[英]How to convert a QByteArray in little endian format to a unsigned long
I have a QByteArray with 4 values in little endian format我有一个 QByteArray 有 4 个小端格式的值
QByteArray ba;
ba.append(0xbb);
ba.append(0x1c);
ba.append(0x51);
ba.append(0x1e);
to convert ba to big endian I do the following :要将 ba 转换为大端,我执行以下操作:
baBigEndian[0] = ba[3];
baBigEndian[1] = ba[2];
baBigEndian[2] = ba[1];
baBigEndian[3] = ba[0];
to convert the big endian array to an unsigned long i tried the following:要将大端数组转换为 unsigned long,我尝试了以下操作:
baBigEndian.toULong(&ok,10);
The little endian byte array is correctly converted to big endian but the .toULong returns 0 in stead of 508632251.小端字节数组正确转换为大端,但 .toULong 返回 0 而不是 508632251。
How can I convert the baBigEndian array to an unsigned long?如何将 baBigEndian 数组转换为无符号长整数? Or is there a way to directly convert from a little endian array to an unsigned long?
或者有没有办法直接从小端数组转换为无符号长数组?
Thanks in advance!提前致谢!
toULong()
won't work, since it expects the QByteArray to contain a string representation of the number in ASCII format (eg "0xbb1c511e"
, which is 10 ASCII bytes), and your QByteArray contains the literal binary bytes instead (eg 0xbb1c511e
, which is 4 binary bytes). toULong()
将不起作用,因为它期望 QByteArray 包含 ASCII 格式的数字的字符串表示(例如"0xbb1c511e"
,即 10 个 ASCII 字节),而您的 QByteArray 包含文字二进制字节(例如0xbb1c511e
,这是 4 个二进制字节)。
Assuming your QByteArray contains the four bytes in big-endian format (as it does after step 2 in your example code), then this would work:假设您的 QByteArray 包含大端格式的四个字节(就像您的示例代码中的第 2 步之后那样),那么这将起作用:
unsigned long val = ntohl(*((const unsigned long *)ba.data()));
Note however that sizeof(unsigned long)
is not guaranteed to be 4 bytes on all platforms, so you'd be better off using a fixed-width type that is guaranteed to always be 4 bytes wide instead, eg但是请注意
sizeof(unsigned long)
不能保证在所有平台上都是 4 个字节,所以你最好使用一个固定宽度的类型,它保证总是 4 个字节宽,例如
quint32 val = ntohl(*((const quint32 *)ba.data()));
Try memcpy
试试
memcpy
quint32 value = 0; //or qint32
memcpy(&value, baBigEndian.data(), sizeof(quint32));//or baBigEndian instead baBigEndian.data() if you use plain array instead QByteArray
Also, it can be done with reinterpret_cast
but I do not recommend you to use reinterpret_cast
because I had some problems on arm
processors (while on x86
it works fine).此外,它可以通过
reinterpret_cast
完成,但我不建议您使用reinterpret_cast
因为我在arm
处理器上遇到了一些问题(而在x86
它工作正常)。
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