bitmap.c

Lib files of linux kernel

 * 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 *ubuf = 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) | unhex(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()
 *
 * @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 *)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 would be written to buf, if it
 * all fit.
 */
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 would be
 * generated for the given input, excluding the trailing '\0', as
 * per ISO C99.
 */
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
 * @bp: read nul-terminated user string from this buffer
 * @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
 */
int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
{
	unsigned a, b;

	bitmap_zero(maskp, nmaskbits);
	do {
		if (!isdigit(*bp))
			return -EINVAL;
		b = a = simple_strtoul(bp, (char **)&bp, BASEDEC);
		if (*bp == '-') {
			bp++;
			if (!isdigit(*bp))
				return -EINVAL;
			b = simple_strtoul(bp, (char **)&bp, BASEDEC);
		}
		if (!(a <= b))
			return -EINVAL;
		if (b >= nmaskbits)
			return -ERANGE;
		while (a <= b) {
			set_bit(a, maskp);
			a++;
		}
		if (*bp == ',')
			bp++;
	} while (*bp != '\0' && *bp != '\n');
	return 0;
}
EXPORT_SYMBOL(bitmap_parselist);

/**
 * bitmap_pos_to_ord(buf, pos, bits)
 *	@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(buf, ord, bits)
 *	@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.
 */
static 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 (oldbit = find_first_bit(src, bits);
	     oldbit < bits;
	     oldbit = find_next_bit(src, bits, oldbit + 1)) {
	     	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);

/**