libavcodec/eval.c

   1 /*
   2  * simple arithmetic expression evaluator
   3  *
   4  * Copyright (c) 2002 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  *
  20  */
  21
  22 /**
  23  * @file eval.c
  24  * simple arithmetic expression evaluator.
  25  *
  26  * see http://joe.hotchkiss.com/programming/eval/eval.html
  27  */
  28
  29 #include "avcodec.h"
  30 #include "mpegvideo.h"
  31
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <math.h>
  36
  37 #ifndef NAN
  38   #define NAN 0
  39 #endif
  40
  41 #ifndef M_PI
  42 #define M_PI 3.14159265358979323846
  43 #endif
  44
  45 typedef struct Parser{
  46     int stack_index;
  47     char *s;
  48     double *const_value;
  49     const char **const_name;          // NULL terminated
  50     double (**func1)(void *, double a); // NULL terminated
  51     const char **func1_name;          // NULL terminated
  52     double (**func2)(void *, double a, double b); // NULL terminated
  53     char **func2_name;          // NULL terminated
  54     void *opaque;
  55 } Parser;
  56
  57 static double evalExpression(Parser *p);
  58
  59 static int strmatch(const char *s, const char *prefix){
  60     int i;
  61     for(i=0; prefix[i]; i++){
  62         if(prefix[i] != s[i]) return 0;
  63     }
  64     return 1;
  65 }
  66
  67 static double evalPrimary(Parser *p){
  68     double d, d2=NAN;
  69     char *next= p->s;
  70     int i;
  71
  72     /* number */
  73     d= strtod(p->s, &next);
  74     if(next != p->s){
  75         p->s= next;
  76         return d;
  77     }
  78
  79     /* named constants */
  80     for(i=0; p->const_name && p->const_name[i]; i++){
  81         if(strmatch(p->s, p->const_name[i])){
  82             p->s+= strlen(p->const_name[i]);
  83             return p->const_value[i];
  84         }
  85     }
  86
  87     p->s= strchr(p->s, '(');
  88     if(p->s==NULL){
  89         av_log(NULL, AV_LOG_ERROR, "Parser: missing ( in \"%s\"\n", next);
  90         return NAN;
  91     }
  92     p->s++; // "("
  93     d= evalExpression(p);
  94     if(p->s[0]== ','){
  95         p->s++; // ","
  96         d2= evalExpression(p);
  97     }
  98     if(p->s[0] != ')'){
  99         av_log(NULL, AV_LOG_ERROR, "Parser: missing ) in \"%s\"\n", next);
 100         return NAN;
 101     }
 102     p->s++; // ")"
 103
 104          if( strmatch(next, "sinh"  ) ) d= sinh(d);
 105     else if( strmatch(next, "cosh"  ) ) d= cosh(d);
 106     else if( strmatch(next, "tanh"  ) ) d= tanh(d);
 107     else if( strmatch(next, "sin"   ) ) d= sin(d);
 108     else if( strmatch(next, "cos"   ) ) d= cos(d);
 109     else if( strmatch(next, "tan"   ) ) d= tan(d);
 110     else if( strmatch(next, "exp"   ) ) d= exp(d);
 111     else if( strmatch(next, "log"   ) ) d= log(d);
 112     else if( strmatch(next, "squish") ) d= 1/(1+exp(4*d));
 113     else if( strmatch(next, "gauss" ) ) d= exp(-d*d/2)/sqrt(2*M_PI);
 114     else if( strmatch(next, "abs"   ) ) d= fabs(d);
 115     else if( strmatch(next, "max"   ) ) d= d > d2 ? d : d2;
 116     else if( strmatch(next, "min"   ) ) d= d < d2 ? d : d2;
 117     else if( strmatch(next, "gt"    ) ) d= d > d2 ? 1.0 : 0.0;
 118     else if( strmatch(next, "gte"    ) ) d= d >= d2 ? 1.0 : 0.0;
 119     else if( strmatch(next, "lt"    ) ) d= d > d2 ? 0.0 : 1.0;
 120     else if( strmatch(next, "lte"    ) ) d= d >= d2 ? 0.0 : 1.0;
 121     else if( strmatch(next, "eq"    ) ) d= d == d2 ? 1.0 : 0.0;
 122     else if( strmatch(next, "("     ) ) d= d;
 123 //    else if( strmatch(next, "l1"    ) ) d= 1 + d2*(d - 1);
 124 //    else if( strmatch(next, "sq01"  ) ) d= (d >= 0.0 && d <=1.0) ? 1.0 : 0.0;
 125     else{
 126         for(i=0; p->func1_name && p->func1_name[i]; i++){
 127             if(strmatch(next, p->func1_name[i])){
 128                 return p->func1[i](p->opaque, d);
 129             }
 130         }
 131
 132         for(i=0; p->func2_name && p->func2_name[i]; i++){
 133             if(strmatch(next, p->func2_name[i])){
 134                 return p->func2[i](p->opaque, d, d2);
 135             }
 136         }
 137
 138         av_log(NULL, AV_LOG_ERROR, "Parser: unknown function in \"%s\"\n", next);
 139         return NAN;
 140     }
 141
 142     return d;
 143 }
 144
 145 static double evalPow(Parser *p){
 146     int sign= (*p->s == '+') - (*p->s == '-');
 147     p->s += sign&1;
 148     return (sign|1) * evalPrimary(p);
 149 }
 150
 151 static double evalFactor(Parser *p){
 152     double ret= evalPow(p);
 153     while(p->s[0]=='^'){
 154         p->s++;
 155         ret= pow(ret, evalPow(p));
 156     }
 157     return ret;
 158 }
 159
 160 static double evalTerm(Parser *p){
 161     double ret= evalFactor(p);
 162     while(p->s[0]=='*' || p->s[0]=='/'){
 163         if(*p->s++ == '*') ret*= evalFactor(p);
 164         else               ret/= evalFactor(p);
 165     }
 166     return ret;
 167 }
 168
 169 static double evalExpression(Parser *p){
 170     double ret= 0;
 171
 172     if(p->stack_index <= 0) //protect against stack overflows
 173         return NAN;
 174     p->stack_index--;
 175
 176     do{
 177         ret += evalTerm(p);
 178     }while(*p->s == '+' || *p->s == '-');
 179
 180     p->stack_index++;
 181
 182     return ret;
 183 }
 184
 185 double ff_eval(char *s, double *const_value, const char **const_name,
 186                double (**func1)(void *, double), const char **func1_name,
 187                double (**func2)(void *, double, double), char **func2_name,
 188                void *opaque){
 189     Parser p;
 190
 191     p.stack_index=100;
 192     p.s= s;
 193     p.const_value= const_value;
 194     p.const_name = const_name;
 195     p.func1      = func1;
 196     p.func1_name = func1_name;
 197     p.func2      = func2;
 198     p.func2_name = func2_name;
 199     p.opaque     = opaque;
 200
 201     return evalExpression(&p);
 202 }
 203
 204 #ifdef TEST
 205 #undef printf
 206 static double const_values[]={
 207     M_PI,
 208     M_E,
 209     0
 210 };
 211 static const char *const_names[]={
 212     "PI",
 213     "E",
 214     0
 215 };
 216 main(){
 217     int i;
 218     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));
 219
 220     for(i=0; i<1050; i++){
 221         START_TIMER
 222             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);
 223         STOP_TIMER("ff_eval")
 224     }
 225 }
 226 #endif