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<h1 id="sec60" class="chapter">Chapter&#XA0;8&#XA0;&#XA0; Hierarchical Grouping Routines </h1>
<p>These functions allow for the creation and manipulation of FITS HDU
Groups, as defined in "A Hierarchical Grouping Convention for FITS" by
Jennings, Pence, Folk and Schlesinger:</p><p>http://fits.gsfc.nasa.gov/group.html</p><p>A group is a
collection of HDUs whose association is defined by a <span style="font-style:italic">grouping
table</span>. HDUs which are part of a group are referred to as <span style="font-style:italic">member
HDUs</span> or simply as <span style="font-style:italic">members</span>. Grouping table member HDUs may
themselves be grouping tables, thus allowing for the construction of
open-ended hierarchies of HDUs.</p><p>Grouping tables contain one row for each member HDU. The grouping table
columns provide identification information that allows applications to
reference or "point to" the member HDUs. Member HDUs are expected, but
not required, to contain a set of GRPIDn/GRPLCn keywords in their
headers for each grouping table that they are referenced by. In this
sense, the GRPIDn/GRPLCn keywords "link" the member HDU back to its
Grouping table. Note that a member HDU need not reside in the same FITS
file as its grouping table, and that a given HDU may be referenced by
up to 999 grouping tables simultaneously.</p><p>Grouping tables are implemented as FITS binary tables with up to six
pre-defined column TTYPEn values: &#X2019;MEMBER_XTENSION&#X2019;, &#X2019;MEMBER_NAME&#X2019;,
&#X2019;MEMBER_VERSION&#X2019;, &#X2019;MEMBER_POSITION&#X2019;, &#X2019;MEMBER_URI_TYPE&#X2019; and &#X2019;MEMBER_LOCATION&#X2019;.
The first three columns allow member HDUs to be identified by reference to
their XTENSION, EXTNAME and EXTVER keyword values. The fourth column allows
member HDUs to be identified by HDU position within their FITS file.
The last two columns identify the FITS file in which the member HDU resides,
if different from the grouping table FITS file.</p><p>Additional user defined "auxiliary" columns may also be included with any
grouping table. When a grouping table is copied or modified the presence of
auxiliary columns is always taken into account by the grouping support
functions; however, the grouping support functions cannot directly
make use of this data.</p><p>If a grouping table column is defined but the corresponding member HDU
information is unavailable then a null value of the appropriate data type
is inserted in the column field. Integer columns (MEMBER_POSITION,
MEMBER_VERSION) are defined with a TNULLn value of zero (0). Character field
columns (MEMBER_XTENSION, MEMBER_NAME, MEMBER_URI_TYPE, MEMBER_LOCATION)
utilize an ASCII null character to denote a null field value.</p><p>The grouping support functions belong to two basic categories: those that
work with grouping table HDUs (ffgt**) and those that work with member HDUs
(ffgm**). Two functions, fits_copy_group() and fits_remove_group(), have the
option to recursively copy/delete entire groups. Care should be taken when
employing these functions in recursive mode as poorly defined groups could
cause unpredictable results. The problem of a grouping table directly or
indirectly referencing itself (thus creating an infinite loop) is protected
against; in fact, neither function will attempt to copy or delete an HDU
twice.</p>
<h2 id="sec61" class="section">8.1&#XA0;&#XA0;Grouping Table Routines</h2>
<dl class="description"><dt class="dt-description">
<span style="font-weight:bold">1 </span></dt><dd class="dd-description">Create (append) a grouping table at the end of the current FITS file
pointed to by fptr. The grpname parameter provides the grouping table
name (GRPNAME keyword value) and may be set to NULL if no group name
is to be specified. The grouptype parameter specifies the desired
structure of the grouping table and may take on the values:
GT_ID_ALL_URI (all columns created), GT_ID_REF (ID by reference columns),
GT_ID_POS (ID by position columns), GT_ID_ALL (ID by reference and
position columns), GT_ID_REF_URI (ID by reference and FITS file URI
columns), and GT_ID_POS_URI (ID by position and FITS file URI columns). <a id="ffgtcr"></a>
</dd></dl><pre class="verbatim">  int fits_create_group / ffgtcr
      (fitsfile *fptr, char *grpname, int grouptype, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">2 </span></dt><dd class="dd-description">Create (insert) a grouping table just after the CHDU of the current FITS
file pointed to by fptr. All HDUs below the the insertion point will be
shifted downwards to make room for the new HDU. The grpname parameter
provides the grouping table name (GRPNAME keyword value) and may be set to
NULL if no group name is to be specified. The grouptype parameter specifies
the desired structure of the grouping table and may take on the values:
GT_ID_ALL_URI (all columns created), GT_ID_REF (ID by reference columns),
GT_ID_POS (ID by position columns), GT_ID_ALL (ID by reference and
position columns), GT_ID_REF_URI (ID by reference and FITS file URI
columns), and GT_ID_POS_URI (ID by position and FITS file URI columns) <a id="ffgtis"></a>.
