.Dd September 24, 2026
.Dt ENFILADE 3
.Os
.Sh NAME
.Nm enfilade
.Nd small Model-T-style tumbler-addressed enfilade
.Sh SYNOPSIS
.In enfilade.h
.Ft enfilade_t *
.Fn create_enfilade void
.Ft void
.Fn destroy_enfilade "enfilade_t *enf"
.Ft enf_result_t
.Fn put_enfilade "enfilade_t *enf" "const char *tumbler" "void *datum"
.Ft enf_result_t
.Fn remove_enfilade "enfilade_t *enf" "const char *tumbler"
.Ft void *
.Fn getXtumbler_enfilade "enfilade_t *enf" "const char *tumbler"
.Ft enf_result_t
.Fn getXtumbler_values_enfilade "enfilade_t *enf" "const char *tumbler" "void ***items" "size_t *count"
.Ft enf_result_t
.Fn getXrange_values_enfilade "enfilade_t *enf" "int64_t start" "int64_t end" "void ***items" "size_t *count"
.Ft void
.Fn enfilade_visit_data "enfilade_t *enf" "enfilade_datum_visitor visitor" "void *context"
.Sh DESCRIPTION
An
.Nm
is a tree whose local keys are unsigned integer tumbler fields.
Each node can contain terminal datum values and child enfilades at the same
numeric keys.
.Pp
Putting
.Ql 1.2.3
creates the path through keys 1, 2, and 3.  The datum is stored at the final
key.
.Pp
The interface is intentionally small and follows the behavior of the
Model-T-style Python reference implementation used by this project.
.Sh CREATION AND LIFETIME
.Fn create_enfilade
returns an empty enfilade or NULL on allocation failure.
.Fn destroy_enfilade
recursively frees the enfilade tree.
.Pp
The enfilade owns its tree nodes but does not own datum pointers supplied by
the caller.  The caller must keep every datum alive for as long as it may be
returned by a lookup and must destroy the enfilade before those datum objects
are destroyed.
.Sh INSERTION
.Fn put_enfilade
stores
.Fa datum
at the exact final field of
.Fa tumbler .
Missing intermediate child enfilades are created automatically.
.Pp
A second insertion at the same final key replaces the existing datum.
.Pp
If a final key already contains a datum and a child subtree, insertion replaces
only the datum.
.Sh REMOVAL
.Fn remove_enfilade
removes only the datum stored at the exact final key.
.Pp
A child subtree at that same key is retained.
Empty intermediate child enfilades are pruned after successful removal.
The datum pointer itself is never freed.
.Pp
A missing exact datum returns
.Dv ENF_ERR_NOT_FOUND .
.Sh EXACT LOOKUP
.Fn getXtumbler_enfilade
returns only the datum stored at the exact final key, or NULL if none exists or
the path is invalid.
.Pp
For callers that need reference-style flattened lookup,
.Fn getXtumbler_values_enfilade
walks every component except the last as a child path, then returns a newly
allocated array containing the datum at the final key followed by all data in
its child subtree.
.Pp
The caller owns the returned array and releases it with
.Xr free 3 .
The datum pointers remain owned by the caller.
.Sh RANGE
.Fn getXrange_values_enfilade
walks numeric keys at the current enfilade level from
.Fa start
through
.Fa end ,
inclusive, and recursively flattens their contents.
A negative
.Fa end
means there is no upper bound.
.Pp
This operation deliberately remains the existing
.Dq range
interface.  It is not a parser for dotted tumbler intervals.
.Sh TRAVERSAL
.Fn enfilade_visit_data
visits every stored datum.  The visitor callback is not retained after the
call.
The callback must not be assumed to outlive the traversal call.
.Sh EXAMPLE
.Bd -literal -offset indent
#include "enfilade.h"
#include <stdio.h>

int main(void)
{
    enfilade_t *e = create_enfilade();
    int value = 42;
    void *found;

    if (!e) return 1;
    if (put_enfilade(e, "1.2.3", &value).code != ENF_OK)
        return 1;

    found = getXtumbler_enfilade(e, "1.2.3");
    if (found)
        printf("%d\\n", *(int *)found);

    destroy_enfilade(e);
    return 0;
}
.Ed
.Sh ERRORS
.Bl -tag -width ENF_ERR_NOT_FOUND
.It Dv ENF_OK
Success.
.It Dv ENF_ERR_NULL
A required pointer was null.
.It Dv ENF_ERR_ADDR
The tumbler text is malformed.
.It Dv ENF_ERR_NOT_FOUND
A requested datum or intermediate child was absent.
.It Dv ENF_ERR_NOMEM
An allocation failed.
.El
.Sh THREADING
The enfilade structure does not provide internal locking.
External synchronization is required if multiple threads may access the same
instance concurrently.
.Sh SCOPE
This package implements the small tumbler-keyed tree only.  It does not
implement the broader Green machinery such as WIDs, DISPs, orgls, POOMs,
Spanfilades, persistent CRUM storage, rearrangement, or version management.
.Sh SEE ALSO
.Xr tumbler 3 ,
.Xr enfilade-s7 7 ,
.Xr ensifer 7
.Sh REFERENCES
.Lk https://raw.githubusercontent.com/enkiv2/ds-lib/refs/heads/master/Enfilade.py
.Pp
.Lk https://sentido-labs.com/en/library/201904240732/Xanadu%20Hypertext%20Documents.html