/*
   * lib/bitmap.c
   * Helper functions for bitmap.h.
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */

  #include <linux/export.h>
  #include <linux/thread_info.h>

  #include <linux/ctype.h>
  #include <linux/errno.h>
  #include <linux/bitmap.h>
  #include <linux/bitops.h>

  #include <linux/bug.h>

  #include <asm/uaccess.h>
  
  /*
   * bitmaps provide an array of bits, implemented using an an
   * array of unsigned longs.  The number of valid bits in a
   * given bitmap does _not_ need to be an exact multiple of
   * BITS_PER_LONG.
   *
   * The possible unused bits in the last, partially used word
   * of a bitmap are 'don't care'.  The implementation makes
   * no particular effort to keep them zero.  It ensures that
   * their value will not affect the results of any operation.
   * The bitmap operations that return Boolean (bitmap_empty,
   * for example) or scalar (bitmap_weight, for example) results
   * carefully filter out these unused bits from impacting their
   * results.
   *
   * These operations actually hold to a slightly stronger rule:
   * if you don't input any bitmaps to these ops that have some
   * unused bits set, then they won't output any set unused bits
   * in output bitmaps.
   *
   * The byte ordering of bitmaps is more natural on little
   * endian architectures.  See the big-endian headers
   * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
   * for the best explanations of this ordering.
   */
  
  int __bitmap_empty(const unsigned long *bitmap, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_empty);
  
  int __bitmap_full(const unsigned long *bitmap, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (~bitmap[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_full);
  
  int __bitmap_equal(const unsigned long *bitmap1,
  		const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] != bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_equal);
  
  void __bitmap_complement(unsigned long *dst, const unsigned long *src, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		dst[k] = ~src[k];
  
  	if (bits % BITS_PER_LONG)
  		dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
  }
  EXPORT_SYMBOL(__bitmap_complement);

  /**

   * __bitmap_shift_right - logical right shift of the bits in a bitmap

   *   @dst : destination bitmap
   *   @src : source bitmap
   *   @shift : shift by this many bits
   *   @bits : bitmap size, in bits

   *
   * Shifting right (dividing) means moving bits in the MS -> LS bit
   * direction.  Zeros are fed into the vacated MS positions and the
   * LS bits shifted off the bottom are lost.
   */
  void __bitmap_shift_right(unsigned long *dst,
  			const unsigned long *src, int shift, int bits)
  {
  	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
  	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
  	unsigned long mask = (1UL << left) - 1;
  	for (k = 0; off + k < lim; ++k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take lower rem bits of
  		 * word above and make them the top rem bits of result.
  		 */
  		if (!rem || off + k + 1 >= lim)
  			upper = 0;
  		else {
  			upper = src[off + k + 1];
  			if (off + k + 1 == lim - 1 && left)
  				upper &= mask;
  		}
  		lower = src[off + k];
  		if (left && off + k == lim - 1)
  			lower &= mask;
  		dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
  		if (left && k == lim - 1)
  			dst[k] &= mask;
  	}
  	if (off)
  		memset(&dst[lim - off], 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_right);

  /**

   * __bitmap_shift_left - logical left shift of the bits in a bitmap

   *   @dst : destination bitmap
   *   @src : source bitmap
   *   @shift : shift by this many bits
   *   @bits : bitmap size, in bits

   *
   * Shifting left (multiplying) means moving bits in the LS -> MS
   * direction.  Zeros are fed into the vacated LS bit positions
   * and those MS bits shifted off the top are lost.
   */
  
  void __bitmap_shift_left(unsigned long *dst,
  			const unsigned long *src, int shift, int bits)
  {
  	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
  	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
  	for (k = lim - off - 1; k >= 0; --k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take upper rem bits of
  		 * word below and make them the bottom rem bits of result.
  		 */
  		if (rem && k > 0)
  			lower = src[k - 1];
  		else
  			lower = 0;
  		upper = src[k];
  		if (left && k == lim - 1)
  			upper &= (1UL << left) - 1;
  		dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
  		if (left && k + off == lim - 1)
  			dst[k + off] &= (1UL << left) - 1;
  	}
  	if (off)
  		memset(dst, 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_left);

  int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);

  	unsigned long result = 0;

  
  	for (k = 0; k < nr; k++)

  		result |= (dst[k] = bitmap1[k] & bitmap2[k]);
  	return result != 0;

