source: XIOS/trunk/extern/src_netcdf4/ocnode.c @ 409

/* Copyright 2009, UCAR/Unidata and OPeNDAP, Inc.
   See the COPYRIGHT file for more information. */

#include "config.h"
#include "ocinternal.h"
#include "ocdebug.h"

static const unsigned int MAX_UINT = 0xffffffff;

static OCerror occomputeskipdatar(OCstate*, OCnode*, ocoffset_t offset);
static int mergedas1(OCnode* dds, OCnode* das);
static int converttype(OCtype etype, char* value, char* memory);
static char* pathtostring(OClist* path, char* separator, int usecdfname);
static void computefullname(OCnode* node);

/* Process ocnodes to fix various semantic issues*/
void
occomputesemantics(OClist* ocnodes)
{
    unsigned int i;
    OCASSERT((ocnodes != NULL));
    for(i=0;i<oclistlength(ocnodes);i++) {
        OCnode* node = (OCnode*)oclistget(ocnodes,i);
        /* set the container for dims*/
        if(node->octype == OC_Dimension && node->dim.array != NULL) {
            node->container = node->dim.array->container;
        }
    }
}

void
occomputefullnames(OCnode* root)
{
    unsigned int i;
    if(root->name != NULL) computefullname(root);
    if(root->subnodes != NULL) { /* recurse*/
        for(i=0;i<oclistlength(root->subnodes);i++) {
            OCnode* node = (OCnode*)oclistget(root->subnodes,i);
            occomputefullnames(node);
        }
    }
}

static void
computefullname(OCnode* node)
{
    char* tmp;
    char* fullname;
    OClist* path;

    OCASSERT((node->name != NULL));
    path = oclistnew();
    occollectpathtonode(node,path);
    tmp = pathtostring(path,PATHSEPARATOR,1);
    if(tmp == NULL) {
        fullname = nulldup(node->name);
    } else {
        fullname = tmp;
    }
    node->fullname = fullname;
    oclistfree(path);
}

/* Convert path to a string; leave off the dataset name*/
static char*
pathtostring(OClist* path, char* separator, int usecdfname)
{
    int slen,i,len;
    char* pathname;
    if(path == NULL || (len = oclistlength(path))==0) return NULL;
    for(slen=0,i=0;i<len;i++) {
        OCnode* node = (OCnode*)oclistget(path,i);
        if(node->container == NULL || node->name == NULL) continue;
        slen += strlen(node->name);
    }
    slen += ((len-1)*strlen(separator));
    slen += 1;   /* for null terminator*/
    pathname = (char*)ocmalloc(slen);
    MEMCHECK(pathname,NULL);
    pathname[0] = '\0';
    for(i=0;i<len;i++) {
        OCnode* node = (OCnode*)oclistget(path,i);
        if(node->container == NULL || node->name == NULL) continue;
        if(strlen(pathname) > 0) strcat(pathname,separator);
        strcat(pathname,node->name);
    }
    return pathname;
}

/* Collect the set of nodes ending in "node"*/
void
occollectpathtonode(OCnode* node, OClist* path)
{
    if(node == NULL) return;
    occollectpathtonode(node->container,path);
    oclistpush(path,(ocelem)node);
}

OCnode*
ocmakenode(char* name, OCtype ptype, OCnode* root)
{
    OCnode* cdf = (OCnode*)ocmalloc(sizeof(OCnode));
    MEMCHECK(cdf,(OCnode*)NULL);
    memset((void*)cdf,0,sizeof(OCnode));
    cdf->magic = OCMAGIC;
    cdf->name = (name?nulldup(name):NULL);
    cdf->octype = ptype;
    cdf->array.dimensions = NULL;
    cdf->root = root;
    return cdf;
}