</dd></dl><pre class="verbatim">  int fits_insert_group / ffgtis
      (fitsfile *fptr, char *grpname, int grouptype, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">3 </span></dt><dd class="dd-description">Change the structure of an existing grouping table pointed to by
gfptr. The grouptype parameter (see fits_create_group() for valid
parameter values) specifies the new structure of the grouping table. This
function only adds or removes grouping table columns, it does not add
or delete group members (i.e., table rows). If the grouping table already
has the desired structure then no operations are performed and function
simply returns with a (0) success status code. If the requested structure
change creates new grouping table columns, then the column values for all
existing members will be filled with the null values appropriate to the
column type. <a id="ffgtch"></a>
</dd></dl><pre class="verbatim">  int fits_change_group / ffgtch
      (fitsfile *gfptr, int grouptype, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">4 </span></dt><dd class="dd-description">Remove the group defined by the grouping table pointed to by gfptr, and
optionally all the group member HDUs. The rmopt parameter specifies the
action to be taken for
all members of the group defined by the grouping table. Valid values are:
OPT_RM_GPT (delete only the grouping table) and OPT_RM_ALL (recursively
delete all HDUs that belong to the group). Any groups containing the
grouping table gfptr as a member are updated, and if rmopt == OPT_RM_GPT
all members have their GRPIDn and GRPLCn keywords updated accordingly.
If rmopt == OPT_RM_ALL, then other groups that contain the deleted members
of gfptr are updated to reflect the deletion accordingly. <a id="ffgtrm"></a>
</dd></dl><pre class="verbatim">  int fits_remove_group / ffgtrm
      (fitsfile *gfptr, int rmopt, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">5 </span></dt><dd class="dd-description">Copy (append) the group defined by the grouping table pointed to by infptr,
and optionally all group member HDUs, to the FITS file pointed to by
outfptr. The cpopt parameter specifies the action to be taken for all
members of the group infptr. Valid values are: OPT_GCP_GPT (copy only
the grouping table) and OPT_GCP_ALL (recursively copy ALL the HDUs that
belong to the group defined by infptr). If the cpopt == OPT_GCP_GPT then
the members of infptr have their GRPIDn and GRPLCn keywords updated to
reflect the existence of the new grouping table outfptr, since they now
belong to the new group. If cpopt == OPT_GCP_ALL then the new
grouping table outfptr only contains pointers to the copied member HDUs
and not the original member HDUs of infptr. Note that, when
cpopt == OPT_GCP_ALL, all members of the group defined by infptr will be
copied to a single FITS file pointed to by outfptr regardless of their
file distribution in the original group. <a id="ffgtcp"></a>
</dd></dl><pre class="verbatim">  int fits_copy_group / ffgtcp
      (fitsfile *infptr, fitsfile *outfptr, int cpopt, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">6 </span></dt><dd class="dd-description"> Merge the two groups defined by the grouping table HDUs infptr and outfptr
by combining their members into a single grouping table. All member HDUs
(rows) are copied from infptr to outfptr. If mgopt == OPT_MRG_COPY then
infptr continues to exist unaltered after the merge. If the mgopt ==