  }
  EXPORT_SYMBOL(__bitmap_and);
  
  void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] | bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_or);
  
  void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] ^ bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_xor);

  int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);

  	unsigned long result = 0;

  
  	for (k = 0; k < nr; k++)

  		result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
  	return result != 0;

  }
  EXPORT_SYMBOL(__bitmap_andnot);
  
  int __bitmap_intersects(const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & bitmap2[k])
  			return 1;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 1;
  	return 0;
  }
  EXPORT_SYMBOL(__bitmap_intersects);
  
  int __bitmap_subset(const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & ~bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_subset);

  int __bitmap_weight(const unsigned long *bitmap, int bits)
  {
  	int k, w = 0, lim = bits/BITS_PER_LONG;
  
  	for (k = 0; k < lim; k++)

  		w += hweight_long(bitmap[k]);

  
  	if (bits % BITS_PER_LONG)

  		w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));

  
  	return w;
  }

  EXPORT_SYMBOL(__bitmap_weight);

  void bitmap_set(unsigned long *map, int start, int nr)
  {
  	unsigned long *p = map + BIT_WORD(start);
  	const int size = start + nr;
  	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
  
  	while (nr - bits_to_set >= 0) {
  		*p |= mask_to_set;
  		nr -= bits_to_set;
  		bits_to_set = BITS_PER_LONG;
  		mask_to_set = ~0UL;
  		p++;
  	}
  	if (nr) {
  		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
  		*p |= mask_to_set;
  	}
  }
  EXPORT_SYMBOL(bitmap_set);
  
  void bitmap_clear(unsigned long *map, int start, int nr)
  {
  	unsigned long *p = map + BIT_WORD(start);
  	const int size = start + nr;
  	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
  
  	while (nr - bits_to_clear >= 0) {
  		*p &= ~mask_to_clear;
  		nr -= bits_to_clear;
  		bits_to_clear = BITS_PER_LONG;
  		mask_to_clear = ~0UL;
  		p++;
  	}
  	if (nr) {
  		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
  		*p &= ~mask_to_clear;
  	}
  }
  EXPORT_SYMBOL(bitmap_clear);
  
  /*
   * bitmap_find_next_zero_area - find a contiguous aligned zero area
   * @map: The address to base the search on
   * @size: The bitmap size in bits
   * @start: The bitnumber to start searching at
   * @nr: The number of zeroed bits we're looking for
   * @align_mask: Alignment mask for zero area
   *
   * The @align_mask should be one less than a power of 2; the effect is that
   * the bit offset of all zero areas this function finds is multiples of that
   * power of 2. A @align_mask of 0 means no alignment is required.
   */
  unsigned long bitmap_find_next_zero_area(unsigned long *map,
  					 unsigned long size,
  					 unsigned long start,
  					 unsigned int nr,
  					 unsigned long align_mask)
  {
  	unsigned long index, end, i;
  again:
  	index = find_next_zero_bit(map, size, start);
  
  	/* Align allocation */
  	index = __ALIGN_MASK(index, align_mask);
  
  	end = index + nr;
  	if (end > size)
  		return end;
  	i = find_next_bit(map, end, index);
  	if (i < end) {
  		start = i + 1;
  		goto again;
  	}
  	return index;
  }
  EXPORT_SYMBOL(bitmap_find_next_zero_area);

  /*

   * Bitmap printing & parsing functions: first version by Nadia Yvette Chambers,

   * second version by Paul Jackson, third by Joe Korty.
   */
  
  #define CHUNKSZ				32
  #define nbits_to_hold_value(val)	fls(val)

  #define BASEDEC 10		/* fancier cpuset lists input in decimal */
  
  /**
   * bitmap_scnprintf - convert bitmap to an ASCII hex string.
   * @buf: byte buffer into which string is placed
   * @buflen: reserved size of @buf, in bytes
   * @maskp: pointer to bitmap to convert
   * @nmaskbits: size of bitmap, in bits
   *
   * Exactly @nmaskbits bits are displayed.  Hex digits are grouped into

   * comma-separated sets of eight digits per set.  Returns the number of
   * characters which were written to *buf, excluding the trailing \0.

