NSMethodSignature

Provides type information about method arguments and return values. Supports MetaABI and method frame layout.

Base Class

NSObject

Implemented Protocols

• MulleObjCImmutableProtocols
• NSCopying

Instance Variables

uint32_t                            _bits;    // Method descriptor bits
uint16_t                            _count;   // Number of types
uint16_t                            _extra;   // Extra storage size
char                               *_types;   // Type encodings
MulleObjCMethodSignatureTypeInfo   *_infos;  // Type information

Methods

Creation

• +signatureWithObjCTypes: - Creates signature from type string
• +_signatureWithObjCTypes:descriptorBits: - Internal creation method

Method Information

• -isOneway - Checks if method is oneway
• -isVariadic - Checks if method has variable arguments
• -_descriptorBits - Gets method descriptor bits
• -frameLength - Gets frame storage length
• -mulleMetaABIFrameLength - Gets MetaABI frame length

Type Information

• -methodReturnLength - Gets return value size
• -methodReturnType - Gets return value type
• -getArgumentTypeAtIndex: - Gets argument type at index
• -numberOfArguments - Gets total argument count
• -mulleSignatureTypeInfoAtIndex: - Gets type info at index

MetaABI Support

• -_methodMetaABIReturnType - Gets MetaABI return type
• -_methodMetaABIParameterType - Gets MetaABI parameter type
• -mulleInvocationSize - Gets required invocation storage size

Usage Example

// Get method signature
NSMethodSignature *sig = [target methodSignatureForSelector:@selector(method:)];

// Check argument count
NSUInteger args = [sig numberOfArguments];  // Includes self and _cmd

// Get argument types
char *type = [sig getArgumentTypeAtIndex:2];  // First user argument

// Get return type
char *returnType = [sig methodReturnType];

// Check method properties
BOOL isOneway = [sig isOneway];
BOOL hasVarArgs = [sig isVariadic];

// Get sizes for allocation
NSUInteger frameSize = [sig frameLength];
NSUInteger metaABISize = [sig mulleMetaABIFrameLength];

Important Notes

1. Type Encoding
   • Uses Objective-C type encodings
   • Includes method qualifiers
   • Supports complex types
   • Handles MetaABI types
2. Memory Layout
   • Provides frame layout info
   • Supports MetaABI optimization
   • Handles alignment requirements
   • Manages variable storage
3. Performance
   • Caches type information
   • Optimizes MetaABI access
   • Minimizes parsing overhead
   • Reuses type info objects
4. Thread Safety
   • Thread-safe for reading
   • Immutable after creation
   • Safe to share between threads
5. MetaABI Types

typedef enum {
    MulleObjCMetaABITypeVoid = 0,
    MulleObjCMetaABITypeVoidPointer = 1,
    MulleObjCMetaABITypeParameterBlock = 2
} MulleObjCMetaABIType;