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https://github.com/Unidata/netcdf-c.git
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208 lines
6.5 KiB
C
208 lines
6.5 KiB
C
/*********************************************************************
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* Copyright 2018, UCAR/Unidata
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* See netcdf/COPYRIGHT file for copying and redistribution conditions.
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*********************************************************************/
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#include "d4includes.h"
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#include "d4chunk.h"
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/**************************************************/
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/* Header flags */
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#define LAST_CHUNK (1)
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#define ERR_CHUNK (2)
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#define LITTLE_ENDIAN_CHUNK (4)
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#define NOCHECKSUM_CHUNK (8)
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#define ALL_CHUNK_FLAGS (LAST_CHUNK|ERR_CHUNK|LITTLE_ENDIAN_CHUNK|NOCHECKSUM_CHUNK)
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/**************************************************/
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/*
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Given a packet as read from the wire via http (or a file), convert in
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place from chunked format to a single continguous set of bytes. If an
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error packet is recovered, then make that available to the caller and
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return an error. Also return whether the data was big endian encoded
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and whether it has checksums.
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Notes:
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*/
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/* Define a local struct for convenience */
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struct HDR {unsigned int flags; unsigned int count;};
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/* Forward */
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static void* getheader(void* p, struct HDR* hdr, int hostlittleendian);
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static int processerrchunk(NCD4meta* metadata, void* errchunk, unsigned int count);
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/**************************************************/
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int
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NCD4_dechunk(NCD4meta* metadata)
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{
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unsigned char* p;
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unsigned char* q;
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struct HDR hdr;
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if(metadata->mode == NCD4_DSR)
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return THROW(NC_EDMR);
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metadata->serial.errdata = NULL;
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metadata->serial.dmr = NULL;
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metadata->serial.dap = NULL;
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metadata->serial.hostlittleendian = NCD4_isLittleEndian();
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metadata->serial.remotelittleendian = 0; /* do not actually know yet */
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metadata->serial.remotechecksumming = 0; /* do not actually know yet */
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metadata->localchecksumming = 0; /* do not actually know yet */
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/* Assume proper mode has been inferred already. */
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/* Verify the mode; assume that the <?xml...?> is optional */
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q = metadata->serial.rawdata;
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if(memcmp(q,"<?xml",strlen("<?xml"))==0
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|| memcmp(q,"<Dataset",strlen("<Dataset"))==0) {
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if(metadata->mode != NCD4_DMR)
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return THROW(NC_EDMR);
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/* setup as dmr only */
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metadata->serial.dmr = (char*)metadata->serial.rawdata; /* temp */
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metadata->serial.dmr[metadata->serial.rawsize-1] = '\0';
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metadata->serial.dmr = strdup((char *)q);
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if(metadata->serial.dmr == NULL)
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return THROW(NC_ENOMEM);
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return THROW(NC_NOERR);
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}
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/* We must be processing a DAP mode packet */
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p = metadata->serial.rawdata;
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metadata->serial.dap = p;
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#ifdef D4DUMPRAW
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NCD4_tagdump(metadata->serial.rawsize,metadata->serial.rawdata,0,"RAW");
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#endif
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/* Get the DMR chunk header*/
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p = getheader(p,&hdr,metadata->serial.hostlittleendian);
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if(hdr.count == 0)
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return THROW(NC_EDMR);
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if(hdr.flags & ERR_CHUNK) {
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return processerrchunk(metadata, (void*)p, hdr.count);
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}
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metadata->serial.remotechecksumming = ((hdr.flags & NOCHECKSUM_CHUNK) ? 0 : 1);
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metadata->localchecksumming = metadata->serial.remotechecksumming;
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metadata->serial.remotelittleendian = ((hdr.flags & LITTLE_ENDIAN_CHUNK) ? 1 : 0);
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metadata->serial.dmr = (char*)p;
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metadata->serial.dmr[hdr.count-1] = '\0';
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metadata->serial.dmr = strdup(metadata->serial.dmr);
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if(metadata->serial.dmr == NULL)
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return THROW(NC_ENOMEM);
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p += hdr.count;
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if(hdr.flags & LAST_CHUNK)
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return THROW(NC_ENODATA);
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/* Read and compress the data chunks */
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q = metadata->serial.dap;
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for(;;) {
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p = getheader(p,&hdr,metadata->serial.hostlittleendian);
