| private static Populate83FileNameFromRandomBytes ( byte bytes, int byteCount, char chars, int charCount ) : void | ||
| bytes | byte | |
| byteCount | int | |
| chars | char | |
| charCount | int | |
| return | void | |
private static unsafe string CreateTempSubdirectoryCore(string?prefix)
{
ValueStringBuilder builder = new ValueStringBuilder(stackalloc char[PathInternal.MaxShortPath]);
Path.GetTempPath(ref builder);
// ensure the base TEMP directory exists
CreateDirectory(PathHelper.Normalize(ref builder));
builder.Append(prefix);
const int RandomFileNameLength = 12; // 12 == 8 + 1 (for period) + 3
int initialTempPathLength = builder.Length;
builder.EnsureCapacity(initialTempPathLength + RandomFileNameLength);
// For generating random file names
// 8 random bytes provides 12 chars in our encoding for the 8.3 name.
const int RandomKeyLength = 8;
byte * pKey = stackalloc byte[RandomKeyLength];
// to avoid an infinite loop, only try as many as GetTempFileNameW will create
const int MaxAttempts = ushort.MaxValue;
int attempts = 0;
while (attempts < MaxAttempts)
{
// simulate a call to Path.GetRandomFileName() without allocating an intermediate string
Interop.GetRandomBytes(pKey, RandomKeyLength);
Path.Populate83FileNameFromRandomBytes(pKey, RandomKeyLength, builder.RawChars.Slice(builder.Length, RandomFileNameLength));
builder.Length += RandomFileNameLength;
string path = PathHelper.Normalize(ref builder);
bool directoryCreated = Interop.Kernel32.CreateDirectory(path, null);
if (!directoryCreated)
{
// in the off-chance that the directory already exists, try again
int error = Marshal.GetLastPInvokeError();
if (error == Interop.Errors.ERROR_ALREADY_EXISTS)
{
builder.Length = initialTempPathLength;
attempts++;
continue;
}
throw Win32Marshal.GetExceptionForWin32Error(error, path);
}
builder.Dispose();
return(path);
}
throw new IOException(SR.IO_MaxAttemptsReached);
}
public static unsafe string GetRandomFileName()
{
byte *buffer = stackalloc byte[8];
Interop.GetRandomBytes(buffer, 8);
return(string.Create <IntPtr>(12, (IntPtr)(void *)buffer, (SpanAction <char, IntPtr>)((span, key) => Path.Populate83FileNameFromRandomBytes((byte *)(void *)key, 8, span))));
}