Optimize class lookup

Gets rid of a small amount of class lookup and reduces codegen slightly from the main library by encoding the classes directly into data structures where possible.

Source/Objects/GTLRRuntimeCommon.m

@@ -320,9 +320,7 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
   // These are the "fixed" return classes, but some properties will require
   // looking up the return class instead (because it is a subclass of
   // GTLRObject).
-  const char *returnClassName;
   Class       returnClass;
-  BOOL extractReturnClass;
 
 } GTLRDynamicImpInfo;
 
@@ -347,6 +345,18 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
   //   T@"GTLRLink",D
   //   T@"NSArray",D
 
+  // References to classes that we can put in static structures.
+  extern const struct {} GTLRNSArrayClass __asm__("_OBJC_CLASS_$_NSArray");
+  extern const struct {} GTLRNSObjectClass __asm__("_OBJC_CLASS_$_NSObject");
+  extern const struct {} GTLRNSStringClass __asm__("_OBJC_CLASS_$_NSString");
+  extern const struct {} GTLRNSNumberClass __asm__("_OBJC_CLASS_$_NSNumber");
+  extern const struct {} GTLRDateTimeClass
+      __asm__("_OBJC_CLASS_$_" GTLR_CLASSNAME_CSTR(GTLRDateTime));
+  extern const struct {} GTLRDurationClass
+      __asm__("_OBJC_CLASS_$_" GTLR_CLASSNAME_CSTR(GTLRDuration));
+
+	// Denotes that the class is dynamic and must be resolved.
+  const Class kLookupClass = (__bridge Class)(void *)0x1;
 
   static GTLRDynamicImpInfo kImplInfo[] = {
 #if !defined(__LP64__) || !__LP64__
@@ -355,67 +365,59 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
       GTLRPropertyTypeInt32,
       "v@:i",
       "i@:",
-      nil, nil,
-      NO
+      Nil,
     },
     { // NSUInteger on 32bit
       "TI",
       GTLRPropertyTypeUInt32,
       "v@:I",
       "I@:",
-      nil, nil,
-      NO
+      Nil,
     },
 #endif
     { // NSInteger on 64bit, long long on 32bit and 64bit.
       "Tq",
       GTLRPropertyTypeLongLong,
       "v@:q",
       "q@:",
-      nil, nil,
-      NO
+      Nil,
     },
     { // NSUInteger on 64bit, long long on 32bit and 64bit.
       "TQ",
       GTLRPropertyTypeULongLong,
       "v@:Q",
       "Q@:",
-      nil, nil,
-      NO
+      Nil,
     },
     { // float
       "Tf",
       GTLRPropertyTypeFloat,
       "v@:f",
       "f@:",
-      nil, nil,
-      NO
+      Nil,
     },
     { // double
       "Td",
       GTLRPropertyTypeDouble,
       "v@:d",
       "d@:",
-      nil, nil,
-      NO
+      Nil,
     },
 #if defined(OBJC_BOOL_IS_BOOL) && OBJC_BOOL_IS_BOOL
     { // BOOL as bool
       "TB",
       GTLRPropertyTypeBool,
       "v@:B",
       "B@:",
-      nil, nil,
-      NO
+      Nil,
     },
 #elif defined(OBJC_BOOL_IS_CHAR) && OBJC_BOOL_IS_CHAR
     { // BOOL as char
       "Tc",
       GTLRPropertyTypeBool,
       "v@:c",
       "c@:",
-      nil, nil,
-      NO
+      Nil,
     },
 #else
  #error unknown definition for ObjC BOOL type
@@ -425,73 +427,52 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
       GTLRPropertyTypeNSString,
       "v@:@",
       "@@:",
-      "NSString", nil,
-      NO
+      (__bridge Class)&GTLRNSStringClass,
     },
     { // NSNumber
       "T@\"NSNumber\"",
       GTLRPropertyTypeNSNumber,
       "v@:@",
       "@@:",
-      "NSNumber", nil,
-      NO
+      (__bridge Class)&GTLRNSNumberClass,
     },
     { // GTLRDateTime
       "T@\"" GTLR_CLASSNAME_CSTR(GTLRDateTime) "\"",
       GTLRPropertyTypeGTLRDateTime,
       "v@:@",
       "@@:",
-      GTLR_CLASSNAME_CSTR(GTLRDateTime), nil,
-      NO
+      (__bridge Class)&GTLRNSNumberClass,
     },
     { // GTLRDuration
       "T@\"" GTLR_CLASSNAME_CSTR(GTLRDuration) "\"",
       GTLRPropertyTypeGTLRDuration,
       "v@:@",
       "@@:",
-      GTLR_CLASSNAME_CSTR(GTLRDuration), nil,
-      NO
+      (__bridge Class)&GTLRDurationClass,
     },
     { // NSArray with type
       "T@\"NSArray\"",
       GTLRPropertyTypeNSArray,
       "v@:@",
       "@@:",
-      "NSArray", nil,
-      NO
+      (__bridge Class)&GTLRNSArrayClass,
     },
     { // id (any of the objects above)
       "T@,",
       GTLRPropertyTypeNSObject,
       "v@:@",
       "@@:",
-      "NSObject", nil,
-      NO
+      (__bridge Class)&GTLRNSObjectClass,
     },
     { // GTLRObject - Last, cause it's a special case and prefix is general
       "T@\"",
       GTLRPropertyTypeGTLRObject,
       "v@:@",
       "@@:",
-      nil, nil,
-      YES
+      kLookupClass,
     },
   };
 
-  static BOOL hasLookedUpClasses = NO;
-  if (!hasLookedUpClasses) {
-    // Unfortunately, you can't put [NSString class] into the static structure,
-    // so this lookup has to be done at runtime.
-    hasLookedUpClasses = YES;
-    for (uint32_t idx = 0; idx < sizeof(kImplInfo)/sizeof(kImplInfo[0]); ++idx) {
-      if (kImplInfo[idx].returnClassName) {
-        kImplInfo[idx].returnClass = objc_getClass(kImplInfo[idx].returnClassName);
-        NSCAssert1(kImplInfo[idx].returnClass != nil,
-                   @"GTLRRuntimeCommon: class lookup failed: %s", kImplInfo[idx].returnClassName);
-      }
-    }
-  }
-
   const char *attr = property_getAttributes(prop);
 
   const char *dynamicMarker = strstr(attr, ",D");
@@ -521,7 +502,7 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
     return NULL;
   }
 
-  if (result->extractReturnClass && outReturnClass) {
+  if (result->returnClass == kLookupClass && outReturnClass) {
 
     // add a null at the next quotation mark
     char *attrCopy = strdup(attr);
@@ -532,7 +513,7 @@ typedef NS_ENUM(NSUInteger, GTLRPropertyType) {
 
       // Lookup the return class
       *outReturnClass = objc_getClass(classNameStart);
-      if (*outReturnClass == nil) {
+      if (*outReturnClass == Nil) {
         GTLR_DEBUG_LOG(@"GTLRRuntimeCommon: did not find class with name \"%s\" "
                        @"for property \"%s\" with attributes \"%s\"",
                        classNameStart, property_getName(prop), attr);