eval.c File Reference

simple arithmetic expression evaluator. More...

#include <float.h>
#include "attributes.h"
#include "avutil.h"
#include "common.h"
#include "eval.h"
#include "log.h"
#include "mathematics.h"
#include "time.h"
#include "avstring.h"

Go to the source code of this file.

Data Structures
struct	Parser
struct	AVExpr

Macros
#define	VARS   10
#define	IS_IDENTIFIER_CHAR(c)   ((c) - '0' <= 9U || (c) - 'a' <= 25U || (c) - 'A' <= 25U || (c) == '_')

Functions
double	av_strtod (const char *numstr, char **tail)
	Parse the string in numstr and return its value as a double.
static int	strmatch (const char *s, const char *prefix)
static double	etime (double v)
static double	eval_expr (Parser *p, AVExpr *e)
static int	parse_expr (AVExpr **e, Parser *p)
void	av_expr_free (AVExpr *e)
	Free a parsed expression previously created with av_expr_parse().
static int	parse_primary (AVExpr **e, Parser *p)
static AVExpr *	make_eval_expr (int type, int value, AVExpr *p0, AVExpr *p1)
static int	parse_pow (AVExpr **e, Parser *p, int *sign)
static int	parse_dB (AVExpr **e, Parser *p, int *sign)
static int	parse_factor (AVExpr **e, Parser *p)
static int	parse_term (AVExpr **e, Parser *p)
static int	parse_subexpr (AVExpr **e, Parser *p)
static int	verify_expr (AVExpr *e)
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.
double	av_expr_eval (AVExpr *e, const double *const_values, void *opaque)
	Evaluate a previously parsed expression.
int	av_expr_parse_and_eval (double *d, 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.

Variables
static const AVClass	eval_class = { "Eval", av_default_item_name, NULL, LIBAVUTIL_VERSION_INT, 0x42, 0x42 }
static const int8_t	si_prefixes ['z'- 'E'+1]
struct {
const char *   name
double   value
}	constants []

Detailed Description

simple arithmetic expression evaluator.

see http://joe.hotchkiss.com/programming/eval/eval.html

Definition in file eval.c.

Macro Definition Documentation

#define VARS   10

Definition at line 52 of file eval.c.

Referenced by av_expr_parse(), and eval_expr().

#define IS_IDENTIFIER_CHAR

(

c

)

((c) - '0' <= 9U || (c) - 'a' <= 25U || (c) - 'A' <= 25U || (c) == '_')

Definition at line 129 of file eval.c.

Referenced by strmatch().

Function Documentation

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 for 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

Definition at line 90 of file eval.c.

Referenced by ff_parse_sample_rate(), parse_number_or_die(), parse_points_str(), parse_primary(), var_read_float(), and yae_set_tempo().

static int strmatch ( const char *  s, const char *  prefix  )

static

Definition at line 131 of file eval.c.

Referenced by parse_primary().

static double etime ( double  v )

static

Definition at line 162 of file eval.c.

Referenced by parse_primary().

static double eval_expr ( Parser *  p, AVExpr *  e  )

static

Definition at line 167 of file eval.c.

Referenced by av_expr_eval().

static int parse_expr ( AVExpr **  e, Parser *  p  )

static

Definition at line 575 of file eval.c.

Referenced by av_expr_parse(), and parse_primary().

void av_expr_free

(

AVExpr *

e

)

Free a parsed expression previously created with av_expr_parse().

Definition at line 303 of file eval.c.

Referenced by av_expr_free(), av_expr_parse(), av_expr_parse_and_eval(), avfilter_free(), config_input(), config_props(), ff_rate_control_uninit(), ffmpeg_cleanup(), geq_uninit(), parse_expr(), parse_factor(), parse_primary(), parse_subexpr(), parse_term(), process_command(), set_enable_expr(), set_expr(), and uninit().

static int parse_primary ( AVExpr **  e, Parser *  p  )

static

Definition at line 313 of file eval.c.

Referenced by parse_dB(), and parse_pow().

static AVExpr* make_eval_expr ( int  type, int  value, AVExpr *  p0, AVExpr *  p1  )

static

Definition at line 466 of file eval.c.

Referenced by parse_expr(), parse_factor(), parse_subexpr(), and parse_term().

static int parse_pow ( AVExpr **  e, Parser *  p, int *  sign  )

static

Definition at line 478 of file eval.c.

Referenced by parse_dB().

static int parse_dB ( AVExpr **  e, Parser *  p, int *  sign  )

static

Definition at line 485 of file eval.c.

Referenced by parse_factor().

static int parse_factor ( AVExpr **  e, Parser *  p  )

static

Definition at line 500 of file eval.c.

Referenced by parse_term().

static int parse_term ( AVExpr **  e, Parser *  p  )

static

Definition at line 527 of file eval.c.