OPT_MRG_MOV then infptr is deleted after the merge. In both cases,
the GRPIDn and GRPLCn keywords of the member HDUs are updated accordingly. <a id="ffgtmg"></a>
</dd></dl><pre class="verbatim">  int fits_merge_groups / ffgtmg
      (fitsfile *infptr, fitsfile *outfptr, int mgopt, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">7 </span></dt><dd class="dd-description">"Compact" the group defined by grouping table pointed to by gfptr. The
compaction is achieved by merging (via fits_merge_groups()) all direct
member HDUs of gfptr that are themselves grouping tables. The cmopt
parameter defines whether the merged grouping table HDUs remain after
merging (cmopt == OPT_CMT_MBR) or if they are deleted after merging
(cmopt == OPT_CMT_MBR_DEL). If the grouping table contains no direct
member HDUs that are themselves grouping tables then this function
does nothing. Note that this function is not recursive, i.e., only the
direct member HDUs of gfptr are considered for merging. <a id="ffgtcm"></a>
</dd></dl><pre class="verbatim">  int fits_compact_group / ffgtcm
      (fitsfile *gfptr, int cmopt, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">8 </span></dt><dd class="dd-description">Verify the integrity of the grouping table pointed to by gfptr to make
sure that all group members are accessible and that all links to other
grouping tables are valid. The firstfailed parameter returns the member
ID (row number) of the first member HDU to fail verification (if positive
value) or the first group link to fail (if negative value). If gfptr is
successfully verified then firstfailed contains a return value of 0. <a id="ffgtvf"></a>
</dd></dl><pre class="verbatim">  int fits_verify_group / ffgtvf
      (fitsfile *gfptr, &gt; long *firstfailed, int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">9 </span></dt><dd class="dd-description"> Open a grouping table that contains the member HDU pointed to by mfptr.
The grouping table to open is defined by the grpid parameter, which
contains the keyword index value of the GRPIDn/GRPLCn keyword(s) that
link the member HDU mfptr to the grouping table. If the grouping table
resides in a file other than the member HDUs file then an attempt is
first made to open the file readwrite, and failing that readonly. A
pointer to the opened grouping table HDU is returned in gfptr.<p>Note that it is possible, although unlikely and undesirable, for the
GRPIDn/GRPLCn keywords in a member HDU header to be non-continuous, e.g.,
GRPID1, GRPID2, GRPID5, GRPID6. In such cases, the grpid index value
specified in the function call shall identify the (grpid)th GRPID value.
In the above example, if grpid == 3, then the group specified by GRPID5
would be opened. <a id="ffgtop"></a>
</p></dd></dl><pre class="verbatim">  int fits_open_group / ffgtop
      (fitsfile *mfptr, int group, &gt; fitsfile **gfptr, int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">10</span></dt><dd class="dd-description"> Add a member HDU to an existing grouping table pointed to by gfptr.
The member HDU may either be pointed to mfptr (which must be positioned
to the member HDU) or, if mfptr == NULL, identified by the hdupos parameter
(the HDU position number, Primary array == 1) if both the grouping table
and the member HDU reside in the same FITS file. The new member HDU shall
have the appropriate GRPIDn and GRPLCn keywords created in its header.