   */
  int bitmap_scnprintf(char *buf, unsigned int buflen,
  	const unsigned long *maskp, int nmaskbits)
  {
  	int i, word, bit, len = 0;
  	unsigned long val;
  	const char *sep = "";
  	int chunksz;
  	u32 chunkmask;
  
  	chunksz = nmaskbits & (CHUNKSZ - 1);
  	if (chunksz == 0)
  		chunksz = CHUNKSZ;

  	i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;

  	for (; i >= 0; i -= CHUNKSZ) {
  		chunkmask = ((1ULL << chunksz) - 1);
  		word = i / BITS_PER_LONG;
  		bit = i % BITS_PER_LONG;
  		val = (maskp[word] >> bit) & chunkmask;
  		len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
  			(chunksz+3)/4, val);
  		chunksz = CHUNKSZ;
  		sep = ",";
  	}
  	return len;
  }
  EXPORT_SYMBOL(bitmap_scnprintf);
  
  /**

   * __bitmap_parse - convert an ASCII hex string into a bitmap.
   * @buf: pointer to buffer containing string.
   * @buflen: buffer size in bytes.  If string is smaller than this

   *    then it must be terminated with a \0.

   * @is_user: location of buffer, 0 indicates kernel space

   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Commas group hex digits into chunks.  Each chunk defines exactly 32
   * bits of the resultant bitmask.  No chunk may specify a value larger

   * than 32 bits (%-EOVERFLOW), and if a chunk specifies a smaller value
   * then leading 0-bits are prepended.  %-EINVAL is returned for illegal

   * characters and for grouping errors such as "1,,5", ",44", "," and "".
   * Leading and trailing whitespace accepted, but not embedded whitespace.
   */

  int __bitmap_parse(const char *buf, unsigned int buflen,
  		int is_user, unsigned long *maskp,
  		int nmaskbits)

  {
  	int c, old_c, totaldigits, ndigits, nchunks, nbits;
  	u32 chunk;

  	const char __user __force *ubuf = (const char __user __force *)buf;

  
  	bitmap_zero(maskp, nmaskbits);
  
  	nchunks = nbits = totaldigits = c = 0;
  	do {
  		chunk = ndigits = 0;
  
  		/* Get the next chunk of the bitmap */

  		while (buflen) {

  			old_c = c;

  			if (is_user) {
  				if (__get_user(c, ubuf++))
  					return -EFAULT;
  			}
  			else
  				c = *buf++;
  			buflen--;

  			if (isspace(c))
  				continue;
  
  			/*
  			 * If the last character was a space and the current
  			 * character isn't '\0', we've got embedded whitespace.
  			 * This is a no-no, so throw an error.
  			 */
  			if (totaldigits && c && isspace(old_c))
  				return -EINVAL;
  
  			/* A '\0' or a ',' signal the end of the chunk */
  			if (c == '\0' || c == ',')
  				break;
  
  			if (!isxdigit(c))
  				return -EINVAL;
  
  			/*
  			 * Make sure there are at least 4 free bits in 'chunk'.
  			 * If not, this hexdigit will overflow 'chunk', so
  			 * throw an error.
  			 */
  			if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
  				return -EOVERFLOW;

  			chunk = (chunk << 4) | hex_to_bin(c);

  			ndigits++; totaldigits++;
  		}
  		if (ndigits == 0)
  			return -EINVAL;
  		if (nchunks == 0 && chunk == 0)
  			continue;
  
  		__bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
  		*maskp |= chunk;
  		nchunks++;
  		nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
  		if (nbits > nmaskbits)
  			return -EOVERFLOW;

  	} while (buflen && c == ',');

  
  	return 0;
  }

  EXPORT_SYMBOL(__bitmap_parse);
  
  /**

   * bitmap_parse_user - convert an ASCII hex string in a user buffer into a bitmap

   *
   * @ubuf: pointer to user buffer containing string.
   * @ulen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Wrapper for __bitmap_parse(), providing it with user buffer.
   *
   * We cannot have this as an inline function in bitmap.h because it needs
   * linux/uaccess.h to get the access_ok() declaration and this causes
   * cyclic dependencies.
   */
  int bitmap_parse_user(const char __user *ubuf,
  			unsigned int ulen, unsigned long *maskp,
  			int nmaskbits)
  {
  	if (!access_ok(VERIFY_READ, ubuf, ulen))
  		return -EFAULT;

  	return __bitmap_parse((const char __force *)ubuf,
  				ulen, 1, maskp, nmaskbits);

  }
  EXPORT_SYMBOL(bitmap_parse_user);

  
  /*
   * bscnl_emit(buf, buflen, rbot, rtop, bp)
   *
   * Helper routine for bitmap_scnlistprintf().  Write decimal number
   * or range to buf, suppressing output past buf+buflen, with optional

   * comma-prefix.  Return len of what was written to *buf, excluding the
   * trailing \0.

