COMPR: COMPRESS extension for NNTP

This module provides optional support for data compression and decompression according to RFC 8054. More...

Macros
#define	MAIN_ERR_PREFIX   "COMPR: "
	Message prefix for COMPRESSION module.
#define	CMPR_DEBUG   0
	Print debug messages to stdout if nonzero.
#define	CMPR_BUFSIZE   (size_t) 32768
	Size of internal data buffers. More...
#define	CMPR_ZLIB_WINDOW_BITS   -15
	Window size for DEFLATE algorithm. More...
#define	CMPR_ZLIB_MEM_LEVEL   9
	Memory usage for DEFLATE algorithm. More...

Functions
posix_ssize_t	cmpr_send (void *stream, const void *buf, size_t len)
	Send data. More...
int	cmpr_flush (void *stream)
	Flush TX direction. More...
int	cmpr_terminate (void *stream)
	Flush TX direction and terminate data stream. More...
posix_ssize_t	cmpr_recv (void *stream, void *buf, size_t len, int peek)
	Receive data. More...
struct cmpr_stream *	cmpr_stream_constructor (unsigned int alg, int sd, ssize_t(*tx_send)(int, const void *, size_t, int), ssize_t(*rx_recv)(int, void *, size_t, int))
	Compressed data stream object constructor. More...
void	cmpr_stream_destructor (void *stream)
	Destroy compressed data stream object allocated by compression module. More...
int	cmpr_init (void)
	Initialize compression module.
void	cmpr_exit (void)
	Shutdown compress module.

Flush options for TX direction of compressed data streams
The flags can be bitwise ORed together.
#define	CMPR_FLUSH_NO   0
#define	CMPR_FLUSH_YES   1
#define	CMPR_FLUSH_END   2

Compression algorithms
#define	CMPR_ALG_DEFLATE   0x0001U
	DEFLATE according to RFC 1951.

Detailed Description

This module provides optional support for data compression and decompression according to RFC 8054.

Currently the following algorithms are supported:

• DEFLATE according to RFC 1951

Note

This module currently works only if the zlib library is available.

Macro Definition Documentation

CMPR_BUFSIZE

#define CMPR_BUFSIZE   (size_t) 32768

Size of internal data buffers.

Attention

The zlib data type uInt must be capable of holding this value.

Definition at line 94 of file compression.c.

CMPR_ZLIB_MEM_LEVEL

#define CMPR_ZLIB_MEM_LEVEL   9

Memory usage for DEFLATE algorithm.

Speed vs. memory usage tradeoff for zlib (integer value from 1 to 9)
1: Minimum memory usage for minimum speed
9: Maximum memory usage for maximum speed

Definition at line 124 of file compression.c.

CMPR_ZLIB_WINDOW_BITS

#define CMPR_ZLIB_WINDOW_BITS   -15

Window size for DEFLATE algorithm.

Compression ratio vs. memory usage tradeoff (integer value from -8 to -15). Negative base two logarithm of the window size (size of the history buffer) for zlib. The negative sign selects raw data without container.
-8: Worst compression and minimum memory usage (256 Byte)
-15: Best compression and maximum memory usage (32 KiByte)

Attention

Don't change this value until you know what you are doing. It must match the setup of the peer.

Definition at line 114 of file compression.c.

Function Documentation

cmpr_flush()

int cmpr_flush

(

void *

stream

)

Flush TX direction.

Parameters

[in]

stream

Pointer to stream object pointer

Returns

• 0 on success
• -1 on error

Definition at line 384 of file compression.c.

References MAIN_ERR_PREFIX.

cmpr_recv()

posix_ssize_t cmpr_recv	(	void *	stream,
		void *	buf,
		size_t	len,
		int	peek
	)

Receive data.

Parameters

[in]	stream	Pointer to stream object pointer
[out]	buf	Pointer to data buffer
[in]	len	Number of octets to receive
[in]	peek	Data should stay available for reading if nonzero

Attention

A nonzero value must be used for the len parameter!

Returns

• Number of bytes received
• 0 if underlaying protocol lost connection
• -1 on error

Definition at line 443 of file compression.c.

References CMPR_ALG_DEFLATE, CMPR_BUFSIZE, MAIN_ERR_PREFIX, and PRINT_ERROR.

cmpr_send()

posix_ssize_t cmpr_send	(	void *	stream,
		const void *	buf,
		size_t	len
	)

Send data.

Parameters

[in]	stream	Pointer to stream object pointer
[in]	buf	Pointer to data buffer
[in]	len	Number of octets to send

Returns

• Number of bytes sent
• -1 on error

Definition at line 362 of file compression.c.

References MAIN_ERR_PREFIX.

cmpr_stream_constructor()

struct cmpr_stream* cmpr_stream_constructor	(	unsigned int	alg,
		int	sd,
		ssize_t(*)(int, const void *, size_t, int)	tx_send,
		ssize_t(*)(int, void *, size_t, int)	rx_recv
	)

Compressed data stream object constructor.

Parameters

[in]	alg	Compression algorithm (use CMPR_ALG_xxx constants)
[in]	sd	Socket descriptor or stream handle of undelaying protocol
[in]	tx_send	Send function to underlaying protocol
[in]	rx_recv	Receive function for underlaying protocol

Attention

The functions to access the undelaying protocol tx_send() and rx_recv() are expected to behave like send() and recv() defined by POSIX.1-2001 with compatibility to the 4.2BSD implementation regarding flags).

Returns

• Pointer to constructed object on success
• NULL on error

Definition at line 615 of file compression.c.

References CMPR_ALG_DEFLATE, CMPR_BUFSIZE, and PRINT_ERROR.

cmpr_stream_destructor()

void cmpr_stream_destructor

(

void *

stream

)

Destroy compressed data stream object allocated by compression module.

Parameters

[in]

stream

Pointer to object

Note

The pointer p is allowed to be NULL and no operation is performed in this case.

Definition at line 768 of file compression.c.

References CMPR_ALG_DEFLATE, and PRINT_ERROR.

cmpr_terminate()

int cmpr_terminate

(

void *

stream

)

Flush TX direction and terminate data stream.

Parameters

[in]

stream

Pointer to stream object pointer

Returns

• 0 on success
• -1 on error

Definition at line 410 of file compression.c.

References MAIN_ERR_PREFIX.