh"  ) ) d->a.func0 = tanh;
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    else if( strmatch(next, "sin"   ) ) d->a.func0 = sin;
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    else if( strmatch(next, "cos"   ) ) d->a.func0 = cos;
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    else if( strmatch(next, "tan"   ) ) d->a.func0 = tan;
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    else if( strmatch(next, "atan"  ) ) d->a.func0 = atan;
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    else if( strmatch(next, "asin"  ) ) d->a.func0 = asin;
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    else if( strmatch(next, "acos"  ) ) d->a.func0 = acos;
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    else if( strmatch(next, "exp"   ) ) d->a.func0 = exp;
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    else if( strmatch(next, "log"   ) ) d->a.func0 = log;
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    else if( strmatch(next, "abs"   ) ) d->a.func0 = fabs;
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    else if( strmatch(next, "squish") ) d->type = e_squish;
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    else if( strmatch(next, "gauss" ) ) d->type = e_gauss;
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    else if( strmatch(next, "mod"   ) ) d->type = e_mod;
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    else if( strmatch(next, "max"   ) ) d->type = e_max;
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    else if( strmatch(next, "min"   ) ) d->type = e_min;
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    else if( strmatch(next, "eq"    ) ) d->type = e_eq;
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    else if( strmatch(next, "gte"   ) ) d->type = e_gte;
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    else if( strmatch(next, "gt"    ) ) d->type = e_gt;
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    else if( strmatch(next, "lte"   ) ) { AVExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gt; }
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    else if( strmatch(next, "lt"    ) ) { AVExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gte; }
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    else if( strmatch(next, "ld"    ) ) d->type = e_ld;
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    else if( strmatch(next, "st"    ) ) d->type = e_st;
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    else if( strmatch(next, "while" ) ) d->type = e_while;
259
    else {
260
        for(i=0; p->func1_name && p->func1_name[i]; i++){
261
            if(strmatch(next, p->func1_name[i])){
262
                d->a.func1 = p->func1[i];
263
                d->type = e_func1;
264
                return d;
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            }
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        }
267

    
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        for(i=0; p->func2_name && p->func2_name[i]; i++){
269
            if(strmatch(next, p->func2_name[i])){
270
                d->a.func2 = p->func2[i];
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                d->type = e_func2;
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                return d;
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            }
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        }
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        *p->error = "unknown function";
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        ff_free_expr(d);
278
        return NULL;
279
    }
280

    
281
    return d;
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}
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static AVExpr * new_eval_expr(int type, int value, AVExpr *p0, AVExpr *p1){
285
    AVExpr * e = av_mallocz(sizeof(AVExpr));
286
    if (!e)
287
        return NULL;
288
    e->type     =type   ;
289
    e->value    =value  ;
290
    e->param[0] =p0     ;
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    e->param[1] =p1     ;
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    return e;
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}
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295
static AVExpr * parse_pow(Parser *p, int *sign){
296
    *sign= (*p->s == '+') - (*p->s == '-');
297
    p->s += *sign&1;
298
    return parse_primary(p);
299
}
300

    
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static AVExpr * parse_factor(Parser *p){
302
    int sign, sign2;
303
    AVExpr * e = parse_pow(p, &sign);
304
    while(p->s[0]=='^'){
305
        p->s++;
306
        e= new_eval_expr(e_pow, 1, e, parse_pow(p, &sign2));
307
        if (!e)
308
            return NULL;
309
        if (e->param[1]) e->param[1]->value *= (sign2|1);
310
    }
311
    if (e) e->value *= (sign|1);
312
    return e;
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}
314

    
315
static AVExpr * parse_term(Parser *p){
316
    AVExpr * e = parse_factor(p);
317
    while(p->s[0]=='*' || p->s[0]=='/'){
318
        int c= *p->s++;
319
        e= new_eval_expr(c == '*' ? e_mul : e_div, 1, e, parse_factor(p));
320
        if (!e)
321
            return NULL;
322
    }
323
    return e;
324
}
325

