Add SerdNodes class for storing a cache of nodes

6 files changed, 309 insertions, 3 deletions

diff --git a/serd/serd.h b/serd/serd.h
index 4fc2dc63..17febad9 100644
--- a/serd/serd.h
+++ b/serd/serd.h
@@ -62,6 +62,14 @@ extern "C" {
 typedef struct SerdWorldImpl SerdWorld;
 
 /**
+   Nodes.
+
+   A hashing container for nodes that can be used for interning and simplified
+   memory management.
+*/
+typedef struct SerdNodesImpl SerdNodes;
+
+/**
    Statement.
 
    A subject, predicate, and object, with optional graph context.
@@ -1301,6 +1309,63 @@ serd_writer_finish(SerdWriter* writer);
 
 /**
    @}
+   @name Nodes
+   @{
+*/
+
+/**
+   Create a new node set.
+*/
+SERD_API
+SerdNodes*
+serd_nodes_new(void);
+
+/**
+   Free `nodes` and all nodes that are stored in it.
+
+   Note that this invalidates any pointers previously returned from
+   `serd_nodes_intern()` or `serd_nodes_manage()` calls on `nodes`.
+*/
+SERD_API
+void
+serd_nodes_free(SerdNodes* nodes);
+
+/**
+   Intern `node`.
+
+   Multiple calls with equivalent nodes will return the same pointer.
+
+   @return A node that is different than, but equivalent to, `node`.
+*/
+SERD_API
+const SerdNode*
+serd_nodes_intern(SerdNodes* nodes, const SerdNode* node);
+
+/**
+   Manage `node`.
+
+   Like `serd_nodes_intern`, but takes ownership of `node`, freeing it and
+   returning a previously interned/managed equivalent node if necessary.
+
+   @return A node that is equivalent to `node`.
+*/
+SERD_API
+const SerdNode*
+serd_nodes_manage(SerdNodes* nodes, SerdNode* node);
+
+/**
+   Dereference `node`.
+
+   Decrements the reference count of `node`, and frees the internally stored
+   equivalent node if this was the last reference.  Does nothing if no node
+   equivalent to `node` is stored in `nodes`.
+*/
+SERD_API
+void
+serd_nodes_deref(SerdNodes* nodes, const SerdNode* node);
+
+/**
+   @}
    @name Statement
    @{
 */
diff --git a/src/node.c b/src/node.c
index 223598c4..d20fbb1f 100644
--- a/src/node.c
+++ b/src/node.c
@@ -98,7 +98,7 @@ serd_node_check_padding(const SerdNode* node)
 #endif
 }
 
-static size_t
+size_t
 serd_node_total_size(const SerdNode* node)
 {
 	const size_t len = sizeof(SerdNode) + serd_node_pad_size(node->n_bytes);
diff --git a/src/node.h b/src/node.h
index 0763168f..bfd9ebf5 100644
--- a/src/node.h
+++ b/src/node.h
@@ -41,6 +41,7 @@ serd_node_buffer_c(const SerdNode* node)
 
 SerdNode* serd_node_malloc(size_t n_bytes, SerdNodeFlags flags, SerdType type);
 void      serd_node_set(SerdNode** dst, const SerdNode* src);
+size_t    serd_node_total_size(const SerdNode* node);
 void      serd_node_zero_pad(SerdNode* node);
 SerdNode* serd_new_resolved_uri_i(const char* str, const SerdURI* base);
 
