bsearch.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 62 行

.\" SCCSID: @(#)bsearch.3	8.1	9/11/90
.TH bsearch 3 
.SH Name
bsearch \- binary search a sorted table
.SH Syntax
.nf
.B #include <stdlib.h>
.PP
.B "void *bsearch (\fIkey\fP, \fIbase\fP, \fInel\fP, sizeof (*\fIkey\fP), \fIcompar\fP)"
.B "void *\fIkey, *base\fP;
.br
.B size_t \fInel\fP;
.B int (*\fIcompar\fP)\^( )\^;
.fi
.SH Description
.NXR "bsearch subroutine"
.NXR "bsearch subroutine" "tsearch subroutine"
.NXR "binary search routine"
The
.PN bsearch
subroutine
is a binary search routine generalized from Knuth (6.2.1) Algorithm B.
It returns a pointer into a table indicating where
a datum may be found.
The table must be previously sorted in increasing order
according to a provided comparison function.
The
.I key\^
points to the datum to be sought in the table.
The
.I base\^
points to the element at the base of the table.
The
.I nel\^
is the number of elements in the table.
The
.I compar\^
is the name of the comparison function,
which is called with two arguments that point
to the elements being compared.
The function must return
an integer less than, equal to, or greater than zero
according to whether the first argument is to be considered
less than, equal to, or greater than the second.
.SH Diagnostics
A NULL
pointer is returned if the key cannot be found in the table.
.SS Notes
The pointers to the key and the
element at the base of the table should be
of type pointer-to-element,
and cast to type pointer-to-character.
.PP
The comparison function need not compare every byte,
so arbitrary data may be contained in the elements in addition to the values
being compared.
.PP
Although declared as type pointer-to-character,
the value returned should be cast into type pointer-to-element.
.SH See Also
hsearch(3), lsearch(3), qsort(3), tsearch(3)