.Dd September 5, 1996
.Dt LIBSEARCHSTR 3
.Os NetBSD 1.2BETA
.Sh NAME
.Nm searchstr_maketbl ,
.Nm searchstr ,
.Nd fast block searching
.Sh SYNOPSIS
.Fd #include <searchstr.h>
.br
.Nm cc
.Op Ar arguments
.Fl lsearchstr
.br
.Ft void
.Fn searchstr_maketbl "unsigned char (*table)[256]" "const unsigned char *string" "unsigned int len" "const unsigned char equiv[256]"
.Ft int
.Fn searchstr "const unsigned char *string" "unsigned int stringlen" "unsigned char (*table)[256]" "unsigned int tablelen"
.Sh DESCRIPTION
These functions are an implementation of a very fast algorithm for
searching a large block of memory for small block.  It can also do
mapping of characters to equivalent characters, such as case folding or
stripping accents.
.Pp
.Fn searchstr_maketbl
constructs a searching table.  The
.Fa string
and
.Fa len
arguments describe the small block of memory, the block that is being
searched for.  (The name
.Dq string
is perhaps a misnomer, since there is no restriction on content; NUL
bytes are not special.)
.Fa table
points to an array of
.Fa len
blocks of 256 bytes;
.Fn searchstr_maketbl
constructs an internal table in this space.
.Fa equiv
is an "equivalence" vector; all bytes, both in the block of memory
being searched and in the supplied block to search for, are effectively
passed through this table before being compared.  (That is, rather than
comparing, say,
.Dl mem[i] == str[j]
then the comparison is effectively
.Dl equiv[mem[i]] == equiv[str[j]]
instead.)
.Pp
.Fn searchstr
actually performs the search.
.Fa string
and
.Fa stringlen
describe the block of memory to be searched;
.Fa table
is the table constructed by
.Fn searchstr_maketbl ,
and
.Fa tablelen
must match the
.Fa len
argument to the
.Fn searchstr_maketbl
call that constructed the table.  The returned value is an index into
.Fa string
which matches the first byte of the searched-for string, or \-1 if the
search failed.
.Sh BUGS
Code blindly assumes 8-bit
.Do
char
.Dc Ns s.
.Pp
Maximum length of the string to be searched for is 255, or maybe 256.
.Sh AUTHOR
der Mouse,
.Aq mouse@rodents.montreal.qc.ca .