Question

我创建了这两种方法，将Native utf-8字符串（char *）转换为托管字符串，反之亦然。以下代码完成了这项工作：

public IntPtr NativeUtf8FromString(string managedString)
{
    byte[] buffer = Encoding.UTF8.GetBytes(managedString); // not null terminated
    Array.Resize(ref buffer, buffer.Length + 1);
    buffer[buffer.Length - 1] = 0; // terminating 0
    IntPtr nativeUtf8 = Marshal.AllocHGlobal(buffer.Length);
    Marshal.Copy(buffer, 0, nativeUtf8, buffer.Length);
    return nativeUtf8;
}

string StringFromNativeUtf8(IntPtr nativeUtf8)
{
    int size = 0;
    byte[] buffer = {};
    do
    {
        ++size;
        Array.Resize(ref buffer, size);
        Marshal.Copy(nativeUtf8, buffer, 0, size);
    } while (buffer[size - 1] != 0); // till 0 termination found

    if (1 == size)
    {
        return ""; // empty string
    }

    Array.Resize(ref buffer, size - 1); // remove terminating 0
    return Encoding.UTF8.GetString(buffer);
}

当NativeUtf8FromString没问题时，StringFromNativeUtf8是一个混乱，但我唯一可以运行的安全代码。使用不安全的代码我可以使用字节*但我不想要不安全的代码。有没有其他人可以想到我不必为每个包含的字节复制字符串以找到0终止。

我只是在这里添加unsave代码：

public unsafe string StringFromNativeUtf8(IntPtr nativeUtf8)
{
    byte* bytes = (byte*)nativeUtf8.ToPointer();
    int size = 0;
    while (bytes[size] != 0)
    {
        ++size;
    }
    byte[] buffer = new byte[size];
    Marshal.Copy((IntPtr)nativeUtf8, buffer, 0, size);
    return Encoding.UTF8.GetString(buffer);
}

如你所见，它并不丑陋，只需要不安全。

Answer 1

执行strlen（）执行完全相同的操作。请考虑保留缓冲区，代码确实会产生垃圾。

    public static IntPtr NativeUtf8FromString(string managedString) {
        int len = Encoding.UTF8.GetByteCount(managedString);
        byte[] buffer = new byte[len + 1];
        Encoding.UTF8.GetBytes(managedString, 0, managedString.Length, buffer, 0);
        IntPtr nativeUtf8 = Marshal.AllocHGlobal(buffer.Length);
        Marshal.Copy(buffer, 0, nativeUtf8, buffer.Length);
        return nativeUtf8;
    }

    public static string StringFromNativeUtf8(IntPtr nativeUtf8) {
        int len = 0;
        while (Marshal.ReadByte(nativeUtf8, len) != 0) ++len;
        byte[] buffer = new byte[len];
        Marshal.Copy(nativeUtf8, buffer, 0, buffer.Length);
        return Encoding.UTF8.GetString(buffer);
    }

Answer 2

比Hans的解决方案快一点（缓冲区副本少1个）：

private unsafe IntPtr AllocConvertManagedStringToNativeUtf8(string input) {
    fixed (char* pInput = input) {
        var len = Encoding.UTF8.GetByteCount(pInput, input.Length);
        var pResult = (byte*)Marshal.AllocHGlobal(len + 1).ToPointer();
        var bytesWritten = Encoding.UTF8.GetBytes(pInput, input.Length, pResult, len);
        Trace.Assert(len == bytesWritten);
        pResult[len] = 0;
        return (IntPtr)pResult;
    }
}

private unsafe string MarshalNativeUtf8ToManagedString(IntPtr pStringUtf8)
    => MarshalNativeUtf8ToManagedString((byte*)pStringUtf8);

private unsafe string MarshalNativeUtf8ToManagedString(byte* pStringUtf8) {
    var len = 0;
    while (pStringUtf8[len] != 0) len++;
    return Encoding.UTF8.GetString(pStringUtf8, len);
}

我在这里演示字符串的双向传递：

var input = "Hello, World!";
var native = AllocConvertManagedStringToNativeUtf8(input);
var copy = MarshalNativeUtf8ToManagedString(native);
Marshal.FreeHGlobal(native); // don't leak unmanaged memory!
Trace.Assert(input == copy); // prove they're equal!

Answer 3

Marshal.PtrToStringUTF8 和 Marshal.StringToCoTaskMemUTF8 已添加到 .NET 5 (.NET Standard 2.1)

.net中的转换：Native Utf-8＆lt; - ＆gt;托管字符串

3 个答案: