// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <helpers/bitmask.h>

/* How many bits in an unsigned long */
#define bitsperlong (8 * sizeof(unsigned long))

/* howmany(a,b) : how many elements of size b needed to hold all of a */
#define howmany(x, y) (((x)+((y)-1))/(y))

/* How many longs in mask of n bits */
#define longsperbits(n) howmany(n, bitsperlong)

#define max(a, b) ((a) > (b) ? (a) : (b))

/*
 * Allocate and free `struct bitmask *`
 */

/* Allocate a new `struct bitmask` with a size of n bits */
struct bitmask *bitmask_alloc(unsigned int n)
{
        struct bitmask *bmp;

        bmp = malloc(sizeof(*bmp));
        if (bmp == 0)
                return 0;
        bmp->size = n;
        bmp->maskp = calloc(longsperbits(n), sizeof(unsigned long));
        if (bmp->maskp == 0) {
                free(bmp);
                return 0;
        }
        return bmp;
}

/* Free `struct bitmask` */
void bitmask_free(struct bitmask *bmp)
{
        if (bmp == 0)
                return;
        free(bmp->maskp);
        bmp->maskp = (unsigned long *)0xdeadcdef;  /* double free tripwire */
        free(bmp);
}

/*
 * The routines _getbit() and _setbit() are the only
 * routines that actually understand the layout of bmp->maskp[].
 *
 * On little endian architectures, this could simply be an array of
 * bytes.  But the kernel layout of bitmasks _is_ visible to userspace
 * via the sched_(set/get)affinity calls in Linux 2.6, and on big
 * endian architectures, it is painfully obvious that this is an
 * array of unsigned longs.
 */

/* Return the value (0 or 1) of bit n in bitmask bmp */
static unsigned int _getbit(const struct bitmask *bmp, unsigned int n)
{
        if (n < bmp->size)
                return (bmp->maskp[n/bitsperlong] >> (n % bitsperlong)) & 1;
        else
                return 0;
}

/* Set bit n in bitmask bmp to value v (0 or 1) */
static void _setbit(struct bitmask *bmp, unsigned int n, unsigned int v)
{
        if (n < bmp->size) {
                if (v)
                        bmp->maskp[n/bitsperlong] |= 1UL << (n % bitsperlong);
                else
                        bmp->maskp[n/bitsperlong] &=
                                ~(1UL << (n % bitsperlong));
        }
}

/*
 * When parsing bitmask lists, only allow numbers, separated by one
 * of the allowed next characters.
 *
 * The parameter 'sret' is the return from a sscanf "%u%c".  It is
 * -1 if the sscanf input string was empty.  It is 0 if the first
 * character in the sscanf input string was not a decimal number.
 * It is 1 if the unsigned number matching the "%u" was the end of the
 * input string.  It is 2 if one or more additional characters followed
 * the matched unsigned number.  If it is 2, then 'nextc' is the first
 * character following the number.  The parameter 'ok_next_chars'
 * is the nul-terminated list of allowed next characters.
 *
 * The mask term just scanned was ok if and only if either the numbers
 * matching the %u were all of the input or if the next character in
 * the input past the numbers was one of the allowed next characters.
 */
static int scan_was_ok(int sret, char nextc, const char *ok_next_chars)
{
        return sret == 1 ||
                (sret == 2 && strchr(ok_next_chars, nextc) != NULL);
}

static const char *nexttoken(const char *q,  int sep)
{
        if (q)
                q = strchr(q, sep);
        if (q)
                q++;
        return q;
}

/* Set a single bit i in bitmask */
struct bitmask *bitmask_setbit(struct bitmask *bmp, unsigned int i)
{
        _setbit(bmp, i, 1);
        return bmp;
}

/* Set all bits in bitmask: bmp = ~0 */
struct bitmask *bitmask_setall(struct bitmask *bmp)
{
        unsigned int i;
        for (i = 0; i < bmp->size; i++)
                _setbit(bmp, i, 1);
        return bmp;
}

/* Clear all bits in bitmask: bmp = 0 */
struct bitmask *bitmask_clearall(struct bitmask *bmp)
{
        unsigned int i;
        for (i = 0; i < bmp->size; i++)
                _setbit(bmp, i, 0);
        return bmp;
}

