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/** @file
EFI_FILE_PROTOCOL.Read() member function for the Virtio Filesystem driver.
Copyright (C) 2020, Red Hat, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "VirtioFsDxe.h"
/**
Read from a regular file.
**/
STATIC
EFI_STATUS
ReadRegularFile (
IN OUT VIRTIO_FS_FILE *VirtioFsFile,
IN OUT UINTN *BufferSize,
OUT VOID *Buffer
)
{
VIRTIO_FS *VirtioFs;
EFI_STATUS Status;
VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE FuseAttr;
UINTN Transferred;
UINTN Left;
VirtioFs = VirtioFsFile->OwnerFs;
//
// The UEFI spec forbids reads that start beyond the end of the file.
//
Status = VirtioFsFuseGetAttr (VirtioFs, VirtioFsFile->NodeId, &FuseAttr);
if (EFI_ERROR (Status) || VirtioFsFile->FilePosition > FuseAttr.Size) {
return EFI_DEVICE_ERROR;
}
Status = EFI_SUCCESS;
Transferred = 0;
Left = *BufferSize;
while (Left > 0) {
UINT32 ReadSize;
//
// FUSE_READ cannot express a >=4GB buffer size.
//
ReadSize = (UINT32)MIN ((UINTN)MAX_UINT32, Left);
Status = VirtioFsFuseReadFileOrDir (
VirtioFs,
VirtioFsFile->NodeId,
VirtioFsFile->FuseHandle,
FALSE, // IsDir
VirtioFsFile->FilePosition + Transferred,
&ReadSize,
(UINT8 *)Buffer + Transferred
);
if (EFI_ERROR (Status) || ReadSize == 0) {
break;
}
Transferred += ReadSize;
Left -= ReadSize;
}
*BufferSize = Transferred;
VirtioFsFile->FilePosition += Transferred;
//
// If we managed to read some data, return success. If zero bytes were
// transferred due to zero-sized buffer on input or due to EOF on first read,
// return SUCCESS. Otherwise, return the error due to which zero bytes were
// transferred.
//
return (Transferred > 0) ? EFI_SUCCESS : Status;
}
EFI_STATUS
EFIAPI
VirtioFsSimpleFileRead (
IN EFI_FILE_PROTOCOL *This,
IN OUT UINTN *BufferSize,
OUT VOID *Buffer
)
{
VIRTIO_FS_FILE *VirtioFsFile;
EFI_STATUS Status;
VirtioFsFile = VIRTIO_FS_FILE_FROM_SIMPLE_FILE (This);
if (VirtioFsFile->IsDirectory) {
Status = EFI_NO_MEDIA;
} else {
Status = ReadRegularFile (VirtioFsFile, BufferSize, Buffer);
}
return Status;
}
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