FFmpeg: libavcodec/eval.c Source File

00001 /*
00002  * simple arithmetic expression evaluator
00003  *
00004  * Copyright (c) 2002-2006 Michael Niedermayer <michaelni@gmx.at>
00005  * Copyright (c) 2006 Oded Shimon <ods15@ods15.dyndns.org>
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00022  */
00023 
00031 #include "avcodec.h"
00032 #include "eval.h"
00033 
00034 #include <stdio.h>
00035 #include <stdlib.h>
00036 #include <string.h>
00037 #include <math.h>
00038 
00039 #ifndef NAN
00040   #define NAN 0.0/0.0
00041 #endif
00042 
00043 #ifndef M_PI
00044 #define M_PI 3.14159265358979323846
00045 #endif
00046 
00047 typedef struct Parser{
00048     int stack_index;
00049     char *s;
00050     const double *const_value;
00051     const char * const *const_name;          // NULL terminated
00052     double (**func1)(void *, double a); // NULL terminated
00053     const char **func1_name;          // NULL terminated
00054     double (**func2)(void *, double a, double b); // NULL terminated
00055     const char **func2_name;          // NULL terminated
00056     void *opaque;
00057     const char **error;
00058 #define VARS 10
00059     double var[VARS];
00060 } Parser;
00061 
00062 static const int8_t si_prefixes['z' - 'E' + 1]={
00063     ['y'-'E']= -24,
00064     ['z'-'E']= -21,
00065     ['a'-'E']= -18,
00066     ['f'-'E']= -15,
00067     ['p'-'E']= -12,
00068     ['n'-'E']= - 9,
00069     ['u'-'E']= - 6,
00070     ['m'-'E']= - 3,
00071     ['c'-'E']= - 2,
00072     ['d'-'E']= - 1,
00073     ['h'-'E']=   2,
00074     ['k'-'E']=   3,
00075     ['K'-'E']=   3,
00076     ['M'-'E']=   6,
00077     ['G'-'E']=   9,
00078     ['T'-'E']=  12,
00079     ['P'-'E']=  15,
00080     ['E'-'E']=  18,
00081     ['Z'-'E']=  21,
00082     ['Y'-'E']=  24,
00083 };
00084 
00089 static double av_strtod(const char *name, char **tail) {
00090     double d;
00091     char *next;
00092     d = strtod(name, &next);
00093     /* if parsing succeeded, check for and interpret postfixes */
00094     if (next!=name) {
00095 
00096         if(*next >= 'E' && *next <= 'z'){
00097             int e= si_prefixes[*next - 'E'];
00098             if(e){
00099                 if(next[1] == 'i'){
00100                     d*= pow( 2, e/0.3);
00101                     next+=2;
00102                 }else{
00103                     d*= pow(10, e);
00104                     next++;
00105                 }
00106             }
00107         }
00108 
00109         if(*next=='B') {
00110             d*=8;
00111             next++;
00112         }
00113     }
00114     /* if requested, fill in tail with the position after the last parsed
00115        character */
00116     if (tail)
00117         *tail = next;
00118     return d;
00119 }
00120 
00121 static int strmatch(const char *s, const char *prefix){
00122     int i;
00123     for(i=0; prefix[i]; i++){
00124         if(prefix[i] != s[i]) return 0;
00125     }
00126     return 1;
00127 }
00128 
00129 struct ff_expr_s {
00130     enum {
00131         e_value, e_const, e_func0, e_func1, e_func2,
00132         e_squish, e_gauss, e_ld,
00133         e_mod, e_max, e_min, e_eq, e_gt, e_gte,
00134         e_pow, e_mul, e_div, e_add,
00135         e_last, e_st, e_while,
00136     } type;
00137     double value; // is sign in other types
00138     union {
00139         int const_index;
00140         double (*func0)(double);
00141         double (*func1)(void *, double);
00142         double (*func2)(void *, double, double);
00143     } a;
00144     AVEvalExpr * param[2];
00145 };
00146 
00147 static double eval_expr(Parser * p, AVEvalExpr * e) {
00148     switch (e->type) {
00149         case e_value:  return e->value;
