Ubuntu Manpage: msr_pack - Packing of Mini-SEED records.

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);
       }

AUTHOR

       Chad Trabant
       IRIS Data Management Center