本文介绍了如何检查NSData对象是否包含子NSData?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个NSData对象,其中包含一些我需要的数据。我想做的就是找出数据 FF D8的位置(JPEG数据的开始)
I have an NSData object which contains some data I need. What I wanted to do is to find out the position of data "FF D8" (start of JPEG data)
如何实现这样的工作?
推荐答案
首先获取范围,然后获取数据:
First get the range, then get the data:
// The magic start data object is only created once safely and
// then reused each time
static NSData* magicStartData = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
static const uint8_t magic[] = { 0xff, 0xd8 };
magicStartData = [NSData dataWithBytesNoCopy:(void*)magic length:2 freeWhenDone:NO];
});
// assume data is the NSData with embedded data
NSRange range = [data rangeOfData:magicStartData options:0 range:NSMakeRange(0, [data length])];
if (range.location != NSNotFound) {
// This assumes the subdata doesn't have a specific range and is just everything
// after the magic, otherwise adjust
NSData* subdata = [data subdataWithRange:NSMakeRange(range.location, [data length] - range.location)];
}
这篇关于如何检查NSData对象是否包含子NSData?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!