asn_bit_data.c

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/*
 * Copyright (c) 2005-2017 Lev Walkin <vlm@lionet.info>.
 * All rights reserved.
 * Redistribution and modifications are permitted subject to BSD license.
 */
#include <etsi_its_spatem_ts_coding/asn_system.h>
#include <etsi_its_spatem_ts_coding/asn_internal.h>
#include <etsi_its_spatem_ts_coding/asn_bit_data.h>
 
/*
 * Create a contiguous non-refillable bit data structure.
 * Can be freed by FREEMEM().
 */
asn_bit_data_t *
asn_bit_data_new_contiguous(const void *data, size_t size_bits) {
    size_t size_bytes = (size_bits + 7) / 8;
    asn_bit_data_t *pd;
    uint8_t *bytes;
 
    /* Get the extensions map */
    pd = CALLOC(1, sizeof(*pd) + size_bytes + 1);
    if(!pd) {
        return NULL;
    }
    bytes = (void *)(((char *)pd) + sizeof(*pd));
    memcpy(bytes, data, size_bytes);
    bytes[size_bytes] = 0;
    pd->buffer = bytes;
    pd->nboff = 0;
    pd->nbits = size_bits;
 
    return pd;
}
 
 
char *
asn_bit_data_string(asn_bit_data_t *pd) {
        static char buf[2][32];
        static int n;
        n = (n+1) % 2;
    snprintf(buf[n], sizeof(buf[n]),
             "{m=%" ASN_PRI_SIZE " span %" ASN_PRI_SIZE "[%" ASN_PRI_SIZE
             "..%" ASN_PRI_SIZE "] (%" ASN_PRI_SIZE ")}",
             pd->moved, ((uintptr_t)(pd->buffer) & 0xf), pd->nboff, pd->nbits,
             pd->nbits - pd->nboff);
    return buf[n];
}
 
void
asn_get_undo(asn_bit_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
asn_get_few_bits(asn_bit_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 = asn_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 = asn_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 = (((uint32_t)buf[0] << 24) + (buf[1] << 16)
                        + (buf[2] << 8) + (buf[3])) >> (32 - off);
        else if(nbits <= 31) {
                asn_bit_data_t tpd = *pd;
                /* Here are we with our 31-bits limit plus 1..7 bits offset. */
                asn_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  = asn_get_few_bits(&tpd, nbits - 24) << 24;
                accum |= asn_get_few_bits(&tpd, 24);
        } else {
                asn_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 != NULL)?pd->buffer[0]:0),
                (int)(pd->nbits - pd->nboff),
                (int)accum);
 
        return accum;
}
 
/*
 * Extract a large number of bits from the specified PER data pointer.
 */
int
asn_get_many_bits(asn_bit_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 = asn_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 = asn_get_few_bits(pd, 24);
                        if(value < 0) return -1;
                        *(dst++) = value >> 16;
                        *(dst++) = value >> 8;
                        *(dst++) = value;
                        nbits -= 24;
                } else {
                        value = asn_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;
}
 
/*
 * Put a small number of bits (<= 31).
 */
int
asn_put_few_bits(asn_bit_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, (void *)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) {
                size_t complete_bytes;
                if(!po->buffer) po->buffer = po->tmpspace;
                complete_bytes = (po->buffer - po->tmpspace);
                ASN_DEBUG("[PER output %ld complete + %ld]",
                        (long)complete_bytes, (long)po->flushed_bytes);
                if(po->output(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 {
                if(asn_put_few_bits(po, bits >> (obits - 24), 24)) return -1;
                if(asn_put_few_bits(po, bits, obits - 24)) return -1;
        }
 
        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
asn_put_many_bits(asn_bit_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(asn_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(asn_put_few_bits(po, value, nbits))
                                return -1;
                        break;
                }
        }
 
        return 0;
}
 
 
int
asn_put_aligned_flush(asn_bit_outp_t *po) {
    uint32_t unused_bits = (0x7 & (8 - (po->nboff & 0x07)));
    size_t complete_bytes =
        (po->buffer ? po->buffer - po->tmpspace : 0) + ((po->nboff + 7) >> 3);
 
    if(unused_bits) {
        po->buffer[po->nboff >> 3] &= ~0u << unused_bits;
    }
 
    if(po->output(po->tmpspace, complete_bytes, po->op_key) < 0) {
        return -1;
    } else {
        po->buffer = po->tmpspace;
        po->nboff = 0;
        po->nbits = 8 * sizeof(po->tmpspace);
        po->flushed_bytes += complete_bytes;
        return 0;
    }
}