e2sm/lib/BIT_STRING_oer.c

/*
 * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
 * All rights reserved.
 * Redistribution and modifications are permitted subject to BSD license.
 */
#ifndef ASN_DISABLE_OER_SUPPORT

#include <asn_internal.h>
#include <BIT_STRING.h>
#include <errno.h>

asn_dec_rval_t
BIT_STRING_decode_oer(const asn_codec_ctx_t *opt_codec_ctx,
                      const asn_TYPE_descriptor_t *td,
                      const asn_oer_constraints_t *constraints, void **sptr,
                      const void *ptr, size_t size) {
    BIT_STRING_t *st = (BIT_STRING_t *)*sptr;
    const asn_oer_constraints_t *cts =
        constraints ? constraints : td->encoding_constraints.oer_constraints;
    ssize_t ct_size = cts ? cts->size : -1;
    asn_dec_rval_t rval = {RC_OK, 0};
    size_t expected_length = 0;

    (void)opt_codec_ctx;

    if(!st) {
        st = (BIT_STRING_t *)(*sptr = CALLOC(1, sizeof(*st)));
        if(!st) ASN__DECODE_FAILED;
    }

    if(ct_size >= 0) {
        expected_length = (ct_size + 7) >> 3;
        st->bits_unused = (8 - (ct_size & 7)) & 7;
    } else {
        /*
         * X.696 (08/2015) #13.3.1
         * Encode length determinant as _number of octets_, but only
         * if upper bound is not equal to lower bound.
         */
        ssize_t len_len = oer_fetch_length(ptr, size, &expected_length);
        if(len_len > 0) {
            ptr = (const char *)ptr + len_len;
            size -= len_len;
        } else if(len_len == 0) {
            ASN__DECODE_STARVED;
        } else if(len_len < 0) {
            ASN__DECODE_FAILED;
        }

        if(expected_length < 1) {
            ASN__DECODE_FAILED;
        } else if(expected_length > size) {
            ASN__DECODE_STARVED;
        }

        st->bits_unused = ((const uint8_t *)ptr)[0];
        if(st->bits_unused & ~7) {
            ASN_DEBUG("%s: unused bits outside of 0..7 range", td->name);
            ASN__DECODE_FAILED;
        }
        ptr = (const char *)ptr + 1;
        size--;
        expected_length--;
        rval.consumed = len_len + 1;
    }

    if(size < expected_length) {
        ASN__DECODE_STARVED;
    } else {
        uint8_t *buf = MALLOC(expected_length + 1);
        if(buf == NULL) {
            ASN__DECODE_FAILED;
        } else {
            memcpy(buf, ptr, expected_length);
            buf[expected_length] = '\0';
        }
        FREEMEM(st->buf);
        st->buf = buf;
        st->size = expected_length;
        if(expected_length > 0) {
            buf[expected_length - 1] &= (0xff << st->bits_unused);
        }

        rval.consumed += expected_length;
        return rval;
    }
}

/*
 * Encode as Canonical OER.
 */
asn_enc_rval_t
BIT_STRING_encode_oer(const asn_TYPE_descriptor_t *td,
                      const asn_oer_constraints_t *constraints,
                      const void *sptr, asn_app_consume_bytes_f *cb,
                      void *app_key) {
    const BIT_STRING_t *st = (const BIT_STRING_t *)sptr;
    asn_enc_rval_t erval = {0, 0, 0};
    const asn_oer_constraints_t *cts =
        constraints ? constraints : td->encoding_constraints.oer_constraints;
    ssize_t ct_size = cts ? cts->size : -1;
    size_t trailing_zeros = 0;
    int fix_last_byte = 0;

    if(!st) ASN__ENCODE_FAILED;

    if(st->bits_unused & ~7) {
        ASN_DEBUG("BIT STRING unused bits %d out of 0..7 range",
                  st->bits_unused);
        ASN__ENCODE_FAILED;
    }
    if(st->bits_unused && !(st->size && st->buf)) {
        ASN_DEBUG("BIT STRING %s size 0 can't support unused bits %d", td->name,
                  st->bits_unused);
        ASN__ENCODE_FAILED;
    }

    if(ct_size >= 0) {
        size_t ct_bytes = (ct_size + 7) >> 3;
        if(st->size > ct_bytes) {
            ASN_DEBUG("More bits in BIT STRING %s (%" ASN_PRI_SSIZE ") than constrained %" ASN_PRI_SSIZE "",
                      td->name, 8 * st->size - st->bits_unused, ct_size);
            ASN__ENCODE_FAILED;
        }
        trailing_zeros = ct_bytes - st->size;   /* Allow larger constraint */
    } else {
        uint8_t ub = st->bits_unused & 7;
        ssize_t len_len = oer_serialize_length(1 + st->size, cb, app_key);
        if(len_len < 0) ASN__ENCODE_FAILED;
        if(cb(&ub, 1, app_key) < 0) {
            ASN__ENCODE_FAILED;
        }
        erval.encoded += len_len + 1;
    }

    if(st->bits_unused) {
        if(st->buf[st->size - 1] & (0xff << st->bits_unused)) {
            fix_last_byte = 1;
        }
    }

    if(cb(st->buf, st->size - fix_last_byte, app_key) < 0) {
        ASN__ENCODE_FAILED;
    }

    if(fix_last_byte) {
        uint8_t b = st->buf[st->size - 1] & (0xff << st->bits_unused);
        if(cb(&b, 1, app_key) < 0) {
            ASN__ENCODE_FAILED;
        }
    }

    erval.encoded += st->size;

    if(trailing_zeros) {
        static uint8_t zeros[16];
        while(trailing_zeros > 0) {
            int ret;
            if(trailing_zeros < sizeof(zeros)) {
                ret = cb(zeros, trailing_zeros, app_key);
                erval.encoded += trailing_zeros;
            } else {
                ret = cb(zeros, sizeof(zeros), app_key);
                erval.encoded += sizeof(zeros);
            }
            if(ret < 0) ASN__ENCODE_FAILED;
        }
    }

    return erval;
}


#endif  /* ASN_DISABLE_OER_SUPPORT */