NSCache is very slow. Use an per-instance NSMutableDictionary instead

Author: stig

Classes/SBJsonStreamWriter.h

@@ -82,7 +82,9 @@
 
  */
 
-@interface SBJsonStreamWriter : NSObject
+@interface SBJsonStreamWriter : NSObject {
+    NSMutableDictionary *cache;
+}
 
 @property (nonatomic, assign) SBJsonStreamWriterState *state; // Internal
 @property (nonatomic, readonly, retain) NSMutableArray *stateStack; // Internal 

Classes/SBJsonStreamWriter.m

@@ -39,8 +39,6 @@
 static NSNumber *kPositiveInfinity;
 static NSNumber *kNegativeInfinity;
 
-static id kStaticStringCache;
-
 
 @implementation SBJsonStreamWriter
 
@@ -57,16 +55,6 @@ + (void)initialize {
     kNegativeInfinity = [NSNumber numberWithDouble:-INFINITY];
     kTrue = [NSNumber numberWithBool:YES];
     kFalse = [NSNumber numberWithBool:NO];
-    
-    Class cacheClass = NSClassFromString(@"NSCache");
-    if (cacheClass) {
-        NSLog(@"%s NSCache supported", __FUNCTION__);
-        kStaticStringCache = [[cacheClass alloc] init];
-    }else {
-        NSLog(@"%s NSCache not supported", __FUNCTION__);
-    }
-
-    
 }
 
 #pragma mark Housekeeping
@@ -79,6 +67,7 @@ - (id)init {
 		maxDepth = 32u;
         stateStack = [[NSMutableArray alloc] initWithCapacity:maxDepth];
         state = [SBJsonStreamWriterStateStart sharedInstance];
+        cache = [[NSMutableDictionary alloc] initWithCapacity:32];
     }
 	return self;
 }
@@ -87,6 +76,7 @@ - (void)dealloc {
 	self.error = nil;
     self.state = nil;
     [stateStack release];
+    [cache release];
 	[super dealloc];
 }
 
@@ -294,7 +284,7 @@ - (BOOL)writeString:(NSString*)string {
 	[state appendSeparator:self];
 	if (humanReadable) [state appendWhitespace:self];
 
-	NSMutableData *buf = [kStaticStringCache objectForKey:string];
+	NSMutableData *buf = [cache objectForKey:string];
 	if (!buf) {
 
         NSUInteger len = [string lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
@@ -321,7 +311,7 @@ - (BOOL)writeString:(NSString*)string {
             [buf appendBytes:utf8 + written length:i - written];
 
         [buf appendBytes:"\"" length:1];
-        [kStaticStringCache setObject:buf forKey:string];
+        [cache setObject:buf forKey:string];
     }
 
 	[delegate writer:self appendBytes:[buf bytes] length:[buf length]];