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per_support.c

/*
 * Copyright (c) 2005, 2006, 2007 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=%d span %+d[%d..%d] (%d)}",
            pd->moved,
            (((int)pd->buffer) & 0xf),
            pd->nboff, pd->nbits,
            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)", nleft, 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 %+d[%d..%d]:%02x (%d) => 0x%x]",
            nbits, nleft,
            pd->moved,
            (((int)pd->buffer) & 0xf),
            pd->nboff, pd->nbits,
            pd->buffer[0],
            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", 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;
}

/*
 * Put the normally small non-negative whole number.
 * X.691, #10.6
 */
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);
}


/*
 * 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, 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 %d complete + %d]",
                  complete_bytes, 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,
            po->nboff - obits, off, buf[0], omsk&0xff, buf[0] & omsk);

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

      ASN_DEBUG("[PER out %u/%x => %02x buf+%d]",
            (int)bits, (int)bits, buf[0], 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;
}


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