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author | Aki <please@ignore.pl> | 2021-10-01 23:46:47 +0200 |
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committer | Aki <please@ignore.pl> | 2021-10-01 23:46:47 +0200 |
commit | ddd76aa4e1571c8d5965709db5c3cd47a89c9a38 (patch) | |
tree | 4e07bfaebede6531a70984fdebc855bca52f394a /zlib/contrib/puff/README | |
parent | 3a507e08b1d4e5970b27401a7e6517570d529400 (diff) | |
parent | c2d2c3551501110fddd78674d5435bfaa70382a3 (diff) | |
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Diffstat (limited to 'zlib/contrib/puff/README')
-rw-r--r-- | zlib/contrib/puff/README | 63 |
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diff --git a/zlib/contrib/puff/README b/zlib/contrib/puff/README new file mode 100644 index 0000000..bbc4cb5 --- /dev/null +++ b/zlib/contrib/puff/README @@ -0,0 +1,63 @@ +Puff -- A Simple Inflate +3 Mar 2003 +Mark Adler +madler@alumni.caltech.edu + +What this is -- + +puff.c provides the routine puff() to decompress the deflate data format. It +does so more slowly than zlib, but the code is about one-fifth the size of the +inflate code in zlib, and written to be very easy to read. + +Why I wrote this -- + +puff.c was written to document the deflate format unambiguously, by virtue of +being working C code. It is meant to supplement RFC 1951, which formally +describes the deflate format. I have received many questions on details of the +deflate format, and I hope that reading this code will answer those questions. +puff.c is heavily commented with details of the deflate format, especially +those little nooks and cranies of the format that might not be obvious from a +specification. + +puff.c may also be useful in applications where code size or memory usage is a +very limited resource, and speed is not as important. + +How to use it -- + +Well, most likely you should just be reading puff.c and using zlib for actual +applications, but if you must ... + +Include puff.h in your code, which provides this prototype: + +int puff(unsigned char *dest, /* pointer to destination pointer */ + unsigned long *destlen, /* amount of output space */ + unsigned char *source, /* pointer to source data pointer */ + unsigned long *sourcelen); /* amount of input available */ + +Then you can call puff() to decompress a deflate stream that is in memory in +its entirety at source, to a sufficiently sized block of memory for the +decompressed data at dest. puff() is the only external symbol in puff.c The +only C library functions that puff.c needs are setjmp() and longjmp(), which +are used to simplify error checking in the code to improve readabilty. puff.c +does no memory allocation, and uses less than 2K bytes off of the stack. + +If destlen is not enough space for the uncompressed data, then inflate will +return an error without writing more than destlen bytes. Note that this means +that in order to decompress the deflate data successfully, you need to know +the size of the uncompressed data ahead of time. + +If needed, puff() can determine the size of the uncompressed data with no +output space. This is done by passing dest equal to (unsigned char *)0. Then +the initial value of *destlen is ignored and *destlen is set to the length of +the uncompressed data. So if the size of the uncompressed data is not known, +then two passes of puff() can be used--first to determine the size, and second +to do the actual inflation after allocating the appropriate memory. Not +pretty, but it works. (This is one of the reasons you should be using zlib.) + +The deflate format is self-terminating. If the deflate stream does not end +in *sourcelen bytes, puff() will return an error without reading at or past +endsource. + +On return, *sourcelen is updated to the amount of input data consumed, and +*destlen is updated to the size of the uncompressed data. See the comments +in puff.c for the possible return codes for puff(). |