Merge pull request #196 from rgerhards/improve-performance

Performance improvements

json_object.c

@@ -69,7 +69,7 @@ static struct lh_table *json_object_table;
 static void json_object_init(void) __attribute__ ((constructor));
 static void json_object_init(void) {
 	MC_DEBUG("json_object_init: creating object table\n");
-	json_object_table = lh_kptr_table_new(128, "json_object_table", NULL);
+	json_object_table = lh_kptr_table_new(128, NULL);
 }
 
 static void json_object_fini(void) __attribute__ ((destructor));
@@ -95,9 +95,18 @@ static void json_object_fini(void)
 #endif /* REFCOUNT_DEBUG */
 
 
+/* helper for accessing the optimized string data component in json_object
+ */
+static const char *
+get_string_component(struct json_object *jso)
+{
+	return (jso->o.c_string.len < LEN_DIRECT_STRING_DATA) ?
+		   jso->o.c_string.str.data : jso->o.c_string.str.ptr;
+}
+
 /* string escaping */
 
-static int json_escape_str(struct printbuf *pb, char *str, int len)
+static int json_escape_str(struct printbuf *pb, const char *str, int len)
 {
 	int pos = 0, start_offset = 0;
 	unsigned char c;
@@ -362,7 +371,8 @@ static int json_object_object_to_json_string(struct json_object* jso,
 
 static void json_object_lh_entry_free(struct lh_entry *ent)
 {
-	free(ent->k);
+	if (!ent->k_is_constant)
+		free(ent->k);
 	json_object_put((struct json_object*)ent->v);
 }
 
@@ -380,7 +390,7 @@ struct json_object* json_object_new_object(void)
 	jso->_delete = &json_object_object_delete;
 	jso->_to_json_string = &json_object_object_to_json_string;
 	jso->o.c_object = lh_kchar_table_new(JSON_OBJECT_DEF_HASH_ENTRIES,
-					NULL, &json_object_lh_entry_free);
+					&json_object_lh_entry_free);
 	if (!jso->o.c_object)
 	{
 		json_object_generic_delete(jso);
@@ -403,6 +413,31 @@ struct lh_table* json_object_get_object(struct json_object *jso)
 	}
 }
 
+void json_object_object_add_ex(struct json_object* jso,
+	const char *const key,
+	struct json_object *const val,
+	const unsigned opts)
+{
+	// We lookup the entry and replace the value, rather than just deleting
+	// and re-adding it, so the existing key remains valid.
+	json_object *existing_value = NULL;
+	struct lh_entry *existing_entry;
+	const unsigned long hash = lh_get_hash(jso->o.c_object, (void*)key);
+	existing_entry = (opts & JSON_C_OBJECT_ADD_KEY_IS_NEW) ? NULL : 
+			      lh_table_lookup_entry_w_hash(jso->o.c_object, (void*)key, hash);
+	if (!existing_entry)
+	{
+		void *const k = (opts & JSON_C_OBJECT_KEY_IS_CONSTANT) ?
+					(void*)key : strdup(key);
+		lh_table_insert_w_hash(jso->o.c_object, k, val, hash, opts);
+		return;
+	}
+	existing_value = (void *)existing_entry->v;
+	if (existing_value)
+		json_object_put(existing_value);
+	existing_entry->v = val;
+}
+
 void json_object_object_add(struct json_object* jso, const char *key,
 			    struct json_object *val)
 {
@@ -410,10 +445,11 @@ void json_object_object_add(struct json_object* jso, const char *key,
 	// and re-adding it, so the existing key remains valid.
 	json_object *existing_value = NULL;
 	struct lh_entry *existing_entry;
-	existing_entry = lh_table_lookup_entry(jso->o.c_object, (void*)key);
+	const unsigned long hash = lh_get_hash(jso->o.c_object, (void*)key);
+	existing_entry = lh_table_lookup_entry_w_hash(jso->o.c_object, (void*)key, hash);
 	if (!existing_entry)
 	{
-		lh_table_insert(jso->o.c_object, strdup(key), val);
+		lh_table_insert_w_hash(jso->o.c_object, strdup(key), val, hash, 0);
 		return;
 	}
 	existing_value = (json_object  *)existing_entry->v;
@@ -422,6 +458,7 @@ void json_object_object_add(struct json_object* jso, const char *key,
 	existing_entry->v = val;
 }
 
