我有一个 NSData 对象,其中包含我需要的一些数据。我想做的是找出数据“FF D8”的位置(JPEG数据的开始)
我怎样才能完成这样的工作?
最佳答案
先获取范围,然后获取数据:
// 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)];
}
关于cocoa - 如何检查 NSData 对象是否包含子 NSData?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18477710/