C struct box/unbox for Silver

gistfile1.m

id sv_vm_box(SVStructBoxData* boxData, void* objc_value) {
    id object = class_createInstance(NSClassFromString(boxData.name), 0);
    for(SVStructOffsetData* offset in boxData.offsetData) {
        void* data = objc_value+offset.offset;
        id f_value = get_sv_value_from_objc_value(data, [offset.typeEncoding UTF8String]);
        object_setInstanceVariable(object, [offset.fieldName UTF8String], f_value);
    }
    return object;
}

void * sv_vm_unbox(void* objc_value,SVStructBoxData* boxData,id sv_value) {
    void * object = malloc(boxData.size);
    for(SVStructOffsetData* offset in boxData.offsetData) {
        id val;
        object_getInstanceVariable(sv_value, [offset.fieldName UTF8String], (void**)&val);
        void * c_val = value_buffer_for_objc_type([offset.typeEncoding UTF8String]);
        set_objc_value_from_sv_value(c_val, val, [offset.typeEncoding UTF8String]);
        void * ptr = object + offset.offset;
        ptr = c_val;
    }
    return object;
}

void sv_vm_create_box_for_struct_type( NSString * typeEncoding ) {
    if(!sv_struct_box_data)
        sv_struct_box_data = [NSMutableDictionary dictionary];
    if([typeEncoding rangeOfString:@"\""].location == NSNotFound)
        return;
    typeEncoding = [typeEncoding substringFromIndex:1];
    NSScanner * typeScanner = [NSScanner scannerWithString:typeEncoding];
    NSString * typeName = nil;
    NSString * className = nil;
    [typeScanner scanUpToString:@"=" intoString:&typeName];
    [typeScanner scanString:@"=" intoString:NULL];
    if([sv_struct_box_data objectForKey:typeName])
       return;
    className = [typeName hasPrefix:@"_"] ? [typeName substringFromIndex:1] : typeName;
    if(NSClassFromString(className))
        return;
    long currentOffset = 0;
    NSMutableArray * boxData = [NSMutableArray array];
    Class _boxClass = objc_allocateClassPair([NSObject class], [className UTF8String], 0);
    while(![typeScanner isAtEnd]) {
        NSString * fieldName = nil;
        NSString * fieldEncoding = nil;
        [typeScanner scanString:@"\"" intoString:NULL];
        [typeScanner scanUpToString:@"\"" intoString:&fieldName];
        [typeScanner scanString:@"\"" intoString:NULL];
        NSString * fieldData = [[typeScanner string] substringFromIndex:[typeScanner scanLocation]];
        if([fieldData hasPrefix:@"{"]) {
            fieldData = [fieldData substringFromIndex:1];
            int bcount = 1;
            NSMutableString * sdata = [NSMutableString stringWithString:@"{"];
            while(bcount) {
                NSString * temp;
                [typeScanner scanUpToString:@"}" intoString:&temp];
                [sdata appendString:temp];
                while([temp rangeOfString:@"{"].location != NSNotFound) {
                    bcount++;
                    temp = [temp substringFromIndex:([temp rangeOfString:@"{"].location + 1)];
                }
                [typeScanner scanString:@"}" intoString:&temp];
                [sdata appendString:temp];
                bcount--;
            }
            fieldEncoding = sdata;
        } else {
            [typeScanner scanUpToString:@"\"" intoString:&fieldEncoding];
            if([typeScanner isAtEnd])
                fieldEncoding = [fieldEncoding substringToIndex:[fieldEncoding length]-1];
        }
        ffi_type* type = ffi_type_for_objc_type([fieldEncoding UTF8String]);
        long size = size_for_objc_type([fieldEncoding UTF8String]);
        if(!class_addIvar(_boxClass, [fieldName UTF8String], sizeof(id), log2(sizeof(id)), @encode(id))) {
            OCLog(@"silver",warning,@"Failed to add ivar %@ to boxing class...",fieldName);
        } 
        if (!class_addMethod(_boxClass, NSSelectorFromString(fieldName), (IMP)__sv_stubPropertyGetter, "@@:")) {
            OCLog(@"silver",warning,@"Failed to add get property for %@ to boxing class...",fieldName);
        }
        
        if (!class_addMethod(_boxClass,
                             NSSelectorFromString([NSString stringWithFormat:@"set%@:",
                                                   [fieldName capitalizedString]]), (IMP)__sv_stubPropertySetter, "v@:@")) {
            OCLog(@"silver",warning,@"Failed to add set property %@ to boxing class...",fieldName);
        }
        SVStructOffsetData * offsetData = [[SVStructOffsetData alloc] init];
        offsetData.fieldName = fieldName;
        offsetData.typeEncoding = fieldEncoding;
        offsetData.offset = currentOffset;
        offsetData.type = type;
        currentOffset += size;
        [boxData addObject:offsetData];
    }
    objc_registerClassPair(_boxClass);
    SVStructBoxData* data = [[SVStructBoxData alloc] init];
    data.name = typeName;
    data.offsetData = boxData;
    // Create the FFI type for the structure from the offset datas
    ffi_type * ffi_st_type = (ffi_type*)malloc(sizeof(ffi_type*));
    [[NSGarbageCollector defaultCollector] disableCollectorForPointer:ffi_st_type];
    ffi_st_type->size = 0;
    ffi_st_type->alignment = 0;
    ffi_st_type->elements = (ffi_type**)malloc((boxData.count + 1) * sizeof(ffi_type*));
    int ix;
    for(ix = 0; ix < boxData.count; ix++) {
        if([(SVStructOffsetData*)[boxData objectAtIndex:ix] type])
            ffi_st_type->elements[ix] = [(SVStructOffsetData*)[boxData objectAtIndex:ix] type];
        else
            ffi_st_type->elements[ix] = &ffi_type_void;
    }
    ffi_st_type->elements[ix] = NULL;
    data.size = currentOffset;
    data.type = ffi_st_type;
    [sv_struct_box_data setObject:data forKey:typeName];
}