Referenced by parse_subexpr().

static int parse_subexpr ( AVExpr **  e, Parser *  p  )

static

Definition at line 551 of file eval.c.

Referenced by parse_expr().

static int verify_expr ( AVExpr *  e )

static

Definition at line 605 of file eval.c.

Referenced by 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

Definition at line 641 of file eval.c.

Referenced by av_expr_parse_and_eval(), config_input(), config_props(), ff_rate_control_init(), geq_init(), init(), modplug_read_header(), process_command(), set_enable_expr(), set_expr(), and transcode_init().

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

Definition at line 692 of file eval.c.

Referenced by av_expr_parse_and_eval(), config_props(), DEFINE_BLEND(), do_video_out(), draw_text(), eval_expr(), ff_filter_frame_framed(), filter_frame(), filter_plane(), geq_filter_frame(), get_qscale(), init(), modplug_read_packet(), request_frame(), select_frame(), send_next(), and update_context().

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

Definition at line 702 of file eval.c.

Referenced by av_parse_ratio(), config_input(), config_output_props(), config_props(), func_eval_expr(), init(), main(), and set_string_number().

Variable Documentation

const AVClass eval_class = { "Eval", av_default_item_name, NULL, LIBAVUTIL_VERSION_INT, 0x42, 0x42 }

static

Definition at line 56 of file eval.c.

Referenced by av_expr_parse().

const int8_t si_prefixes['z'- 'E'+1]

static

Initial value:

= {
    ['y'-'E']= -24,
    ['z'-'E']= -21,
    ['a'-'E']= -18,
    ['f'-'E']= -15,
    ['p'-'E']= -12,
    ['n'-'E']= - 9,
    ['u'-'E']= - 6,
    ['m'-'E']= - 3,
    ['c'-'E']= - 2,
    ['d'-'E']= - 1,
    ['h'-'E']=   2,
    ['k'-'E']=   3,
    ['K'-'E']=   3,
    ['M'-'E']=   6,
    ['G'-'E']=   9,
    ['T'-'E']=  12,
    ['P'-'E']=  15,
    ['E'-'E']=  18,
    ['Z'-'E']=  21,
    ['Y'-'E']=  24,
}

Definition at line 58 of file eval.c.

Referenced by av_strtod().

const char* name

Definition at line 82 of file eval.c.

double value

Definition at line 83 of file eval.c.

Referenced by ape_tag_read_field(), arith2_get_scaled_value(), asf_write_header1(), av_dict_set(), av_opt_set_from_string(), avi_read_tag(), avpriv_tak_parse_streaminfo(), check_4block_inter(), check_block(), decode_block(), decode_byterun(), decode_info_header(), decode_motion(), decode_skip_count(), dtshd_read_header(), encode_gbrp10(), encode_gbrp12(), encode_rgb48_10bit(), ff_bgmc_decode(), ff_draw_round_to_sub(), ff_hevc_rem_intra_luma_pred_mode_decode(), ff_hevc_sao_band_position_decode(), ff_log2_q15(), ff_parse_fmtp(), ff_read_riff_info(), ff_svq1_packet_checksum(), ff_tadd_string_metadata(), get_bucket(), get_scale(), get_tag(), gxf_material_tags(), gxf_track_tags(), handle_connect_error(), id3v2_3_metadata_split_date(), init_loop_filter(), last_significant_coeff_suffix_decode(), make_eval_expr(), mov_metadata_raw(), mov_read_timecode_track(), mpegaudio_tableinit(), mxf_read_pixel_layout(), nist_read_header(), nsv_parse_NSVf_header(), opt_preset(), pack_float_sample(), pack_int32(), pcx_rle_decode(), process_command(), process_float(), process_options(), put_bits(), qdm2_decode(), qdm2_decode_fft_packets(), qdm2_get_se_vlc(), qdm2_get_vlc(), quantize(), quantize_value(), radix_sort_pass(), read_info_chunk(), read_tag(), read_var_block_data(), reverse_decorr(), reverse_mono_decorr(), rtmp_write_amf_data(), scan_word(), set_control(), set_meta(), subviewer_read_header(), sunrast_decode_frame(), sunrast_image_write_image(), tgq_decode_block(), tiff_decode_tag(), tta_decode_frame(), tta_encode_frame(), update_band_masking(), var_read_metadata(), vc1_decode_i_block(), vc1_decode_i_block_adv(), vc1_decode_intra_block(), vc1_decode_p_block(), vivo_read_header(), vlc_decode_block(), vp56_rac_gets(), vp8_rac_get_uint(), wv_get_value_float(), and xor_32_to_8().

struct { ... } constants[]

Initial value:

= {
    { "E",   M_E   },
    { "PI",  M_PI  },
    { "PHI", M_PHI },
}

Referenced by parse_primary().