meta.h File Reference

hl7 meta data structures for message_t More...

#include <stdio.h>
#include "bom.h"

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Classes
struct	hl7_meta_t
	HL7 Seperator configuration. More...

Typedefs
typedef struct hl7_meta_t	hl7_meta_t
	HL7 Seperator configuration. More...
typedef enum line_delimiter_t	line_delimiter_t
	possible line endings

Enumerations
enum	line_delimiter_t { DELIM_NONE = 0, DELIM_CR, DELIM_LF, DELIM_CRLF }
	possible line endings More...

Functions
hl7_meta_t *	init_hl7_meta_t (void)
	initialize the seperator data structure More...
char *	hl7_meta_string (hl7_meta_t *meta)
	generate printable string of the meta data More...
void	free_hl7_meta (hl7_meta_t *hl7_meta)
	free the data structure More...
line_delimiter_t	find_line_delimiter (FILE *fd)
	find line delimiter More...
int	read_meta (hl7_meta_t *hl7_meta, FILE *fd)
	read up until the 2nd field delimiter More...

Detailed Description

hl7 meta data structures for message_t

meta_t contains information in all hl7 separators of a file and the BOM.

read_meta() can detect the delimiters of a file pointed to by *fd.

find_line_delimiter() will seek the first CR or LF and will detect if CRLF is present. In case of CRLF the attribute crlf is set to 1 else 0 or -1 (initial value when no detection has happened yet).

https://docs.microsoft.com/en-us/biztalk/adapters-and-accelerators/accelerator-hl7/message-delimiters

Delimiter	Value	Usage
Segment terminator	<cr> 0x0D	A carriage return terminates a segment record. You cannot change this value.
Field separator	|	A pipe character separates two adjacent data fields within a segment. This character also separates the segment ID from the first data field in each segment.
Component separator	^	A hat character separates adjacent components of data fields where allowed by the HL7 standard.
Repetition separator	~	A tilde character separates multiple occurrences of components or subcomponents in a field where allowed by the HL7 standard.
Escape character	\	You use an escape character with any field that conforms to an ST, TX, or FT data type, or with the data (fourth) component of the ED data type. If no escape characters exist in a message, you can omit this character. However, you must include it if you use subcomponents in the message.
Subcomponent separator	&	An ampersand character separates adjacent subcomponents of data fields where allowed by the HL7 standard. If there are no subcomponents, then you can omit this character.

Typedef Documentation

hl7_meta_t

typedef struct hl7_meta_t hl7_meta_t

HL7 Seperator configuration.

See also

meta.h

Enumeration Type Documentation

line_delimiter_t

enum line_delimiter_t

possible line endings

Enumerator
DELIM_NONE	undefined, not found
DELIM_CR	Default HL7: 0x0D
DELIM_LF	Unix: 0x0A
DELIM_CRLF	Windows: 0x0D, 0x0A (must be other than all others ;)

Function Documentation

find_line_delimiter()

line_delimiter_t find_line_delimiter

(

FILE *

fd

)

find line delimiter

This method will forward an FILE pointer upon it finds the first \n, \r or EOF. The FILE pointer will be restored to it's original position.

Parameters

fd	file pointer at theb eginnign of a file

Returns

0 if unknown.

free_hl7_meta()

void free_hl7_meta

(

hl7_meta_t *

hl7_meta

)

free the data structure

make sure nothing points to the elements in this structure. All elements in the structure will be freed (including bom).

Parameters

hl7_meta

the meta structure

hl7_meta_string()

char* hl7_meta_string

(

hl7_meta_t *

meta

)

generate printable string of the meta data

Parameters

meta	a hopefully populated meta data struct

Returns

formatted string

init_hl7_meta_t()

hl7_meta_t* init_hl7_meta_t

(

void

)

initialize the seperator data structure

Returns

initialized hl7_meta_t struct

read_meta()

int read_meta	(	hl7_meta_t *	hl7_meta,
		FILE *	fd
	)

read up until the 2nd field delimiter

read up to 8 bytes to find all hl7 delimiters. This method assumes that it is reading an MSH segment (file pointer must be positioned at 'M').

Do not use it on any other hl7 segment!

This metod will detect all separators if they are defined. If not, separators will be left at the default.

The user must make sure to parse the right segment. fd must be pointing to the start character of an MSH or MSA segment.

The file pointer is reset at the end of this method and reset back to the byte after the BOM.

If no BOM detection has been done and meta->bom still is NULL, we'll run detect_bom() first. To prevent this, initialize the bom object with a length of 0.

Todo:

check if file length, there might only be 5 characters in it or less. handle error condition.

Note

do not re-use hl7_meta for different files, always detect separators before parsing.

this method fails if there is only one field separator, i.e. MSH| will return 1. even tho it may or maynot be a valid hl7 file MSH-2 is not followed by MSH-1 and therefore a reliable detection is not possible.

Return codes:

• 0: success
• 1: the field delimiter was not found after the delimiters
• 2: premature file end
• 3: file does not begin with MSH

Parameters

hl7_meta	pointer to an empty metadata structure
fd	file pointer pointing to the beginning of MSH or MSA segment

Returns

0 on succes, error code otherwise