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Diffstat (limited to 'man/2/rabin')
| -rw-r--r-- | man/2/rabin | 54 |
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diff --git a/man/2/rabin b/man/2/rabin new file mode 100644 index 00000000..daceeaaf --- /dev/null +++ b/man/2/rabin @@ -0,0 +1,54 @@ +.TH RABIN 2 +.SH NAME +rabin \- rabin fingerprinting +.SH SYNOPSIS +.EX +include "rabin.m"; +rabin := load Rabin Rabin->PATH; +Rcfg, Rfile: import rabin; + +init: fn(bufio: Bufio); +open: fn(rcfg: ref Rcfg, b: ref Iobuf, min, max: int): (ref Rfile, string); + +Rcfg: adt { + mk: fn(prime, width, mod: int): (ref Rcfg, string); +}; + +Rfile: adt { + read: fn(r: self ref Rfile): (array of byte, big, string); +}; +.EE +.SH DESCRIPTION +.B Rabin +implements a data fingerprinting algorithm. A rolling checksum is calculated while reading data. Certain checksum values are taken to be data boundaries and used to split the data into chunks. +.PP +.B Rcfg +represents the parameters to the algorithm; +.B Rcfg.mk +creates a new instance. +.I Prime +should be a prime number. +.I Width +is the width of the rolling checksum window in bytes. A wider window results in more diverse boundary patterns. A window of 30 bytes should be reasonable for most uses. +.I Mod +effectively sets the mean desired chunk size. The rolling checksum is calculated modulo +.IR mod . +All three parameters influence where chunk boundaries will be found. +.PP +.B Rfile +represents a file to read chunks from. +.B Open +returns an initialised Rfile or an error string. +.I Min +and +.I max +are the minimum and maximum size in bytes of chunks that will be returned. Only the last chunk in a file can be smaller than the minimum chunk size. Note that the mean chunk size may be off due to these parameters. +Data is read from +.B Iobuf +.IR b . +.B Rfile.read +returns subsequent chunks of data and the file offset at which they were found, or an error message. After end of file, the returned chunks are zero bytes long. +.SH SOURCE +.B /appl/lib/rabin.b +.SH AUTHOR +Mechiel Lukkien, during GSoC 2007 |