   */
  static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
  {
  	if (len > 0)
  		len += scnprintf(buf + len, buflen - len, ",");
  	if (rbot == rtop)
  		len += scnprintf(buf + len, buflen - len, "%d", rbot);
  	else
  		len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
  	return len;
  }
  
  /**
   * bitmap_scnlistprintf - convert bitmap to list format ASCII string
   * @buf: byte buffer into which string is placed
   * @buflen: reserved size of @buf, in bytes
   * @maskp: pointer to bitmap to convert
   * @nmaskbits: size of bitmap, in bits
   *
   * Output format is a comma-separated list of decimal numbers and
   * ranges.  Consecutively set bits are shown as two hyphen-separated
   * decimal numbers, the smallest and largest bit numbers set in
   * the range.  Output format is compatible with the format
   * accepted as input by bitmap_parselist().
   *

   * The return value is the number of characters which were written to *buf
   * excluding the trailing '\0', as per ISO C99's scnprintf.

   */
  int bitmap_scnlistprintf(char *buf, unsigned int buflen,
  	const unsigned long *maskp, int nmaskbits)
  {
  	int len = 0;
  	/* current bit is 'cur', most recently seen range is [rbot, rtop] */
  	int cur, rbot, rtop;

  	if (buflen == 0)
  		return 0;
  	buf[0] = 0;

  	rbot = cur = find_first_bit(maskp, nmaskbits);
  	while (cur < nmaskbits) {
  		rtop = cur;
  		cur = find_next_bit(maskp, nmaskbits, cur+1);
  		if (cur >= nmaskbits || cur > rtop + 1) {
  			len = bscnl_emit(buf, buflen, rbot, rtop, len);
  			rbot = cur;
  		}
  	}
  	return len;
  }
  EXPORT_SYMBOL(bitmap_scnlistprintf);
  
  /**

   * __bitmap_parselist - convert list format ASCII string to bitmap

   * @buf: read nul-terminated user string from this buffer

   * @buflen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @is_user: location of buffer, 0 indicates kernel space

   * @maskp: write resulting mask here

   * @nmaskbits: number of bits in mask to be written
   *
   * Input format is a comma-separated list of decimal numbers and
   * ranges.  Consecutively set bits are shown as two hyphen-separated
   * decimal numbers, the smallest and largest bit numbers set in
   * the range.
   *

   * Returns 0 on success, -errno on invalid input strings.
   * Error values:
   *    %-EINVAL: second number in range smaller than first
   *    %-EINVAL: invalid character in string
   *    %-ERANGE: bit number specified too large for mask

   */

  static int __bitmap_parselist(const char *buf, unsigned int buflen,
  		int is_user, unsigned long *maskp,
  		int nmaskbits)

  {
  	unsigned a, b;

  	int c, old_c, totaldigits;

  	const char __user __force *ubuf = (const char __user __force *)buf;

  	int exp_digit, in_range;

  	totaldigits = c = 0;

  	bitmap_zero(maskp, nmaskbits);
  	do {

  		exp_digit = 1;
  		in_range = 0;
  		a = b = 0;
  
  		/* Get the next cpu# or a range of cpu#'s */
  		while (buflen) {
  			old_c = c;
  			if (is_user) {
  				if (__get_user(c, ubuf++))
  					return -EFAULT;
  			} else
  				c = *buf++;
  			buflen--;
  			if (isspace(c))
  				continue;
  
  			/*
  			 * If the last character was a space and the current
  			 * character isn't '\0', we've got embedded whitespace.
  			 * This is a no-no, so throw an error.
  			 */
  			if (totaldigits && c && isspace(old_c))
  				return -EINVAL;
  
  			/* A '\0' or a ',' signal the end of a cpu# or range */
  			if (c == '\0' || c == ',')
  				break;
  
  			if (c == '-') {
  				if (exp_digit || in_range)
  					return -EINVAL;
  				b = 0;
  				in_range = 1;
  				exp_digit = 1;
  				continue;
  			}
  
  			if (!isdigit(c))

  				return -EINVAL;

  
  			b = b * 10 + (c - '0');
  			if (!in_range)
  				a = b;
  			exp_digit = 0;
  			totaldigits++;

