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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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* This file is part of Libav.
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* Libav 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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* Libav 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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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; 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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* simple arithmetic expression evaluator.
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* see http://joe.hotchkiss.com/programming/eval/eval.html
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typedef struct Parser {
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const double *const_values;
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const char * const *const_names; // NULL terminated
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double (* const *funcs1)(void *, double a); // NULL terminated
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const char * const *func1_names; // NULL terminated
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double (* const *funcs2)(void *, double a, double b); // NULL terminated
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const char * const *func2_names; // NULL terminated
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static const AVClass class = { "Eval", av_default_item_name, NULL, LIBAVUTIL_VERSION_INT, offsetof(Parser,log_offset), offsetof(Parser,log_ctx) };
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static const int8_t si_prefixes['z' - 'E' + 1] = {
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double av_strtod(const char *numstr, char **tail)
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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 >= 'E' && *next <= 'z') {
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int e= si_prefixes[*next - 'E'];
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/* if requested, fill in tail with the position after the last parsed
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#define IS_IDENTIFIER_CHAR(c) ((c) - '0' <= 9U || (c) - 'a' <= 25U || (c) - 'A' <= 25U || (c) == '_')
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static int strmatch(const char *s, const char *prefix)
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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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/* return 1 only if the s identifier is terminated */
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return !IS_IDENTIFIER_CHAR(s[i]);
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e_value, e_const, e_func0, e_func1, e_func2,
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e_squish, e_gauss, e_ld, e_isnan,
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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, e_floor, e_ceil, e_trunc,
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double value; // is sign in other types
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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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struct AVExpr *param[2];
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static double eval_expr(Parser *p, AVExpr *e)
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case e_value: return e->value;
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case e_const: return e->value * p->const_values[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_isnan: return e->value * !!isnan(eval_expr(p, e->param[0]));
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case e_floor: return e->value * floor(eval_expr(p, e->param[0]));
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case e_ceil : return e->value * ceil (eval_expr(p, e->param[0]));
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case e_trunc: return e->value * trunc(eval_expr(p, e->param[0]));
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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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double d = eval_expr(p, e->param[0]);
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double d2 = eval_expr(p, e->param[1]);
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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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static int parse_expr(AVExpr **e, Parser *p);
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void av_expr_free(AVExpr *e)
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av_expr_free(e->param[0]);
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av_expr_free(e->param[1]);
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static int parse_primary(AVExpr **e, Parser *p)
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AVExpr *d = av_mallocz(sizeof(AVExpr));
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char *next = p->s, *s0 = p->s;
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return AVERROR(ENOMEM);
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d->value = av_strtod(p->s, &next);
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/* named constants */
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for (i=0; p->const_names && p->const_names[i]; i++) {
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if (strmatch(p->s, p->const_names[i])) {
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p->s+= strlen(p->const_names[i]);
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d->a.const_index = i;
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p->s= strchr(p->s, '(');
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av_log(p, AV_LOG_ERROR, "Undefined constant or missing '(' in '%s'\n", s0);
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return AVERROR(EINVAL);
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if (*next == '(') { // special case do-nothing
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if ((ret = parse_expr(&d, p)) < 0)
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if (p->s[0] != ')') {
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av_log(p, AV_LOG_ERROR, "Missing ')' in '%s'\n", s0);
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return AVERROR(EINVAL);
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if ((ret = parse_expr(&(d->param[0]), p)) < 0) {
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parse_expr(&d->param[1], p);
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if (p->s[0] != ')') {
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av_log(p, AV_LOG_ERROR, "Missing ')' or too many args in '%s'\n", s0);
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return AVERROR(EINVAL);
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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, "isnan" )) d->type = e_isnan;
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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;
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else if (strmatch(next, "floor" )) d->type = e_floor;
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else if (strmatch(next, "ceil" )) d->type = e_ceil;
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else if (strmatch(next, "trunc" )) d->type = e_trunc;
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for (i=0; p->func1_names && p->func1_names[i]; i++) {
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if (strmatch(next, p->func1_names[i])) {
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d->a.func1 = p->funcs1[i];
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for (i=0; p->func2_names && p->func2_names[i]; i++) {
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if (strmatch(next, p->func2_names[i])) {
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d->a.func2 = p->funcs2[i];
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av_log(p, AV_LOG_ERROR, "Unknown function in '%s'\n", s0);
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return AVERROR(EINVAL);
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static AVExpr *new_eval_expr(int type, int value, AVExpr *p0, AVExpr *p1)
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AVExpr *e = av_mallocz(sizeof(AVExpr));
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static int parse_pow(AVExpr **e, Parser *p, int *sign)
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*sign= (*p->s == '+') - (*p->s == '-');
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return parse_primary(e, p);
