sync code with last improvements from OpenBSD

lib/xcb-util-image/image/xcb_bitops.h

@@ -0,0 +1,212 @@
+#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 n == 32 ? ~0 : (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().
+ * @ingroup xcb__bitops
+ */
+_X_INLINE static uint32_t
+xcb_roundup_2 (uint32_t base, uint32_t pad)
+{
+    return (base + pad - 1) & -pad;
+}
+
+/**
+ * Round down to the next power-of-two unit size.
+ * @param base Number to be rounded down.
+ * @param pad Multiple to be rounded to; must be a power of two.
+ * @return Rounded-down number.
+ *
+ * Rounds @p base down to a multiple of @p pad, where @p pad
+ * is a power of two.  The more general case is handled by
+ * xcb_rounddown().
+ * @ingroup xcb__bitops
+ */
+_X_INLINE static uint32_t
+xcb_rounddown_2 (uint32_t base, uint32_t pad)
+{
+    return base & -pad;
+}
+
+/**
+ * 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;
+    return b - b % pad;
+}
+
+
+/**
+ * Round down to the next unit size.
+ * @param base Number to be rounded down.
+ * @param pad Multiple to be rounded to.
+ * @return Rounded-down number.
+ *
+ * This is a general routine for rounding @p base down
+ * to a multiple of @p pad.  If you know that @p pad
+ * is a power of two, you should probably call xcb_rounddown_2()
+ * instead.
+ * @ingroup xcb__bitops
+ */
+_X_INLINE static uint32_t
+xcb_rounddown (uint32_t base, uint32_t pad)
+{
+    /* faster if pad is a power of two */
+    if (((pad - 1) & pad) == 0)
+	return base & -pad;
+    return base - base % 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__ */