per_support.c

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/*
 * Copyright (c) 2005-2014 Lev Walkin <vlm@lionet.info>.
 * All rights reserved.
 * Redistribution and modifications are permitted subject to BSD license.
 */
#include <asn_system.h>
#include <asn_internal.h>
#include <per_support.h>

char *
per_data_string(asn_per_data_t *pd) {
    static char buf[2][32];
    static int n;
    n = (n+1) % 2;
    snprintf(buf[n], sizeof(buf),
        "{m=%ld span %+ld[%d..%d] (%d)}",
        (long)pd->moved,
        (((long)pd->buffer) & 0xf),
        (int)pd->nboff, (int)pd->nbits,
        (int)(pd->nbits - pd->nboff));
    return buf[n];
}

void
per_get_undo(asn_per_data_t *pd, int nbits) {
    if((ssize_t)pd->nboff < nbits) {
        assert((ssize_t)pd->nboff < nbits);
    } else {
        pd->nboff -= nbits;
        pd->moved -= nbits;
    }
}

/*
 * Extract a small number of bits (<= 31) from the specified PER data pointer.
 */
int32_t
per_get_few_bits(asn_per_data_t *pd, int nbits) {
    size_t off; /* Next after last bit offset */
    ssize_t nleft;  /* Number of bits left in this stream */
    uint32_t accum;
    const uint8_t *buf;

    if(nbits < 0)
        return -1;

    nleft = pd->nbits - pd->nboff;
    if(nbits > nleft) {
        int32_t tailv, vhead;
        if(!pd->refill || nbits > 31) return -1;
        /* Accumulate unused bytes before refill */
        ASN_DEBUG("Obtain the rest %d bits (want %d)",
            (int)nleft, (int)nbits);
        tailv = per_get_few_bits(pd, nleft);
        if(tailv < 0) return -1;
        /* Refill (replace pd contents with new data) */
        if(pd->refill(pd))
            return -1;
        nbits -= nleft;
        vhead = per_get_few_bits(pd, nbits);
        /* Combine the rest of previous pd with the head of new one */
        tailv = (tailv << nbits) | vhead;  /* Could == -1 */
        return tailv;
    }

    /*
     * Normalize position indicator.
     */
    if(pd->nboff >= 8) {
        pd->buffer += (pd->nboff >> 3);
        pd->nbits  -= (pd->nboff & ~0x07);
        pd->nboff  &= 0x07;
    }
    pd->moved += nbits;
    pd->nboff += nbits;
    off = pd->nboff;
    buf = pd->buffer;

    /*
     * Extract specified number of bits.
     */
    if(off <= 8)
        accum = nbits ? (buf[0]) >> (8 - off) : 0;
    else if(off <= 16)
        accum = ((buf[0] << 8) + buf[1]) >> (16 - off);
    else if(off <= 24)
        accum = ((buf[0] << 16) + (buf[1] << 8) + buf[2]) >> (24 - off);
    else if(off <= 31)
        accum = ((buf[0] << 24) + (buf[1] << 16)
            + (buf[2] << 8) + (buf[3])) >> (32 - off);
    else if(nbits <= 31) {
        asn_per_data_t tpd = *pd;
        /* Here are we with our 31-bits limit plus 1..7 bits offset. */
        per_get_undo(&tpd, nbits);
        /* The number of available bits in the stream allow
         * for the following operations to take place without
         * invoking the ->refill() function */
        accum  = per_get_few_bits(&tpd, nbits - 24) << 24;
        accum |= per_get_few_bits(&tpd, 24);
    } else {
        per_get_undo(pd, nbits);
        return -1;
    }

    accum &= (((uint32_t)1 << nbits) - 1);

    ASN_DEBUG("  [PER got %2d<=%2d bits => span %d %+ld[%d..%d]:%02x (%d) => 0x%x]",
        (int)nbits, (int)nleft,
        (int)pd->moved,
        (((long)pd->buffer) & 0xf),
        (int)pd->nboff, (int)pd->nbits,
        pd->buffer[0],
        (int)(pd->nbits - pd->nboff),
        (int)accum);

    return accum;
}

/*
 * Extract a large number of bits from the specified PER data pointer.
 */
int
per_get_many_bits(asn_per_data_t *pd, uint8_t *dst, int alright, int nbits) {
    int32_t value;

    if(alright && (nbits & 7)) {
        /* Perform right alignment of a first few bits */
        value = per_get_few_bits(pd, nbits & 0x07);
        if(value < 0) return -1;
        *dst++ = value; /* value is already right-aligned */
        nbits &= ~7;
    }

    while(nbits) {
        if(nbits >= 24) {
            value = per_get_few_bits(pd, 24);
            if(value < 0) return -1;
            *(dst++) = value >> 16;
            *(dst++) = value >> 8;
            *(dst++) = value;
            nbits -= 24;
        } else {
            value = per_get_few_bits(pd, nbits);
            if(value < 0) return -1;
            if(nbits & 7) { /* implies left alignment */
                value <<= 8 - (nbits & 7),
                nbits += 8 - (nbits & 7);
                if(nbits > 24)
                    *dst++ = value >> 24;
            }
            if(nbits > 16)
                *dst++ = value >> 16;
            if(nbits > 8)
                *dst++ = value >> 8;
            *dst++ = value;
            break;
        }
    }

    return 0;
}

/*
 * Get the length "n" from the stream.
 */
ssize_t
uper_get_length(asn_per_data_t *pd, int ebits, int *repeat) {
    ssize_t value;