diff --git a/src/nodes.c b/src/nodes.c
new file mode 100644
index 00000000..b5792962
--- /dev/null
+++ b/src/nodes.c
@@ -0,0 +1,142 @@
+/*
+  Copyright 2011-2018 David Robillard <http://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 "node.h"
+
+#include "serd/serd.h"
+#include "zix/common.h"
+#include "zix/digest.h"
+#include "zix/hash.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct {
+	size_t    refs;
+	SerdNode* node;
+} NodesEntry;
+
+typedef struct {
+	size_t          refs;
+	const SerdNode* node;
+} NodesSearchKey;
+
+struct SerdNodesImpl {
+	ZixHash* hash;
+};
+
+static uint32_t
+nodes_hash(const void* n)
+{
+	const SerdNode* node = ((const NodesEntry*)n)->node;
+	uint32_t        hash = zix_digest_start();
+	hash = zix_digest_add(hash, node, serd_node_total_size(node));
+	return hash;
+}
+
+static bool
+nodes_equal(const void* a, const void* b)
+{
+	const SerdNode* a_node = ((const NodesEntry*)a)->node;
+	const SerdNode* b_node = ((const NodesEntry*)b)->node;
+	const size_t    a_size = serd_node_total_size(a_node);
+	const size_t    b_size = serd_node_total_size(b_node);
+	return ((a_node == b_node) ||
+	        (a_size == b_size && !memcmp(a_node, b_node, a_size)));
+}
+
+static void
+free_entry(void* value, void* user_data)
+{
+	(void)user_data;
+
+	NodesEntry* entry = (NodesEntry*)value;
+	serd_node_free(entry->node);
+}
+
+SerdNodes*
+serd_nodes_new(void)
+{
+	SerdNodes* nodes = (SerdNodes*)calloc(1, sizeof(SerdNodes));
+	nodes->hash = zix_hash_new(nodes_hash, nodes_equal, sizeof(NodesEntry));
+	return nodes;
+}
+
+void
+serd_nodes_free(SerdNodes* nodes)
+{
+	zix_hash_foreach(nodes->hash, free_entry, nodes);
+	zix_hash_free(nodes->hash);
+	free(nodes);
+}
+
+const SerdNode*
+serd_nodes_intern(SerdNodes* nodes, const SerdNode* node)
+{
+	if (!node) {
+		return NULL;
+	}
+
+	NodesSearchKey key      = { 1, node };
+	NodesEntry*    inserted = NULL;
+	switch (zix_hash_insert(nodes->hash, &key, (void**)&inserted)) {
+	case ZIX_STATUS_EXISTS:
+		assert(serd_node_equals(inserted->node, node));
+		++inserted->refs;
+		break;
+	case ZIX_STATUS_SUCCESS:
+		inserted->node = serd_node_copy(node);
+	default: break;
+	}
+
+	return inserted ? inserted->node : NULL;
+}
+
+const SerdNode*
+serd_nodes_manage(SerdNodes* nodes, SerdNode* node)
+{
+	if (!node) {
+		return NULL;
+	}
+
+	NodesSearchKey key      = { 1, node };
+	NodesEntry*    inserted = NULL;
+	switch (zix_hash_insert(nodes->hash, &key, (void**)&inserted)) {
+	case ZIX_STATUS_EXISTS:
+		assert(serd_node_equals(inserted->node, node));
+		serd_node_free(node);
+		++inserted->refs;
+		break;
+	default: break;
+	}
+
+	return inserted ? inserted->node : NULL;
+}
+
+void
+serd_nodes_deref(SerdNodes* nodes, const SerdNode* node)
+{
+	NodesSearchKey key   = { 1, node };
+	NodesEntry*    entry = (NodesEntry*)zix_hash_find(nodes->hash, &key);
+	if (entry && --entry->refs == 0) {
+		SerdNode* const intern_node = entry->node;
+		zix_hash_remove(nodes->hash, entry);
+		serd_node_free(intern_node);
+	}
+}
diff --git a/tests/nodes_test.c b/tests/nodes_test.c
new file mode 100644
index 00000000..ac2e56c0
--- /dev/null
+++ b/tests/nodes_test.c
@@ -0,0 +1,93 @@
+/*
+  Copyright 2018 David Robillard <http://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.
+*/
+
+#undef NDEBUG
+
+#include "serd/serd.h"
+
+#include <assert.h>
+#include <stddef.h>
+
+static int
+test_intern(void)
+{
+	SerdNodes* nodes = serd_nodes_new();
+	SerdNode*  node  = serd_new_string("node");
+
+	const SerdNode* interned1 = serd_nodes_intern(nodes, node);
+	assert(serd_node_equals(node, interned1));
+
+	const SerdNode* interned2 = serd_nodes_intern(nodes, node);
+	assert(serd_node_equals(node, interned2));
+	assert(interned1 == interned2);
+
+	serd_node_free(node);
+	serd_nodes_free(nodes);
+	return 0;
+}
+
+static int
+test_manage(void)
+{
+	SerdNodes* nodes = serd_nodes_new();
+	SerdNode*  node  = serd_new_string("node");
+
+	assert(!serd_nodes_manage(nodes, NULL));
+
+	const SerdNode* managed1 = serd_nodes_manage(nodes, node);
+	assert(managed1 == node);
+
+	SerdNode*       equal    = serd_new_string("node");
+	const SerdNode* managed2 = serd_nodes_manage(nodes, equal);
+	assert(managed2 == node);
+
+	serd_nodes_free(nodes);
+	return 0;
+}
+
+static int
+test_deref(void)
+{
+	SerdNodes*      nodes   = serd_nodes_new();
+	const SerdNode* managed = serd_nodes_manage(nodes, serd_new_string("node"));
+
+	serd_nodes_deref(nodes, managed);
+
+	SerdNode*       node     = serd_new_string("node");
+	const SerdNode* interned = serd_nodes_intern(nodes, node);
+
+	assert(interned != node);
+
+	serd_node_free(node);
+	serd_nodes_free(nodes);
+	return 0;
+}
+
+int
+main(void)
+{
+	typedef int (*TestFunc)(void);
+
+	const TestFunc tests[] = { test_intern, test_manage, test_deref, NULL };
+
+	for (const TestFunc* t = tests; *t; ++t) {
+		if ((*t)()) {
+			return 1;
+		}
+	}
+
+	return 0;
+}
diff --git a/wscript b/wscript
index dbb97987..81a9b1a9 100644
--- a/wscript
+++ b/wscript
@@ -79,6 +79,7 @@ lib_source = ['src/base64.c',
               'src/env.c',
               'src/n3.c',
               'src/node.c',
+              'src/nodes.c',
               'src/reader.c',
               'src/sink.c',
               'src/statement.c',
@@ -87,7 +88,9 @@ lib_source = ['src/base64.c',
               'src/system.c',
               'src/uri.c',
               'src/world.c',
-              'src/writer.c']
+              'src/writer.c',
+              'src/zix/digest.c',
+              'src/zix/hash.c']
 
 def build(bld):
     # C Headers
@@ -147,7 +150,8 @@ def build(bld):
         for prog in [('serdi_static', 'src/serdi.c'),
                      ('cursor_test', 'tests/cursor_test.c'),
                      ('serd_test', 'tests/serd_test.c'),
-                     ('read_chunk_test', 'tests/read_chunk_test.c')]:
+                     ('read_chunk_test', 'tests/read_chunk_test.c'),
+                     ('nodes_test', 'tests/nodes_test.c')]:
             bld(features     = 'c cprogram',
                 source       = prog[1],
                 use          = 'libserd_profiled',
@@ -418,6 +422,7 @@ def test(tst):
 
     with tst.group('Unit') as check:
         check(['./cursor_test'])
+        check(['./nodes_test'])
         check(['./serd_test'])
         check(['./read_chunk_test'])