---
name: "msr_parse_selection"
section: "3"
platform: "linux"
package: "libmseed-doc"
version: "2.19.8-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/msr_parse_selection"
---

# msr\_parse\_selection(3)

Detect and parse a SEED data record from a memory buffer

## NAME

msr\_parse - Detect and parse a SEED data record from a memory buffer

## SYNOPSIS

```
#include <libmseed.h>
int  msr_parse ( char *record, int recbuflen, MSRecord **ppmsr,
                 int reclen, flag dataflag, flag verbose );
int  msr_parse_selection ( char *recbuf, int recbuflen,
                           int64_t *offset, MSRecord **ppmsr,
                           int reclen, Selections *selections,
                           flag dataflag, flag verbose );
int  ms_detect ( const char *record, int recbuflen );
```

## DESCRIPTION

**msr\_parse** will parse a SEED data record from the *record* buffer and populate the MSRecord structure at *ppmsr*, allocating one if needed.  The *recbuflen* argument is the length of the *record* buffer.  Records must begin at the start of the buffer.

If *reclen* is 0 or negative the length of record is automatically determined, otherwise *reclen* should be the correct record length.  For auto detection of record length the record should include a 1000 blockette or be followed by another record header in the buffer.

If *dataflag* is true (non-zero) the data samples will be unpacked when parsing the record.  This argument is passed directly to **[msr\_unpack(3)](/msr_unpack/3.md)**.

**msr\_parse\_selection** will parse the first SEED data record from the *recbuf* buffer that matches the optional *selections*. The *offset* value indicates where to start searching the buffer. On success, the MSRecord structure at *ppmsr* is populated and the *offset* to the record in the buffer is set.  See the example below for the intended usage pattern.

**ms\_detect** determines whether the supplied *record* buffer contains a SEED data record by verifying known signatures, if a record is found the record length is determined by:

1\) Searching the buffer up to *recbuflen* for a Blockette 1000.

2\) If no Blockette 1000 is found search at MINRECLEN-byte offsets for the fixed section of the next header in the buffer, thereby implying the record length.

## RETURN VALUES

**msr\_parse** returns values:

```
  0 : On success and populates the supplied MSRecord.
 >0 : Data record was detected but not enough data is present in buffer,
      the value returned is a hint of how much more data is needed.
 <0 : On error a negative libmseed error value is returned.
ms_detect returns values:
 -1 : Data record not detected or error
  0 : Data record detected but could not determine length
 >0 : Length of the data record in bytes
```

## EXAMPLE USAGE OF MS\_PARSE\_SELECTION()

The **ms\_parse\_selection()** routine uses the initial setting of *offset* as the starting point to search the buffer.  On successful parsing of a miniSEED record the value of *offset* will be the offset in the buffer to the record parsed.

To properly parse all records matching specificed selection criteria, a caller must check and manage the value of *offset*.  In particular, when the end of the buffer is reached a value of MS\_GENERROR will be returned and the caller should check if the offset is still within the buffer length to determine if this is a parsing error or simply the end of the buffer.

The following example illustrates the intended usage:

```
  char *recbuf = <memory buffer containing records>;
  int64_t recbuflen = <length of buffer>;
  int64_t offset = 0;
  MSRecord *msr = NULL;
  int reclen = -1;
  Selections *selections = NULL;
  flag dataflag = 1;
  flag verbose = 0;
  // You probaby want to set Selections
  // For example with a call to ms_readselectionsfile (&selections, selectfile)
  /* Loop over all selected records in recbuf */
  while ( offset < recbuflen )
    {
      if ( msr_parse_selection (recbuf, recbuflen, &offset, &msr, reclen, selections, dataflag, verbose) )
        {
          /* Only print error if offset is still within buffer length */
          if ( verbose && offset < recbuflen )
          ms_log (2, "Error parsing record at offset %"PRId64"0, offset);
        }
      else /* Successfully found and parsed record */
        {
          /* Do something with the record, for example print the details */
          msr_print (msr, verbose);
          /* Increment offset in buffer for subsequent call to msr_parse_selection() */
          offset += msr->reclen;
        }
    }
  /* Clean up */
  msr_free (&msr);
  if ( selections )
    ms_freeselections (selections);
```

## SEE ALSO

**[msr\_unpack(3)](/msr_unpack/3.md)**, **[ms\_parse\_raw(3)](/ms_parse_raw/3.md)** and **[ms\_errorstr(3)](/ms_errorstr/3.md)**

## AUTHOR

```
Chad Trabant
IRIS Data Management Center
```