    *repeat = 0;

    if(ebits >= 0) return per_get_few_bits(pd, ebits);

    value = per_get_few_bits(pd, 8);
    if(value < 0) return -1;
    if((value & 128) == 0)  /* #10.9.3.6 */
        return (value & 0x7F);
    if((value & 64) == 0) { /* #10.9.3.7 */
        value = ((value & 63) << 8) | per_get_few_bits(pd, 8);
        if(value < 0) return -1;
        return value;
    }
    value &= 63;    /* this is "m" from X.691, #10.9.3.8 */
    if(value < 1 || value > 4)
        return -1;
    *repeat = 1;
    return (16384 * value);
}

/*
 * Get the normally small length "n".
 * This procedure used to decode length of extensions bit-maps
 * for SET and SEQUENCE types.
 */
ssize_t
uper_get_nslength(asn_per_data_t *pd) {
    ssize_t length;

    ASN_DEBUG("Getting normally small length");

    if(per_get_few_bits(pd, 1) == 0) {
        length = per_get_few_bits(pd, 6) + 1;
        if(length <= 0) return -1;
        ASN_DEBUG("l=%d", (int)length);
        return length;
    } else {
        int repeat;
        length = uper_get_length(pd, -1, &repeat);
        if(length >= 0 && !repeat) return length;
        return -1; /* Error, or do not support >16K extensions */
    }
}

/*
 * Get the normally small non-negative whole number.
 * X.691, #10.6
 */
ssize_t
uper_get_nsnnwn(asn_per_data_t *pd) {
    ssize_t value;

    value = per_get_few_bits(pd, 7);
    if(value & 64) {    /* implicit (value < 0) */
        value &= 63;
        value <<= 2;
        value |= per_get_few_bits(pd, 2);
        if(value & 128) /* implicit (value < 0) */
            return -1;
        if(value == 0)
            return 0;
        if(value >= 3)
            return -1;
        value = per_get_few_bits(pd, 8 * value);
        return value;
    }

    return value;
}

/*
 * X.691-11/2008, #11.6
 * Encoding of a normally small non-negative whole number
 */
int
uper_put_nsnnwn(asn_per_outp_t *po, int n) {
    int bytes;

    if(n <= 63) {
        if(n < 0) return -1;
        return per_put_few_bits(po, n, 7);
    }
    if(n < 256)
        bytes = 1;
    else if(n < 65536)
        bytes = 2;
    else if(n < 256 * 65536)
        bytes = 3;
    else
        return -1;  /* This is not a "normally small" value */
    if(per_put_few_bits(po, bytes, 8))
        return -1;

    return per_put_few_bits(po, n, 8 * bytes);
}


/* X.691-2008/11, #11.5.6 -> #11.3 */
int uper_get_constrained_whole_number(asn_per_data_t *pd, unsigned long *out_value, int nbits) {
    unsigned long lhalf;    /* Lower half of the number*/
    long half;

    if(nbits <= 31) {
        half = per_get_few_bits(pd, nbits);
        if(half < 0) return -1;
        *out_value = half;
        return 0;
    }

    if((size_t)nbits > 8 * sizeof(*out_value))
        return -1;  /* RANGE */

    half = per_get_few_bits(pd, 31);
    if(half < 0) return -1;

    if(uper_get_constrained_whole_number(pd, &lhalf, nbits - 31))
        return -1;

    *out_value = ((unsigned long)half << (nbits - 31)) | lhalf;
    return 0;
}


/* X.691-2008/11, #11.5.6 -> #11.3 */
int uper_put_constrained_whole_number_s(asn_per_outp_t *po, long v, int nbits) {
    /*
     * Assume signed number can be safely coerced into
     * unsigned of the same range.
     * The following testing code will likely be optimized out
     * by compiler if it is true.
     */
    unsigned long uvalue1 = ULONG_MAX;
             long svalue  = uvalue1;
    unsigned long uvalue2 = svalue;
    assert(uvalue1 == uvalue2);
    return uper_put_constrained_whole_number_u(po, v, nbits);
}

int uper_put_constrained_whole_number_u(asn_per_outp_t *po, unsigned long v, int nbits) {
    if(nbits <= 31) {
        return per_put_few_bits(po, v, nbits);
    } else {
        /* Put higher portion first, followed by lower 31-bit */
        if(uper_put_constrained_whole_number_u(po, v >> 31, nbits - 31))
            return -1;
        return per_put_few_bits(po, v, 31);
    }
}