+
 int json_object_object_length(struct json_object *jso)
 {
 	return lh_table_length(jso->o.c_object);
@@ -538,7 +575,7 @@ int32_t json_object_get_int(struct json_object *jso)
 	 * Parse strings into 64-bit numbers, then use the
 	 * 64-to-32-bit number handling below.
 	 */
-	if (json_parse_int64(jso->o.c_string.str, &cint64) != 0)
+	if (json_parse_int64(get_string_component(jso), &cint64) != 0)
 		return 0; /* whoops, it didn't work. */
 	o_type = json_type_int;
   }
@@ -586,7 +623,7 @@ int64_t json_object_get_int64(struct json_object *jso)
 	case json_type_boolean:
 		return jso->o.c_boolean;
 	case json_type_string:
-		if (json_parse_int64(jso->o.c_string.str, &cint) == 0)
+		if (json_parse_int64(get_string_component(jso), &cint) == 0)
 			return cint;
 	default:
 		return 0;
@@ -693,10 +730,10 @@ double json_object_get_double(struct json_object *jso)
     return jso->o.c_boolean;
   case json_type_string:
     errno = 0;
-    cdouble = strtod(jso->o.c_string.str,&errPtr);
+    cdouble = strtod(get_string_component(jso), &errPtr);
 
     /* if conversion stopped at the first character, return 0.0 */
-    if (errPtr == jso->o.c_string.str)
+    if (errPtr == get_string_component(jso))
         return 0.0;
 
     /*
@@ -736,14 +773,15 @@ static int json_object_string_to_json_string(struct json_object* jso,
 						 int flags)
 {
 	sprintbuf(pb, "\"");
-	json_escape_str(pb, jso->o.c_string.str, jso->o.c_string.len);
+	json_escape_str(pb, get_string_component(jso), jso->o.c_string.len);
 	sprintbuf(pb, "\"");
 	return 0;
 }
 
 static void json_object_string_delete(struct json_object* jso)
 {
-	free(jso->o.c_string.str);
+	if(jso->o.c_string.len >= LEN_DIRECT_STRING_DATA)
+		free(jso->o.c_string.str.ptr);
 	json_object_generic_delete(jso);
 }
 
@@ -754,33 +792,43 @@ struct json_object* json_object_new_string(const char *s)
 		return NULL;
 	jso->_delete = &json_object_string_delete;
 	jso->_to_json_string = &json_object_string_to_json_string;
-	jso->o.c_string.str = strdup(s);
-	if (!jso->o.c_string.str)
-	{
-		json_object_generic_delete(jso);
-		errno = ENOMEM;
-		return NULL;
-	}
 	jso->o.c_string.len = strlen(s);
+	if(jso->o.c_string.len < LEN_DIRECT_STRING_DATA) {
+		memcpy(jso->o.c_string.str.data, s, jso->o.c_string.len);
+	} else {
+		jso->o.c_string.str.ptr = strdup(s);
+		if (!jso->o.c_string.str.ptr)
+		{
+			json_object_generic_delete(jso);
+			errno = ENOMEM;
+			return NULL;
+		}
+	}
 	return jso;
 }
 
 struct json_object* json_object_new_string_len(const char *s, int len)
 {
+	char *dstbuf;
 	struct json_object *jso = json_object_new(json_type_string);
 	if (!jso)
 		return NULL;
 	jso->_delete = &json_object_string_delete;
 	jso->_to_json_string = &json_object_string_to_json_string;
-	jso->o.c_string.str = (char*)malloc(len + 1);
-	if (!jso->o.c_string.str)
-	{
-		json_object_generic_delete(jso);
-		errno = ENOMEM;
-		return NULL;
+	if(len < LEN_DIRECT_STRING_DATA) {
+		dstbuf = jso->o.c_string.str.data;
+	} else {
+		jso->o.c_string.str.ptr = (char*)malloc(len + 1);
+		if (!jso->o.c_string.str.ptr)
+		{
+			json_object_generic_delete(jso);
+			errno = ENOMEM;
+			return NULL;
+		}
+		dstbuf = jso->o.c_string.str.ptr;
 	}
-	memcpy(jso->o.c_string.str, (void *)s, len);
-	jso->o.c_string.str[len] = '\0';
+	memcpy(dstbuf, (void *)s, len);
+	dstbuf[len] = '\0';
 	jso->o.c_string.len = len;
 	return jso;
 }
@@ -792,7 +840,7 @@ const char* json_object_get_string(struct json_object *jso)
 	switch(jso->o_type)
 	{
 	case json_type_string:
-		return jso->o.c_string.str;
+		return get_string_component(jso);
 	default:
 		return json_object_to_json_string(jso);
 	}