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static int parse_factor(AVExpr **e, Parser *p)
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int sign, sign2, ret;
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AVExpr *e0, *e1, *e2;
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if ((ret = parse_pow(&e0, p, &sign)) < 0)
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if ((ret = parse_pow(&e2, p, &sign2)) < 0) {
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e0 = new_eval_expr(e_pow, 1, e1, e2);
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return AVERROR(ENOMEM);
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if (e0->param[1]) e0->param[1]->value *= (sign2|1);
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if (e0) e0->value *= (sign|1);
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static int parse_term(AVExpr **e, Parser *p)
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AVExpr *e0, *e1, *e2;
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if ((ret = parse_factor(&e0, p)) < 0)
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while (p->s[0]=='*' || p->s[0]=='/') {
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if ((ret = parse_factor(&e2, p)) < 0) {
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e0 = new_eval_expr(c == '*' ? e_mul : e_div, 1, e1, e2);
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return AVERROR(ENOMEM);
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static int parse_subexpr(AVExpr **e, Parser *p)
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AVExpr *e0, *e1, *e2;
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if ((ret = parse_term(&e0, p)) < 0)
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while (*p->s == '+' || *p->s == '-') {
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if ((ret = parse_term(&e2, p)) < 0) {
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e0 = new_eval_expr(e_add, 1, e1, e2);
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return AVERROR(ENOMEM);
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static int parse_expr(AVExpr **e, Parser *p)
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AVExpr *e0, *e1, *e2;
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if (p->stack_index <= 0) //protect against stack overflows
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return AVERROR(EINVAL);
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if ((ret = parse_subexpr(&e0, p)) < 0)
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while (*p->s == ';') {
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if ((ret = parse_subexpr(&e2, p)) < 0) {
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e0 = new_eval_expr(e_last, 1, e1, e2);
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return AVERROR(ENOMEM);
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static int verify_expr(AVExpr *e)
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case e_const: return 1;
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return verify_expr(e->param[0]);
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default: return verify_expr(e->param[0]) && verify_expr(e->param[1]);
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int av_expr_parse(AVExpr **expr, const char *s,
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const char * const *const_names,
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const char * const *func1_names, double (* const *funcs1)(void *, double),
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const char * const *func2_names, double (* const *funcs2)(void *, double, double),
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int log_offset, void *log_ctx)
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char *w = av_malloc(strlen(s) + 1);
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return AVERROR(ENOMEM);
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if (!isspace(*s++)) *wp++ = s[-1];
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p.const_names = const_names;
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p.func1_names = func1_names;
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p.func2_names = func2_names;
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p.log_offset = log_offset;
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if ((ret = parse_expr(&e, &p)) < 0)
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av_log(&p, AV_LOG_ERROR, "Invalid chars '%s' at the end of expression '%s'\n", p.s, s0);
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ret = AVERROR(EINVAL);
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if (!verify_expr(e)) {
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ret = AVERROR(EINVAL);
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double av_expr_eval(AVExpr *e, const double *const_values, void *opaque)
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p.const_values = const_values;
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return eval_expr(&p, e);
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int av_expr_parse_and_eval(double *d, const char *s,
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const char * const *const_names, const double *const_values,
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const char * const *func1_names, double (* const *funcs1)(void *, double),
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const char * const *func2_names, double (* const *funcs2)(void *, double, double),
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void *opaque, int log_offset, void *log_ctx)
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int ret = av_expr_parse(&e, s, const_names, func1_names, funcs1, func2_names, funcs2, log_offset, log_ctx);
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*d = av_expr_eval(e, const_values, opaque);
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return isnan(*d) ? AVERROR(EINVAL) : 0;
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static double const_values[] = {
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static const char *const_names[] = {
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const char **expr, *exprs[] = {
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"1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",
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"bar + PI + E + 100f*2 + foo",
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"13k + 12f - foo(1, 2)",
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/* compute 1+2+...+N */
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"st(0, 1); while(lte(ld(0), 100), st(1, ld(1)+ld(0));st(0, ld(0)+1)); ld(1)",
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"st(1, 1); st(2, 2); st(0, 1); while(lte(ld(0),10), st(3, ld(1)+ld(2)); st(1, ld(2)); st(2, ld(3)); st(0, ld(0)+1)); ld(3)",
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"st(0, 1); while(lte(ld(0),100), st(1, ld(1)+ld(0)); st(0, ld(0)+1))",
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for (expr = exprs; *expr; expr++) {
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printf("Evaluating '%s'\n", *expr);
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av_expr_parse_and_eval(&d, *expr,
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const_names, const_values,
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NULL, NULL, NULL, NULL, NULL, 0, NULL);
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printf("'%s' -> %f\n\n", *expr, d);
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av_expr_parse_and_eval(&d, "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",
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const_names, const_values,
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NULL, NULL, NULL, NULL, NULL, 0, NULL);
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printf("%f == 12.7\n", d);
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av_expr_parse_and_eval(&d, "80G/80Gi",
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const_names, const_values,
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NULL, NULL, NULL, NULL, NULL, 0, NULL);
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printf("%f == 0.931322575\n", d);
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for (i=0; i<1050; i++) {
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av_expr_parse_and_eval(&d, "1+(5-2)^(3-1)+1/2+sin(PI)-max(-2.2,-3.1)",
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const_names, const_values,
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NULL, NULL, NULL, NULL, NULL, 0, NULL);
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STOP_TIMER("av_expr_parse_and_eval")