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NAME

       msr_pack - Packing of Mini-SEED records.

SYNOPSIS

       #include <libmseed.h>

       int       msr_pack ( MSRecord *msr,
                            void (*record_handler) (char *, int, void *),
                            void *handlerdata, int64_t *packedsamples,
                            flag flush, flag verbose );

       int       msr_pack_header ( MSRecord *msr, flag normalize,
                                   flag verbose );

DESCRIPTION

       msr_pack  creates  (packs)  Mini-SEED  data  records.  Using the record header values in a
       MSRecord data structure, msr, as a template, the common header fields and  blockettes  are
       packed  into a record header.  A Blockette 1000 will be added if one is not present in the
       template.  The data samples at MSRecord.datasamples are  packed  in  the  encoding  format
       indicated   by   the   MSRecord.encoding   field.    The  MSRecord.datasamples  array  and
       MSRecord.numsamples value will not be changed by this routine.  It is  the  responsibility
       of the calling routine to adjust the data buffer if desired.  This routine will modify the
       start time and sequence number of the MSRecord template as it packs records.

       The key characteristics of data record & quality indicator, record length, encoding format
       and  byte  order  of  packed records are taken from MSRecord.dataquality, MSRecord.reclen,
       MSRecord.encoding  and  MSRecord.byteorder  respectively.   Default   values   for   these
       quantities  will  be used when the indicator is 0 or the reclen, encoding or byteorder are
       -1 respectively.  The default values are: dataquality = 'D', reclen = 4096 bytes, encoding
       = 11 (Steim2) and byteorder = 1 (MSBF or big-endian).

       MSRecord.dataquality should be either 'D', 'R', 'Q' or 'M'.

       MSRecord.reclen  should  be  set  to the desired data record length in bytes which must be
       expressible as 2 raised to the power of X where X is between (and including) 8 to 20.

       MSRecord.encoding should be set to one of the following supported Mini-SEED data  encoding
       formats:  DE_ASCII  (0),  DE_INT16  (1),  DE_INT32  (3),  DE_FLOAT32  (4), DE_FLOAT64 (5),
       DE_STEIM1 (10) and DE_STEIM2 (11).  The encoding aliases are defined in libmseed.h.

       MSRecord.sampletype should indicated the sample type as either 'a'  (ASCII),  'i'  (32-bit
       integers), 'f' (32-bit floats) or 'd' (64-bit doubles).

       The  encoding  format  must  be  appropriate  for  the  sample  type.   For example, Steim
       compression and integer encoding  formats  require  integer  samples  and  float  encoding
       formats require the appropriate size floats as input.  As a counter example, float samples
       cannot be packed using Steim compression or integer encoding formats.

       MSRecord.byteorder must be either 0 (LSBF or little-endian) or 1 (MBF or big-endian).

       Each time a complete record is packed it will be passed to the  record_handler()  function
       which  expects  three  arguments:  1)  a char * to the record buffer, 2) the length of the
       record in bytes and 3) a void pointer supplied by the caller.  It is the responsibility of
       record_handler()  to  process  the  record,  the  memory  will  be  re-used  or freed when
       record_handler() returns.  This function pointer is required, there is  no  other  way  to
       access the packed records.

       The  handlerdata  pointer  will  be  passed as the 3rd argument to record_handler().  This
       allows the caller to optionally pass data directly to the record_handler().

       The integer pointed to by packedsamples will be set to the total number of samples  packed
       if not NULL.

       If  the  flush  flag  is  not  zero all of the data will be packed into records, otherwise
       records will only be packed while there are enough  data  samples  to  completely  fill  a
       record.

       The verbose flag controls verbosity, a value of zero will result in no diagnostic output.

       msr_pack_header  packs  header  information,  fixed  section and blockettes, in a MSRecord
       structure into the Mini-SEED record at MSRecord.record.  This  is  useful  for  re-packing
       record    headers    after    modification.    The   normalize   flag   controls   whether
       msr_normalize_header() is called before the header is  packed.   Normalizing  updates  the
       SEED  structures  associated with the MSRecord with values using the MSRecord base members
       (e.g. MSRecord.network, MSRecord.samplerate, etc.).  Normally this should be set  to  true
       (1)  unless  the associated SEED structures have been directly modified.  The verbose flag
       controls verbosity, a value of zero will result in no diagnostic output.

PACKING OVERRIDES

       The following macros and environment variables effect the packing of Mini-SEED:

       Macros:
       MS_PACKHEADERBYTEORDER(X)
       MS_PACKDATABYTEORDER(X)

       Environment variables:
       PACK_HEADER_BYTEORDER
       PACK_DATA_BYTEORDER

       These macros and environment variables force  the  byte  order  of  the  header  and  data
       respectively.   They could be set to either 0 (little endian) or 1 (big endian).  Normally
       the byte order of the header and data is determined by the byteorder flag of the MSRecord,
       this  capability  is  included  to support any combination of byte orders in a generalized
       way.

COMPRESSION HISTORY

       When the encoding format is Steim 1 or 2 compression contiguous records  will  be  created
       including  compression  history.   Put simply, this means that the first difference in the
       compression series will be the difference between the first sample of the  current  record
       and the last sample of the previous record.  For the first record in a series (no previous
       record), a so-called cold start, the first difference will be zero.

       The compression history can be  seeded  by  allocating  the  StreamState  struct  for  the
       MSRecord  and  setting  the lastintsample member to the integer sample value that preceded
       the first sample in the current series and setting the comphistory flag to true (1).

RETURN VALUES

       msr_pack returns the number records created on success and -1 on error.

       msr_pack_header returns the header length in bytes on success and -1 on error.

EXAMPLE

       Skeleton code for creating (packing) Mini-SEED records with msr_pack(3):

       static void record_handler (char *record, int reclen, void *srcname) {
         if ( fwrite(record, reclen, 1, outfile) != 1 )
           {
             ms_log (2, "Error writing %s to output file0, (char *)srcname);
           }
       }

       main() {
         int64_t psamples;
         int precords;
         MSRecord *msr;
         char srcname[50];

         msr = msr_init (NULL);

         /* Populate MSRecord values */
         strcpy (msr->network, "XX");
         strcpy (msr->station, "TEST");
         strcpy (msr->channel, "BHE");
         msr->starttime = ms_seedtimestr2hptime ("2004,350,00:00:00.00");
         msr->samprate = 40.0;
         msr->reclen = 4096;         /* 4096 byte record length */
         msr->encoding = DE_STEIM2;  /* Steim 2 compression */
         msr->byteorder = 1;         /* big endian byte order */

         msr->datasamples = dataptr; /* pointer to 32-bit integer data samples */
         msr->numsamples = 1234;
         msr->sampletype = 'i';      /* declare type to be 32-bit integers */

         msr_srcname (msr, srcname, 0);

         /* Pack the record(s) */
         precords = msr_pack (msr, &record_handler, srcname, &psamples, 1, verbose);

         ms_log (0, "Packed %"PRId64" samples into %d records0,
                    psamples, precords);

         msr_free (&msr);
       }

SEE ALSO

       ms_intro(3), mst_pack(3), mst_packgroup(3), msr_normalize_header(3) and msr_unpack(3).

AUTHOR

       Chad Trabant
       IRIS Data Management Center