json_object.h

@@ -63,6 +63,36 @@ extern "C" {
  */
 #define JSON_C_TO_STRING_NOZERO     (1<<2)
 
+/**
+ * A flag for the json_object_object_add_ex function which
+ * causes the value to be added without a check if it already exists.
+ * Note: it is the responsibilty of the caller to ensure that no
+ * key is added multiple times. If this is done, results are
+ * unpredictable. While this option is somewhat dangerous, it
+ * permits potentially large performance savings in code that
+ * knows for sure the key values are unique (e.g. because the
+ * code adds a well-known set of constant key values).
+ */
+#define JSON_C_OBJECT_ADD_KEY_IS_NEW (1<<1)
+/**
+ * A flag for the json_object_object_add_ex function which
+ * flags the key as being constant memory. This means that
+ * the key will NOT be copied via strdup(), resulting in a
+ * potentially huge performance win (malloc, strdup and
+ * free are usually performance hogs). It is acceptable to
+ * use this flag for keys in non-constant memory blocks if
+ * the caller ensure that the memory holding the key lives
+ * longer than the corresponding json object. However, this
+ * is somewhat dangerous and should only be done if really
+ * justified.
+ * The general use-case for this flag is cases where the
+ * key is given as a real constant value in the function
+ * call, e.g. as in
+ *   json_object_object_add_ex(obj, "ip", json,
+ *       JSON_C_OBJECT_KEY_IS_CONSTANT);
+ */
+#define JSON_C_OBJECT_KEY_IS_CONSTANT (1<<2)
+
 #undef FALSE
 #define FALSE ((json_bool)0)
 
@@ -283,6 +313,22 @@ extern int json_object_object_length(struct json_object* obj);
 extern void json_object_object_add(struct json_object* obj, const char *key,
 				   struct json_object *val);
 
+/** Add an object field to a json_object of type json_type_object
+ *
+ * The semantics are identical to json_object_object_add, except that an
+ * additional flag fields gives you more control over some detail aspects
+ * of processing. See the description of JSON_C_OBJECT_ADD_* flags for more
+ * details.
+ *
+ * @param obj the json_object instance
+ * @param key the object field name (a private copy will be duplicated)
+ * @param val a json_object or NULL member to associate with the given field
+ * @param opts process-modifying options. To specify multiple options, use 
+ *             arithmetic or (OPT1|OPT2)
+ */
+extern void json_object_object_add_ex(struct json_object* obj, const char *key,
+				   struct json_object *val, const unsigned opts);
+
 /** Get the json_object associate with a given object field
  *
  * *No* reference counts will be changed.  There is no need to manually adjust

json_object_private.h

@@ -16,6 +16,8 @@
 extern "C" {
 #endif
 
+#define LEN_DIRECT_STRING_DATA 32 /**< how many bytes are directly stored in json_object for strings? */
+
 typedef void (json_object_private_delete_fn)(struct json_object *o);
 
 struct json_object
@@ -32,7 +34,13 @@ struct json_object
     struct lh_table *c_object;
     struct array_list *c_array;
     struct {
-        char *str;
+	union {
+		/* optimize: if we have small strings, we can store them
+		 * directly. This saves considerable CPU cycles AND memory.
+		 */
+		char *ptr;
+		char data[LEN_DIRECT_STRING_DATA];
+	} str;
         int len;
     } c_string;
   } o;

linkhash.c

@@ -31,6 +31,27 @@
 #include "random_seed.h"
 #include "linkhash.h"
 
