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+/**
+ * \file
+ *
+ * \brief CLZ/CTZ C implementation.
+ *
+ * Copyright (c) 2009 Atmel Corporation. All rights reserved.
+ *
+ * \asf_license_start
+ *
+ * \page License
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * 3. The name of Atmel may not be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * 4. This software may only be redistributed and used in connection with an
+ *    Atmel microcontroller product.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
+ * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * \asf_license_stop
+ *
+ */
+#ifndef CLZ_CTH_H
+#define CLZ_CTH_H
+
+/**
+ * \brief Count leading zeros in unsigned integer
+ *
+ * This macro takes unsigned integers of any size, and evaluates to a call to
+ * the clz-function for its size. These functions count the number of zeros,
+ * starting with the MSB, before a one occurs in the integer.
+ *
+ * \param x Unsigned integer to count the leading zeros in.
+ *
+ * \return The number of leading zeros in \a x.
+ */
+#define clz(x)    compiler_demux_size(sizeof(x), clz, (x))
+
+/**
+ * \internal
+ * \brief Count leading zeros in unsigned, 8-bit integer
+ *
+ * \param x Unsigned byte to count the leading zeros in.
+ *
+ * \return The number of leading zeros in \a x.
+ */
+__always_inline static uint8_t
+clz8 (uint8_t x)
+{
+  uint8_t bit = 0;
+
+  if (x & 0xf0)
+    {
+      x >>= 4;
+    }
+  else
+    {
+      bit += 4;
+    }
+
+  if (x & 0x0c)
+    {
+      x >>= 2;
+    }
+  else
+    {
+      bit += 2;
+    }
+
+  if (!(x & 0x02))
+    {
+      bit++;
+    }
+
+  return bit;
+
+}
+
+/**
+ * \internal
+ * \brief Count leading zeros in unsigned, 16-bit integer
+ *
+ * \param x Unsigned word to count the leading zeros in.
+ *
+ * \return The number of leading zeros in \a x.
+ */
+__always_inline static uint8_t
+clz16 (uint16_t x)
+{
+  uint8_t bit = 0;
+
+  if (x & 0xff00)
+    {
+      x >>= 8;
+    }
+  else
+    {
+      bit += 8;
+    }
+
+  return bit + clz8 (x);
+}
+
+/**
+ * \internal
+ * \brief Count leading zeros in unsigned, 32-bit integer
+ *
+ * \param x Unsigned double word to count the leading zeros in.
+ *
+ * \return The number of leading zeros in \a x.
+ */
+__always_inline static uint8_t
+clz32 (uint32_t x)
+{
+  uint8_t bit = 0;
+
+  if (x & 0xffff0000)
+    {
+      x >>= 16;
+    }
+  else
+    {
+      bit += 16;
+    }
+
+  return bit + clz16 (x);
+}
+
+/**
+ * \brief Count trailing zeros in unsigned integer
+ *
+ * This macro takes unsigned integers of any size, and evaluates to a call to
+ * the ctz-function for its size. These functions count the number of zeros,
+ * starting with the LSB, before a one occurs in the integer.
+ *
+ * \param x Unsigned integer to count the trailing zeros in.
+ *
+ * \return The number of trailing zeros in \a x.
+ */
+#define ctz(x)    compiler_demux_size(sizeof(x), ctz, (x))
+
+/**
+ * \internal
+ * \brief Count trailing zeros in unsigned, 8-bit integer
+ *
+ * \param x Unsigned byte to count the trailing zeros in.
+ *
+ * \return The number of leading zeros in \a x.
+ */
+__always_inline static uint8_t
+ctz8 (uint8_t x)
+{
+  uint8_t bit = 0;
+
+  if (!(x & 0x0f))
+    {
+      bit += 4;
+      x >>= 4;
+    }
+  if (!(x & 0x03))
+    {
+      bit += 2;
+      x >>= 2;
+    }
+  if (!(x & 0x01))
+    bit++;
+
+  return bit;
+}
+
+/**
+ * \internal
+ * \brief Count trailing zeros in unsigned, 16-bit integer
+ *
+ * \param x Unsigned word to count the trailing zeros in.
+ *
+ * \return The number of trailing zeros in \a x.
+ */
+__always_inline static uint8_t
+ctz16 (uint16_t x)
+{
+  uint8_t bit = 0;
+
+  if (!(x & 0x00ff))
+    {
+      bit += 8;
+      x >>= 8;
+    }
+
+  return bit + ctz8 (x);
+}
+
+/**
+ * \internal
+ * \brief Count trailing zeros in unsigned, 32-bit integer
+ *
+ * \param x Unsigned double word to count the trailing zeros in.
+ *
+ * \return The number of trailing zeros in \a x.
+ */
+__always_inline static uint8_t
+ctz32 (uint32_t x)
+{
+  uint8_t bit = 0;
+
+  if (!(x & 0x0000ffff))
+    {
+      bit += 16;
+      x >>= 16;
+    }
+
+  return bit + ctz16 (x);
+}
+
+#endif /* CLZ_CTZ_H */