  		}
  		if (!(a <= b))
  			return -EINVAL;
  		if (b >= nmaskbits)
  			return -ERANGE;
  		while (a <= b) {
  			set_bit(a, maskp);
  			a++;
  		}

  	} while (buflen && c == ',');

  	return 0;
  }

  
  int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
  {
  	char *nl  = strchr(bp, '
  ');
  	int len;
  
  	if (nl)
  		len = nl - bp;
  	else
  		len = strlen(bp);
  
  	return __bitmap_parselist(bp, len, 0, maskp, nmaskbits);
  }

  EXPORT_SYMBOL(bitmap_parselist);

  
  /**
   * bitmap_parselist_user()
   *
   * @ubuf: pointer to user buffer containing string.
   * @ulen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Wrapper for bitmap_parselist(), providing it with user buffer.
   *
   * We cannot have this as an inline function in bitmap.h because it needs
   * linux/uaccess.h to get the access_ok() declaration and this causes
   * cyclic dependencies.
   */
  int bitmap_parselist_user(const char __user *ubuf,
  			unsigned int ulen, unsigned long *maskp,
  			int nmaskbits)
  {
  	if (!access_ok(VERIFY_READ, ubuf, ulen))
  		return -EFAULT;

  	return __bitmap_parselist((const char __force *)ubuf,

  					ulen, 1, maskp, nmaskbits);
  }
  EXPORT_SYMBOL(bitmap_parselist_user);

  /**

   * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap

   *	@buf: pointer to a bitmap
   *	@pos: a bit position in @buf (0 <= @pos < @bits)
   *	@bits: number of valid bit positions in @buf
   *
   * Map the bit at position @pos in @buf (of length @bits) to the
   * ordinal of which set bit it is.  If it is not set or if @pos

   * is not a valid bit position, map to -1.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @pos
   * values 4 through 7 will get mapped to 0 through 3, respectively,
   * and other @pos values will get mapped to 0.  When @pos value 7
   * gets mapped to (returns) @ord value 3 in this example, that means
   * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
   *
   * The bit positions 0 through @bits are valid positions in @buf.
   */
  static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
  {

  	int i, ord;

  	if (pos < 0 || pos >= bits || !test_bit(pos, buf))
  		return -1;

  	i = find_first_bit(buf, bits);
  	ord = 0;
  	while (i < pos) {
  		i = find_next_bit(buf, bits, i + 1);
  	     	ord++;

  	}

  	BUG_ON(i != pos);

  	return ord;
  }
  
  /**

   * bitmap_ord_to_pos - find position of n-th set bit in bitmap

   *	@buf: pointer to bitmap
   *	@ord: ordinal bit position (n-th set bit, n >= 0)
   *	@bits: number of valid bit positions in @buf
   *
   * Map the ordinal offset of bit @ord in @buf to its position in @buf.

   * Value of @ord should be in range 0 <= @ord < weight(buf), else
   * results are undefined.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @ord
   * values 0 through 3 will get mapped to 4 through 7, respectively,

   * and all other @ord values return undefined values.  When @ord value 3

   * gets mapped to (returns) @pos value 7 in this example, that means
   * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
   *
   * The bit positions 0 through @bits are valid positions in @buf.
   */

  int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)

  {
  	int pos = 0;
  
  	if (ord >= 0 && ord < bits) {
  		int i;
  
  		for (i = find_first_bit(buf, bits);
  		     i < bits && ord > 0;
  		     i = find_next_bit(buf, bits, i + 1))
  	     		ord--;
  		if (i < bits && ord == 0)
  			pos = i;
  	}
  
  	return pos;
  }
  
  /**
   * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap

   *	@dst: remapped result

   *	@src: subset to be remapped

   *	@old: defines domain of map
   *	@new: defines range of map
   *	@bits: number of bits in each of these bitmaps
   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * If either of the @old and @new bitmaps are empty, or if @src and
   * @dst point to the same location, then this routine copies @src
   * to @dst.

   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to @src, placing the result in
   * @dst, clearing any bits previously set in @dst.
   *

   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @src comes into this routine
   * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
   * 13 and 15 set.