OCattribute*
makeattribute(char* name, OCtype ptype, OClist* values)
{
    OCattribute* att = (OCattribute*)ocmalloc(sizeof(OCattribute)); /* ocmalloc zeros*/
    MEMCHECK(att,(OCattribute*)NULL);
    att->name = nulldup(name);
    att->etype = ptype;
    att->nvalues = oclistlength(values);
    att->values = NULL;
    if(att->nvalues > 0) {
        int i;
        att->values = (char**)ocmalloc(sizeof(char*)*att->nvalues);
        for(i=0;i<att->nvalues;i++)
            att->values[i] = nulldup((char*)oclistget(values,i));
    }
    return att;
}

static void
marklostattribute(OCnode* att)
{
    oc_log(LOGWARN,"Lost attribute: %s",att->name);
}

void*
oclinearize(OCtype etype, unsigned int nstrings, char** strings)
{
    int i;
    size_t typesize;
    char* memp;
    char* memory;

    if(nstrings == 0) return NULL;
    typesize = octypesize(etype);
    memory = (char*)ocmalloc(nstrings*typesize);
    MEMCHECK(memory,NULL);
    memp = memory;
    for(i=0;i<nstrings;i++) {
        char* value = strings[i];
        converttype(etype,value,memp);
        memp += typesize;
    }
    return memory;
}

static int
converttype(OCtype etype, char* value, char* memory)
{
    long iv;
    unsigned long uiv;
    double dv;
    char c[1];
    int outofrange = 0;
#ifdef HAVE_LONG_LONG_INT
    long long llv;
    unsigned long long ullv;
#endif

    switch (etype) {
    case OC_Char:
        if(sscanf(value,"%c",c) != 1) goto fail;
        *((char*)memory) = c[0];
        break;
    case OC_Byte:
        if(sscanf(value,"%ld",&iv) != 1) goto fail;
        else if(iv > OC_BYTE_MAX || iv < OC_BYTE_MIN) {iv = OC_BYTE_MAX; outofrange = 1;}
        *((signed char*)memory) = (signed char)iv;
        break;
    case OC_UByte:
        if(sscanf(value,"%lu",&uiv) != 1) goto fail;
        else if(uiv > OC_UBYTE_MAX) {uiv = OC_UBYTE_MAX; outofrange = 1;}
        *((unsigned char*)memory) = (unsigned char)uiv;
        break;
    case OC_Int16:
        if(sscanf(value,"%ld",&iv) != 1) goto fail;
        else if(iv > OC_INT16_MAX || iv < OC_INT16_MIN) {iv = OC_INT16_MAX; outofrange = 1;}
        *((signed short*)memory) = (signed short)iv;
        break;
    case OC_UInt16:
        if(sscanf(value,"%lu",&uiv) != 1) goto fail;
        else if(uiv > OC_UINT16_MAX) {uiv = OC_UINT16_MAX; outofrange = 1;}
        *((unsigned short*)memory) = (unsigned short)uiv;
        break;
    case OC_Int32:
        if(sscanf(value,"%ld",&iv) != 1) goto fail;
        else if(iv > OC_INT32_MAX || iv < OC_INT32_MIN) {iv = OC_INT32_MAX; outofrange = 1;}
        *((signed int*)memory) = (signed int)iv;
        break;
    case OC_UInt32:
        if(sscanf(value,"%lu",&uiv) != 1) goto fail;
        else if(uiv > OC_UINT32_MAX) {uiv = OC_UINT32_MAX; outofrange = 1;}
        *((unsigned char*)memory) = (unsigned int)uiv;
        break;
#ifdef HAVE_LONG_LONG_INT
    case OC_Int64:
        if(sscanf(value,"%lld",&llv) != 1) goto fail;
        /*else if(iv > OC_INT64_MAX || iv < OC_INT64_MIN) goto fail;*/
        *((signed long long*)memory) = (signed long long)llv;
        break;
    case OC_UInt64:
        if(sscanf(value,"%llu",&ullv) != 1) goto fail;
        *((unsigned long long*)memory) = (unsigned long long)ullv;
        break;
#endif
    case OC_Float32:
        if(sscanf(value,"%lf",&dv) != 1) goto fail;
        *((float*)memory) = (float)dv;
        break;
    case OC_Float64:
        if(sscanf(value,"%lf",&dv) != 1) goto fail;
        *((double*)memory) = (double)dv;
        break;
    case OC_String: case OC_URL:
        *((char**)memory) = nulldup(value);
        break;
    default:
        goto fail;
    }
    if(outofrange)
        oc_log(LOGWARN,"converttype range failure: %d: %s",etype,value);
    return 1;
fail:
    oc_log(LOGERR,"converttype bad value: %d: %s",etype,value);
    return 0;
}


void
ocfreeroot(OCnode* root)
{
    OCtree* tree;
    OCstate* state;
    int i;

    if(root == NULL || root->tree == NULL) return;

    tree = root->tree;
    /* Remove the root from the state->trees list */
    state = tree->state;
    for(i=0;i<oclistlength(state->trees);i++) {
        OCnode* node = (OCnode*)oclistget(state->trees,i);
        if(root == node)
            oclistremove(state->trees,i);
    }
    /* Note: it is ok if state->trees does not contain this root */    
    ocfreetree(tree);
}

void
ocfreetree(OCtree* tree)
{
    if(tree == NULL) return;
    ocfreenodes(tree->nodes);
    ocfree(tree->constraint);
    ocfree(tree->text);
    if(tree->data.xdrs != NULL) {
        xxdr_free(tree->data.xdrs);
    }
    ocfree(tree->data.filename); /* may be null */
    if(tree->data.file != NULL) fclose(tree->data.file);
    ocfree(tree->data.memory);
    ocfree(tree);
}

void
ocfreenodes(OClist* nodes)
{
    unsigned int i,j;
    for(i=0;i<oclistlength(nodes);i++) {
        OCnode* node = (OCnode*)oclistget(nodes,i);
        ocfree(node->name);
        ocfree(node->fullname);
        while(oclistlength(node->att.values) > 0) {
            char* value = (char*)oclistpop(node->att.values);
            ocfree(value);
        }
        while(oclistlength(node->attributes) > 0) {
            OCattribute* attr = (OCattribute*)oclistpop(node->attributes);
            ocfree(attr->name);
            /* If the attribute type is string, then we need to free them*/
            if(attr->etype == OC_String || attr->etype == OC_URL) {
                char** strings = (char**)attr->values;
                for(j=0;j<attr->nvalues;j++) {ocfree(*strings); strings++;}
            }
            ocfree(attr->values);
            ocfree(attr);
        }
        if(node->array.dimensions != NULL) oclistfree(node->array.dimensions);
        if(node->subnodes != NULL) oclistfree(node->subnodes);
        if(node->att.values != NULL) oclistfree(node->att.values);
        if(node->attributes != NULL) oclistfree(node->attributes);
        ocfree(node);
    }
    oclistfree(nodes);
}

/*
In order to be as compatible as possible with libdap,
we try to use the same algorithm for DAS->DDS matching.
As described there, the algorithm is as follows.
    If the [attribute] name contains one or
    more field separators then look for a [DDS]variable whose
    name matches exactly. If the name contains no field separators then
    the look first in the top level [of the DDS] and then in all subsequent
    levels and return the first occurrence found. In general, this
    searches constructor types in the order in which they appear
    in the DDS, but there is no requirement that it do so.

