COMP(2)                                                                COMP(2)



NAME
     comp,uncomp,comp_compress,uncomp_uncompress - data stream compression and
     uncompression

C SYNOPSIS
     #include <comp.h>

     typedef void *(*compallocatort)(sizet);

     typedef void (*compfreet)(void *);

     typedef ssizet (*compoutputt)(void *param, void *buf, sizet buflen);

     void compoptionsdefault(COMPOPTIONS *);

     void compinit(COMPDATA *, compallocatort,
                    compfreet, compoutputt);

     int compbegin(COMPDATA *, COMPOPTIONS *);

     int compcompress(COMPDATA *,
                       const chartype *buf, long buflen);

     int compend(COMPDATA *);

     void compdestroy(COMPDATA *);

     int compgeterrno(COMPDATA *);

     void compclrerrno(UNCOMPDATA *);

     #include <uncomp.h>

     typedef void *(*uncompallocatort)(sizet);

     typedef void (*uncompfreet)(void *);

     typedef ssizet (*uncompoutputt)(void *param, void *buf, sizet buflen);

     void uncompoptionsdefault(UNCOMPOPTIONS *);

     int uncompinit(UNCOMPDATA *, uncompallocatort,
                     uncompfreet, uncompoutputt);

     int uncompbegin(UNCOMPDATA *, UNCOMPOPTIONS *);

     int uncompuncompress(UNCOMPDATA *,
                           const chartype *buf, long buflen);

     int uncompend(UNCOMPDATA *);





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COMP(2)                                                                COMP(2)



     void uncompdestroy(UNCOMPDATA *);

     int uncompgeterrno(UNCOMPDATA *);

     void uncompclrerrno(UNCOMPDATA *);

OVERVIEW
     The comp library and associated system calls allows applications to use
     the compression and decompression algorithms from compress(1) and
     uncompress(1) directly, without having to invoke a separate executable.

     The compression code in this library has been optimized, and if used in
     combination with large buffer file reading can result in improved
     compression times of up to 30% over the standard compress code.

     You must link with the comp library:

          cc -o prog prog.c -lcomp


DESCRIPTION
     Applications wishing to compress data should:


     1    include comp.h header file


     2    define an instance of a COMP_DATA stream (let's call it xxx)


     3    define memory allocator method: void *xxxmalloc(size_t)


     4    define corresponding memory free method: void xxxfree(buf)


     5    define output handler method: ssize_t xxxoutput(param, outbuf,

          outbuflen)


     6    define an instance of COMP_OPTIONS options structure: xxxopts


     7    invoke comp_options_default(&xxxopts) to set default options


     8    invoke comp_init(&xxx, &xxxmalloc, &xxxfree, &xxxoutput)


     9    explicitly set any non-default options desired in xxxopts,

          especially xxxopts.outputparam, which is passed to xxxoutput()


     10   invoke comp_begin(&xxx, &xxxopts)


     11   invoke comp_compress(&xxx, inbuf, inbuflen)


     12   invoke comp_end(&xxx)







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COMP(2)                                                                COMP(2)



     13   repeat steps (9) through (12) as necessary, for each file to be
          compressed.

     14   it is okay to reuse compress structs for other compressed streams,
          by invoking comp_begin() on them again.

     15   invoke comp_destroy(&xxx) to free up allocated memory

     Expect during above:

     1    calls to xxxmalloc() during comp_begin() for space that the
          compressor might need

     2    calls to xxxoutput() during comp_compress() and comp_end(), to emit
          compressed results.

     3    calls to xxxfree() during comp_destroy() and comp_begin().

     To uncompress data:


     1    include uncomp.h header file


     2    define an instance of a UNCOMP_DATA stream (let's call it xxx)


     3    define memory allocator method: void *xxxmalloc(size_t)


     4    define corresponding memory free method: void xxxfree(buf)


     5    define output handler method: ssize_t xxxoutput(param, outbuf,

          outbuflen)


     6    define an instance of UNCOMP_OPTIONS options structure: xxxopts


     7    invoke uncomp_options_default(&xxxopts) to set default options


     8    invoke uncomp_init(&xxx, &xxxmalloc, &xxxfree, &xxxoutput)


     9    explicitly set any non-default options desired in xxxopts,

          especially xxxopts.outputparam, which is passed to xxxoutput()


     10   invoke uncomp_begin(&xxx, &xxxopts)


     11   invoke uncomp_uncompress(&xxx, inbuf, inbuflen)


     12   invoke uncomp_end(&xxx)


     13   repeat steps (9) through (12) as necessary, for each file to be

          compressed.







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COMP(2)                                                                COMP(2)



     14   it is okay to reuse uncompress structs for other compressed streams,
          by invoking uncomp_begin() on them again.

     15   invoke uncomp_destroy(&xxx) to free up allocated memory

     Expect during above:

     1    calls to xxxmalloc() during uncomp_init() for space that the
          uncompressor might need

     2    calls to xxxoutput() during uncomp_uncompress() and uncomp_end(), to
          emit uncompressed results.

     3    calls to xxxfree() during uncomp_destroy() and uncomp_begin()..

SEE ALSO
     compress(1), uncompress(1)

DIAGNOSTICS
     All routines that return a status value return 0 for success, -1 for
     failure.  comp_end and uncomp_end can also return -2 if no gain was had
     by compressing the stream.

































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