transport layer NPL message compressor(encoder) and decompresser(decoder) Currently, we use a very simply custom encoding/decoding algorithm. More...

#include <NPLCodec.h>

Static Public Member Functions
static int	Encode (char dest, const char src, int nSrcSize, uint32 nPublicKey=0)
	encode a byte array from src to dest More...

static int	Decode (char dest, const char src, int nSrcSize, uint32 nPublicKey=0)
	decode a byte array from src to dest More...

static void	UsePlainTextEncoding (bool bUsePlainTextEncoding)
	no matter what public key is used, we will ensure that the encoded message is plain text [0,128) [Not Thread Safe]: one must call this function before sending or receiving any encoded messages. More...

static void	SetGenericKey (const byte *sKey, int nSize)
	set the generic key that is used for encoding/decoding. More...

static int	Compress (string &outstring, const char *src, int nSrcSize, int compressionlevel=-1)
	Compress src to a string buffer using zlib. More...

static int	Decompress (string &outstring, const char *src, int nSrcSize)
	Decompress src to destination. More...

Detailed Description

transport layer NPL message compressor(encoder) and decompresser(decoder) Currently, we use a very simply custom encoding/decoding algorithm.

The idea is to change the NPL codecs implementation very often so that no one will easily decode it without spending a lot of human time.

[thread safe]: class is thread safe.

Member Function Documentation

§ Compress()

int NPLCodec::Compress	(	string &	outstring,
		const char *	src,
		int	nSrcSize,
		int	compressionlevel = `-1`
	)

static

Compress src to a string buffer using zlib.

[Thread safe]

Parameters

outstring	the output buffer to store compressed data. Data will be appended to it.
src	the input source bytes
nSrcSize	length of source in byte
compressionlevel	compression level, which is an integer in the range of -1 to 9. Lower compression levels result in faster execution, but less compression. Higher levels result in greater compression, but slower execution. The zlib constant Z_DEFAULT_COMPRESSION, equal to -1, provides a good compromise between compression and speed and is equivalent to level 6. Level 0 actually does no compression at all, and in fact expands the data slightly to produce the zlib format (it is not a byte-for-byte copy of the input).

Returns: : -1 if failed, 1 if succeed.

§ Decode()

int NPLCodec::Decode	(	char *	dest,
		const char *	src,
		int	nSrcSize,
		uint32	nPublicKey = `0`
	)

static

decode a byte array from src to dest

The current custom algorithm is as follow.

Note: : this algorithm allows the dest to be the same as src, which performs decoding in place of src

Parameters

dest	the destination buffer, which needs to be at least nSrcSize in length
src	the input source bytes to decode
nSrcSize	length of source in byte
nPublicKey	the public key. Sometimes, we use the message length as public key to make the message more difficult to decode

Returns: : the number of bytes written to dest.

shift the private key by nPublicKey mod private key size.
for each src char, computer the dest char as XOR of src and private key
increase src, dest, and private key by 1 byte, and repeat 2. If private key char is '\0', reset the private key to the beginning.

§ Decompress()

int NPLCodec::Decompress	(	string &	outstring,
		const char *	src,
		int	nSrcSize
	)

static

Decompress src to destination.

[Thread safe]:

Parameters

outstring	the output buffer to store decompressed data. Data will be appended to it.
src	the input source bytes
nSrcSize	length of source in byte

§ Encode()

int NPLCodec::Encode	(	char *	dest,
		const char *	src,
		int	nSrcSize,
		uint32	nPublicKey = `0`
	)

static

encode a byte array from src to dest

Note: : this algorithm allows the dest to be the same as src, which performs encoding in place of src

Parameters

dest	the destination buffer, which needs to be at least nSrcSize in length
src	the input source bytes to encode
nSrcSize	length of source in byte
nPublicKey	the public key. Sometimes, we use the message length as public key to make the message more difficult to decode

Returns: : the number of bytes written to dest.

§ SetGenericKey()

void NPLCodec::SetGenericKey	(	const byte *	sKey,
		int	nSize
	)

static

set the generic key that is used for encoding/decoding.

If this is not called, the default internal key is used for message encoding. [Not Thread Safe]: one must call this function before sending or receiving any encoded messages. so it is usually called when the game engine starts.

Parameters

sKey	the byte array of key
nSize	size in bytes of the sKey. default is 64 bytes

§ UsePlainTextEncoding()

void NPLCodec::UsePlainTextEncoding ( bool bUsePlainTextEncoding )

static

no matter what public key is used, we will ensure that the encoded message is plain text [0,128) [Not Thread Safe]: one must call this function before sending or receiving any encoded messages.

so it is usually called when the game engine starts.

The documentation for this class was generated from the following files:

Client/trunk/ParaEngineClient/NPL/NPLCodec.h
Client/trunk/ParaEngineClient/NPL/NPLCodec.cpp

Static Public Member Functions

Detailed Description

Member Function Documentation

§ Compress()

§ Decode()

§ Decompress()

§ Encode()

§ SetGenericKey()

§ UsePlainTextEncoding()