From ea53dc5af6a216b46a84944ee870c5ce18dcfe90 Mon Sep 17 00:00:00 2001
From: Dmitry Stogov <dmitry@php.net>
Date: Tue, 20 Apr 2010 10:49:22 +0000
Subject: [PATCH] Added an optimization which saves memory and emalloc/efree
 calls for empty HashTables

---
 NEWS             |  2 ++
 Zend/zend_hash.c | 57 +++++++++++++++++++++++++++++-------------------
 2 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/NEWS b/NEWS
index d83cf0669a..d3ed2af710 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,8 @@
 - Upgraded bundled sqlite to version 3.6.23.1. (Ilia)
 - Upgraded bundled PCRE to version 8.02. (Ilia)
 
+- Added an optimization which saves memory and emalloc/efree calls for empty
+  HashTables (Stas, Dmitry)
 - Added Tokyo Cabinet abstract DB support to ext/dba. (Michael Maclean)
 - Added Jenkins's one-at-a-time hash support to ext/hash. (Martin Jansen)
 - Added FNV-1 hash support to ext/hash. (Michael Maclean)
diff --git a/Zend/zend_hash.c b/Zend/zend_hash.c
index d8b40872db..69b6bdc169 100644
--- a/Zend/zend_hash.c
+++ b/Zend/zend_hash.c
@@ -132,12 +132,18 @@ ZEND_API ulong zend_hash_func(const char *arKey, uint nKeyLength)
 		(p)->pDataPtr=NULL;												\
 	}
 
-
+#define CHECK_INIT(ht) do {												\
+	if (UNEXPECTED((ht)->nTableMask == 0)) {								\
+		(ht)->nTableMask = (ht)->nTableSize - 1;						\
+		(ht)->arBuckets = (Bucket **) pecalloc((ht)->nTableSize, sizeof(Bucket *), (ht)->persistent);	\
+	}																	\
+} while (0)
+ 
+static const Bucket *uninitialized_bucket = NULL;
 
 ZEND_API int _zend_hash_init(HashTable *ht, uint nSize, hash_func_t pHashFunction, dtor_func_t pDestructor, zend_bool persistent ZEND_FILE_LINE_DC)
 {
 	uint i = 3;
-	Bucket **tmp;
 
 	SET_INCONSISTENT(HT_OK);
 
@@ -151,9 +157,9 @@ ZEND_API int _zend_hash_init(HashTable *ht, uint nSize, hash_func_t pHashFunctio
 		ht->nTableSize = 1 << i;
 	}
 
-	ht->nTableMask = ht->nTableSize - 1;
+	ht->nTableMask = 0;	/* 0 means that ht->arBuckets is uninitialized */
 	ht->pDestructor = pDestructor;
-	ht->arBuckets = NULL;
+	ht->arBuckets = (Bucket**)&uninitialized_bucket;
 	ht->pListHead = NULL;
 	ht->pListTail = NULL;
 	ht->nNumOfElements = 0;
@@ -162,21 +168,6 @@ ZEND_API int _zend_hash_init(HashTable *ht, uint nSize, hash_func_t pHashFunctio
 	ht->persistent = persistent;
 	ht->nApplyCount = 0;
 	ht->bApplyProtection = 1;
-	
-	/* Uses ecalloc() so that Bucket* == NULL */
-	if (persistent) {
-		tmp = (Bucket **) calloc(ht->nTableSize, sizeof(Bucket *));
-		if (!tmp) {
-			return FAILURE;
-		}
-		ht->arBuckets = tmp;
-	} else {
-		tmp = (Bucket **) ecalloc_rel(ht->nTableSize, sizeof(Bucket *));
-		if (tmp) {
-			ht->arBuckets = tmp;
-		}
-	}
-	
 	return SUCCESS;
 }
 
@@ -212,6 +203,8 @@ ZEND_API int _zend_hash_add_or_update(HashTable *ht, const char *arKey, uint nKe
 		return FAILURE;
 	}
 
