iOS内存无法分配

Question

我正在ARC自动转换项目中工作.

我有一个巨大的文本文件(14MB)的内容存储在NSString *_documentDataString.

现在我有这个循环:

- (void)scanParts
{
    NSString *boundary = [boundaryPrefix stringByAppendingString:_header.boundary];

    NSMutableArray *parts = [NSMutableArray array];

    NSInteger currentLocation = [_documentDataString rangeOfString:boundary].location;

    BOOL reachedTheEnd = NO;
    while(!reachedTheEnd)
    {
        NSInteger nextBoundaryLocation = [[_documentDataString substringFromIndex:currentLocation + 1]
                                          rangeOfString:boundary].location;

        if(nextBoundaryLocation == NSNotFound)
        {
            reachedTheEnd = YES;
        }
        else
        {
            nextBoundaryLocation += currentLocation + 1;

            //[parts addObject:[_documentDataString substringWithRange:
              //                NSMakeRange(currentLocation, nextBoundaryLocation - currentLocation)]];

            currentLocation = nextBoundaryLocation;
        }
    }
}

但是,我开始收到这些错误:

 malloc: *** mmap(size=6496256) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug

出了什么问题？

运行此循环时,我甚至开始收到此错误:

while(true)
{
    NSInteger nextBoundaryLocation = [[_documentDataString substringFromIndex:currentLocation + 1]
                                          rangeOfString:boundary].location;
}

Answer 1

将substringFromIndex:在

NSInteger nextBoundaryLocation = [[_documentDataString substringFromIndex:currentLocation + 1]
                                      rangeOfString:boundary].location;

创建一个(临时的,自动释放的)子字符串,该子字符串仅在当前自动释放池被销毁时被释放(例如,当程序控制返回到主事件循环时).

您可以用.替换该代码

NSInteger nextBoundaryLocation = [_documentDataString rangeOfString:boundary
             options:0
               range:NSMakeRange(currentLocation + 1, [_documentDataString length] - (currentLocation + 1))].location;

(希望)避免创建临时字符串.请注意,这nextBoundaryLocation是相对于字符串的开头,所以

nextBoundaryLocation += currentLocation + 1;

没有必要了.

或者,您可以简单地替换完整的循环

NSArray *parts = [_documentDataString componentsSeparatedByString:boundary];