per_decoder.c

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#include <asn_application.h>
#include <asn_internal.h>
#include <per_decoder.h>

/*
 * Decode a "Production of a complete encoding", X.691#10.1.
 * The complete encoding contains at least one byte, and is an integral
 * multiple of 8 bytes.
 */
asn_dec_rval_t
uper_decode_complete(asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td, void **sptr, const void *buffer, size_t size) {
    asn_dec_rval_t rval;

    rval = uper_decode(opt_codec_ctx, td, sptr, buffer, size, 0, 0);
    if(rval.consumed) {
        /*
         * We've always given 8-aligned data,
         * so convert bits to integral bytes.
         */
        rval.consumed += 7;
        rval.consumed >>= 3;
    } else if(rval.code == RC_OK) {
        if(size) {
            if(((const uint8_t *)buffer)[0] == 0) {
                rval.consumed = 1;  /* 1 byte */
            } else {
                ASN_DEBUG("Expecting single zeroed byte");
                rval.code = RC_FAIL;
            }
        } else {
            /* Must contain at least 8 bits. */
            rval.code = RC_WMORE;
        }
    }

    return rval;
}

asn_dec_rval_t
uper_decode(asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td, void **sptr, const void *buffer, size_t size, int skip_bits, int unused_bits) {
    asn_codec_ctx_t s_codec_ctx;
    asn_dec_rval_t rval;
    asn_per_data_t pd;

    if(skip_bits < 0 || skip_bits > 7
    || unused_bits < 0 || unused_bits > 7
    || (unused_bits > 0 && !size))
        _ASN_DECODE_FAILED;

    /*
     * Stack checker requires that the codec context
     * must be allocated on the stack.
     */
    if(opt_codec_ctx) {
        if(opt_codec_ctx->max_stack_size) {
            s_codec_ctx = *opt_codec_ctx;
            opt_codec_ctx = &s_codec_ctx;
        }
    } else {
        /* If context is not given, be security-conscious anyway */
        memset(&s_codec_ctx, 0, sizeof(s_codec_ctx));
        s_codec_ctx.max_stack_size = _ASN_DEFAULT_STACK_MAX;
        opt_codec_ctx = &s_codec_ctx;
    }

    /* Fill in the position indicator */
    memset(&pd, 0, sizeof(pd));
    pd.buffer = (const uint8_t *)buffer;
    pd.nboff = skip_bits;
    pd.nbits = 8 * size - unused_bits; /* 8 is CHAR_BIT from <limits.h> */
    if(pd.nboff > pd.nbits)
        _ASN_DECODE_FAILED;

    /*
     * Invoke type-specific decoder.
     */
    if(!td->uper_decoder)
        _ASN_DECODE_FAILED; /* PER is not compiled in */
    rval = td->uper_decoder(opt_codec_ctx, td, 0, sptr, &pd);
    if(rval.code == RC_OK) {
        /* Return the number of consumed bits */
        rval.consumed = ((pd.buffer - (const uint8_t *)buffer) << 3)
                    + pd.nboff - skip_bits;
        ASN_DEBUG("PER decoding consumed %ld, counted %ld",
            (long)rval.consumed, (long)pd.moved);
        assert(rval.consumed == pd.moved);
    } else {
        /* PER codec is not a restartable */
        rval.consumed = 0;
    }
    return rval;
}