#include <ntddk.h>
#include "ntifs.h"

NTSTATUS
FileDiskOpenFile (
    IN PDEVICE_OBJECT   DeviceObject,
    IN PIRP             Irp
    )
{
    PDEVICE_EXTENSION               device_extension;
    POPEN_FILE_INFORMATION          open_file_information;
    UNICODE_STRING                  ufile_name;
    NTSTATUS                        status;
    OBJECT_ATTRIBUTES               object_attributes;
    FILE_END_OF_FILE_INFORMATION    file_eof;
    FILE_BASIC_INFORMATION          file_basic;
    FILE_STANDARD_INFORMATION       file_standard;
    FILE_ALIGNMENT_INFORMATION      file_alignment;

    PAGED_CODE();

    ASSERT(DeviceObject != NULL);
    ASSERT(Irp != NULL);

    device_extension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;

    open_file_information = (POPEN_FILE_INFORMATION) Irp->AssociatedIrp.SystemBuffer;

    if (DeviceObject->DeviceType != FILE_DEVICE_CD_ROM)
		//FILE_DEVICE_CD_ROM在ntddk.h中定義為0x00000002
    {
        device_extension->read_only = open_file_information->ReadOnly;
    }

    device_extension->file_name.Length = open_file_information->FileNameLength;
    device_extension->file_name.MaximumLength = open_file_information->FileNameLength;
    device_extension->file_name.Buffer = ExAllocatePool(NonPagedPool, open_file_information->FileNameLength);

    RtlCopyMemory(
        device_extension->file_name.Buffer,
        open_file_information->FileName,
        open_file_information->FileNameLength
        );

    status = RtlAnsiStringToUnicodeString(
        &ufile_name,
        &device_extension->file_name,
        TRUE
        );

    if (!NT_SUCCESS(status))
    {
        ExFreePool(device_extension->file_name.Buffer);
        Irp->IoStatus.Status = status;
        Irp->IoStatus.Information = 0;
        return status;
    }

    InitializeObjectAttributes(
        &object_attributes,
        &ufile_name,
        OBJ_CASE_INSENSITIVE,
        NULL,
        NULL
        );
	//OBJ_CASE_INSENSITIVE在ntdef.h中定義為0x00000040L

    status = ZwCreateFile(
        &device_extension->file_handle,
        device_extension->read_only ? GENERIC_READ : GENERIC_READ | GENERIC_WRITE,
        &object_attributes,
        &Irp->IoStatus,
        NULL,
        FILE_ATTRIBUTE_NORMAL,
        device_extension->read_only ? FILE_SHARE_READ : 0,
        FILE_OPEN,
        FILE_NON_DIRECTORY_FILE |
        FILE_RANDOM_ACCESS |
        FILE_NO_INTERMEDIATE_BUFFERING |
        FILE_SYNCHRONOUS_IO_NONALERT,
        NULL,
        0
        );
	//GENERIC_READ在ntddk.h中定義為0x80000000L
	//GENERIC_WRITE在ntddk.h中定義為0x40000000L
	//FILE_ATTRIBUTE_NORMAL在ntddk.h中定義為0x00000080
	//FILE_OPEN在ntddk.h中定義為0x00000001
	//FILE_NON_DIRECTORY_FILE在ntddk.h中定義為0x00000040
	//FILE_RANDOM_ACCESS在ntddk.h中定義為0x00000800
	//FILE_NO_INTERMEDIATE_BUFFERING在ntddk.h中定義為0x00000008
	//FILE_SYNCHRONOUS_IO_NONALERT在ntddk.h中定義為0x00000020

    if (status == STATUS_OBJECT_NAME_NOT_FOUND || status == STATUS_NO_SUCH_FILE)
		//STATUS_OBJECT_NAME_NOT_FOUND在ntstatus.h中定義為((NTSTATUS)0xC0000034L)
		//STATUS_NO_SUCH_FILE在ntstatus.h中定義為((NTSTATUS)0xC000000FL)
    {
        if (device_extension->read_only || open_file_information->FileSize.QuadPart == 0)
        {
            ExFreePool(device_extension->file_name.Buffer);
            RtlFreeUnicodeString(&ufile_name);

