【ROS-数据格式】 LDP、结构体correspondence和laser_data的数据格式

1、laser_data.h（可不看）

三个结构体都在该文件下，单个结构体解释请看本文小部分

#ifndef H_LASER_DATA
#define H_LASER_DATA

#include <sys/time.h>
#include <stdio.h>

#include "restrict.h"

struct correspondence;

typedef struct {
	double p[2];
	double rho, phi;
} point2d;

struct laser_data {
	int nrays;
	double  min_theta;
	double  max_theta;
	
	double * restrict theta;
	
	int    * restrict valid;
	double * restrict readings;
	
	int    * restrict cluster;
	
	double * restrict alpha;
	double * restrict cov_alpha;
	int    * restrict alpha_valid;

	double * restrict readings_sigma;

	double * restrict true_alpha;
	
	struct correspondence*  restrict corr;

	double true_pose[3];		
	double odometry[3];	
	double estimate[3];	
	

	/** Cartesian representation */
	point2d *  restrict points;
	/** Cartesian representation, in "world" (laser_ref) coordinates. 
	    Computed using ld_compute_world_coords() */
	point2d *  restrict points_w;

	/** Timestamp */
	struct timeval tv;
	char hostname[32];


	/* Jump tables needed by find_correspondences_tricks(). */
	int * restrict up_bigger, 
	    * restrict up_smaller, 
	    * restrict down_bigger, 
	    * restrict down_smaller;	
};

struct correspondence {
	/** 1 if this correspondence is valid  */
	int valid; 
	/** Closest point in the other scan.  */
	int j1;
	/** Second closest point in the other scan.  */
	int j2;
	/** Type of correspondence (point to point, or point to line) */
	enum { corr_pp = 0, corr_pl = 1} type;
	/** Squared distance from p(i) to point j1 */
	double dist2_j1; 
};

typedef struct laser_data* LDP;

/** This returns a new structure, with all fields initialized */
LDP ld_alloc_new(int nrays);

/** This DOES free() the pointer  */
void ld_free(LDP);

/** This allocs the fields in the given structure. Use ld_alloc_new(), not this. */
void ld_alloc(LDP, int nrays);

/** This does NOT free the pointer. Don't use -- use ld_alloc_new()/ld_free() instead. */
void ld_dealloc(LDP);

/** Fills the x,y fields in "points" by transforming (theta, reading) to cartesian */
void ld_compute_cartesian(LDP);

/** Computes the "points_w" coordinates by roto-translating "points" */
void ld_compute_world_coords(LDP, const double *pose);

/** Fills the fields: *up_bigger, *up_smaller, *down_bigger, *down_smaller.*/
void ld_create_jump_tables(LDP);

/** Computes an hash of the correspondences */
unsigned int ld_corr_hash(LDP);

/** Returns the number of valid correspondences. */
int ld_num_valid_correspondences(LDP);

/** Do an extensive sanity check about the data contained in the structure. */
int ld_valid_fields(LDP);

/** A simple clustering algorithm. Sets the `cluster' field in the structure. */
void ld_simple_clustering(LDP ld, double threshold);

/** A cool orientation estimation algorithm. Needs cluster. */
void ld_compute_orientation(LDP ld, int size_neighbourhood, double sigma);




/** 
	Tries to read a laser scan from file. If error or EOF, it returns 0.
	Whitespace is skipped. If first valid char is '{', it tries to read 
	it as JSON. If next char is 'F' (first character of "FLASER"),
	it tries to read in Carmen format. Else, 0 is returned. 
*/
LDP ld_read_smart(FILE*);

/** 
	Tries to read a laser scan from a string.
*/
LDP ld_read_smart_string(const char*);


/** Read next FLASER line in file (initializes ld). 
	Returns 0 on failure. If the file is EOF, it returns 1 
	and sets ld to 0.
	You probably want to use the ld_read_smart() function. */
int ld_read_next_laser_carmen(FILE*, LDP*ld);

/** Read laser data from a Carmen-formatted line */
LDP ld_from_carmen_string(const char*line);

/** Reads all the scans it can find. */
int ld_read_all(FILE*file, LDP **array, int*num);

/** Read a scan every interval (1=all)*/
int ld_read_some_scans(FILE*file, LDP **array, int*num, int interval);

/** Write a scan in carmen format */
void ld_write_as_carmen(LDP ld, FILE * stream);

/** Write a scan according to out_format = {"carmen", "json"} */
void ld_write_format(LDP ld, FILE*stream, const char * out_format);


void possible_interval(
	const double *p_i_w, LDP laser_sens, 
	double max_angular_correction_deg, double max_linear_correction, int*from, int*to, int*start_cell);


#include "laser_data_inline.h"

#endif

2、 laser_data

struct laser_data {
	int nrays;
	double  min_theta;
	double  max_theta;
	
	double * restrict theta;
	
	int    * restrict valid;
	double * restrict readings;
	
	int    * restrict cluster;
	
	double * restrict alpha;
	double * restrict cov_alpha;
	int    * restrict alpha_valid;

	double * restrict readings_sigma;

	double * restrict true_alpha;
	
	struct correspondence*  restrict corr;

	double true_pose[3];		
	double odometry[3];	
	double estimate[3];	
	

