ms_find_reclen.3

.TH MS_FIND_RECLEN 3 2006/11/08 "Libmseed API"
.SH NAME
ms_find_reclen - Determine SEED record data length

.SH SYNOPSIS
.nf
.B #include <libmseed.h>

.BI "int  \fBms_find_reclen\fP ( const char *" recbuf ", int " recbuflen ",
.BI "                            FILE " *fileptr " );
.fi

.SH DESCRIPTION
\fBms_find_reclen\fP verifies that the specified \fIrecbuf\fP buffer
contains a SEED data record by looking for data record signatures in
the fixed section data header and determines the data record length by
1) searching the buffer up to \fIrecbuflen\fP bytes for a Blockette
1000 and, failing that, 2) if \fIfileptr\fP is not NULL reading the
next 48 bytes from the file and looking for a data record signature
(with detection of the next data record implying the length of the
current record).  If data is read from \fIfileptr\fP the read position
is returned to it's position prior to this function call.

The MS_ISVALIDHEADER macro is used to verify that the buffer contains
a valid SEED data record.  When searching for the next record header
to determine record length one of the macros MS_ISVALIDHEADER or
MS_ISVALIDBLANK must test positively for a record to be detected.
Blank/noise records are records with a valid SEED sequence number
followed by ASCII space characters to the end of the record.

\fBms_find_reclen\fP will return 0 when it detects that the buffer
contains a SEED data record but cannot determine the record length.
This happens when no Blockette 1000 is not found within
\fIrecbuflen\fP bytes and, assuming a valid \fIfileptr\fP is supplied,
no record header is detected in the next 48 bytes of the file.  The
idea is to then read more data from the file (i.e. the next larger,
valid record length) and call \fBms_find_reclen\fP again and so on
until the record length can be determined.

.SH RETURN VALUES
\fBms_find_reclen\fP returns the length of the Mini-SEED record in
bytes or 0 if a data record was detected but the length could not be
determined or -1 when no data record was detected.

.SH SEE ALSO
\fBms_readmsr(3)\fP, \fBms_readtraces(3)\fP and \fBmsr_unpack(3)\fP.

.SH AUTHOR
.nf
Chad Trabant
IRIS Data Management Center
.fi