00150         case e_const:  return e->value * p->const_value[e->a.const_index];
00151         case e_func0:  return e->value * e->a.func0(eval_expr(p, e->param[0]));
00152         case e_func1:  return e->value * e->a.func1(p->opaque, eval_expr(p, e->param[0]));
00153         case e_func2:  return e->value * e->a.func2(p->opaque, eval_expr(p, e->param[0]), eval_expr(p, e->param[1]));
00154         case e_squish: return 1/(1+exp(4*eval_expr(p, e->param[0])));
00155         case e_gauss: { double d = eval_expr(p, e->param[0]); return exp(-d*d/2)/sqrt(2*M_PI); }
00156         case e_ld:     return e->value * p->var[av_clip(eval_expr(p, e->param[0]), 0, VARS-1)];
00157         case e_while: {
00158             double d = NAN;
00159             while(eval_expr(p, e->param[0]))
00160                 d=eval_expr(p, e->param[1]);
00161             return d;
00162         }
00163         default: {
00164             double d = eval_expr(p, e->param[0]);
00165             double d2 = eval_expr(p, e->param[1]);
00166             switch (e->type) {
00167                 case e_mod: return e->value * (d - floor(d/d2)*d2);
00168                 case e_max: return e->value * (d >  d2 ?   d : d2);
00169                 case e_min: return e->value * (d <  d2 ?   d : d2);
00170                 case e_eq:  return e->value * (d == d2 ? 1.0 : 0.0);
00171                 case e_gt:  return e->value * (d >  d2 ? 1.0 : 0.0);
00172                 case e_gte: return e->value * (d >= d2 ? 1.0 : 0.0);
00173                 case e_pow: return e->value * pow(d, d2);
00174                 case e_mul: return e->value * (d * d2);
00175                 case e_div: return e->value * (d / d2);
00176                 case e_add: return e->value * (d + d2);
00177                 case e_last:return e->value * d2;
00178                 case e_st : return e->value * (p->var[av_clip(d, 0, VARS-1)]= d2);
00179             }
00180         }
00181     }
00182     return NAN;
00183 }
00184 
00185 static AVEvalExpr * parse_expr(Parser *p);
00186 
00187 void ff_eval_free(AVEvalExpr * e) {
00188     if (!e) return;
00189     ff_eval_free(e->param[0]);
00190     ff_eval_free(e->param[1]);
00191     av_freep(&e);
00192 }
00193 
00194 static AVEvalExpr * parse_primary(Parser *p) {
00195     AVEvalExpr * d = av_mallocz(sizeof(AVEvalExpr));
00196     char *next= p->s;
00197     int i;
00198 
00199     /* number */
00200     d->value = av_strtod(p->s, &next);
00201     if(next != p->s){
00202         d->type = e_value;
00203         p->s= next;
00204         return d;
00205     }
00206     d->value = 1;
00207 
00208     /* named constants */
00209     for(i=0; p->const_name && p->const_name[i]; i++){
00210         if(strmatch(p->s, p->const_name[i])){
00211             p->s+= strlen(p->const_name[i]);
00212             d->type = e_const;
00213             d->a.const_index = i;
00214             return d;
00215         }
00216     }
00217 
00218     p->s= strchr(p->s, '(');
00219     if(p->s==NULL){
00220         *p->error = "undefined constant or missing (";
00221         p->s= next;
00222         ff_eval_free(d);
00223         return NULL;
00224     }
00225     p->s++; // "("
00226     if (*next == '(') { // special case do-nothing
00227         av_freep(&d);
00228         d = parse_expr(p);
00229         if(p->s[0] != ')'){
00230             *p->error = "missing )";
00231             ff_eval_free(d);
00232             return NULL;
00233         }
00234         p->s++; // ")"
00235         return d;
00236     }
00237     d->param[0] = parse_expr(p);
00238     if(p->s[0]== ','){
00239         p->s++; // ","
00240         d->param[1] = parse_expr(p);
00241     }
00242     if(p->s[0] != ')'){
00243         *p->error = "missing )";
