Question

我有这些处理下载的方法

但初始化NSMutableData

时出错

NSNumber *filesize;
NSMutableData *data;

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    filesize = [NSNumber numberWithUnsignedInteger:[response expectedContentLength]];

}

- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)recievedData {


    if (data==nil) {
        data =  [[NSMutableData alloc] initWithCapacity:[filesize floatValue]];
    }


    [data appendData:recievedData];
    NSNumber *resourceLength = [NSNumber numberWithUnsignedInteger:[data length]]; //MAGIC
    float progress = [resourceLength floatValue] / [filesize floatValue];
    progressBar.progress = progress;



}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{

    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error "
                                                        message:@" " delegate:self cancelButtonTitle: @"OK"
                                              otherButtonTitles:nil];
    [alertView show];

    connection1=nil;
    [connection1 cancel];



}

- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {

}

此处生成错误

data = [[NSMutableData alloc] initWithCapacity：[filesize floatValue]];

[NSConcreteMutableData initWithCapacity：]：荒谬容量：4294967295，最大大小：2147483648字节'

Answer 1

如果NSURLResponse expectedContentLength不知道长度，它将返回-1（文档说NSURLResponseUnknownLength，这是一个初始化为-1的常量。）

然后，您可以使用一种有趣的方式从long long（NSURLResponse expectedContentLength的结果类型）到NSNumber numberWithUnsignedInteger和NSNumber floatValue到NSUInteger（NSMutableData initWithCapacity:的参数1}}）。结果是-1（内部表示为0xffffffff）最终为4294967295（内部也表示为0xffffffff）。

在这种情况下，您必须测试NSURLResponseUnknownLength并使用不同的初始容量。并且不要使用NSNumber。如果签名long long在合理范围内，只需将其转换为无符号NSUInteger。

NSMutableData initWithCapacity荒谬的容量？

1 个答案: