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Chapter 16
BitMaps
This chapter describes the bitmap type and the functions for manipulating
a bitmap type.
BitMap Type
prbitmap_t
Define a BitMap type.
syntax
#include "prbit.h"
typedef unsigned long prbitmap_t;
description
Use prbitmap_t as an array to define a bitmap of more than the 32 bits
implied by a single prbitmap_t instance.
BitMap Functions
The API defined for the BitMap functions is consistent across all platforms..
PR_TEST_BIT
Test a bit within an array of prbitmap_t.
Syntax
#include <prbit.h>
PRIntn PR_TEST_BIT(prbitmap_t *_map, PRInt32 _bit);
Parameter
_map
|
Address of the bitmap containing _bit |
_bit
|
The number of the bit within _map to be referenced. |
Returns
non-zero if _bit within _map is on, else zero.
Description
PR_TEST_BIT tests the bit at relative position _bit within bitmap
_map. The macro evaluates to true if the bit is set, else it evaluates
to zero.
PR_SET_BIT
Set a bit within an array of prbitmap_t.
Syntax
#include <prbit.h>
void PR_SET_BIT(prbitmap_t *_map, PRInt32 _bit);
Parameter
_map
|
Address of the bitmap containing _bit |
_bit
|
The number of the bit within _map to be referenced. |
Returns
void
Description
PR_SET_BIT sets bit _bit in bitmap _map to one.
PR_CLEAR_BIT
Set a bit within an array of prbitmap_t.
Syntax
#include <prbit.h>
void PR_CLEAR_BIT(prbitmap_t *_map, PRInt32 _bit);
Parameter
_map
|
Address of the bitmap containing _bit |
_bit
|
The number of the bit within _map to be referenced. |
Returns
void
Description
PR_CLEAR_BIT sets bit _bit in bitmap _map to zero.
PR_CeilingLog2
Ceiling of Log2 of a number.
Syntax
#include <prbit.h>
PRIntn PR_CeilingLog2(PRUint32 i);
Parameter
i
|
Argument to be evaluated |
Returns
Ceiling of Log2 of i.
Description
PR_CeilingLog2() takes the log2 of i, converting result to the smallest
integer that is greater than or equal to log2(i).
Think of it as: Ceil(Log2(i));
Example
PRIntn j = PR_CeilingLog2( 32 ); /* After execution, j == 5 */
PR_FloorLog2
Floor of Log2 of a number.
Syntax
#include <prbit.h>
PRIntn PR_FloorLog2(PRUint32 i);
Parameter
i
|
Argument to be evaluated |
Returns
Floor of Log2 of i.
Description
PR_FloorLog2() takes the log2 of i, converting the result to the largest
integer that is less than or equal to log2(i).
Think of it as: Floor(Log2(i));
PR_CEILING_LOG2
Ceiling of Log2 of a number.
Syntax
#include <prbit.h>
void PR_CEILING_LOG2(PRUint32 _log, PRUint32 i);
Parameter
_log
|
Result of operation |
i
|
Argument to be evaluated. |
Returns
void
Description
Same as PR_CeilingLog2(). Implemented as a macro.
PR_FLOOR_LOG2
Floor of Log2 of a number.
Syntax
#include <prbit.h>
void PR_FLOOR_LOG2(PRUint32 _log, PRUint32 i);
Parameter
_log
|
Result of operation |
i
|
Argument to be evaluated. |
Returns
void
Description
Same as PR_FloorLog2(). Implemented as a macro.
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Last Updated: Tue Jul 14 10:26:12 PDT 1998
Copyright © 1998 Netscape
Communications Corporation
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