    Note: If a dataset contains two constructor types which have field names
    that are the same (say point.x and pair.x) one should use fully qualified
    names to get each of those variables.
*/

int
ocddsdasmerge(OCstate* state, OCnode* dasroot, OCnode* ddsroot)
{
    OClist* dasglobals = oclistnew();
    OClist* dasnodes = oclistnew();
    OClist* varnodes = oclistnew();
    OClist* ddsnodes;
    unsigned int i,j;

    if(dasroot->tree == NULL || dasroot->tree->dxdclass != OCDAS)
        return OCTHROW(OC_EINVAL);
    if(ddsroot->tree == NULL || (ddsroot->tree->dxdclass != OCDDS
        && ddsroot->tree->dxdclass != OCDATADDS))
        return OCTHROW(OC_EINVAL);

    ddsnodes = ddsroot->tree->nodes;

    /* 1. collect all the relevant DAS nodes;
          namely those that contain at least one
          attribute value.
          Simultaneously look for potential ambiguities
          if found; complain but continue: result are indeterminate.
          also collect globals separately*/
    for(i=0;i<oclistlength(dasroot->tree->nodes);i++) {
        OCnode* das = (OCnode*)oclistget(dasroot->tree->nodes,i);
        int hasattributes = 0;
        if(das->octype == OC_Attribute) continue; /* ignore these for now*/
        if(das->name == NULL || das->att.isglobal) {
            oclistpush(dasglobals,(ocelem)das);
            continue;
        }
        for(j=0;j<oclistlength(das->subnodes);j++) {
            OCnode* subnode = (OCnode*)oclistget(das->subnodes,j);
            if(subnode->octype == OC_Attribute) {hasattributes = 1; break;}
        }
        if(hasattributes) {
            /* Look for previously collected nodes with same name*/
            for(j=0;j<oclistlength(dasnodes);j++) {
                OCnode* das2 = (OCnode*)oclistget(dasnodes,j);
                if(das->name == NULL || das2->name == NULL) continue;
                if(strcmp(das->name,das2->name)==0) {
                    oc_log(LOGWARN,"oc_mergedas: potentially ambiguous DAS name: %s",das->name);
                }
            }
            oclistpush(dasnodes,(ocelem)das);
        }
    }

    /* 2. collect all the leaf DDS nodes (of type OC_Primitive)*/
    for(i=0;i<oclistlength(ddsnodes);i++) {
        OCnode* dds = (OCnode*)oclistget(ddsnodes,i);
        if(dds->octype == OC_Primitive) oclistpush(varnodes,(ocelem)dds);
    }

    /* 3. For each das node, locate matching DDS node(s) and attach
          attributes to the DDS node(s).
          Match means:
          1. DAS->fullname :: DDS->fullname
          2. DAS->name :: DDS->fullname (support DAS names with embedded '.'
          3. DAS->name :: DDS->name
    */
    for(i=0;i<oclistlength(dasnodes);i++) {
        OCnode* das = (OCnode*)oclistget(dasnodes,i);
        for(j=0;j<oclistlength(varnodes);j++) {
            OCnode* dds = (OCnode*)oclistget(varnodes,j);
            if(strcmp(das->fullname,dds->fullname)==0
               || strcmp(das->name,dds->fullname)==0
               || strcmp(das->name,dds->name)==0) {
                mergedas1(dds,das);
                /* remove from dasnodes list*/
                oclistset(dasnodes,i,(ocelem)NULL);
            }
        }
    }

    /* 4. If there are attributes left, then complain about them being lost.*/
    for(i=0;i<oclistlength(dasnodes);i++) {
        OCnode* das = (OCnode*)oclistget(dasnodes,i);
        if(das != NULL) marklostattribute(das);
    }

    /* 5. Assign globals*/
    for(i=0;i<oclistlength(dasglobals);i++) {
        OCnode* das = (OCnode*)oclistget(dasglobals,i);
        mergedas1(ddsroot,das);
    }
    /* cleanup*/
    oclistfree(dasglobals);
    oclistfree(dasnodes);
    oclistfree(varnodes);
    return OCTHROW(OC_NOERR);
}

static int
mergedas1(OCnode* dds, OCnode* das)
{
    unsigned int i;
    int stat = OC_NOERR;
    if(das == NULL) return OC_NOERR; /* nothing to do */
    if(dds->attributes == NULL) dds->attributes = oclistnew();
    /* assign the simple attributes in the das set to this dds node*/
    for(i=0;i<oclistlength(das->subnodes);i++) {
        OCnode* attnode = (OCnode*)oclistget(das->subnodes,i);
        if(attnode->octype == OC_Attribute) {
            OCattribute* att = makeattribute(attnode->name,
                                                attnode->etype,
                                                attnode->att.values);
            oclistpush(dds->attributes,(ocelem)att);
        }
    }
    return OCTHROW(stat);
}



