source: mainline/uspace/lib/c/generic/capa.c@ bb4d0b5

/*
 * Copyright (c) 2025 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR 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.
 */

/** @addtogroup libc
 * @{
 */
/**
 * @file Storage capacity specification.
 */

#include <assert.h>
#include <capa.h>
#include <errno.h>
#include <imath.h>
#include <stddef.h>
#include <stdio.h>
#include <str.h>

/** Simplified capacity parameters */
enum {
        /** Simplified capacity maximum integer digits */
        scapa_max_idig = 3,
        /** Simplified capacity maximum significant digits */
        scapa_max_sdig = 4
};

static const char *cu_str[] = {
        [cu_byte] = "B",
        [cu_kbyte] = "kB",
        [cu_mbyte] = "MB",
        [cu_gbyte] = "GB",
        [cu_tbyte] = "TB",
        [cu_pbyte] = "PB",
        [cu_ebyte] = "EB",
        [cu_zbyte] = "ZB",
        [cu_ybyte] = "YB"
};

void capa_from_blocks(uint64_t nblocks, size_t block_size, capa_spec_t *capa)
{
        uint64_t tsize;

        tsize = nblocks * block_size;
        capa->m = tsize;
        capa->dp = 0;
        capa->cunit = cu_byte;
}

/** Convert capacity to blocks.
 *
 * If the value of bytes is not integer, it is properly rounded. If the number
 * of bytes is not divisible by the number of blocks, it is rounded
 * up to an integer number of blocks.
 *
 * A capacity value entails precision, i.e. it corresponds to a range
 * of values. @a cvsel selects the value to return. @c cv_nom gives
 * the nominal (middle) value, @c cv_min gives the minimum value
 * and @c cv_max gives the maximum value.
 */
errno_t capa_to_blocks(capa_spec_t *capa, capa_vsel_t cvsel, size_t block_size,
    uint64_t *rblocks)
{
        int exp;
        uint64_t bytes;
        uint64_t f;
        uint64_t adj;
        uint64_t blocks;
        uint64_t rem;
        errno_t rc;

        exp = capa->cunit * 3 - capa->dp;
        if (exp < 0) {
                rc = ipow10_u64(-exp, &f);
                if (rc != EOK)
                        return ERANGE;
                bytes = (capa->m + (f / 2)) / f;
                if (bytes * f - (f / 2) != capa->m)
                        return ERANGE;
        } else {
                rc = ipow10_u64(exp, &f);
                if (rc != EOK)
                        return ERANGE;

                adj = 0;
                switch (cvsel) {
                case cv_nom:
                        adj = 0;
                        break;
                case cv_min:
                        adj = -(f / 2);
                        break;
                case cv_max:
                        adj = f / 2 - 1;
                        break;
                }

                bytes = capa->m * f + adj;
                if ((bytes - adj) / f != capa->m)
                        return ERANGE;
        }

        rem = bytes % block_size;
        if ((bytes + rem) < bytes)
                return ERANGE;

        blocks = (bytes + rem) / block_size;

        *rblocks = blocks;
        return EOK;
}

/** Simplify and round capacity to a human-friendly form.
 *
 * Change unit and round the number so that we have at most three integer
 * digits and at most two fractional digits, e.g abc.xy <unit>.
 */
void capa_simplify(capa_spec_t *capa)
{
        uint64_t div;
        uint64_t maxv;
        unsigned sdig;
        unsigned rdig;
        errno_t rc;

        /* Change units so that we have at most @c scapa_max_idig integer digits */
        rc = ipow10_u64(scapa_max_idig, &maxv);
        assert(rc == EOK);

        rc = ipow10_u64(capa->dp, &div);
        assert(rc == EOK);

        /* Change units until we have no more than scapa_max_idig integer digits */
        while (capa->m / div >= maxv) {
                ++capa->cunit;
                capa->dp += 3;
                div = div * 1000;
        }

        /* Round the number so that we have at most @c scapa_max_sdig significant digits */
        sdig = 1 + ilog10_u64(capa->m); /* number of significant digits */
        if (sdig > scapa_max_sdig) {
                /* Number of digits to remove */
                rdig = sdig - scapa_max_sdig;
                if (rdig > capa->dp)
                        rdig = capa->dp;

                rc = ipow10_u64(rdig, &div);
                assert(rc == EOK);

                /* Division with rounding */
                capa->m = (capa->m + (div / 2)) / div;
                capa->dp -= rdig;
        }

        /*
         * If we rounded up from something like 999.95 to 1000.0,, we still
         * have more than scapa_max_idig integer digits and need to change
         * units once more.
         */
        rc = ipow10_u64(capa->dp, &div);
        assert(rc == EOK);

        if (capa->m / div >= 1000) {
                ++capa->cunit;
                capa->dp += 3;

                /*
                 * We now have one more significant digit than we want
                 * so round to one less digits
                 */
                capa->m = (capa->m + 5) / 10;
                --capa->dp;
        }
}

