eval.h File Reference

simple arithmetic expression evaluator More...

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Typedefs
typedef struct AVExpr	AVExpr

Functions
int	av_expr_parse_and_eval (double *res, const char *s, const char *const *const_names, const double *const_values, const char *const *func1_names, double(*const *funcs1)(void *, double), const char *const *func2_names, double(*const *funcs2)(void *, double, double), void *opaque, int log_offset, void *log_ctx)
	Parse and evaluate an expression. More...
int	av_expr_parse (AVExpr **expr, const char *s, const char *const *const_names, const char *const *func1_names, double(*const *funcs1)(void *, double), const char *const *func2_names, double(*const *funcs2)(void *, double, double), int log_offset, void *log_ctx)
	Parse an expression. More...
double	av_expr_eval (AVExpr *e, const double *const_values, void *opaque)
	Evaluate a previously parsed expression. More...
int	av_expr_count_vars (AVExpr *e, unsigned *counter, int size)
	Track the presence of variables and their number of occurrences in a parsed expression. More...
int	av_expr_count_func (AVExpr *e, unsigned *counter, int size, int arg)
	Track the presence of user provided functions and their number of occurrences in a parsed expression. More...
void	av_expr_free (AVExpr *e)
	Free a parsed expression previously created with av_expr_parse(). More...
double	av_strtod (const char *numstr, char **tail)
	Parse the string in numstr and return its value as a double. More...

Detailed Description

simple arithmetic expression evaluator

Definition in file eval.h.

Typedef Documentation

AVExpr

typedef struct AVExpr AVExpr

Definition at line 29 of file eval.h.

Function Documentation

av_expr_parse_and_eval()

int av_expr_parse_and_eval	(	double *	res,
		const char *	s,
		const char *const *	const_names,
		const double *	const_values,
		const char *const *	func1_names,
		double(**)(void *, double)	funcs1,
		const char *const *	func2_names,
		double(**)(void *, double, double)	funcs2,
		void *	opaque,
		int	log_offset,
		void *	log_ctx
	)

Parse and evaluate an expression.

Note, this is significantly slower than av_expr_eval().

Parameters

res	a pointer to a double where is put the result value of the expression, or NAN in case of error
s	expression as a zero terminated string, for example "1+2^3+5*5+sin(2/3)"
const_names	NULL terminated array of zero terminated strings of constant identifiers, for example {"PI", "E", 0}
const_values	a zero terminated array of values for the identifiers from const_names
func1_names	NULL terminated array of zero terminated strings of funcs1 identifiers
funcs1	NULL terminated array of function pointers for functions which take 1 argument
func2_names	NULL terminated array of zero terminated strings of funcs2 identifiers
funcs2	NULL terminated array of function pointers for functions which take 2 arguments
opaque	a pointer which will be passed to all functions from funcs1 and funcs2
log_ctx	parent logging context

Returns

>= 0 in case of success, a negative value corresponding to an AVERROR code otherwise

av_expr_parse()

int av_expr_parse	(	AVExpr **	expr,
		const char *	s,
		const char *const *	const_names,
		const char *const *	func1_names,
		double(**)(void *, double)	funcs1,
		const char *const *	func2_names,
		double(**)(void *, double, double)	funcs2,
		int	log_offset,
		void *	log_ctx
	)

Parse an expression.

Parameters

expr	a pointer where is put an AVExpr containing the parsed value in case of successful parsing, or NULL otherwise. The pointed to AVExpr must be freed with av_expr_free() by the user when it is not needed anymore.
s	expression as a zero terminated string, for example "1+2^3+5*5+sin(2/3)"
const_names	NULL terminated array of zero terminated strings of constant identifiers, for example {"PI", "E", 0}
func1_names	NULL terminated array of zero terminated strings of funcs1 identifiers
funcs1	NULL terminated array of function pointers for functions which take 1 argument
func2_names	NULL terminated array of zero terminated strings of funcs2 identifiers
funcs2	NULL terminated array of function pointers for functions which take 2 arguments
log_ctx	parent logging context

Returns

>= 0 in case of success, a negative value corresponding to an AVERROR code otherwise

av_expr_eval()

double av_expr_eval	(	AVExpr *	e,
		const double *	const_values,
		void *	opaque
	)

Evaluate a previously parsed expression.

Parameters

const_values	a zero terminated array of values for the identifiers from av_expr_parse() const_names
opaque	a pointer which will be passed to all functions from funcs1 and funcs2

Returns

the value of the expression

av_expr_count_vars()

int av_expr_count_vars	(	AVExpr *	e,
		unsigned *	counter,
		int	size
	)

Track the presence of variables and their number of occurrences in a parsed expression.

Parameters

counter	a zero-initialized array where the count of each variable will be stored
size	size of array

Returns

0 on success, a negative value indicates that no expression or array was passed or size was zero

av_expr_count_func()

int av_expr_count_func	(	AVExpr *	e,
		unsigned *	counter,
		int	size,
		int	arg
	)

Track the presence of user provided functions and their number of occurrences in a parsed expression.

Parameters

counter	a zero-initialized array where the count of each function will be stored if you passed 5 functions with 2 arguments to av_expr_parse() then for arg=2 this will use upto 5 entries.
size	size of array
arg	number of arguments the counted functions have

Returns

0 on success, a negative value indicates that no expression or array was passed or size was zero

av_expr_free()

void av_expr_free

(

AVExpr *

e

)

Free a parsed expression previously created with av_expr_parse().

av_strtod()

double av_strtod	(	const char *	numstr,
		char **	tail
	)

Parse the string in numstr and return its value as a double.

If the string is empty, contains only whitespaces, or does not contain an initial substring that has the expected syntax for a floating-point number, no conversion is performed. In this case, returns a value of zero and the value returned in tail is the value of numstr.

Parameters

numstr	a string representing a number, may contain one of the International System number postfixes, for example 'K', 'M', 'G'. If 'i' is appended after the postfix, powers of 2 are used instead of powers of 10. The 'B' postfix multiplies the value by 8, and can be appended after another postfix or used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as postfix.
tail	if non-NULL puts here the pointer to the char next after the last parsed character