FLEX/Classes/Utility/Runtime/FLEXBlockDescription.m

//
//  FLEXBlockDescription.m
//  FLEX
//
//  Created by Oliver Letterer on 2012-09-01
//  Forked from CTObjectiveCRuntimeAdditions (MIT License)
//  https://github.com/ebf/CTObjectiveCRuntimeAdditions
//
//  Copyright (c) 2012 EBF-EDV Beratung Föllmer GmbH
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this
//  software and associated documentation files (the "Software"), to deal in the Software
//  without restriction, including without limitation the rights to use, copy, modify, merge,
//  publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
//  to whom the Software is furnished to do so, subject to the following conditions:
//  The above copyright notice and this permission notice shall be included in all copies or
//  substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
//  BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
//  DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#import "FLEXBlockDescription.h"
#import "FLEXRuntimeUtility.h"

struct block_object {
    void *isa;
    int flags;
    int reserved;
    void (*invoke)(void *, ...);
    struct block_descriptor {
        unsigned long int reserved;    // NULL
        unsigned long int size;     // sizeof(struct Block_literal_1)
        // optional helper functions
        void (*copy_helper)(void *dst, void *src);     // IFF (1<<25)
        void (*dispose_helper)(void *src);             // IFF (1<<25)
        // required ABI.2010.3.16
        const char *signature;                         // IFF (1<<30)
    } *descriptor;
    // imported variables
};

@implementation FLEXBlockDescription

+ (instancetype)describing:(id)block {
    return [[self alloc] initWithObjcBlock:block];
}

- (id)initWithObjcBlock:(id)block {
    self = [super init];
    if (self) {
        _block = block;
        
        struct block_object *blockRef = (__bridge struct block_object *)block;
        _flags = blockRef->flags;
        _size = blockRef->descriptor->size;
        
        if (_flags & FLEXBlockOptionHasSignature) {
            void *signatureLocation = blockRef->descriptor;
            signatureLocation += sizeof(unsigned long int);
            signatureLocation += sizeof(unsigned long int);
            
            if (_flags & FLEXBlockOptionHasCopyDispose) {
                signatureLocation += sizeof(void(*)(void *dst, void *src));
                signatureLocation += sizeof(void (*)(void *src));
            }
            
            const char *signature = (*(const char **)signatureLocation);
            _signatureString = @(signature);
            
            @try {
                _signature = [NSMethodSignature signatureWithObjCTypes:signature];
            } @catch (NSException *exception) { }
        }
        
        NSMutableString *summary = [NSMutableString stringWithFormat:
            @"Type signature: %@\nSize: %@\nIs global: %@\nHas constructor: %@\nIs stret: %@",
            self.signatureString ?: @"nil", @(self.size),
            @((BOOL)(_flags & FLEXBlockOptionIsGlobal)),
            @((BOOL)(_flags & FLEXBlockOptionHasCtor)),
            @((BOOL)(_flags & FLEXBlockOptionHasStret))
        ];
        
        if (!self.signature) {
            [summary appendFormat:@"\nNumber of arguments: %@", @(self.signature.numberOfArguments)];
        }
        
        _summary = summary.copy;
        _sourceDeclaration = [self buildLikelyDeclaration];
    }
    
    return self;
}

- (BOOL)isCompatibleForBlockSwizzlingWithMethodSignature:(NSMethodSignature *)methodSignature {
    if (!self.signature) {
        return NO;
    }
    
    if (self.signature.numberOfArguments != methodSignature.numberOfArguments + 1) {
        return NO;
    }
    
    if (strcmp(self.signature.methodReturnType, methodSignature.methodReturnType) != 0) {
        return NO;
    }
    
    for (int i = 0; i < methodSignature.numberOfArguments; i++) {
        if (i == 1) {
            // SEL in method, IMP in block
            if (strcmp([methodSignature getArgumentTypeAtIndex:i], ":") != 0) {
                return NO;
            }
            
            if (strcmp([self.signature getArgumentTypeAtIndex:i + 1], "^?") != 0) {
                return NO;
            }
        } else {
            if (strcmp([self.signature getArgumentTypeAtIndex:i], [self.signature getArgumentTypeAtIndex:i + 1]) != 0) {
                return NO;
            }
        }
    }
    
    return YES;
}

- (NSString *)buildLikelyDeclaration {
    NSMethodSignature *signature = self.signature;
    NSUInteger numberOfArguments = signature.numberOfArguments;
    const char *returnType       = signature.methodReturnType;
    
    // Return type
    NSMutableString *decl = [NSMutableString stringWithString:@"^"];
    if (returnType[0] != FLEXTypeEncodingVoid) {
        [decl appendString:[FLEXRuntimeUtility readableTypeForEncoding:@(returnType)]];
        [decl appendString:@" "];
    }
    
    // Arguments
    if (numberOfArguments) {
        [decl appendString:@"("];
        for (NSUInteger i = 1; i < numberOfArguments; i++) {
            const char *argType = [self.signature getArgumentTypeAtIndex:i] ?: "?";
            NSString *readableArgType = [FLEXRuntimeUtility readableTypeForEncoding:@(argType)];
            [decl appendFormat:@"%@ arg%@, ", readableArgType, @(i)];
        }
        
        [decl deleteCharactersInRange:NSMakeRange(decl.length-2, 2)];
        [decl appendString:@")"];
    }
    
    return decl.copy;
}

@end