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.\" Hyphenation exceptions
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.\" gd_nentries.3.  The gd_nentries man page.
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.\" Copyright (C) 2012, 2016 D. V. Wiebe
.\"
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.\"
.\" This file is part of the GetData project.
.\"
.\" Permission is granted to copy, distribute and/or modify this document
.\" under the terms of the GNU Free Documentation License, Version 1.2 or
.\" any later version published by the Free Software Foundation; with no
.\" Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
.\" Texts.  A copy of the license is included in the `COPYING.DOC' file
.\" as part of this distribution.
.\"
.TH gd_nentries 3 "25 December 2016" "Version 0.10.0" "GETDATA"

.SH NAME
gd_nentries, gd_nfields, gd_nfields_by_type gd_nmfields, gd_nmfields_by_type,
gd_nmvectors, gd_nvectors \(em count field entries in a Dirfile

.SH SYNOPSIS
.SC
.B #include <getdata.h>
.HP
.BI "unsigned int gd_nentries(DIRFILE *" dirfile ,
.BI "const char *" parent ", unsigned int " type ", unsigned int " flags );
.HP
.BI "unsigned int gd_nfields(DIRFILE *" dirfile );
.HP
.BI "unsigned int gd_nfields_by_type(DIRFILE *" dirfile ", gd_entype_t " type );
.HP
.BI "unsigned int gd_nmfields(DIRFILE *" dirfile ", const char *" parent );
.HP
.BI "unsigned int gd_nmfields_by_type(DIRFILE *" dirfile ,
.BI "const char *" parent ", gd_entype_t " type );
.HP
.BI "unsigned int gd_nmvectors(DIRFILE *" dirfile ", const char *" parent );
.HP
.BI "unsigned int gd_nvectors(DIRFILE *" dirfile );
.EC

.SH DESCRIPTION
The
.FN gd_nentries
function queries a dirfile(5) database specified by
.ARG dirfile
and counts the number of metadata entries satisfying the provided criteria.  If
.ARG parent
is non-NULL, metafields under the field specified by
.ARG parent
are considered; otherwise, top-level fields are considered, and metafields
ignored.

The
.ARG type
argument should be one of the following symbols indicating an explicit entry
type to count:
.IP
.SC
.BR GD_BIT_ENTRY ", " GD_CARRAY_ENTRY ", " GD_CONST_ENTRY ", " GD_DIVIDE_ENTRY ,
.BR GD_INDEX_ENTRY ", " GD_INDIR_ENTRY ", " GD_LINCOM_ENTRY ,
.BR GD_LINTERP_ENTRY ", " GD_MPLEX_ENTRY ", " GD_MULTIPLY_ENTRY ,
.BR GD_PHASE_ENTRY ", " GD_POLYNOM_ENTRY ", " GD_RAW_ENTRY ", " GD_RECIP_ENTRY ,
.BR GD_SARRAY_ENTRY ", " GD_SBIT_ENTRY ", " GD_SINDIR_ENTRY ,
.BR GD_STRING_ENTRY ", " GD_WINDOW_ENTRY .
.EC
.PP
.RB ( GD_INDEX_ENTRY
is a special field type for the implicit
.I INDEX
field) or else one of the following special symbols:
.DD "GD_ALL_ENTRIES \fR(=0)"
Count entries of all types.
.DD GD_ALIAS_ENTRIES
Count only aliases.  This is the only way to get a count including aliases which
do not point to valid field codes.
.DD GD_SCALAR_ENTRIES
Count only scalar field types
.RB ( CONST ", " CARRAY ", " SARRAY ", " STRING ).
.DD GD_VECTOR_ENTRIES
Count only numeric-valued vector field types (all field types except
.B SINDIR
and the scalar field types listed above).
.PP
The
.ARG flags
argument should be zero or more of the following flags, bitwise or'd together:
.DD GD_ENTRIES_HIDDEN
Include hidden entries (see
.F3 gd_hidden )
in the count: normally hidden entries are skipped;
.DD GD_ENTRIES_NOALIAS
Exclude aliases from the count: normally aliases are considered the same as
their target (that is: a field with
.I n
aliases, plus its canonical name, will be counted
.IR n +1
times).

.PP
This function has a subset of the functionality of the
.F3 gd_match_entries
function (q.v.).

.SS Special Cases
The call
.RS
.BI gd_nfields( dirfile );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", NULL, GD_ALL_ENTRIES, 0);
.RE
.PP
The call
.RS
.BI gd_nfields_by_type( dirfile ", " type );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", NULL, " type ", 0);"
.RE
.PP
The call
.RS
.BI gd_nmfields( dirfile ", " parent );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", " parent ", GD_ALL_ENTRIES, 0);"
.RE
.PP
The call
.RS
.BI gd_nmfields_by_type( dirfile ", " parent ", " type );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", " parent ", " type ", 0);"
.RE
.PP
The call
.RS
.BI gd_nmvectors( dirfile ", " parent );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", " parent ", GD_VECTOR_ENTRIES, 0);"
.RE
.PP
The call
.RS
.BI gd_nvectors( dirfile );
.RE
.PP
is equivalent to
.RS
.BI gd_nentries( dirfile ", NULL, GD_VECTOR_ENTRIES, 0);"
.RE

.SH RETURN VALUE
Upon successful completion, these functions return an unsigned in indicating
the number of entries in the database satisfying the supplied criteria.

On error, these functions return zero and store a negative-valued error code in
the
.B DIRFILE
object which may be retrieved by a subsequent call to
.F3 gd_error .
Possible error codes are:
.DD GD_E_BAD_CODE
The supplied parent field code was not found, or referred to a metafield itself.
.DD GD_E_BAD_DIRFILE
The supplied dirfile was invalid.
.DD GD_E_BAD_ENTRY
The
.ARG type
parameter supplied was not one of the symbols listed above.
.PP
A descriptive error string for the error may be obtained by calling
.F3 gd_error_string .

.SH HISTORY
The
.FN get_nfields
function appeared in GetData-0.3.0.

The
.FN get_nfields_by_type ,
.FN get_nmfields ,
.FN get_nmfields_by_type ,
.FN get_nmvectors ,
and
.FN get_nvectors
functions appeared in GetData-0.4.0.

In GetData-0.7.0, these functions were renamed to
.FN gd_nfields ,
.FN gd_nfields_by_type ,
.FN gd_nmfields ,
.FN gd_nmfields_by_type ,
.FN gd_nmvectors ,
and
.FN gd_nvectors .

The
.FN gd_nentries
function appeared in GetData-0.8.0.

.SH SEE ALSO
dirfile(5),
.F3 gd_open ,
.F3 gd_entry_list ,
.F3 gd_error ,
.F3 gd_error_string ,
.F3 gd_hidden ,
.F3 gd_match_entries