objective-c - 使用 RubyMotion 处理指针

Question

我正在尝试将以下方法移植到 RubyMotion

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    NSInteger       dataLength = [data length];
    const uint8_t * dataBytes  = [data bytes];
    NSInteger       bytesWritten;
    NSInteger       bytesWrittenSoFar;

    bytesWrittenSoFar = 0;
    do {
        bytesWritten = [self.downloadStream write:&dataBytes[bytesWrittenSoFar] maxLength:dataLength - bytesWrittenSoFar];
        assert(bytesWritten != 0);
        if (bytesWritten == -1) {
            [self cleanupConnectionSuccessful:NO];
            break;
        } else {
            bytesWrittenSoFar += bytesWritten;
        }
    } while (bytesWrittenSoFar != dataLength);

    self.progressContentLength += dataLength;
}

(来自robertmryan/download-manager)

这就是我目前拥有的，它在使用 connection:didReceiveData:': can't convert Fixnum into String (TypeError)

调用 downloadStream 时崩溃

def connection(connection, didReceiveData:data)
  dataLength = data.length
  dataBytes = data.bytes
  bytesWritten = 0
  bytesWrittenSoFar = 0

  begin
    maxLength = dataLength - bytesWrittenSoFar
    buffer = dataBytes[bytesWrittenSoFar]
    bytesWritten = self.downloadStream.write buffer, maxLength: maxLength # CRASH
    if bytesWritten == -1
      self.cleanupConnectionSuccessful false
      break
    else
      bytesWrittenSoFar += bytesWritten
    end
  end while bytesWrittenSoFar != dataLength

  self.progressContentLength += dataLength

  if self.delegate.respondsToSelector('downloadDidReceiveData:')
    self.delegate.downloadDidReceiveData(self)
  end
end

我意识到我的转换忽略了指针可能是幼稚和错误的。我查看了 RubyMotion 文档，但它们有点稀疏，而且我对 C 的理解还不够强，不知道如何在此处应用它。一些建议将不胜感激。

Answer 1

NSData 的bytes 方法返回一个Pointer 类型(http://www.rubymotion.com/developer-center/api/Pointer.html)。

Pointer 类型中的 [] 方法使您可以从指针开始访问该位置的元素。在我看来，bytes 返回类型为“C”(unsigned char)的Pointer，所以当您尝试访问 Pointer 时，dataBytes[bytesWrittenSoFar] 你只获得了一个 Fixnum，它是从指针开始的那个字节的值。

要完成您想做的事，您需要以下内容:

bytesWrittenSoFar = 0

begin
  maxLength = dataLength - bytesWrittenSoFar
  buffer = dataBytes + bytesWrittenSoFar
  bytesWritten = self.downloadStream.write buffer, maxLength: maxLength
  if bytesWritten == -1
    self.cleanupConnectionSuccessful false
    break
  else
    bytesWrittenSoFar += bytesWritten
  end
end while bytesWrittenSoFar != dataLength

我还没有运行它，但我希望它有效。