+/* hash functions */
+static unsigned long lh_char_hash(const void *k);
+static unsigned long lh_perllike_str_hash(const void *k);
+static lh_hash_fn *char_hash_fn = lh_char_hash;
+
+int
+json_global_set_string_hash(const int h)
+{
+	switch(h) {
+	case JSON_C_STR_HASH_DFLT:
+		char_hash_fn = lh_char_hash;
+		break;
+	case JSON_C_STR_HASH_PERLLIKE:
+		char_hash_fn = lh_perllike_str_hash;
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
 void lh_abort(const char *msg, ...)
 {
 	va_list ap;
@@ -40,7 +61,7 @@ void lh_abort(const char *msg, ...)
 	exit(1);
 }
 
-unsigned long lh_ptr_hash(const void *k)
+static unsigned long lh_ptr_hash(const void *k)
 {
 	/* CAW: refactored to be 64bit nice */
 	return (unsigned long)((((ptrdiff_t)k * LH_PRIME) >> 4) & ULONG_MAX);
@@ -404,7 +425,21 @@ static uint32_t hashlittle( const void *key, size_t length, uint32_t initval)
   return c;
 }
 
-unsigned long lh_char_hash(const void *k)
+/* a simple hash function similiar to what perl does for strings.
+ * for good results, the string should not be excessivly large.
+ */
+static unsigned long lh_perllike_str_hash(const void *k) 
+{
+    const char *rkey = (char*) k;
+    unsigned hashval = 1;
+
+    while (*rkey)
+        hashval = hashval * 33 + *rkey++;
+
+    return hashval;
+}
+
+static unsigned long lh_char_hash(const void *k)
 {
 	static volatile int random_seed = -1;
 
@@ -430,7 +465,7 @@ int lh_char_equal(const void *k1, const void *k2)
 	return (strcmp((const char*)k1, (const char*)k2) == 0);
 }
 
-struct lh_table* lh_table_new(int size, const char *name,
+struct lh_table* lh_table_new(int size,
 			      lh_entry_free_fn *free_fn,
 			      lh_hash_fn *hash_fn,
 			      lh_equal_fn *equal_fn)
@@ -442,7 +477,6 @@ struct lh_table* lh_table_new(int size, const char *name,
 	if(!t) lh_abort("lh_table_new: calloc failed\n");
 	t->count = 0;
 	t->size = size;
-	t->name = name;
 	t->table = (struct lh_entry*)calloc(size, sizeof(struct lh_entry));
 	if(!t->table) lh_abort("lh_table_new: calloc failed\n");
 	t->free_fn = free_fn;
@@ -452,16 +486,16 @@ struct lh_table* lh_table_new(int size, const char *name,
 	return t;
 }
 
-struct lh_table* lh_kchar_table_new(int size, const char *name,
+struct lh_table* lh_kchar_table_new(int size,
 				    lh_entry_free_fn *free_fn)
 {
-	return lh_table_new(size, name, free_fn, lh_char_hash, lh_char_equal);
+	return lh_table_new(size, free_fn, char_hash_fn, lh_char_equal);
 }
 
-struct lh_table* lh_kptr_table_new(int size, const char *name,
+struct lh_table* lh_kptr_table_new(int size,
 				   lh_entry_free_fn *free_fn)
 {
-	return lh_table_new(size, name, free_fn, lh_ptr_hash, lh_ptr_equal);
+	return lh_table_new(size, free_fn, lh_ptr_hash, lh_ptr_equal);
 }
 
 void lh_table_resize(struct lh_table *t, int new_size)
@@ -469,7 +503,7 @@ void lh_table_resize(struct lh_table *t, int new_size)
 	struct lh_table *new_t;
 	struct lh_entry *ent;
 
-	new_t = lh_table_new(new_size, t->name, NULL, t->hash_fn, t->equal_fn);
+	new_t = lh_table_new(new_size, NULL, t->hash_fn, t->equal_fn);
 	ent = t->head;
 	while(ent) {
 		lh_table_insert(new_t, ent->k, ent->v);
@@ -480,7 +514,6 @@ void lh_table_resize(struct lh_table *t, int new_size)
 	t->size = new_size;
 	t->head = new_t->head;
 	t->tail = new_t->tail;
-	t->resizes++;
 	free(new_t);
 }
 