#ifdef OCIGNORE

int
ocddsdasmerge(OCstate* state, OCnode* ddsroot, OCnode* dasroot)
{
    int i,j;
    int stat = OC_NOERR;
    OClist* globals = oclistnew();
    if(dasroot == NULL) return OCTHROW(stat);
    /* Start by looking for global attributes*/
    for(i=0;i<oclistlength(dasroot->subnodes);i++) {
        OCnode* node = (OCnode*)oclistget(dasroot->subnodes,i);
        if(node->att.isglobal) {
            for(j=0;j<oclistlength(node->subnodes);j++) {
                OCnode* attnode = (OCnode*)oclistget(node->subnodes,j);
                Attribute* att = makeattribute(attnode->name,
                                                attnode->etype,
                                                attnode->att.values);
                oclistpush(globals,(ocelem)att);
            }
        }
    }
    ddsroot->attributes = globals;
    /* Now try to match subnode names with attribute set names*/
    for(i=0;i<oclistlength(dasroot->subnodes);i++) {
        OCnode* das = (OCnode*)oclistget(dasroot->subnodes,i);
        int match = 0;
        if(das->att.isglobal) continue;
        if(das->octype == OC_Attributeset) {
            for(j=0;j<oclistlength(ddsroot->subnodes) && !match;j++) {
                OCnode* dds = (OCnode*)oclistget(ddsroot->subnodes,j);
                if(strcmp(das->name,dds->name) == 0) {
                    match = 1;
                    stat = mergedas1(dds,das);
                    if(stat != OC_NOERR) break;
                }
            }
        }
        if(!match) {marklostattribute(das);}
    }
    if(stat == OC_NOERR) ddsroot->attributed = 1;
    return OCTHROW(stat);
}

/* Merge das attributes into the dds node*/

static int
mergedas1(OCnode* dds, OCnode* das)
{
    int i,j;
    int stat = OC_NOERR;
    if(dds->attributes == NULL) dds->attributes = oclistnew();
    /* assign the simple attributes in the das set to this dds node*/
    for(i=0;i<oclistlength(das->subnodes);i++) {
        OCnode* attnode = (OCnode*)oclistget(das->subnodes,i);
        if(attnode->octype == OC_Attribute) {
            Attribute* att = makeattribute(attnode->name,
                                                attnode->etype,
                                                attnode->att.values);
            oclistpush(dds->attributes,(ocelem)att);
        }
    }
    /* Try to merge any enclosed sets with subnodes of dds*/
    for(i=0;i<oclistlength(das->subnodes);i++) {
        OCnode* dasnode = (OCnode*)oclistget(das->subnodes,i);
        int match = 0;
        if(dasnode->octype == OC_Attribute) continue; /* already dealt with above*/
        for(j=0;j<oclistlength(dds->subnodes) && !match;j++) {
            OCnode* ddsnode = (OCnode*)oclistget(dds->subnodes,j);
            if(strcmp(dasnode->name,ddsnode->name) == 0) {
                match = 1;
                stat = mergedas1(ddsnode,dasnode);
                if(stat != OC_NOERR) break;
            }
        }
        if(!match) {marklostattribute(dasnode);}
    }
    return OCTHROW(stat);
}
#endif

static void
ocuncorrelate(OCnode* root)
{
    OCtree* tree = root->tree;
    unsigned int i;
    if(tree == NULL) return;
    for(i=0;i<oclistlength(tree->nodes);i++) {
        OCnode* node = (OCnode*)oclistget(tree->nodes,i);
        node->datadds = NULL;
    }        
}