/*
 * Put a small number of bits (<= 31).
 */
int
per_put_few_bits(asn_per_outp_t *po, uint32_t bits, int obits) {
    size_t off; /* Next after last bit offset */
    size_t omsk;    /* Existing last byte meaningful bits mask */
    uint8_t *buf;

    if(obits <= 0 || obits >= 32) return obits ? -1 : 0;

    ASN_DEBUG("[PER put %d bits %x to %p+%d bits]",
            obits, (int)bits, po->buffer, (int)po->nboff);

    /*
     * Normalize position indicator.
     */
    if(po->nboff >= 8) {
        po->buffer += (po->nboff >> 3);
        po->nbits  -= (po->nboff & ~0x07);
        po->nboff  &= 0x07;
    }

    /*
     * Flush whole-bytes output, if necessary.
     */
    if(po->nboff + obits > po->nbits) {
        int complete_bytes = (po->buffer - po->tmpspace);
        ASN_DEBUG("[PER output %ld complete + %ld]",
            (long)complete_bytes, (long)po->flushed_bytes);
        if(po->outper(po->tmpspace, complete_bytes, po->op_key) < 0)
            return -1;
        if(po->nboff)
            po->tmpspace[0] = po->buffer[0];
        po->buffer = po->tmpspace;
        po->nbits = 8 * sizeof(po->tmpspace);
        po->flushed_bytes += complete_bytes;
    }

    /*
     * Now, due to sizeof(tmpspace), we are guaranteed large enough space.
     */
    buf = po->buffer;
    omsk = ~((1 << (8 - po->nboff)) - 1);
    off = (po->nboff + obits);

    /* Clear data of debris before meaningful bits */
    bits &= (((uint32_t)1 << obits) - 1);

    ASN_DEBUG("[PER out %d %u/%x (t=%d,o=%d) %x&%x=%x]", obits,
        (int)bits, (int)bits,
        (int)po->nboff, (int)off,
        buf[0], (int)(omsk&0xff),
        (int)(buf[0] & omsk));

    if(off <= 8)    /* Completely within 1 byte */
        po->nboff = off,
        bits <<= (8 - off),
        buf[0] = (buf[0] & omsk) | bits;
    else if(off <= 16)
        po->nboff = off,
        bits <<= (16 - off),
        buf[0] = (buf[0] & omsk) | (bits >> 8),
        buf[1] = bits;
    else if(off <= 24)
        po->nboff = off,
        bits <<= (24 - off),
        buf[0] = (buf[0] & omsk) | (bits >> 16),
        buf[1] = bits >> 8,
        buf[2] = bits;
    else if(off <= 31)
        po->nboff = off,
        bits <<= (32 - off),
        buf[0] = (buf[0] & omsk) | (bits >> 24),
        buf[1] = bits >> 16,
        buf[2] = bits >> 8,
        buf[3] = bits;
    else {
        per_put_few_bits(po, bits >> (obits - 24), 24);
        per_put_few_bits(po, bits, obits - 24);
    }

    ASN_DEBUG("[PER out %u/%x => %02x buf+%ld]",
        (int)bits, (int)bits, buf[0],
        (long)(po->buffer - po->tmpspace));

    return 0;
}


/*
 * Output a large number of bits.
 */
int
per_put_many_bits(asn_per_outp_t *po, const uint8_t *src, int nbits) {

    while(nbits) {
        uint32_t value;

        if(nbits >= 24) {
            value = (src[0] << 16) | (src[1] << 8) | src[2];
            src += 3;
            nbits -= 24;
            if(per_put_few_bits(po, value, 24))
                return -1;
        } else {
            value = src[0];
            if(nbits > 8)
                value = (value << 8) | src[1];
            if(nbits > 16)
                value = (value << 8) | src[2];
            if(nbits & 0x07)
                value >>= (8 - (nbits & 0x07));
            if(per_put_few_bits(po, value, nbits))
                return -1;
            break;
        }
    }

    return 0;
}

/*
 * Put the length "n" (or part of it) into the stream.
 */
ssize_t
uper_put_length(asn_per_outp_t *po, size_t length) {

    if(length <= 127)   /* #10.9.3.6 */
        return per_put_few_bits(po, length, 8)
            ? -1 : (ssize_t)length;
    else if(length < 16384) /* #10.9.3.7 */
        return per_put_few_bits(po, length|0x8000, 16)
            ? -1 : (ssize_t)length;

    length >>= 14;
    if(length > 4) length = 4;

    return per_put_few_bits(po, 0xC0 | length, 8)
            ? -1 : (ssize_t)(length << 14);
}


/*
 * Put the normally small length "n" into the stream.
 * This procedure used to encode length of extensions bit-maps
 * for SET and SEQUENCE types.
 */
int
uper_put_nslength(asn_per_outp_t *po, size_t length) {

    if(length <= 64) {
        /* #10.9.3.4 */
        if(length == 0) return -1;
        return per_put_few_bits(po, length-1, 7) ? -1 : 0;
    } else {
        if(uper_put_length(po, length) != (ssize_t)length) {
            /* This might happen in case of >16K extensions */
            return -1;
        }
    }

    return 0;
}