	/** Cartesian representation */
	point2d *  restrict points;
	/** Cartesian representation, in "world" (laser_ref) coordinates. 
	    Computed using ld_compute_world_coords() */
	point2d *  restrict points_w;

	/** Timestamp */
	struct timeval tv;
	char hostname[32];


	/* Jump tables needed by find_correspondences_tricks(). */
	int * restrict up_bigger, 
	    * restrict up_smaller, 
	    * restrict down_bigger, 
	    * restrict down_smaller;	
};

3、correspondence

struct correspondence {
	/** 1 if this correspondence is valid  */
	int valid; 
	/** Closest point in the other scan.  */
	int j1;
	/** Second closest point in the other scan.  */
	int j2;
	/** Type of correspondence (point to point, or point to line) */
	enum { corr_pp = 0, corr_pl = 1} type;
	/** Squared distance from p(i) to point j1 */
	double dist2_j1; 
};

4、LDP

typedef struct laser_data* LDP;

/** This returns a new structure, with all fields initialized */
//这将返回一个新的结构，并初始化所有字段
LDP ld_alloc_new(int nrays);

/** This DOES free() the pointer  */
//这将执行free()指针
void ld_free(LDP);

/** This allocs the fields in the given structure. Use ld_alloc_new(), not this. */
void ld_alloc(LDP, int nrays);

/** This does NOT free the pointer. Don't use -- use ld_alloc_new()/ld_free() instead. */
void ld_dealloc(LDP);

/** Fills the x,y fields in "points" by transforming (theta, reading) to cartesian */
//通过将(theta, reading)变换为笛卡尔坐标来填充“点”中的x,y字段
void ld_compute_cartesian(LDP);

/** Computes the "points_w" coordinates by roto-translating "points" */
//通过roto- translation“points”计算“points_w”坐标
void ld_compute_world_coords(LDP, const double *pose);

/** Fills the fields: *up_bigger, *up_smaller, *down_bigger, *down_smaller.*/
//填充字段:*up_bigger， *up_smaller， *down_bigger， *down_smaller。
void ld_create_jump_tables(LDP);

/** Computes an hash of the correspondences */
//计算对应的哈希值
unsigned int ld_corr_hash(LDP);

/** Returns the number of valid correspondences. */
//返回有效的通信数。
int ld_num_valid_correspondences(LDP);

/** Do an extensive sanity check about the data contained in the structure. */
//对结构中包含的数据进行全面检查。
int ld_valid_fields(LDP);

/** A simple clustering algorithm. Sets the `cluster' field in the structure. */
//一个简单的聚类算法。在结构中设置‘cluster’字段。
void ld_simple_clustering(LDP ld, double threshold);

/** A cool orientation estimation algorithm. Needs cluster. */
//一种很酷的方向估计算法。需要集群。
void ld_compute_orientation(LDP ld, int size_neighbourhood, double sigma);




/** 
	Tries to read a laser scan from file. If error or EOF, it returns 0. Whitespace is skipped. If first valid char is '{', it tries to read it as JSON. If next char is 'F' (first character of "FLASER"), it tries to read in Carmen format. Else, 0 is returned. 
*/
//尝试从文件中读取激光扫描。如果是error或EOF，则返回0。空格是跳过。
//如果第一个有效的字符是'{'，它会尝试将其读取为JSON。如果下一个字符是'F' ("FLASER"的第一个字符)，
//它将尝试以Carmen格式读取。否则，返回0。
LDP ld_read_smart(FILE*);

/** 
	Tries to read a laser scan from a string.
	尝试从字符串读取激光扫描。
*/
LDP ld_read_smart_string(const char*);


/** Read next FLASER line in file (initializes ld). 
	Returns 0 on failure. If the file is EOF, it returns 1  and sets ld to 0.
	You probably want to use the ld_read_smart() function.
	读取文件中的下一个FLASER行(初始化ld)。
	失败时返回0。如果文件是EOF，则返回1并将ld设置为0。
	您可能需要使用ld_read_smart()函数。
 */
int ld_read_next_laser_carmen(FILE*, LDP*ld);

/** Read laser data from a Carmen-formatted line */
//从carmen格式的行读取激光数据
LDP ld_from_carmen_string(const char*line);

/** Reads all the scans it can find. */
//读取所有能找到的扫描结果。
int ld_read_all(FILE*file, LDP **array, int*num);

/** Read a scan every interval (1=all)*/
//每隔一段时间读取一次扫描(1=all)
int ld_read_some_scans(FILE*file, LDP **array, int*num, int interval);

/** Write a scan in carmen format */
//用carmen格式写扫描
void ld_write_as_carmen(LDP ld, FILE * stream);

/** Write a scan according to out_format = {"carmen", "json"} */
//根据out_format = {"carmen"， "json"}写一个扫描
void ld_write_format(LDP ld, FILE*stream, const char * out_format);


void possible_interval(
	const double *p_i_w, LDP laser_sens, 
	double max_angular_correction_deg, double max_linear_correction, int*from, int*to, int*start_cell);