/* True if all bits are clear */
int bitmask_isallclear(const struct bitmask *bmp)
{
        unsigned int i;
        for (i = 0; i < bmp->size; i++)
                if (_getbit(bmp, i))
                        return 0;
        return 1;
}

/* True if specified bit i is set */
int bitmask_isbitset(const struct bitmask *bmp, unsigned int i)
{
        return _getbit(bmp, i);
}

/* Number of lowest set bit (min) */
unsigned int bitmask_first(const struct bitmask *bmp)
{
        return bitmask_next(bmp, 0);
}

/* Number of highest set bit (max) */
unsigned int bitmask_last(const struct bitmask *bmp)
{
        unsigned int i;
        unsigned int m = bmp->size;
        for (i = 0; i < bmp->size; i++)
                if (_getbit(bmp, i))
                        m = i;
        return m;
}

/* Number of next set bit at or above given bit i */
unsigned int bitmask_next(const struct bitmask *bmp, unsigned int i)
{
        unsigned int n;
        for (n = i; n < bmp->size; n++)
                if (_getbit(bmp, n))
                        break;
        return n;
}

/*
 * Parses a comma-separated list of numbers and ranges of numbers,
 * with optional ':%u' strides modifying ranges, into provided bitmask.
 * Some examples of input lists and their equivalent simple list:
 *      Input           Equivalent to
 *      0-3             0,1,2,3
 *      0-7:2           0,2,4,6
 *      1,3,5-7         1,3,5,6,7
 *      0-3:2,8-15:4    0,2,8,12
 */
int bitmask_parselist(const char *buf, struct bitmask *bmp)
{
        const char *p, *q;

        bitmask_clearall(bmp);

        q = buf;
        while (p = q, q = nexttoken(q, ','), p) {
                unsigned int a;         /* begin of range */
                unsigned int b;         /* end of range */
                unsigned int s;         /* stride */
                const char *c1, *c2;    /* next tokens after '-' or ',' */
                char nextc;             /* char after sscanf %u match */
                int sret;               /* sscanf return (number of matches) */

                sret = sscanf(p, "%u%c", &a, &nextc);
                if (!scan_was_ok(sret, nextc, ",-"))
                        goto err;
                b = a;
                s = 1;
                c1 = nexttoken(p, '-');
                c2 = nexttoken(p, ',');
                if (c1 != NULL && (c2 == NULL || c1 < c2)) {
                        sret = sscanf(c1, "%u%c", &b, &nextc);
                        if (!scan_was_ok(sret, nextc, ",:"))
                                goto err;
                        c1 = nexttoken(c1, ':');
                        if (c1 != NULL && (c2 == NULL || c1 < c2)) {
                                sret = sscanf(c1, "%u%c", &s, &nextc);
                                if (!scan_was_ok(sret, nextc, ","))
                                        goto err;
                        }
                }
                if (!(a <= b))
                        goto err;
                if (b >= bmp->size)
                        goto err;
                while (a <= b) {
                        _setbit(bmp, a, 1);
                        a += s;
                }
        }
        return 0;
err:
        bitmask_clearall(bmp);
        return -1;
}

/*
 * emit(buf, buflen, rbot, rtop, len)
 *
 * Helper routine for bitmask_displaylist().  Write decimal number
 * or range to buf+len, 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 emit(char *buf, int buflen, int rbot, int rtop, int len)
{
        if (len > 0)
                len += snprintf(buf + len, max(buflen - len, 0), ",");
        if (rbot == rtop)
                len += snprintf(buf + len, max(buflen - len, 0), "%d", rbot);
        else
                len += snprintf(buf + len, max(buflen - len, 0), "%d-%d",
                                rbot, rtop);
        return len;
}

/*
 * Write decimal list representation of bmp to buf.
 *
 * 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 bitmask_displaylist(char *buf, int buflen, const struct bitmask *bmp)
{
        int len = 0;
        /* current bit is 'cur', most recently seen range is [rbot, rtop] */
        unsigned int cur, rbot, rtop;

        if (buflen > 0)
                *buf = 0;
        rbot = cur = bitmask_first(bmp);
        while (cur < bmp->size) {
                rtop = cur;
                cur = bitmask_next(bmp, cur+1);
                if (cur >= bmp->size || cur > rtop + 1) {
                        len = emit(buf, buflen, rbot, rtop, len);
                        rbot = cur;
                }
        }
        return len;
}