    
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static AVExpr * parse_subexpr(Parser *p) {
327
    AVExpr * e = parse_term(p);
328
    while(*p->s == '+' || *p->s == '-') {
329
        e= new_eval_expr(e_add, 1, e, parse_term(p));
330
        if (!e)
331
            return NULL;
332
    };
333

    
334
    return e;
335
}
336

    
337
static AVExpr * parse_expr(Parser *p) {
338
    AVExpr * e;
339

    
340
    if(p->stack_index <= 0) //protect against stack overflows
341
        return NULL;
342
    p->stack_index--;
343

    
344
    e = parse_subexpr(p);
345

    
346
    while(*p->s == ';') {
347
        p->s++;
348
        e= new_eval_expr(e_last, 1, e, parse_subexpr(p));
349
        if (!e)
350
            return NULL;
351
    };
352

    
353
    p->stack_index++;
354

    
355
    return e;
356
}
357

    
358
static int verify_expr(AVExpr * e) {
359
    if (!e) return 0;
360
    switch (e->type) {
361
        case e_value:
362
        case e_const: return 1;
363
        case e_func0:
364
        case e_func1:
365
        case e_squish:
366
        case e_ld:
367
        case e_gauss: return verify_expr(e->param[0]);
368
        default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);
369
    }
370
}
371

    
372
AVExpr *ff_parse_expr(const char *s, const char * const *const_name,
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               double (**func1)(void *, double), const char **func1_name,
374
               double (**func2)(void *, double, double), const char **func2_name,
375
               const char **error){
376
    Parser p;
377
    AVExpr *e = NULL;
378
    char *w = av_malloc(strlen(s) + 1);
379
    char *wp = w;
380

    
381
    if (!w)
382
        goto end;
383

    
384
    while (*s)
385
        if (!isspace(*s++)) *wp++ = s[-1];
386
    *wp++ = 0;
387

    
388
    p.stack_index=100;
389
    p.s= w;
390
    p.const_name = const_name;
391
    p.func1      = func1;
392
    p.func1_name = func1_name;
393
    p.func2      = func2;
394
    p.func2_name = func2_name;
395
    p.error= error;
396

    
397
    e = parse_expr(&p);
398
    if (!verify_expr(e)) {
399
        ff_free_expr(e);
400
        e = NULL;
401
    }
402
end:
403
    av_free(w);
404
    return e;
405
}
406

    
407
double ff_eval_expr(AVExpr * e, const double *const_value, void *opaque) {
408
    Parser p;
409

    
410
    p.const_value= const_value;
411
    p.opaque     = opaque;
412
    return eval_expr(&p, e);
413
}
414

    
415
double ff_parse_and_eval_expr(const char *s, const double *const_value, const char * const *const_name,
416
               double (**func1)(void *, double), const char **func1_name,
417
               double (**func2)(void *, double, double), const char **func2_name,
418
               void *opaque, const char **error){
419
    AVExpr * e = ff_parse_expr(s, const_name, func1, func1_name, func2, func2_name, error);
420
    double d;
421
    if (!e) return NAN;
422
    d = ff_eval_expr(e, const_value, opaque);
423
    ff_free_expr(e);
424
    return d;
425
}
426

    
427
#ifdef TEST
428
#undef printf
429
static double const_values[]={
430
    M_PI,
431
    M_E,
432
    0
433
};
434
static const char *const_names[]={
435
    "PI",
436
    "E",
437
    0
438
};
439
int main(void){
440
    int i;
441
    printf("%f == 12.7\n", ff_parse_and_eval_expr("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));
442
    printf("%f == 0.931322575\n", ff_parse_and_eval_expr("80G/80Gi", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));
443

    
444
    for(i=0; i<1050; i++){
445
        START_TIMER
446
            ff_parse_and_eval_expr("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL);
447
        STOP_TIMER("ff_parse_and_eval_expr")
448
    }
449
    return 0;
450
}
451
#endif