static OCerror
occorrelater(OCnode* dds, OCnode* dxd)
{
    int i,j;
    OCerror ocstat = OC_NOERR;

    if(dds->octype != dxd->octype) {
        OCTHROWCHK((ocstat = OC_EINVAL)); goto fail;
    }
    if(dxd->name != NULL && dxd->name != NULL
       && strcmp(dxd->name,dds->name) != 0) {
        OCTHROWCHK((ocstat = OC_EINVAL)); goto fail;
    } else if(dxd->name != dxd->name) { /* test NULL==NULL */
        OCTHROWCHK((ocstat = OC_EINVAL)); goto fail;
    }

    if(dxd->array.rank != dds->array.rank) {
        OCTHROWCHK((ocstat = OC_EINVAL)); goto fail;
    }

    dds->datadds = dxd;

    switch (dds->octype) {
    case OC_Dataset:
    case OC_Structure:
    case OC_Grid:
    case OC_Sequence:
        /* Remember: there may be fewer datadds fields than dds fields */
        for(i=0;i<oclistlength(dxd->subnodes);i++) {
            OCnode* dxd1 = (OCnode*)oclistget(dxd->subnodes,i);
            for(j=0;j<oclistlength(dds->subnodes);j++) {
                OCnode* dds1 = (OCnode*)oclistget(dds->subnodes,j);
                if(strcmp(dxd1->name,dds1->name) == 0) {
                    ocstat = occorrelater(dds1,dxd1);
                    if(ocstat != OC_NOERR) {OCTHROWCHK(ocstat); goto fail;}
                    break;
                }
            }
        }
        break;
    case OC_Dimension:
    case OC_Primitive:
        break;
    default: OCPANIC1("unexpected node type: %d",dds->octype);
    }
    /* Correlate the dimensions */
    if(dds->array.rank > 0) {
        for(i=0;i<oclistlength(dxd->subnodes);i++) {
            OCnode* ddsdim = (OCnode*)oclistget(dds->array.dimensions,i);
            OCnode* dxddim = (OCnode*)oclistget(dxd->array.dimensions,i);
            ocstat = occorrelater(ddsdim,dxddim);
            if(!ocstat) goto fail;          
        }       
    }

fail:
    return OCTHROW(ocstat);

}

OCerror
occorrelate(OCnode* dds, OCnode* dxd)
{
    if(dds == NULL || dxd == NULL) return OC_EINVAL;
    ocuncorrelate(dds);
    return occorrelater(dds,dxd);
}

/*
Mark cacheable those primitive String/URL typed nodes
that are contained only in structures with rank > 0.
*/
void
ocmarkcacheable(OCstate* state, OCnode* ddsroot)
{
    int i,j;
#ifdef OCIGNORE
    int ok;
#endif
    OClist* treenodes = ddsroot->tree->nodes;
    OClist* path = oclistnew();
    for(i=0;i<oclistlength(treenodes);i++) {
        OCnode* node = (OCnode*)oclistget(treenodes,i);
        if(node->octype != OC_Primitive) continue;
        if(node->etype != OC_String && node->etype != OC_URL) continue;
        /* collect node path */
        oclistclear(path);
        occollectpathtonode(node,path); 
#ifdef OCIGNORE
        ok = 1;
#endif
        for(j=1;j<oclistlength(path)-1;j++) {/* skip top level dataset and node itself*/
            OCnode* pathnode = (OCnode*)oclistget(path,j);
            if(pathnode->octype != OC_Structure
                || pathnode->array.rank > 0) {
#ifdef OCIGNORE
            ok=0;
#endif
            break;
            }
        }       
#ifdef OCIGNORE
        if(ok) {
            node->cache.cacheable = 1;
            node->cache.valid = 0;
        }
#endif
    }
    oclistfree(path);
}