   */
  void bitmap_remap(unsigned long *dst, const unsigned long *src,
  		const unsigned long *old, const unsigned long *new,
  		int bits)
  {

  	int oldbit, w;

  	if (dst == src)		/* following doesn't handle inplace remaps */
  		return;

  	bitmap_zero(dst, bits);

  
  	w = bitmap_weight(new, bits);

  	for_each_set_bit(oldbit, src, bits) {

  	     	int n = bitmap_pos_to_ord(old, oldbit, bits);

  		if (n < 0 || w == 0)
  			set_bit(oldbit, dst);	/* identity map */
  		else
  			set_bit(bitmap_ord_to_pos(new, n % w, bits), dst);

  	}
  }
  EXPORT_SYMBOL(bitmap_remap);
  
  /**
   * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit

   *	@oldbit: bit position to be mapped
   *	@old: defines domain of map
   *	@new: defines range of map
   *	@bits: number of bits in each of these bitmaps

   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to bit position @oldbit, returning
   * the new bit position.
   *
   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @oldbit is 5, then this routine
   * returns 13.

   */
  int bitmap_bitremap(int oldbit, const unsigned long *old,
  				const unsigned long *new, int bits)
  {

  	int w = bitmap_weight(new, bits);
  	int n = bitmap_pos_to_ord(old, oldbit, bits);
  	if (n < 0 || w == 0)
  		return oldbit;
  	else
  		return bitmap_ord_to_pos(new, n % w, bits);

  }
  EXPORT_SYMBOL(bitmap_bitremap);

  /**
   * bitmap_onto - translate one bitmap relative to another
   *	@dst: resulting translated bitmap
   * 	@orig: original untranslated bitmap
   * 	@relmap: bitmap relative to which translated
   *	@bits: number of bits in each of these bitmaps
   *
   * Set the n-th bit of @dst iff there exists some m such that the
   * n-th bit of @relmap is set, the m-th bit of @orig is set, and
   * the n-th bit of @relmap is also the m-th _set_ bit of @relmap.
   * (If you understood the previous sentence the first time your
   * read it, you're overqualified for your current job.)
   *
   * In other words, @orig is mapped onto (surjectively) @dst,
   * using the the map { <n, m> | the n-th bit of @relmap is the
   * m-th set bit of @relmap }.
   *
   * Any set bits in @orig above bit number W, where W is the
   * weight of (number of set bits in) @relmap are mapped nowhere.
   * In particular, if for all bits m set in @orig, m >= W, then
   * @dst will end up empty.  In situations where the possibility
   * of such an empty result is not desired, one way to avoid it is
   * to use the bitmap_fold() operator, below, to first fold the
   * @orig bitmap over itself so that all its set bits x are in the
   * range 0 <= x < W.  The bitmap_fold() operator does this by
   * setting the bit (m % W) in @dst, for each bit (m) set in @orig.
   *
   * Example [1] for bitmap_onto():
   *  Let's say @relmap has bits 30-39 set, and @orig has bits
   *  1, 3, 5, 7, 9 and 11 set.  Then on return from this routine,
   *  @dst will have bits 31, 33, 35, 37 and 39 set.
   *
   *  When bit 0 is set in @orig, it means turn on the bit in
   *  @dst corresponding to whatever is the first bit (if any)
   *  that is turned on in @relmap.  Since bit 0 was off in the
   *  above example, we leave off that bit (bit 30) in @dst.
   *
   *  When bit 1 is set in @orig (as in the above example), it
   *  means turn on the bit in @dst corresponding to whatever
   *  is the second bit that is turned on in @relmap.  The second
   *  bit in @relmap that was turned on in the above example was
   *  bit 31, so we turned on bit 31 in @dst.
   *
   *  Similarly, we turned on bits 33, 35, 37 and 39 in @dst,
   *  because they were the 4th, 6th, 8th and 10th set bits
   *  set in @relmap, and the 4th, 6th, 8th and 10th bits of
   *  @orig (i.e. bits 3, 5, 7 and 9) were also set.
   *
   *  When bit 11 is set in @orig, it means turn on the bit in