@@ -497,23 +530,21 @@ void lh_table_free(struct lh_table *t)
 }
 
 
-int lh_table_insert(struct lh_table *t, void *k, const void *v)
+int lh_table_insert_w_hash(struct lh_table *t, void *k, const void *v, const unsigned long h, const unsigned opts)
 {
-	unsigned long h, n;
+	unsigned long n;
 
-	t->inserts++;
 	if(t->count >= t->size * LH_LOAD_FACTOR) lh_table_resize(t, t->size * 2);
 
-	h = t->hash_fn(k);
 	n = h % t->size;
 
 	while( 1 ) {
 		if(t->table[n].k == LH_EMPTY || t->table[n].k == LH_FREED) break;
-		t->collisions++;
 		if ((int)++n == t->size) n = 0;
 	}
 
 	t->table[n].k = k;
+	t->table[n].k_is_constant = (opts & JSON_C_OBJECT_KEY_IS_CONSTANT);
 	t->table[n].v = v;
 	t->count++;
 
@@ -529,15 +560,17 @@ int lh_table_insert(struct lh_table *t, void *k, const void *v)
 
 	return 0;
 }
+int lh_table_insert(struct lh_table *t, void *k, const void *v)
+{
+	return lh_table_insert_w_hash(t, k, v, lh_get_hash(t, k), 0);
+}
 
 
-struct lh_entry* lh_table_lookup_entry(struct lh_table *t, const void *k)
+struct lh_entry* lh_table_lookup_entry_w_hash(struct lh_table *t, const void *k, const unsigned long h)
 {
-	unsigned long h = t->hash_fn(k);
 	unsigned long n = h % t->size;
 	int count = 0;
 
-	t->lookups++;
 	while( count < t->size ) {
 		if(t->table[n].k == LH_EMPTY) return NULL;
 		if(t->table[n].k != LH_FREED &&
@@ -548,6 +581,10 @@ struct lh_entry* lh_table_lookup_entry(struct lh_table *t, const void *k)
 	return NULL;
 }
 
+struct lh_entry* lh_table_lookup_entry(struct lh_table *t, const void *k)
+{
+	return lh_table_lookup_entry_w_hash(t, k, lh_get_hash(t, k));
+}
 
 const void* lh_table_lookup(struct lh_table *t, const void *k)
 {

linkhash.h

@@ -41,6 +41,23 @@ extern "C" {
  */
 #define LH_FREED (void*)-2
 
+/**
+ * default string hash function
+ */
+#define JSON_C_STR_HASH_DFLT 0
+
+/**
+ * perl-like string hash function
+ */
+#define JSON_C_STR_HASH_PERLLIKE 1
+
+/**
+ * This function sets the hash function to be used for strings.
+ * Must be one of the JSON_C_STR_HASH_* values.
+ * @returns 0 - ok, -1 if parameter was invalid
+ */
+int json_global_set_string_hash(const int h);
+
 struct lh_entry;
 
 /**
@@ -64,6 +81,7 @@ struct lh_entry {
 	 * The key.
 	 */
 	void *k;
+	int k_is_constant;
 	/**
 	 * The value.
 	 */
@@ -92,36 +110,6 @@ struct lh_table {
 	 */
 	int count;
 
-	/**
-	 * Number of collisions.
-	 */
-	int collisions;
-
-	/**
-	 * Number of resizes.
-	 */
-	int resizes;
-
-	/**
-	 * Number of lookups.
-	 */
-	int lookups;
-
-	/**
-	 * Number of inserts.
-	 */
-	int inserts;
-
-	/**
-	 * Number of deletes.
-	 */
-	int deletes;
-
-	/**
-	 * Name of the hash table.
-	 */
-	const char *name;
-
 	/**
 	 * The first entry.
 	 */
@@ -143,16 +131,6 @@ struct lh_table {
 };
 
