用 iOS 打开一个海峡二进制文件

Question

我编写了一个自定义文件类型，用于保存来自我的 Java 程序的数据。我想在 iPod/Pad/Phone 上获取数据。到目前为止，我编写了这个文件，用于从文件中读取海峡字节值并将它们更改为 NSStrings 和整数。

#import "BinaryFileReader.h"

@implementation BinaryFileReader

- (id)init {
    self = [super init];
    return self;
}

- (id)initWithLocation:(NSString*)filepath {
    if ((self = [super init])) {
        _file = [NSFileHandle fileHandleForReadingAtPath:filepath];
        _fileOffset = 0;
        if (_file == nil)
            NSLog(@"%@%@",@"Failed to open file at path:",filepath);
    }
    return self;
}

- (void)close {
    [_file closeFile];
}

- (int)readInt {
    [_file seekToFileOffset:_fileOffset];
    _databuffer = [_file readDataOfLength:4];
    _fileOffset+=4;
    return (int)[_databuffer bytes];
}

- (NSString*)readNSString {
    int length = [self readInt];
    [_file seekToFileOffset:_fileOffset];
    _databuffer = [_file readDataOfLength:length];
    _fileOffset+=length;
    return [[NSString alloc] initWithData:_databuffer encoding:NSUTF8StringEncoding];
}

- (NSMutableArray*)readNSMutableArrayOfNSString {
    NSMutableArray* array = [[NSMutableArray alloc] init];
    int arrayLength = [self readInt];
    int length;
    for (int i=0; i<arrayLength; i++) {
        length = [self readInt];
        [_file seekToFileOffset:_fileOffset];
        _databuffer = [_file readDataOfLength:length];
        _fileOffset+=length;
        [array addObject:[[NSString alloc] initWithData:_databuffer encoding:NSUTF8StringEncoding]];
    }
    return array;
}

@end

现在，当我尝试使用它来读取 NSStrings 或整数时，它没有得出正确的值。我假设由于 NSStrings 和整数都出现错误，这是 readInt 方法中的问题。有人看到我在这里错过的明显的东西吗？

编辑：

我尝试读取的文件格式以字符串开头。该字符串在使用 readNSString 读取时是正确的字符串，但缺少该字符串的前 1/3。

Java 代码：

public void saveItem() {
    try {
        byte[] bytes;
        FileOutputStream output;
        if (countOccurrences(location.getPath(),'.')==1) {
            System.out.println("Option 1");
            output = new FileOutputStream(location+"/"+name+".dtb");
        } else {
            output = new FileOutputStream(location);
        }

        bytes = name.getBytes("UTF-8");
        output.write(bytes.length);
        output.write(bytes);

        output.write(otherNames.length);
        for (int i=0;i<otherNames.length;i++) {
            bytes = otherNames[i].getBytes("UTF-8");
            output.write(bytes.length);
            output.write(bytes);
        }

        bytes = description.getBytes("UTF-8");
        output.write(bytes.length);
        output.write(bytes);

        bytes = XactCode.getBytes("UTF-8");
        output.write(bytes.length);
        output.write(bytes);

        bytes = SymbilityCode.getBytes("UTF-8");
        output.write(bytes.length);
        output.write(bytes);

        output.write(averageLowPrice);

        output.write(averageHighPrice);

        output.write(averageLifeExpectancy);

        output.close();
        bytes = null;
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Answer 1

这不起作用的原因是您将NSData 转换为int 的方式。 bytes 方法返回一个指向实际数据的指针，您需要遵守该指针才能获得实际值（否则您将只获得指针的内存地址）。

我尝试了两种方法：

int test = 64;
NSData *data = [NSData dataWithBytes:&test length:4];
int test2 = (int)[data bytes]; //This gave me 170382992

和

int test = 64;
NSData *data = [NSData dataWithBytes:&test length:4];
int test2 = *((int *)[data bytes]); //This gave me 64