00244         ff_eval_free(d);
00245         return NULL;
00246     }
00247     p->s++; // ")"
00248 
00249     d->type = e_func0;
00250          if( strmatch(next, "sinh"  ) ) d->a.func0 = sinh;
00251     else if( strmatch(next, "cosh"  ) ) d->a.func0 = cosh;
00252     else if( strmatch(next, "tanh"  ) ) d->a.func0 = tanh;
00253     else if( strmatch(next, "sin"   ) ) d->a.func0 = sin;
00254     else if( strmatch(next, "cos"   ) ) d->a.func0 = cos;
00255     else if( strmatch(next, "tan"   ) ) d->a.func0 = tan;
00256     else if( strmatch(next, "atan"  ) ) d->a.func0 = atan;
00257     else if( strmatch(next, "asin"  ) ) d->a.func0 = asin;
00258     else if( strmatch(next, "acos"  ) ) d->a.func0 = acos;
00259     else if( strmatch(next, "exp"   ) ) d->a.func0 = exp;
00260     else if( strmatch(next, "log"   ) ) d->a.func0 = log;
00261     else if( strmatch(next, "abs"   ) ) d->a.func0 = fabs;
00262     else if( strmatch(next, "squish") ) d->type = e_squish;
00263     else if( strmatch(next, "gauss" ) ) d->type = e_gauss;
00264     else if( strmatch(next, "mod"   ) ) d->type = e_mod;
00265     else if( strmatch(next, "max"   ) ) d->type = e_max;
00266     else if( strmatch(next, "min"   ) ) d->type = e_min;
00267     else if( strmatch(next, "eq"    ) ) d->type = e_eq;
00268     else if( strmatch(next, "gte"   ) ) d->type = e_gte;
00269     else if( strmatch(next, "gt"    ) ) d->type = e_gt;
00270     else if( strmatch(next, "lte"   ) ) { AVEvalExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gt; }
00271     else if( strmatch(next, "lt"    ) ) { AVEvalExpr * tmp = d->param[1]; d->param[1] = d->param[0]; d->param[0] = tmp; d->type = e_gte; }
00272     else if( strmatch(next, "ld"    ) ) d->type = e_ld;
00273     else if( strmatch(next, "st"    ) ) d->type = e_st;
00274     else if( strmatch(next, "while" ) ) d->type = e_while;
00275     else {
00276         for(i=0; p->func1_name && p->func1_name[i]; i++){
00277             if(strmatch(next, p->func1_name[i])){
00278                 d->a.func1 = p->func1[i];
00279                 d->type = e_func1;
00280                 return d;
00281             }
00282         }
00283 
00284         for(i=0; p->func2_name && p->func2_name[i]; i++){
00285             if(strmatch(next, p->func2_name[i])){
00286                 d->a.func2 = p->func2[i];
00287                 d->type = e_func2;
00288                 return d;
00289             }
00290         }
00291 
00292         *p->error = "unknown function";
00293         ff_eval_free(d);
00294         return NULL;
00295     }
00296 
00297     return d;
00298 }
00299 
00300 static AVEvalExpr * new_eval_expr(int type, int value, AVEvalExpr *p0, AVEvalExpr *p1){
00301     AVEvalExpr * e = av_mallocz(sizeof(AVEvalExpr));
00302     e->type     =type   ;
00303     e->value    =value  ;
00304     e->param[0] =p0     ;
00305     e->param[1] =p1     ;
00306     return e;
00307 }
00308 
00309 static AVEvalExpr * parse_pow(Parser *p, int *sign){
00310     *sign= (*p->s == '+') - (*p->s == '-');
00311     p->s += *sign&1;
00312     return parse_primary(p);
00313 }
00314 
00315 static AVEvalExpr * parse_factor(Parser *p){
00316     int sign, sign2;
00317     AVEvalExpr * e = parse_pow(p, &sign);
00318     while(p->s[0]=='^'){
00319         p->s++;
00320         e= new_eval_expr(e_pow, 1, e, parse_pow(p, &sign2));
00321         if (e->param[1]) e->param[1]->value *= (sign2|1);
00322     }
00323     if (e) e->value *= (sign|1);
00324     return e;
00325 }
00326 
00327 static AVEvalExpr * parse_term(Parser *p){
00328     AVEvalExpr * e = parse_factor(p);
00329     while(p->s[0]=='*' || p->s[0]=='/'){
00330         int c= *p->s++;
00331         e= new_eval_expr(c == '*' ? e_mul : e_div, 1, e, parse_factor(p));
