libmseed-usersguide

C编写的格式转换程序

Explanation of fields:

dataquality:
  A SEED data quality indicator, either 'D', 'R', 'Q' or 'M'.   This value
  will be (binary) 0 when the quality is unknown or mixed.

network:
station:
location:
channel:
  MSTrace identifiers as NULL terminated strings.

type:
  A single character trace type indicator.  This field is not used by
  libmseed but could be used for application specific trace
  identification.

starttime:
  MSTrace start time, the time of the first sample, as a high precision
  epoch time (see ms_time(3)).  This time can be converted using the
  various ms_hptime2<X> functions.

endtime:
  MSTrace end time, the time of the last sample, as a high precision
  epoch time (see ms_time(3)).  This time can be converted using the
  various ms_hptime2<X> functions.

samprate:
  The sample rate in samples per second in double precision.

samplecnt:
  The sample count, i.e. number of data samples in the trace.

datasamples:
  A pointer to the data samples.  If no data samples are included this
  will be 0.  The 'numsamples' field indicates how many samples are in
  this array and the 'sampletype' field indicates what type of samples
  they are.

numsamples:
  The number of samples pointed to by the 'datasamples' pointer.

sampletype:
  The type of samples pointed to by the 'datasamples' pointer.
  Supported types are 'a' (ASCII), 'i' (integer), 'f' (float) and
  'd' (double).  The size of each sample type in bytes is returned
  by the get_samplesize(3) lookup routine.

prvtptr:
  A private pointer for general use.  This pointer is not used by
  libmseed and can safely be used by the calling program.

ststate:
  Pointer to a StreamState struct used internally to track stream
  oriented state variables.  Memory for this only allocated when needed.

next:
  A pointer to the next MSTrace structure.  The value will be 0 for the
  last link in a chain of MSTrace structures.


 -- Log Messages --

All of the log and diagnostic messages emitted by the library functions
use the same interface.  The output from this interface can be controlled.
This is useful when the library will be embedded in a larger system with
a custom logging facility.  See the man page for more details.

  ms_log() : the central logging facility.  Behavior is controlled by the
        settings specified with ms_loginit().

  ms_loginit() : set the functions and prefixes used for log,
        diagnostic and error messages.

The default destination for log messages is standard output (stdout),
while all diagnostic (including error) messages go to standard error
(stderr).  Most of the internal messages emmited by the library are
considered diagnostic and will, by default, go to standard error.

The default prefix for log and diagnostic messages is nothing. The
default prefix for diagnostic error messages is "error: ".

There are reentrant versions of these functions that operate directly
on a logging parameter MSLogParam struct.  These are intended for use
in threaded programs or where a complex logging scheme is desired.
See the man pages for more details.


 -- Waveform Data --

Waveform data samples are managed by libmseed in a couple of different
formats depending on how they are unpacked or will be packed.  An
array of samples is completely represented by an array of sample
values, the number of samples and a sample type.  The number of
samples is always the actual number of sample values, not the number
of bytes needed for storing the values.  Samples can be either ASCII,
32-bit integer, 32-bit floats or 64-bit double precision floats.

Sample types are identified by a type character:
'a' - ASCII (8 bits)
'i' - integer (32 bits)
'f' - float (32 bits)
'd' - double (64 bits)

The size of each sample type in bytes is returned by the
get_samplesize(3) lookup routine.


 -- Common Usage --

Example programs using libmseed are provided in the 'examples'
directory of the source code distribution.

One of the most common tasks is to read a file of Mini-SEED records
and either perform some action based on the header values or apply
some process to the data samples.  This task is greatly simplified by
using the library functions ms_readmsr(3) and ms_readtraces(3).  The
ms_readmsr(3) routine will open a specified file and return MSRecord
structures for each Mini-SEED record it reads from the file.  The
ms_readtraces(3) routine will do the same except add all the data read
to a MSTraceGroup, this is ideal for quickly reading data for
processing.  Both of these routines are able to automatically detect
record length.

Skeleton code for reading a file with ms_readmsr(3):

main() {
  MSRecord *msr = NULL;
  int retcode;

  while ( (retcode = msr_readmsr (&msr, filename, 0, NULL, NULL, 1, 0, verbose)) == MS_NOERROR )
    {
       /* Do something with the record here, e.g. print */
       msr_print (msr, verbose);
    }

  if ( retcode != MS_ENDOFFILE )
    ms_log (2, "Cannot read %s: %s\n", filename, ms_errorstr(retcode));

  /* Cleanup memory and close file */
  ms_readmsr (&msr, NULL, 0, NULL, NULL, 0, 0);
}

For reading two files with ms_readtraces(3):

main() {
  MSTraceGroup *mstg = NULL;
  int retcode;

  retcode = ms_readtraces (&mstg, filename, 0, -1.0, -1.0, 0, 1, 0, verbose);

  if ( retcode != MS_ENDOFFILE )
    ms_log (2, "Cannot read %s: %s\n", filename, ms_errorstr(retcode));

  retcode = ms_readtraces (&mstg, filename2, 0, -1.0, -1.0, 0, 1, 0, verbose);

  if ( retcode != MS_ENDOFFILE )
    ms_log (2, "Cannot read %s: %s\n", filename2, ms_errorstr(retcode));

  if ( ! mstg )
    {
      fprintf (stderr, "Error reading file\\n");
      return -1;
    }

  /* Do something with the traces here, e.g. print */
  mst_printtracelist (mstg, 0, verbose, 0);

  mst_freegroup (&mstg);
}

Another common task is to create (pack) Mini-SEED records. The library
supports packing of Mini-SEED either from MSRecord structures, MSTrace
structures or MSTraceGroup collections using, respectively, msr_pack(3),
mst_pack(3) or mst_packgroup(3).  In each case the appropriate data
structure and parameters are provided to the routine along with a
function pointer to a routine that will be called each time a record
is complete and should be disposed of.

When packing Mini-SEED records the concept of a record header template
is used, the template is always in the form of a MSRecord structure.
This allows the calling program to dictate the contents, with a few
exceptions, of the header in the final data records.

Skeleton code for creating (packing) Mini-SEED records with
mst_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 file\n", (char *)srcname);
    }
}

main() {
  int psamples;
  int precords;
  MSTrace *mst;
  char srcname[50];

  mst = mst_init (NULL);

  /* Populate MSTrace values */
  strcpy (mst->network, "XX");
  strcpy (mst->station, "TEST");
  strcpy (mst->channel, "BHE");
  mst->starttime = ms_seedtimestr2hptime ("2004,350,00:00:00.000000");
  mst->samprate = 40.0;

  /* The datasamples pointer and numsamples counter will be adjusted by
     the packing routine, the datasamples array must be dynamic memory
     allocated by the malloc() family of routines. */
  mst->datasamples = dataptr; /* pointer to 32-bit integer data samples */  
  mst->numsamples = 1234;
  mst->sampletype = 'i';      /* declare type to be 32-bit integers */

  mst_srcname (mst, srcname, 0);

  /* Pack 4096 byte, big-endian records, using Steim-2 compression */
  precords = mst_pack (mst, &record_handler, srcname, 4096, DE_STEIM2,
                                     1, &psamples, 1, verbose, NULL);

  ms_log (0, "Packed %d samples into %d records\n", psamples, precords);

  mst_free (&mst);
}