C# Class Blast.Blast

Decompress input to output using the provided infun() and outfun() calls. On success, the return value of blast() is zero. If there is an error in the source data, i.e. it is not in the proper format, then a negative value is returned. If there is not enough input available or there is not enough output space, then a positive error is returned.

The input function is invoked: len = infun(how, &buf), where buf is set by infun() to point to the input buffer, and infun() returns the number of available bytes there. If infun() returns zero, then blast() returns with an input error. (blast() only asks for input if it needs it.) inhow is for use by the application to pass an input descriptor to infun(), if desired.

The output function is invoked: err = outfun(how, buf, len), where the bytes to be written are buf[0..len-1]. If err is not zero, then blast() returns with an output error. outfun() is always called with len <= 4096. outhow is for use by the application to pass an output descriptor to outfun(), if desired.

The return codes are:

At the bottom of blast.c is an example program that uses blast() that can be compiled to produce a command-line decompression filter by defining TEST.

Decode PKWare Compression Library stream.

Decode a code from the stream using huffman table h. Return the symbol or a negative value if there is an error. If all of the lengths are zero, i.e. an empty code, or if the code is incomplete and an invalid code is received, then -9 is returned after reading MAXBITS bits.

Format notes:

Decode PKWare Compression Library stream. Format notes: - First byte is 0 if literals are uncoded or 1 if they are coded. Second byte is 4, 5, or 6 for the number of extra bits in the distance code. This is the base-2 logarithm of the dictionary size minus six. - Compressed data is a combination of literals and length/distance pairs terminated by an end code. Literals are either Huffman coded or uncoded bytes. A length/distance pair is a coded length followed by a coded distance to represent a string that occurs earlier in the uncompressed data that occurs again at the current location. - A bit preceding a literal or length/distance pair indicates which comes next, 0 for literals, 1 for length/distance. - If literals are uncoded, then the next eight bits are the literal, in the normal bit order in th stream, i.e. no bit-reversal is needed. Similarly, no bit reversal is needed for either the length extra bits or the distance extra bits. - Literal bytes are simply written to the output. A length/distance pair is an instruction to copy previously uncompressed bytes to the output. The copy is from distance bytes back in the output stream, copying for length bytes. - Distances pointing before the beginning of the output data are not permitted. - Overlapped copies, where the length is greater than the distance, are allowed and common. For example, a distance of one and a length of 518 simply copies the last byte 518 times. A distance of four and a length of twelve copies the last four bytes three times. A simple forward copy ignoring whether the length is greater than the distance or not implements this correctly.

Check for presence of more input without consuming it. May refill the input buffer.