Note that if the member HDU is already a member of the group then it will
not be added a second time. <a id="ffgtam"></a>
</dd></dl><pre class="verbatim">  int fits_add_group_member / ffgtam
      (fitsfile *gfptr, fitsfile *mfptr, int hdupos, &gt; int *status)
</pre>
<h2 id="sec62" class="section">8.2&#XA0;&#XA0;Group Member Routines</h2>
<dl class="description"><dt class="dt-description">
<span style="font-weight:bold">1 </span></dt><dd class="dd-description"> Return the number of member HDUs in a grouping table gfptr. The number
member HDUs is just the NAXIS2 value (number of rows) of the grouping
table. <a id="ffgtnm"></a>
</dd></dl><pre class="verbatim">  int fits_get_num_members / ffgtnm
      (fitsfile *gfptr, &gt; long *nmembers, int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">2 </span></dt><dd class="dd-description"> Return the number of groups to which the HDU pointed to by mfptr is
linked, as defined by the number of GRPIDn/GRPLCn keyword records that
appear in its header. Note that each time this function is called, the
indices of the GRPIDn/GRPLCn keywords are checked to make sure they
are continuous (ie no gaps) and are re-enumerated to eliminate gaps if
found. <a id="ffgmng"></a>
</dd></dl><pre class="verbatim">  int fits_get_num_groups / ffgmng
      (fitsfile *mfptr, &gt; long *nmembers, int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">3 </span></dt><dd class="dd-description"> Open a member of the grouping table pointed to by gfptr. The member to
open is identified by its row number within the grouping table as given
by the parameter &#X2019;member&#X2019; (first member == 1) . A fitsfile pointer to
the opened member HDU is returned as mfptr. Note that if the member HDU
resides in a FITS file different from the grouping table HDU then the
member file is first opened readwrite and, failing this, opened readonly. <a id="ffgmop"></a>
</dd></dl><pre class="verbatim">  int fits_open_member / ffgmop
      (fitsfile *gfptr, long member, &gt; fitsfile **mfptr, int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">4 </span></dt><dd class="dd-description">Copy (append) a member HDU of the grouping table pointed to by gfptr.
The member HDU is identified by its row number within the grouping table
as given by the parameter &#X2019;member&#X2019; (first member == 1). The copy of the
group member HDU will be appended to the FITS file pointed to by mfptr,
and upon return mfptr shall point to the copied member HDU. The cpopt
parameter may take on the following values: OPT_MCP_ADD which adds a new
entry in gfptr for the copied member HDU, OPT_MCP_NADD which does not add
an entry in gfptr for the copied member, and OPT_MCP_REPL which replaces
the original member entry with the copied member entry. <a id="ffgmcp"></a>
</dd></dl><pre class="verbatim">  int fits_copy_member / ffgmcp
      (fitsfile *gfptr, fitsfile *mfptr, long member, int cpopt, &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">5 </span></dt><dd class="dd-description">Transfer a group member HDU from the grouping table pointed to by
infptr to the grouping table pointed to by outfptr. The member HDU to
transfer is identified by its row number within infptr as specified by
the parameter &#X2019;member&#X2019; (first member == 1). If tfopt == OPT_MCP_ADD then
the member HDU is made
a member of outfptr and remains a member of infptr. If tfopt == OPT_MCP_MOV
then the member HDU is deleted from infptr after the transfer to outfptr. <a id="ffgmtf"></a>
</dd></dl><pre class="verbatim">  int fits_transfer_member / ffgmtf
      (fitsfile *infptr, fitsfile *outfptr, long member, int tfopt,
       &gt; int *status)
</pre><dl class="description"><dt class="dt-description">
<span style="font-weight:bold">6 </span></dt><dd class="dd-description">Remove a member HDU from the grouping table pointed to by gfptr. The
member HDU to be deleted is identified by its row number in the grouping
table as specified by the parameter &#X2019;member&#X2019; (first member == 1). The rmopt
parameter may take on the following values: OPT_RM_ENTRY which
removes the member HDU entry from the grouping table and updates the
member&#X2019;s GRPIDn/GRPLCn keywords, and OPT_RM_MBR which removes the member
HDU entry from the grouping table and deletes the member HDU itself. <a id="ffgmrm"></a>
</dd></dl><pre class="verbatim">  int fits_remove_member / ffgmrm
      (fitsfile *fptr, long member, int rmopt, &gt; int *status)
</pre>
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