gd_bof(3)

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9gd_bof(3)                           GETDATA                          gd_bof(3)
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NAME

14       gd_bof — find the start of data in a Dirfile field
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SYNOPSIS

18       #include <getdata.h>
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20       off_t gd_bof(DIRFILE *dirfile, const char *field_code);
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DESCRIPTION

24       The  gd_bof()  function  queries  a  dirfile(5)  database  specified by
25       dirfile and finds the beginning-of-field marker for  the  vector  field
26       given by field_code.
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28       The  caller  should not assume that the beginning-of-field marker falls
29       on a frame boundary.  The beginning-of-field marker is never negative.
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31       For a RAW field, the beginning-of-field corresponds to the frame offset
32       of  that  field (see gd_frameoffset(3)).  The beginning-of-field marker
33       of the special field INDEX is zero.
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35       The beginning-of-field of a PHASE field is  the  beginning-of-field  of
36       its  input  adjusted  by the PHASE field's shift (or zero, if the shift
37       would make it negative).  The beginning-of-field for all  other  vector
38       fields is the the latest beginning-of-field of any of its input fields.
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40       If  the  beginning-of-field marker of a field is greather than or equal
41       to its end-of-field marker (see gd_eof(3)), then that field contains no
42       data.  For a RAW field, the difference between the locations of the be‐
43       ginning- and end-of-field markers indicates the number  of  samples  of
44       data actually stored on disk.
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46       The  dirfile  argument  must point to a valid DIRFILE object previously
47       created by a call to gd_open(3).
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RETURN VALUE

51       Upon successful completion, gd_bof()  returns  a  non-negative  integer
52       which  is  the  sample  number of the beginning-of-field marker for the
53       specified field.  On error, it returns a  negative-valued  error  code.
54       Possible error codes are:
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56       GD_E_BAD_CODE
57               The  field specified by field_code or one of the fields it uses
58               as input was not found in the database.
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60       GD_E_BAD_DIRFILE
61               The supplied dirfile was invalid.
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63       GD_E_DIMENSION
64               A scalar field was found where a vector field was  expected  in
65               the  definition  of  field_code  or  one of its inputs, or else
66               field_code itself specified a scalar field.
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68       GD_E_INTERNAL_ERROR
69               An internal error occurred in the library while trying to  per‐
70               form  the  task.   This indicates a bug in the library.  Please
71               report the incident to the GetData developers.
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73       GD_E_RECURSE_LEVEL
74               Too many levels of recursion were encountered while  trying  to
75               resolve  field_code.   This usually indicates a circular depen‐
76               dency in field specification in the dirfile.
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78       The error code is also stored in the DIRFILE  object  and  may  be  re‐
79       trieved after this function returns by calling gd_error(3).  A descrip‐
80       tive  error  string  for  the  error  may  be   obtained   by   calling
81       gd_error_string(3).
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HISTORY

85       The gd_bof() function appeared in GetData-0.7.0.
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87       Before  GetData-0.10.0,  this  function  could also fail with the error
88       code GD_E_ALLOC.
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90       In GetData-0.10.0, the error return from this function changed from  -1
91       to a negative-valued error code.
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NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

HISTORY

SEE ALSO