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#ifndef __XCB_BITOPS_H__
#define __XCB_BITOPS_H__
/* Copyright (C) 2007 Bart Massey
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* Except as contained in this notice, the names of the authors or their
* institutions shall not be used in advertising or otherwise to promote the
* sale, use or other dealings in this Software without prior written
* authorization from the authors.
*/
#include <assert.h>
#include <inttypes.h>
#include <X11/Xfuncproto.h>
/**
* @defgroup xcb__bitops XCB Bit Operations
*
* Inline functions for common bit ops used in XCB and elsewhere.
*
* @{
*/
/**
* Create a low-order bitmask.
* @param n Mask size.
* @return Mask.
*
* Create a bitmask with the lower @p n bits set and the
* rest of the word clear.
* @ingroup xcb__bitops
*/
_X_INLINE static uint32_t
xcb_mask(uint32_t n)
{
return (1 << n) - 1;
}
/**
* Population count.
* @param n Integer representing a bitset.
* @return Number of 1 bits in the bitset.
*
* This is a reasonably fast algorithm for counting the bits
* in a 32-bit word. Currently a classic binary
* divide-and-conquer popcount: popcount_2() from
* http://en.wikipedia.org/wiki/Hamming_weight.
* @ingroup xcb__bitops
*/
/* 15 ops, 3 long immediates, 14 stages, 9 alu ops, 9 alu stages */
_X_INLINE static uint32_t
xcb_popcount(uint32_t x)
{
uint32_t m1 = 0x55555555;
uint32_t m2 = 0x33333333;
uint32_t m4 = 0x0f0f0f0f;
x -= (x >> 1) & m1;
x = (x & m2) + ((x >> 2) & m2);
x = (x + (x >> 4)) & m4;
x += x >> 8;
return (x + (x >> 16)) & 0x3f;
}
/**
* Round up to the next power-of-two unit size.
* @param base Number to be rounded up.
* @param pad Multiple to be rounded to; must be a power of two.
* @return Rounded-up number.
*
* Rounds @p base up to a multiple of @p pad, where @p pad
* is a power of two. The more general case is handled by
* xcb_roundup_2().
* @ingroup xcb__bitops
*/
_X_INLINE static uint32_t
xcb_roundup_2 (uint32_t base, uint32_t pad)
{
uint32_t b = base + pad - 1;
return b & ~(pad - 1);
}
/**
* Round up to the next unit size.
* @param base Number to be rounded up.
* @param pad Multiple to be rounded to.
* @return Rounded-up number.
*
* This is a general routine for rounding @p base up
* to a multiple of @p pad. If you know that @p pad
* is a power of two, you should probably call xcb_roundup_2()
* instead.
* @ingroup xcb__bitops
*/
_X_INLINE static uint32_t
xcb_roundup (uint32_t base, uint32_t pad)
{
uint32_t b = base + pad - 1;
/* faster if pad is a power of two */
if (((pad - 1) & pad) == 0)
return b & ~(pad - 1);
return b % pad;
}
/**
* Reverse bits of word.
* @param x Target word.
* @param n Number of low-order bits to reverse.
* @return Word with low @p n bits reversed, all others 0.
*
* Reverses the bottom @p n bits of @p x.
* @ingroup xcb__bitops
*/
_X_INLINE static uint32_t
xcb_bit_reverse(uint32_t x, uint8_t n) {
uint32_t m1 = 0x00ff00ff;
uint32_t m2 = 0x0f0f0f0f;
uint32_t m3 = 0x33333333;
uint32_t m4 = 0x55555555;
x = ((x << 16) | (x >> 16));
x = ((x & m1) << 8) | ((x >> 8) & m1);
x = ((x & m2) << 4) | ((x >> 4) & m2);
x = ((x & m3) << 2) | ((x >> 2) & m3);
x = ((x & m4) << 1) | ((x >> 1) & m4);
x >>= 32 - n;
return x;
}
/**
* Host byte order.
* @return The byte order of the host.
*
* Tests the host's byte order and returns either
* XCB_IMAGE_ORDER_MSB_FIRST or XCB_IMAGE_ORDER_LSB_FIRST
* as appropriate.
* @ingroup xcb__bitops
*/
_X_INLINE static xcb_image_order_t
xcb_host_byte_order(void) {
uint32_t endian_test = 0x01020304;
switch (*(char *)&endian_test) {
case 0x01:
return XCB_IMAGE_ORDER_MSB_FIRST;
case 0x04:
return XCB_IMAGE_ORDER_LSB_FIRST;
}
assert(0);
}
#endif /* __XCB_BITOPS_H__ */
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