/*
Fill in the OCnode.skip fields
*/
OCerror
occomputeskipdata(OCstate* state, OCnode* ddsroot)
{
    OCerror stat = OC_NOERR;
    OCASSERT(ddsroot->octype == OC_Dataset);
    stat = occomputeskipdatar(state,ddsroot,0);    
    return stat;
}

/* Recursive helper for computeskipdata */
static OCerror
occomputeskipdatar(OCstate* state, OCnode* xnode, ocoffset_t offset)
{
    OCerror stat = OC_NOERR;
    int i,nfields;
    int scalar = 0;
    ocoffset_t instancesize = 0;
    ocoffset_t totalsize = 0;

    scalar = (xnode->array.rank == 0 ? 1 : 0);

    /* Set skip count and offset*/
    if(xnode->octype == OC_Sequence)
        xnode->skip.count = OCINDETERMINATE;
    else
        xnode->skip.count = totaldimsize(xnode);

    xnode->skip.offset = offset; /* possibly overridden below */

    switch (xnode->octype) {

    case OC_Primitive:
        switch(xnode->etype) {
        case OC_String: case OC_URL:
            instancesize = OCINDETERMINATE;
            totalsize = OCINDETERMINATE;
            break;
        case OC_Char: case OC_Byte: case OC_UByte:
            if(!scalar) {/*=>packed*/
                instancesize = octypesize(xnode->etype);
                totalsize = instancesize * xnode->skip.count;
                totalsize = RNDUP(totalsize);
                totalsize += 2*XDRUNIT; /* overhead is double count */
                break;
            }
            /* !packed => singleton char object */
            /* fall thru */
        case OC_Int16: case OC_UInt16:
        case OC_Int32: case OC_UInt32:
        case OC_Int64:  case OC_UInt64:
        case OC_Float32: case OC_Float64:
            instancesize = octypesize(xnode->etype);
            instancesize = RNDUP(instancesize); /* make multiple of XDRUNIT */
            totalsize = (instancesize*xnode->skip.count); /* overhead is double count */
            if(!scalar)
                totalsize += 2*XDRUNIT; /* overhead is double count */
            break;

        default:
            OCPANIC("unexpected etype"); /* better not happen */
        }
        break;

    case OC_Sequence:
        offset = (xnode->skip.offset = OCINDETERMINATE); /* do not know field offsets for arbitrary record */
    case OC_Dataset:
    case OC_Grid:    
    case OC_Structure:
        /* Compute size of each field and sum */
        nfields = oclistlength(xnode->subnodes);
        instancesize = 0; /* of structure as a whole */
        for(i=0;i<nfields;i++) {
            OCnode* subnode = (OCnode*)oclistget(xnode->subnodes,i);
            ocoffset_t fieldsize;
            if(offset == OCINDETERMINATE || instancesize == OCINDETERMINATE)
                stat = occomputeskipdatar(state,subnode,OCINDETERMINATE);
            else 
                stat = occomputeskipdatar(state,subnode,offset+instancesize);
            if(stat != OC_NOERR) goto done;
            fieldsize = subnode->skip.totalsize;
            if(instancesize == OCINDETERMINATE || fieldsize == OCINDETERMINATE)
                instancesize = OCINDETERMINATE;
            else
                instancesize += fieldsize; 
        }
        if(instancesize != OCINDETERMINATE) {
            instancesize = RNDUP(instancesize); /* make multiple of XDRUNIT */
            totalsize = (instancesize*xnode->skip.count); /* overhead is single count */
            if(!scalar)
                totalsize += XDRUNIT; /* overhead is single count */
        } else {
            totalsize = OCINDETERMINATE; 
        }
        if(xnode->octype == OC_Sequence) {
            totalsize = OCINDETERMINATE;
            offset = OCINDETERMINATE;
        }
        break;

    default: OCPANIC("unexpected octype"); /* better not happen */
    }

    xnode->skip.offset = offset;
    xnode->skip.instancesize = instancesize;
    xnode->skip.totalsize = totalsize;

done:
    return stat;
}