/** Format capacity as string into a newly allocated buffer.
 *
 * @param capa Capacity
 * @param rstr Place to store pointer to newly allocated string
 * @return EOK on success or an error code
 */
errno_t capa_format(capa_spec_t *capa, char **rstr)
{
        errno_t rc;
        int ret;
        const char *sunit;
        uint64_t ipart;
        uint64_t fpart;
        uint64_t div;

        sunit = NULL;

        assert(capa->cunit < CU_LIMIT);

        rc = ipow10_u64(capa->dp, &div);
        if (rc != EOK)
                return rc;

        ipart = capa->m / div;
        fpart = capa->m % div;

        sunit = cu_str[capa->cunit];
        if (capa->dp > 0) {
                ret = asprintf(rstr, "%" PRIu64 ".%0*" PRIu64 " %s", ipart,
                    (int)capa->dp, fpart, sunit);
        } else {
                ret = asprintf(rstr, "%" PRIu64 " %s", ipart, sunit);
        }

        if (ret < 0)
                return ENOMEM;

        return EOK;
}

/** Format capacity as string into an existing buffer.
 *
 * @param capa Capacity
 * @param buf Buffer for storing string
 * @param bufsize Size of buffer in bytes
 * @return EOK on success or an error code
 */
errno_t capa_format_buf(capa_spec_t *capa, char *buf, size_t bufsize)
{
        errno_t rc;
        const char *sunit;
        uint64_t ipart;
        uint64_t fpart;
        uint64_t div;

        sunit = NULL;

        assert(capa->cunit < CU_LIMIT);

        rc = ipow10_u64(capa->dp, &div);
        if (rc != EOK)
                return rc;

        ipart = capa->m / div;
        fpart = capa->m % div;

        sunit = cu_str[capa->cunit];
        if (capa->dp > 0) {
                snprintf(buf, bufsize, "%" PRIu64 ".%0*" PRIu64 " %s", ipart,
                    (int)capa->dp, fpart, sunit);
        } else {
                snprintf(buf, bufsize, "%" PRIu64 " %s", ipart, sunit);
        }

        return EOK;
}

/** Format capacity of n blocks as string into a newly allocated buffer.
 *
 * This computes the total capacity of the blocks, simplifies it
 * and formats it as string.
 *
 * @param nblocks Number of blocks
 * @param block_size Size of each block in bytes
 * @param rstr Place to store pointer to newly allocated string
 * @return EOK on success or an error code
 */
errno_t capa_blocks_format(uint64_t nblocks, size_t block_size,
    char **rptr)
{
        capa_spec_t capa;

        capa_from_blocks(nblocks, block_size, &capa);
        capa_simplify(&capa);
        return capa_format(&capa, rptr);
}

/** Format capacity of n blocks as string into an existing buffer.
 *
 * This computes the total capacity of the blocks, simplifies it
 * and formats it as string.
 *
 * This function does not return error. If the buffer is too small,
 * the string will be truncated. To make sure it is not truncated,
 * bufsize should be at least CAPA_BLOCKS_BUFSIZE.
 *
 * @param nblocks Number of blocks
 * @param block_size Size of each block in bytes
 * @param buf Buffer for storing string
 * @param bufsize Size of buffer in bytes
 */
void capa_blocks_format_buf(uint64_t nblocks, size_t block_size,
    char *buf, size_t bufsize)
{
        capa_spec_t capa;
        errno_t rc;

        capa_from_blocks(nblocks, block_size, &capa);
        capa_simplify(&capa);

        /* Should not get range error because of nblocks * block_size limits */
        rc = capa_format_buf(&capa, buf, bufsize);
        assert(rc == EOK);
        (void)rc;
}

static errno_t capa_digit_val(char c, int *val)
{
        switch (c) {
        case '0':
                *val = 0;
                break;
        case '1':
                *val = 1;
                break;
        case '2':
                *val = 2;
                break;
        case '3':
                *val = 3;
                break;
        case '4':
                *val = 4;
                break;
        case '5':
                *val = 5;
                break;
        case '6':
                *val = 6;
                break;
        case '7':
                *val = 7;
                break;
        case '8':
                *val = 8;
                break;
        case '9':
                *val = 9;
                break;
        default:
                return EINVAL;
        }

        return EOK;
}

/** Parse string as capacity specification.
 *
 * @param str String (e.g. "100 kB")
 * @param capa Place to store capacity
 * @return EOK on success or an error code
 */
errno_t capa_parse(const char *str, capa_spec_t *capa)
{
        const char *eptr;
        const char *p;
        int d;
        int dp;
        unsigned long m;
        int i;

        m = 0;

        eptr = str;
        while (capa_digit_val(*eptr, &d) == EOK) {
                m = m * 10 + d;
                ++eptr;
        }

        if (*eptr == '.') {
                ++eptr;
                dp = 0;
                while (capa_digit_val(*eptr, &d) == EOK) {
                        m = m * 10 + d;
                        ++dp;
                        ++eptr;
                }
        } else {
                dp = 0;
        }

        while (*eptr == ' ')
                ++eptr;

        if (*eptr == '\0') {
                capa->cunit = cu_byte;
        } else {
                for (i = 0; i < CU_LIMIT; i++) {
                        if (str_lcasecmp(eptr, cu_str[i],
                            str_length(cu_str[i])) == 0) {
                                p = eptr + str_size(cu_str[i]);
                                while (*p == ' ')
                                        ++p;
                                if (*p == '\0')
                                        goto found;
                        }
                }

                return EINVAL;
        found:
                capa->cunit = i;
        }

        capa->m = m;
        capa->dp = dp;
        return EOK;
}

/** @}
 */