 
-/**
- * Pre-defined hash and equality functions
- */
-extern unsigned long lh_ptr_hash(const void *k);
-extern int lh_ptr_equal(const void *k1, const void *k2);
-
-extern unsigned long lh_char_hash(const void *k);
-extern int lh_char_equal(const void *k1, const void *k2);
-
-
 /**
  * Convenience list iterator.
  */
@@ -171,7 +149,6 @@ for(entry = table->head; entry && ((tmp = entry->next) || 1); entry = tmp)
  * Create a new linkhash table.
  * @param size initial table size. The table is automatically resized
  * although this incurs a performance penalty.
- * @param name the table name.
  * @param free_fn callback function used to free memory for entries
  * when lh_table_free or lh_table_delete is called.
  * If NULL is provided, then memory for keys and values
@@ -184,7 +161,7 @@ for(entry = table->head; entry && ((tmp = entry->next) || 1); entry = tmp)
  * and C strings respectively.
  * @return a pointer onto the linkhash table.
  */
-extern struct lh_table* lh_table_new(int size, const char *name,
+extern struct lh_table* lh_table_new(int size,
 				     lh_entry_free_fn *free_fn,
 				     lh_hash_fn *hash_fn,
 				     lh_equal_fn *equal_fn);
@@ -197,7 +174,7 @@ extern struct lh_table* lh_table_new(int size, const char *name,
  * @param free_fn callback function used to free memory for entries.
  * @return a pointer onto the linkhash table.
  */
-extern struct lh_table* lh_kchar_table_new(int size, const char *name,
+extern struct lh_table* lh_kchar_table_new(int size,
 					   lh_entry_free_fn *free_fn);
 
 
@@ -209,7 +186,7 @@ extern struct lh_table* lh_kchar_table_new(int size, const char *name,
  * @param free_fn callback function used to free memory for entries.
  * @return a pointer onto the linkhash table.
  */
-extern struct lh_table* lh_kptr_table_new(int size, const char *name,
+extern struct lh_table* lh_kptr_table_new(int size,
 					  lh_entry_free_fn *free_fn);
 
 
@@ -231,6 +208,21 @@ extern void lh_table_free(struct lh_table *t);
 extern int lh_table_insert(struct lh_table *t, void *k, const void *v);
 
 
+/**
+ * Insert a record into the table. This one accepts the key's hash in additon
+ * to the key. This is an exension to support functions that need to calculate
+ * the hash several times and allows them to do it just once and then pass
+ * in the hash to all utility functions. Depending on use case, this can be a 
+ * very considerate performance improvement.
+ * @param t the table to insert into.
+ * @param k a pointer to the key to insert.
+ * @param v a pointer to the value to insert.
+ * @param h hash value of the key to insert
+ * @param opts opts, a subset of JSON_OBJECT_ADD_* flags is supported
+ */
+extern int lh_table_insert_w_hash(struct lh_table *t, void *k, const void *v, const unsigned long h, const unsigned opts);
+
+
 /**
  * Lookup a record into the table.
  * @param t the table to lookup
@@ -239,6 +231,19 @@ extern int lh_table_insert(struct lh_table *t, void *k, const void *v);
  */
 extern struct lh_entry* lh_table_lookup_entry(struct lh_table *t, const void *k);
 
+/**
+ * Lookup a record into the table. This one accepts the key's hash in additon
+ * to the key. This is an exension to support functions that need to calculate
+ * the hash several times and allows them to do it just once and then pass
+ * in the hash to all utility functions. Depending on use case, this can be a 
+ * very considerate performance improvement.
+ * @param t the table to lookup
+ * @param k a pointer to the key to lookup
+ * @param h hash value of the key to lookup
+ * @return a pointer to the record structure of the value or NULL if it does not exist.
+ */
+extern struct lh_entry* lh_table_lookup_entry_w_hash(struct lh_table *t, const void *k, const unsigned long h);
+
 /**
  * Lookup a record into the table
  * @param t the table to lookup
@@ -285,6 +290,22 @@ extern int lh_table_length(struct lh_table *t);
 void lh_abort(const char *msg, ...);
 void lh_table_resize(struct lh_table *t, int new_size);
 
+
+/**
+ * Calculate the hash of a key for a given table.
+ * This is an exension to support functions that need to calculate
+ * the hash several times and allows them to do it just once and then pass
+ * in the hash to all utility functions. Depending on use case, this can be a 
+ * very considerate performance improvement.
+ * @param t the table (used to obtain hash function)
+ * @param k a pointer to the key to lookup
+ * @return the key's hash
+ */
+static inline unsigned long lh_get_hash(const struct lh_table *t, const void *k)
+{
+	return t->hash_fn(k);
+}
+
 #ifdef __cplusplus
 }
 #endif