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if(hdr.flags & ERR_CHUNK) {
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return processerrchunk(metadata, (void*)p, hdr.count);
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}
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/* data chunk; possibly last; possibly empty */
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if(hdr.count > 0) {
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d4memmove(q,p,hdr.count); /* will overwrite the header */
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p += hdr.count;
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q += hdr.count;
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}
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if(hdr.flags & LAST_CHUNK) break;
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}
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metadata->serial.dapsize = (size_t)DELTA(q,metadata->serial.dap);
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#ifdef D4DUMPDMR
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fprintf(stderr,"%s\n",metadata->serial.dmr);
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fflush(stderr);
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#endif
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#ifdef D4DUMPDAP
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NCD4_tagdump(metadata->serial.dapsize,metadata->serial.dap,0,"DAP");
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#endif
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return THROW(NC_NOERR);
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}
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static int
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processerrchunk(NCD4meta* metadata, void* errchunk, unsigned int count)
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{
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metadata->serial.errdata = (char*)d4alloc(count+1);
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if(metadata->serial.errdata == NULL)
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return THROW(NC_ENOMEM);
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memcpy(metadata->serial.errdata,errchunk,count);
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metadata->serial.errdata[count] = '\0';
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return THROW(NC_ENODATA); /* slight lie */
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}
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/* At the moment, the Hyrax test server
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is serving up the chunk data as little endian.
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So use a heuristic to see which endianness
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makes the more sense.
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This fails for very small dap data sections.
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*/
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static void*
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getheader(void* p, struct HDR* hdr, int hostlittleendian)
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{
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unsigned char bytes[4];
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#ifdef HYRAXHACK
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struct HDR hyrax;
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unsigned char orig[4];
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memcpy(orig,p,sizeof(bytes));/* save a copy */
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#endif
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memcpy(bytes,p,sizeof(bytes));
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p = INCR(p,4); /* on-the-wire hdr is 4 bytes */
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/* assume header is network (big) order */
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hdr->flags = bytes[0]; /* big endian => flags are in byte 0 */
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bytes[0] = 0; /* so we can do byte swap to get count */
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if(hostlittleendian)
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swapinline32(bytes); /* host is little endian */
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hdr->count = *(unsigned int*)bytes; /* get count */
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#ifdef HYRAXHACK
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memcpy(bytes,orig,sizeof(bytes)); /* restore */
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hyrax.flags = bytes[3];
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bytes[3] = 0; /* so we can do byte swap to get count */
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if(!hostlittleendian)
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swapinline32(bytes); /* host is big endian */
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hyrax.count = *(unsigned int*)bytes; /* get count */
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/* See which makes more sense */
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if(hyrax.flags <= ALL_CHUNK_FLAGS && hyrax.count >= 0 && hyrax.count < hdr->count) {
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/* Use hyrax version */
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*hdr = hyrax;
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}
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#endif
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return p;
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}
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/**
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Given a raw response, attempt to infer the mode: DMR, DAP, DSR.
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Since DSR is not standardizes, it becomes the default.
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*/
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int
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NCD4_infermode(NCD4meta* meta)
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{
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d4size_t size = meta->serial.rawsize;
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char* raw = meta->serial.rawdata;
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if(size < 16)
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return THROW(NC_EDAP); /* must have at least this to hold a hdr + partial dmr*/
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if(memcmp(raw,"<?xml",strlen("<?xml"))==0
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|| memcmp(raw,"<Dataset",strlen("<Dataset"))==0) {
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meta->mode = NCD4_DMR;
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goto done;
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}
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raw += 4; /* Pretend we have a DAP hdr */
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if(memcmp(raw,"<?xml",strlen("<?xml"))==0
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|| memcmp(raw,"<Dataset",strlen("<Dataset"))==0) {
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meta->mode = NCD4_DAP;
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goto done;
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}
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/* Default to DSR */
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meta->mode = NCD4_DSR;
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done:
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return NC_NOERR;
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}
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