   *  @dst corresponding to whatever is the twelfth bit that is

   *  turned on in @relmap.  In the above example, there were
   *  only ten bits turned on in @relmap (30..39), so that bit
   *  11 was set in @orig had no affect on @dst.
   *
   * Example [2] for bitmap_fold() + bitmap_onto():
   *  Let's say @relmap has these ten bits set:
   *		40 41 42 43 45 48 53 61 74 95
   *  (for the curious, that's 40 plus the first ten terms of the
   *  Fibonacci sequence.)
   *
   *  Further lets say we use the following code, invoking
   *  bitmap_fold() then bitmap_onto, as suggested above to
   *  avoid the possitility of an empty @dst result:
   *
   *	unsigned long *tmp;	// a temporary bitmap's bits
   *
   *	bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits);
   *	bitmap_onto(dst, tmp, relmap, bits);
   *
   *  Then this table shows what various values of @dst would be, for
   *  various @orig's.  I list the zero-based positions of each set bit.
   *  The tmp column shows the intermediate result, as computed by
   *  using bitmap_fold() to fold the @orig bitmap modulo ten
   *  (the weight of @relmap).
   *
   *      @orig           tmp            @dst
   *      0                0             40
   *      1                1             41
   *      9                9             95
   *      10               0             40 (*)
   *      1 3 5 7          1 3 5 7       41 43 48 61
   *      0 1 2 3 4        0 1 2 3 4     40 41 42 43 45
   *      0 9 18 27        0 9 8 7       40 61 74 95
   *      0 10 20 30       0             40
   *      0 11 22 33       0 1 2 3       40 41 42 43
   *      0 12 24 36       0 2 4 6       40 42 45 53
   *      78 102 211       1 2 8         41 42 74 (*)
   *
   * (*) For these marked lines, if we hadn't first done bitmap_fold()
   *     into tmp, then the @dst result would have been empty.
   *
   * If either of @orig or @relmap is empty (no set bits), then @dst
   * will be returned empty.
   *
   * If (as explained above) the only set bits in @orig are in positions
   * m where m >= W, (where W is the weight of @relmap) then @dst will
   * once again be returned empty.
   *
   * All bits in @dst not set by the above rule are cleared.
   */
  void bitmap_onto(unsigned long *dst, const unsigned long *orig,
  			const unsigned long *relmap, int bits)
  {
  	int n, m;       	/* same meaning as in above comment */
  
  	if (dst == orig)	/* following doesn't handle inplace mappings */
  		return;
  	bitmap_zero(dst, bits);
  
  	/*
  	 * The following code is a more efficient, but less
  	 * obvious, equivalent to the loop:
  	 *	for (m = 0; m < bitmap_weight(relmap, bits); m++) {
  	 *		n = bitmap_ord_to_pos(orig, m, bits);
  	 *		if (test_bit(m, orig))
  	 *			set_bit(n, dst);
  	 *	}
  	 */
  
  	m = 0;

  	for_each_set_bit(n, relmap, bits) {

  		/* m == bitmap_pos_to_ord(relmap, n, bits) */
  		if (test_bit(m, orig))
  			set_bit(n, dst);
  		m++;
  	}
  }
  EXPORT_SYMBOL(bitmap_onto);
  
  /**
   * bitmap_fold - fold larger bitmap into smaller, modulo specified size
   *	@dst: resulting smaller bitmap
   *	@orig: original larger bitmap
   *	@sz: specified size
   *	@bits: number of bits in each of these bitmaps
   *
   * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst.
   * Clear all other bits in @dst.  See further the comment and
   * Example [2] for bitmap_onto() for why and how to use this.
   */
  void bitmap_fold(unsigned long *dst, const unsigned long *orig,
  			int sz, int bits)
  {
  	int oldbit;
  
  	if (dst == orig)	/* following doesn't handle inplace mappings */
  		return;
  	bitmap_zero(dst, bits);

  	for_each_set_bit(oldbit, orig, bits)

  		set_bit(oldbit % sz, dst);
  }
  EXPORT_SYMBOL(bitmap_fold);

  /*
   * Common code for bitmap_*_region() routines.
   *	bitmap: array of unsigned longs corresponding to the bitmap
   *	pos: the beginning of the region
   *	order: region size (log base 2 of number of bits)
   *	reg_op: operation(s) to perform on that region of bitmap

   *

   * Can set, verify and/or release a region of bits in a bitmap,
   * depending on which combination of REG_OP_* flag bits is set.

   *

   * A region of a bitmap is a sequence of bits in the bitmap, of
   * some size '1 << order' (a power of two), aligned to that same
   * '1 << order' power of two.
   *
   * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits).
   * Returns 0 in all other cases and reg_ops.

