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new mdoc bm(3) man page

OPENBSD_2_6
aaron 25 years ago
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67b066fa85
1 changed files with 54 additions and 53 deletions
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      src/lib/libc/string/bm.3

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src/lib/libc/string/bm.3 View File

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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.\" $OpenBSD: bm.3,v 1.3 1999/05/28 01:57:37 aaron Exp $
.\" $OpenBSD: bm.3,v 1.4 1999/06/29 17:49:24 aaron Exp $
.\" .\"
.TH BM 3
.SH NAME
bm_comp, bm_exec, bm_free \- Boyer-Moore string search
.SH SYNOPSIS
.ft B
#include <sys/types.h>
.br
#include <bm.h>
.sp
bm_pat *
.br
bm_comp(u_char *pattern, size_t patlen, u_char freq[256]);
.sp
u_char *
.br
bm_exec(bm_pat *pdesc, u_char *text, size_t len);
.sp
void
.br
bm_free(bm_pat *pdesc);
.SH DESCRIPTION
.Dd June 29, 1999
.Dt BM 3
.Os
.Sh NAME
.Nm bm_comp ,
.Nm bm_exec ,
.Nm bm_free
.Nd Boyer-Moore string search
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <bm.h>
.Ft bm_pat *
.Fn bm_comp "u_char *pattern" "size_t patlen" "u_char freq[256]"
.Ft u_char *
.Fn bm_exec "bm_pat *pdesc" "u_char *text" "size_t len"
.Ft void
.Fn bm_free "bm_pat *pdesc"
.Sh DESCRIPTION
These routines implement an efficient mechanism to find an These routines implement an efficient mechanism to find an
occurrence of a byte string within another byte string. occurrence of a byte string within another byte string.
.PP
.I Bm_comp
evaluates the
.I patlen
.Pp
.Fn bm_comp
evaluates
.Fa patlen
bytes starting at bytes starting at
.IR pattern ,
.Fa pattern ,
and returns a pointer to a structure describing them. and returns a pointer to a structure describing them.
The bytes referenced by The bytes referenced by
.I pattern
.Fa pattern
may be of any value. may be of any value.
.PP
.Pp
The search takes advantage of the frequency distribution of the The search takes advantage of the frequency distribution of the
bytes in the text to be searched. bytes in the text to be searched.
If specified, If specified,
.I freq
.Ar freq
should be an array of 256 values, should be an array of 256 values,
with higher values indicating that the corresponding character occurs with higher values indicating that the corresponding character occurs
more frequently. more frequently.
(A less than optimal frequency distribution can only result in less (A less than optimal frequency distribution can only result in less
than optimal performance, not incorrect results.) than optimal performance, not incorrect results.)
If If
.I freq
is NULL,
.Ar freq
is
.Dv NULL ,
a system default table is used. a system default table is used.
.PP
.I Bm_exec
.Pp
.Fn bm_exec
returns a pointer to the leftmost occurrence of the string given to returns a pointer to the leftmost occurrence of the string given to
.I bm_comp
.Fn bm_comp
within within
.IR text ,
or NULL if none occurs.
.Ar text ,
or
.Dv NULL
if none occurs.
The number of bytes in The number of bytes in
.I text
.Ar text
must be specified by must be specified by
.IR len .
.PP
.Ar len .
.Pp
Space allocated for the returned description is discarded Space allocated for the returned description is discarded
by calling by calling
.I bm_free
.Fn bm_free
with the returned description as an argument. with the returned description as an argument.
.PP
.Pp
The asymptotic speed of The asymptotic speed of
.I bm_exec
.Fn bm_exec
is is
.RI O( len / patlen ).
.PP
.SH SEE ALSO
.IR regexp (3),
.IR strstr (3)
.sp
.IR "Fast String Searching" ,
Hume and Sunday,
Software Practice and Experience,
Vol. 21, 11 (November 1991) pp. 1221-48.
.Pf O Ns Pq len / patlen .
.Sh SEE ALSO
.Xr regexp 3 ,
.Xr strstr 3
.Rs
.%R "Fast String Searching"
.%A "Hume and Sunday"
.%J "Software Practice and Experience"
.%V Volume 21, 11 (November 1991)
.%P 1221-48
.Re

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