Libc-594.9.5.tar.gz

[apple/libc.git] / stdlib / bsearch.3

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.\"     @(#)bsearch.3	8.3 (Berkeley) 4/19/94
.\" $FreeBSD: src/lib/libc/stdlib/bsearch.3,v 1.8 2001/09/07 14:46:35 asmodai Exp $
.\"
.Dd May 20, 2008
.Dt BSEARCH 3
.Os
.Sh NAME
#ifdef UNIFDEF_BLOCKS
.Nm bsearch ,
.Nm bsearch_b
#else
.Nm bsearch
#endif
.Nd binary search of a sorted table
.Sh SYNOPSIS
.In stdlib.h
.Ft void *
.Fn bsearch "const void *key" "const void *base" "size_t nel" "size_t width" "int (*compar) (const void *, const void *)"
#ifdef UNIFDEF_BLOCKS
.Ft void *
.Fn bsearch_b "const void *key" "const void *base" "size_t nel" "size_t width" "int (^compar) (const void *, const void *)"
#endif
.Sh DESCRIPTION
The
.Fn bsearch
function searches an array of
.Fa nel
objects, the initial member of which is
pointed to by
.Fa base ,
for a member that matches the object pointed to by
.Fa key .
The size (in bytes) of each member of the array is specified by
.Fa width .
.Pp
The contents of the array should be in ascending sorted order according
to the comparison function referenced by
.Fa compar .
The
.Fa compar
routine
is expected to have
two arguments which point to the
.Fa key
object and to an array member, in that order.
It should return an integer which is
less than, equal to, or greater than zero if the
.Fa key
object is found, respectively, to be less than, to match, or be
greater than the array member.
#ifdef UNIFDEF_BLOCKS
.Pp
The
.Fn bsearch_b
function is like
.Fn bsearch
except the callback
.Fa compar
is a block pointer instead of a function pointer.
#endif
.Sh RETURN VALUES
The
.Fn bsearch
#ifdef UNIFDEF_BLOCKS
and
.Fn bsearch_b
functions
#else
function
#endif
returns a pointer to a matching member of the array, or a null
pointer if no match is found.
If two members compare as equal, which member is matched is unspecified.
.Sh SEE ALSO
.Xr db 3 ,
.Xr lsearch 3 ,
.Xr qsort 3
.\" .Xr tsearch 3
.Sh STANDARDS
The
.Fn bsearch
function conforms to
.St -isoC .