从 nsdata Objective-c iOS 获取浮点值 [英] get float value from nsdata objective-c iOS

问题描述

我试图从包含多个十六进制值的 NSData 对象中获取浮点值.例如欧共体 51 38 41从这个 4 字节值我想得到浮点值 11.52.我必须如何在 xcode 中执行此操作?

I am trying to get a float value from a NSData object which contains several hex values. e.g. EC 51 38 41 From this 4 Byte values i want to get the float value 11.52. How do i have to do this in xcode?

我用 NSScanner (scanFloat, scanHexFloat)、NSNumberformatter 和 NSNumber 尝试过，我创建了一个字节数组并尝试了 float myFloat = *(float*)&myByteArray.我在 stackoverflow 上找到了所有这些选项.

I have tried it with NSScanner (scanFloat, scanHexFloat), NSNumberformatter and NSNumber, i created an Byte Array and tried float myFloat = *(float*)&myByteArray. All these Options i found here at stackoverflow.

我在 Windows 中用 C# 测试过，没有问题:

I tested it in Windows with C# and there it was no problem:

byte[] bytes = new byte[4] { 0xEC, 0x51, 0x38, 0x41 };

float myFloat = System.BitConverter.ToSingle(bytes, 0);

有谁知道我必须如何在 xcode 中做到这一点???

Does anybody know how i have to do this in xcode???

谢谢，本杰明

推荐答案

从外部协议转换二进制数据时，请始终确保包含正确的字节序交换:

When converting binary data from a foreign protocol always make sure to include proper swapping for endianness:

uint32_t hostData = CFSwapInt32BigToHost(*(const uint32_t *)[data bytes]);
float value = *(float *)(&hostData);

您必须知道编码数据的字节序.您可能需要改用 CFSwapInt32LittleToHost.

You have to know the endianness of the encoded data. You might need to use CFSwapInt32LittleToHost instead.

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