/Users/brianlane/projs/aisparser/c/src/sixbit.h File Reference

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Detailed Description

Header file for sixbit.c.

Author:

Brian C. Lane <bcl@brianlane.com>

Data Structures
struct	sixbit
	sixbit state More...
Defines
#define	SIXBIT_LEN   255
Functions
char __stdcall	binfrom6bit (char ascii)
	Convert an ascii value to a 6-bit binary value.
int __stdcall	init_6bit (sixbit *state)
	Initialize a 6-bit datastream structure.
unsigned long __stdcall	get_6bit (sixbit *state, short numbits)
	Return 0-32 bits from a 6-bit ASCII stream.
unsigned int __stdcall	sixbit_length (sixbit *state)
	Calculate the number of bits remaining in the six_state.
char __stdcall	binto6bit (char value)
	Convert a binary value to a 6-bit ASCII value.

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Define Documentation

#define SIXBIT_LEN   255

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Function Documentation

char __stdcall binfrom6bit

(

char

ascii

)

Convert an ascii value to a 6-bit binary value.

This function checks the ASCII value to make sure it can be coverted. If not, it returns a -1. Otherwise it returns the 6-bit binary value.

Parameters:

ascii

character to convert

returns:

• -1 if it fails
• 6-bit value (0x00-0x3F)

This is used to convert the packed 6-bit value to a binary value. It is not used to convert data from fields such as the name and destination -- Use ais2ascii() instead.

char __stdcall binto6bit

(

char

value

)

Convert a binary value to a 6-bit ASCII value.

This function checks the binary value to make sure it can be coverted. If not, it returns a -1. Otherwise it returns the 6-bit ASCII value.

Parameters:

value

to convert

returns:

• -1 if it fails
• 6-bit ASCII

This is used to convert a 6 bit binary value to the packed 6-bit value It is not used to convert data from fields such as the name and destination -- Use ais2ascii() instead.

unsigned long __stdcall get_6bit	(	sixbit *	state,
		short	numbits
	)

Return 0-32 bits from a 6-bit ASCII stream.

Parameters:

	state	pointer to a sixbit state structure
	numbits	number of bits to return

This function returns the requested number of bits to the calling function. It pulls the bits from the raw 6-bit ASCII as they are needed.

The full string can be addressed by pointing to state->bits and the length can be calculated by strlen(state->bits) * 6, but note that the string also includes any final padding, so when checking lengths take into account that it will be a multiples of 6 bits.

Example:

    sixbit  state;
    unsigned char i;

    init_6bit( &state );
    strcpy( state.bits, "5678901234" );
    i = get_6bit( &state, 6 );

    i == 5

int __stdcall init_6bit

(

sixbit *

state

)

Initialize a 6-bit datastream structure.

Parameters:

state

state of 6-bit parser

This function initializes the state of the sixbit parser variables and 0 terminates the 6-bit string.

Example:

    sixbit state;
    
    init_6bit( &state );

unsigned int __stdcall sixbit_length

(

sixbit *

state

)

Calculate the number of bits remaining in the six_state.

Parameters:

state

returns: Number of bits remaining

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