   */

  
  enum {
  	REG_OP_ISFREE,		/* true if region is all zero bits */
  	REG_OP_ALLOC,		/* set all bits in region */
  	REG_OP_RELEASE,		/* clear all bits in region */
  };
  
  static int __reg_op(unsigned long *bitmap, int pos, int order, int reg_op)

  {

  	int nbits_reg;		/* number of bits in region */
  	int index;		/* index first long of region in bitmap */
  	int offset;		/* bit offset region in bitmap[index] */
  	int nlongs_reg;		/* num longs spanned by region in bitmap */

  	int nbitsinlong;	/* num bits of region in each spanned long */

  	unsigned long mask;	/* bitmask for one long of region */

  	int i;			/* scans bitmap by longs */

  	int ret = 0;		/* return value */

  	/*
  	 * Either nlongs_reg == 1 (for small orders that fit in one long)
  	 * or (offset == 0 && mask == ~0UL) (for larger multiword orders.)
  	 */
  	nbits_reg = 1 << order;
  	index = pos / BITS_PER_LONG;
  	offset = pos - (index * BITS_PER_LONG);
  	nlongs_reg = BITS_TO_LONGS(nbits_reg);
  	nbitsinlong = min(nbits_reg,  BITS_PER_LONG);

  	/*
  	 * Can't do "mask = (1UL << nbitsinlong) - 1", as that
  	 * overflows if nbitsinlong == BITS_PER_LONG.
  	 */

  	mask = (1UL << (nbitsinlong - 1));

  	mask += mask - 1;

  	mask <<= offset;

  	switch (reg_op) {
  	case REG_OP_ISFREE:
  		for (i = 0; i < nlongs_reg; i++) {
  			if (bitmap[index + i] & mask)
  				goto done;
  		}
  		ret = 1;	/* all bits in region free (zero) */
  		break;
  
  	case REG_OP_ALLOC:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] |= mask;
  		break;
  
  	case REG_OP_RELEASE:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] &= ~mask;
  		break;

  	}

  done:
  	return ret;
  }
  
  /**
   * bitmap_find_free_region - find a contiguous aligned mem region
   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@bits: number of bits in the bitmap
   *	@order: region size (log base 2 of number of bits) to find
   *
   * Find a region of free (zero) bits in a @bitmap of @bits bits and
   * allocate them (set them to one).  Only consider regions of length
   * a power (@order) of two, aligned to that power of two, which
   * makes the search algorithm much faster.
   *
   * Return the bit offset in bitmap of the allocated region,
   * or -errno on failure.
   */
  int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
  {

  	int pos, end;		/* scans bitmap by regions of size order */
  
  	for (pos = 0 ; (end = pos + (1 << order)) <= bits; pos = end) {
  		if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  			continue;
  		__reg_op(bitmap, pos, order, REG_OP_ALLOC);
  		return pos;
  	}
  	return -ENOMEM;

  }
  EXPORT_SYMBOL(bitmap_find_free_region);
  
  /**

   * bitmap_release_region - release allocated bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to release
   *	@order: region size (log base 2 of number of bits) to release

   *

   * This is the complement to __bitmap_find_free_region() and releases

   * the found region (by clearing it in the bitmap).

   *
   * No return value.

   */
  void bitmap_release_region(unsigned long *bitmap, int pos, int order)
  {

  	__reg_op(bitmap, pos, order, REG_OP_RELEASE);

  }
  EXPORT_SYMBOL(bitmap_release_region);

  /**
   * bitmap_allocate_region - allocate bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to allocate
   *	@order: region size (log base 2 of number of bits) to allocate

   *
   * Allocate (set bits in) a specified region of a bitmap.

   *

   * Return 0 on success, or %-EBUSY if specified region wasn't

   * free (not all bits were zero).
   */

  int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)
  {

  	if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  		return -EBUSY;
  	__reg_op(bitmap, pos, order, REG_OP_ALLOC);

  	return 0;
  }
  EXPORT_SYMBOL(bitmap_allocate_region);

  
  /**
   * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
   * @dst:   destination buffer
   * @src:   bitmap to copy
   * @nbits: number of bits in the bitmap
   *
   * Require nbits % BITS_PER_LONG == 0.
   */
  void bitmap_copy_le(void *dst, const unsigned long *src, int nbits)
  {
  	unsigned long *d = dst;
  	int i;
  
  	for (i = 0; i < nbits/BITS_PER_LONG; i++) {
  		if (BITS_PER_LONG == 64)
  			d[i] = cpu_to_le64(src[i]);
  		else
  			d[i] = cpu_to_le32(src[i]);
  	}
  }
  EXPORT_SYMBOL(bitmap_copy_le);