+	CHECK_INIT(ht);
+
 	h = zend_inline_hash_func(arKey, nKeyLength);
 	nIndex = h & ht->nTableMask;
 
@@ -278,6 +271,7 @@ ZEND_API int _zend_hash_quick_add_or_update(HashTable *ht, const char *arKey, ui
 		return zend_hash_index_update(ht, h, pData, nDataSize, pDest);
 	}
 
+	CHECK_INIT(ht);
 	nIndex = h & ht->nTableMask;
 	
 	p = ht->arBuckets[nIndex];
@@ -350,6 +344,7 @@ ZEND_API int _zend_hash_index_update_or_next_insert(HashTable *ht, ulong h, void
 	Bucket *p;
 
 	IS_CONSISTENT(ht);
+	CHECK_INIT(ht);
 
 	if (flag & HASH_NEXT_INSERT) {
 		h = ht->nNextFreeElement;
@@ -440,6 +435,9 @@ ZEND_API int zend_hash_rehash(HashTable *ht)
 	uint nIndex;
 
 	IS_CONSISTENT(ht);
+	if (UNEXPECTED(ht->nNumOfElements == 0)) {
+		return SUCCESS;
+	}
 
 	memset(ht->arBuckets, 0, ht->nTableSize * sizeof(Bucket *));
 	p = ht->pListHead;
@@ -530,7 +528,9 @@ ZEND_API void zend_hash_destroy(HashTable *ht)
 		}
 		pefree(q, ht->persistent);
 	}
-	pefree(ht->arBuckets, ht->persistent);
+	if (ht->nTableMask) {
+		pefree(ht->arBuckets, ht->persistent);
+	}
 
 	SET_INCONSISTENT(HT_DESTROYED);
 }
@@ -556,7 +556,9 @@ ZEND_API void zend_hash_clean(HashTable *ht)
 		}
 		pefree(q, ht->persistent);
 	}
-	memset(ht->arBuckets, 0, ht->nTableSize*sizeof(Bucket *));
+	if (ht->nTableMask) {
+		memset(ht->arBuckets, 0, ht->nTableSize*sizeof(Bucket *));
+	}
 	ht->pListHead = NULL;
 	ht->pListTail = NULL;
 	ht->nNumOfElements = 0;
@@ -630,7 +632,9 @@ ZEND_API void zend_hash_graceful_destroy(HashTable *ht)
 	while (p != NULL) {
 		p = zend_hash_apply_deleter(ht, p);
 	}
-	pefree(ht->arBuckets, ht->persistent);
+	if (ht->nTableMask) {
+		pefree(ht->arBuckets, ht->persistent);
+	}
 
 	SET_INCONSISTENT(HT_DESTROYED);
 }
@@ -647,7 +651,9 @@ ZEND_API void zend_hash_graceful_reverse_destroy(HashTable *ht)
 		p = ht->pListTail;
 	}
 
-	pefree(ht->arBuckets, ht->persistent);
+	if (ht->nTableMask) {
+		pefree(ht->arBuckets, ht->persistent);
+	}
 
 	SET_INCONSISTENT(HT_DESTROYED);
 }
@@ -1177,6 +1183,7 @@ ZEND_API int zend_hash_update_current_key_ex(HashTable *ht, int key_type, const
 	p = pos ? (*pos) : ht->pInternalPointer;
 
 	IS_CONSISTENT(ht);
+	CHECK_INIT(ht);
 
 	if (p) {
 		if (key_type == HASH_KEY_IS_LONG) {
@@ -1533,6 +1540,10 @@ void zend_hash_display(const HashTable *ht)
 	Bucket *p;
 	uint i;
 
+	if (UNEXPECTED(ht->nNumOfElements == 0)) {
+		zend_output_debug_string(0, "The hash is empty");
+		return;
+	}
 	for (i = 0; i < ht->nTableSize; i++) {
 		p = ht->arBuckets[i];
 		while (p != NULL) {
-- 
2.40.0