1 files changed, 114 insertions, 0 deletions
diff --git a/plugins/eg-params.lv2/state_map.h b/plugins/eg-params.lv2/state_map.h
new file mode 100644
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--- /dev/null
+++ b/plugins/eg-params.lv2/state_map.h
@@ -0,0 +1,114 @@
+/*
+  LV2 State Map
+  Copyright 2016 David Robillard <d@drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "lv2/atom/atom.h"
+#include "lv2/urid/urid.h"
+
+#include <stdarg.h>
+#include <stdlib.h>
+
+/** Entry in an array that serves as a dictionary of properties. */
+typedef struct {
+	const char* uri;
+	LV2_URID    urid;
+	LV2_Atom*   value;
+} StateMapItem;
+
+/** Comparator for StateMapItems sorted by URID. */
+static int
+state_map_cmp(const void* a, const void* b)
+{
+	const StateMapItem* ka = (const StateMapItem*)a;
+	const StateMapItem* kb = (const StateMapItem*)b;
+	if (ka->urid < kb->urid) {
+		return -1;
+	} else if (kb->urid < ka->urid) {
+		return 1;
+	}
+	return 0;
+}
+
+/** Helper macro for terse state map initialisation. */
+#define STATE_MAP_INIT(type, ptr) \
+	(LV2_ATOM__ ## type), \
+	(sizeof(*ptr) - sizeof(LV2_Atom)), \
+	(ptr)
+
+/**
+   Initialise a state map.
+
+   The variable parameters list must be NULL terminated, and is a sequence of
+   const char* uri, const char* type, uint32_t size, LV2_Atom* value.  The
+   value must point to a valid atom that resides elsewhere, the state map is
+   only an index and does not contain actual state values.  The macro
+   STATE_MAP_INIT can be used to make simpler code when state is composed of
+   standard atom types, for example:
+
+   struct Plugin {
+       LV2_URID_Map* map;
+       StateMapItem  props[3];
+       // ...
+   };
+
+   state_map_init(
+       self->props, self->map, self->map->handle,
+       PLUG_URI "#gain",   STATE_MAP_INIT(Float,  &state->gain),
+       PLUG_URI "#offset", STATE_MAP_INIT(Int,    &state->offset),
+       PLUG_URI "#file",   STATE_MAP_INIT(Path,   &state->file),
+       NULL);
+*/
+static void
+state_map_init(StateMapItem        dict[],
+               LV2_URID_Map*       map,
+               LV2_URID_Map_Handle handle,
+               /* const char* uri, const char* type, uint32_t size, LV2_Atom* value */ ...)
+{
+	// Set dict entries from parameters
+	unsigned i = 0;
+	va_list  args;
+	va_start(args, handle);
+	for (const char* uri; (uri = va_arg(args, const char*)); ++i) {
+		const char*     type  = va_arg(args, const char*);
+		const uint32_t  size  = va_arg(args, uint32_t);
+		LV2_Atom* const value = va_arg(args, LV2_Atom*);
+		dict[i].uri         = uri;
+		dict[i].urid        = map->map(map->handle, uri);
+		dict[i].value       = value;
+		dict[i].value->size = size;
+		dict[i].value->type = map->map(map->handle, type);
+	}
+	va_end(args);
+
+	// Sort for fast lookup by URID by state_map_find()
+	qsort(dict, i, sizeof(StateMapItem), state_map_cmp);
+}
+
+/**
+   Retrieve an item from a state map by URID.
+
+   This takes O(lg(n)) time, and is useful for implementing generic property
+   access with little code, for example to respond to patch:Get messages for a
+   specific property.
+*/
+static StateMapItem*
+state_map_find(StateMapItem dict[], uint32_t n_entries, LV2_URID urid)
+{
+	const StateMapItem key = { NULL, urid, NULL };
+	return (StateMapItem*)bsearch(
+		&key, dict, n_entries, sizeof(StateMapItem), state_map_cmp);
+}
+