00332     }
00333     return e;
00334 }
00335 
00336 static AVEvalExpr * parse_subexpr(Parser *p) {
00337     AVEvalExpr * e = parse_term(p);
00338     while(*p->s == '+' || *p->s == '-') {
00339         e= new_eval_expr(e_add, 1, e, parse_term(p));
00340     };
00341 
00342     return e;
00343 }
00344 
00345 static AVEvalExpr * parse_expr(Parser *p) {
00346     AVEvalExpr * e;
00347 
00348     if(p->stack_index <= 0) //protect against stack overflows
00349         return NULL;
00350     p->stack_index--;
00351 
00352     e = parse_subexpr(p);
00353 
00354     while(*p->s == ';') {
00355         p->s++;
00356         e= new_eval_expr(e_last, 1, e, parse_subexpr(p));
00357     };
00358 
00359     p->stack_index++;
00360 
00361     return e;
00362 }
00363 
00364 static int verify_expr(AVEvalExpr * e) {
00365     if (!e) return 0;
00366     switch (e->type) {
00367         case e_value:
00368         case e_const: return 1;
00369         case e_func0:
00370         case e_func1:
00371         case e_squish:
00372         case e_ld:
00373         case e_gauss: return verify_expr(e->param[0]);
00374         default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);
00375     }
00376 }
00377 
00378 AVEvalExpr * ff_parse(const char *s, const char * const *const_name,
00379                double (**func1)(void *, double), const char **func1_name,
00380                double (**func2)(void *, double, double), const char **func2_name,
00381                const char **error){
00382     Parser p;
00383     AVEvalExpr * e;
00384     char w[strlen(s) + 1], * wp = w;
00385 
00386     while (*s)
00387         if (!isspace(*s++)) *wp++ = s[-1];
00388     *wp++ = 0;
00389 
00390     p.stack_index=100;
00391     p.s= w;
00392     p.const_name = const_name;
00393     p.func1      = func1;
00394     p.func1_name = func1_name;
00395     p.func2      = func2;
00396     p.func2_name = func2_name;
00397     p.error= error;
00398 
00399     e = parse_expr(&p);
00400     if (!verify_expr(e)) {
00401         ff_eval_free(e);
00402         return NULL;
00403     }
00404     return e;
00405 }
00406 
00407 double ff_parse_eval(AVEvalExpr * e, const double *const_value, void *opaque) {
00408     Parser p;
00409 
00410     p.const_value= const_value;
00411     p.opaque     = opaque;
00412     return eval_expr(&p, e);
00413 }
00414 
00415 double ff_eval2(const char *s, const double *const_value, const char * const *const_name,
00416                double (**func1)(void *, double), const char **func1_name,
00417                double (**func2)(void *, double, double), const char **func2_name,
00418                void *opaque, const char **error){
00419     AVEvalExpr * e = ff_parse(s, const_name, func1, func1_name, func2, func2_name, error);
00420     double d;
00421     if (!e) return NAN;
00422     d = ff_parse_eval(e, const_value, opaque);
00423     ff_eval_free(e);
00424     return d;
00425 }
00426 
00427 #ifdef TEST
00428 #undef printf
00429 static double const_values[]={
00430     M_PI,
00431     M_E,
00432     0
00433 };
00434 static const char *const_names[]={
00435     "PI",
00436     "E",
00437     0
00438 };
00439 int main(void){
00440     int i;
00441     printf("%f == 12.7\n", ff_eval2("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));
00442     printf("%f == 0.931322575\n", ff_eval2("80G/80Gi", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL));
00443 
00444     for(i=0; i<1050; i++){
00445         START_TIMER
00446             ff_eval2("1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)", const_values, const_names, NULL, NULL, NULL, NULL, NULL, NULL);
00447         STOP_TIMER("ff_eval2")
00448     }
00449     return 0;
00450 }
00451 #endif