如何确定使用NSURLConnection下载的文件的大小(以字节为单位)? [英] How to determine the size (in bytes) of a file downloading using NSURLConnection?

问题描述

我需要知道我使用NSURLConnection(GET)下载到我的应用程序中文件的大小(以字节为单位).这是我下面的字节接收代码(如果有帮助的话).我需要知道的是如何获取文件大小(以字节为单位)，以便可以使用它来显示UIProgressView.

I need to know the size of the file I am downloading (in bytes) into my app using NSURLConnection (GET). Here is my bytes recieved code below if it helps. What I need to know is how to get the filesize in bytes so that I can use it to show a UIProgressView.

- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)data
// A delegate method called by the NSURLConnection as data arrives.  We just 
// write the data to the file.
{
#pragma unused(theConnection)
    NSInteger       dataLength;
    const uint8_t * dataBytes;
    NSInteger       bytesWritten;
    NSInteger       bytesWrittenSoFar;

    assert(theConnection == self.connection);

    dataLength = [data length];
    dataBytes  = [data bytes];

    bytesWrittenSoFar = 0;
    do {
        bytesWritten = [self.fileStream write:&dataBytes[bytesWrittenSoFar] maxLength:dataLength - bytesWrittenSoFar];
        assert(bytesWritten != 0);
        if (bytesWritten == -1) {
            [self _stopReceiveWithStatus:@"File write error"];
            break;
        } else {
            bytesWrittenSoFar += bytesWritten;

    } while (bytesWrittenSoFar != dataLength);
}

推荐答案

[数据长度]确实以字节为单位返回数据大小，这应该为您提供所需的数字.

[data length] does return the size of the data in bytes which should give you the figure you're looking for.

但是NSData提供了-writeToFile:atomically:和-writeToFile:options:error方法用于将数据写入磁盘，因此我不知道您为什么要编写自己的文件I/O.

But NSData provides -writeToFile:atomically: and -writeToFile:options:error methods for writing data to disk so I don't know why you're writing your own file I/O.

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