            Irp->IoStatus.Status = STATUS_NO_SUCH_FILE;
            Irp->IoStatus.Information = 0;

            return STATUS_NO_SUCH_FILE;
        }
        else
        {
            status = ZwCreateFile(
                &device_extension->file_handle,
                GENERIC_READ | GENERIC_WRITE,
                &object_attributes,
                &Irp->IoStatus,
                &open_file_information->FileSize,
                FILE_ATTRIBUTE_NORMAL,
                0,
                FILE_OPEN_IF,
                FILE_NON_DIRECTORY_FILE |
                FILE_RANDOM_ACCESS |
                FILE_NO_INTERMEDIATE_BUFFERING |
                FILE_SYNCHRONOUS_IO_NONALERT,
                NULL,
                0
                );
			//FILE_OPEN_IF在ntddk.h中定義為0x00000003

            if (!NT_SUCCESS(status))
            {
                ExFreePool(device_extension->file_name.Buffer);
                RtlFreeUnicodeString(&ufile_name);
                return status;
            }

            if (Irp->IoStatus.Information == FILE_CREATED)
            {
                file_eof.EndOfFile.QuadPart = open_file_information->FileSize.QuadPart;

                status = ZwSetInformationFile(
                    device_extension->file_handle,
                    &Irp->IoStatus,
                    &file_eof,
                    sizeof(FILE_END_OF_FILE_INFORMATION),
                    FileEndOfFileInformation
                    );
				//FILE_END_OF_FILE_INFORMATION結構參見ntddk.h

                if (!NT_SUCCESS(status))
                {
                    ExFreePool(device_extension->file_name.Buffer);
                    RtlFreeUnicodeString(&ufile_name);
                    ZwClose(device_extension->file_handle);
                    return status;
                }
            }
        }
    }
    else if (!NT_SUCCESS(status))
    {
        ExFreePool(device_extension->file_name.Buffer);
        RtlFreeUnicodeString(&ufile_name);
        return status;
    }

    RtlFreeUnicodeString(&ufile_name);

    status = ZwQueryInformationFile(
        device_extension->file_handle,
        &Irp->IoStatus,
        &file_basic,
        sizeof(FILE_BASIC_INFORMATION),
        FileBasicInformation
        );
	//FILE_STANDARD_INFORMATION結構參見ntddk.h

    if (!NT_SUCCESS(status))
    {
        ExFreePool(device_extension->file_name.Buffer);
        ZwClose(device_extension->file_handle);
        return status;
    }

    //
    // The NT cache manager can deadlock if a filesystem that is using the cache
    // manager is used in a virtual disk that stores its file on a filesystem
    // that is also using the cache manager, this is why we open the file with
    // FILE_NO_INTERMEDIATE_BUFFERING above, however if the file is compressed
    // or encrypted NT will not honor this request and cache it anyway since it
    // need to store the decompressed/unencrypted data somewhere, therefor we put
    // an extra check here and don't alow disk images to be compressed/encrypted.
    //
    if (file_basic.FileAttributes & (FILE_ATTRIBUTE_COMPRESSED | FILE_ATTRIBUTE_ENCRYPTED))
    {
        ExFreePool(device_extension->file_name.Buffer);
        ZwClose(device_extension->file_handle);
        Irp->IoStatus.Status = STATUS_ACCESS_DENIED;
        Irp->IoStatus.Information = 0;
        return STATUS_ACCESS_DENIED;
    }
	//FILE_ATTRIBUTE_COMPRESSED在ntddk.h中定義為0x00000800
	//FILE_ATTRIBUTE_ENCRYPTED在ntddk.h中定義為0x00004000
	//STATUS_ACCESS_DENIED在ntstatus.h中定義為((NTSTATUS)0xC0000022L)

    status = ZwQueryInformationFile(
        device_extension->file_handle,
        &Irp->IoStatus,
        &file_standard,
        sizeof(FILE_STANDARD_INFORMATION),
        FileStandardInformation
        );

    if (!NT_SUCCESS(status))
    {
        ExFreePool(device_extension->file_name.Buffer);
        ZwClose(device_extension->file_handle);
        return status;
    }

    device_extension->file_size.QuadPart = file_standard.EndOfFile.QuadPart;

    status = ZwQueryInformationFile(
        device_extension->file_handle,
        &Irp->IoStatus,
        &file_alignment,
        sizeof(FILE_ALIGNMENT_INFORMATION),
        FileAlignmentInformation
        );
	//FILE_ALIGNMENT_INFORMATION結構參見ntddk.h

    if (!NT_SUCCESS(status))
    {
        ExFreePool(device_extension->file_name.Buffer);
        ZwClose(device_extension->file_handle);
        return status;
    }

    DeviceObject->AlignmentRequirement = file_alignment.AlignmentRequirement;

    if (device_extension->read_only)
    {
        DeviceObject->Characteristics |= FILE_READ_ONLY_DEVICE;
		//FILE_READ_ONLY_DEVICE在ntddk.h中定義為0x00000002
    }
    else
    {
        DeviceObject->Characteristics &= ~FILE_READ_ONLY_DEVICE;
    }

    device_extension->media_in_device = TRUE;

    Irp->IoStatus.Status = STATUS_SUCCESS;
    Irp->IoStatus.Information = 0;

    return STATUS_SUCCESS;
}