/// <summary>
/// Get the next directory entry for the given handle. **Note** the actual memory used may be allocated
/// by the OS and will be freed when the handle is closed. As such, the handle lifespan MUST be kept tightly
/// controlled. The DirectoryEntry name cannot be accessed after the handle is closed.
///
/// Call <see cref="ReadBufferSize"/> to see what size buffer to allocate.
/// </summary>
internal static int ReadDir(SafeDirectoryHandle dir, Span <byte> buffer, ref DirectoryEntry entry)
{
// The calling pattern for ReadDir is described in src/Native/Unix/System.Native/pal_io.cpp|.h
Debug.Assert(buffer.Length >= ReadBufferSize, "should have a big enough buffer for the raw data");
// ReadBufferSize is zero when the native implementation does not support reading into a buffer.
return(ReadDirR(dir.DangerousGetHandle(), ref MemoryMarshal.GetReference(buffer), ReadBufferSize, ref entry));
}
// The calling pattern for ReadDir is described in src/Native/System.Native/pal_readdir.cpp
internal static int ReadDir(SafeDirectoryHandle dir, out DirectoryEntry outputEntry)
{
bool addedRef = false;
try
{
// We avoid a native string copy into InternalDirectoryEntry.
// - If the platform suppors reading into a buffer, the data is read directly into the buffer. The
// data can be read as long as the buffer is valid.
// - If the platform does not support reading into a buffer, the information returned in
// InternalDirectoryEntry points to native memory owned by the SafeDirectoryHandle. The data is only
// valid until the next call to CloseDir/ReadDir. We extend the reference until we have copied all data
// to ensure it does not become invalid by a CloseDir; and we copy the data so our caller does not
// use the native memory held by the SafeDirectoryHandle.
dir.DangerousAddRef(ref addedRef);
unsafe
{
// s_readBufferSize is zero when the native implementation does not support reading into a buffer.
byte *buffer = stackalloc byte[s_readBufferSize];
InternalDirectoryEntry temp;
int ret = ReadDirR(dir.DangerousGetHandle(), buffer, s_readBufferSize, out temp);
// We copy data into DirectoryEntry to ensure there are no dangling references.
outputEntry = ret == 0 ?
new DirectoryEntry()
{
InodeName = GetDirectoryEntryName(temp), InodeType = temp.InodeType
} :
default(DirectoryEntry);
return(ret);
}
}
finally
{
if (addedRef)
{
dir.DangerousRelease();
}
}
}