EDK2编写UEFI代码，判断指定文件名的文件中是否存在某字符串

以下是一个简单的示例代码，用于在指定文件名的文件中搜索特定字符串：

#include <Uefi.h>
#include <Library/UefiLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/BaseMemoryLib.h>
#include <Protocol/SimpleFileSystem.h>

EFI_STATUS EFIAPI UefiMain(IN EFI_HANDLE ImageHandle, IN EFI_SYSTEM_TABLE *SystemTable)
{
    EFI_STATUS Status;

    // Open the root directory
    EFI_HANDLE DeviceHandle = NULL;
    Status = gBS->LocateDevicePath(&gEfiSimpleFileSystemProtocolGuid, &gEfiDevicePathProtocolGuid, &DeviceHandle);
    if (EFI_ERROR(Status)) {
        Print(L"Failed to locate device path: %r\n", Status);
        return Status;
    }

    EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *FileSystem;
    Status = gBS->OpenProtocol(DeviceHandle, &gEfiSimpleFileSystemProtocolGuid, (VOID **)&FileSystem, ImageHandle, NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL);
    if (EFI_ERROR(Status)) {
        Print(L"Failed to open protocol: %r\n", Status);
        return Status;
    }

    EFI_FILE_PROTOCOL *Root;
    Status = FileSystem->OpenVolume(FileSystem, &Root);
    if (EFI_ERROR(Status)) {
        Print(L"Failed to open root directory: %r\n", Status);
        return Status;
    }

    // Open the file
    CHAR16 *FileName = L"test.txt";
    EFI_FILE_PROTOCOL *File;
    Status = Root->Open(Root, &File, FileName, EFI_FILE_MODE_READ, 0);
    if (EFI_ERROR(Status)) {
        Print(L"Failed to open file %s: %r\n", FileName, Status);
        return Status;
    }

    // Read the file contents
    UINTN BufferSize = 1024;
    CHAR8 Buffer[BufferSize];
    Status = File->Read(File, &BufferSize, Buffer);
    if (EFI_ERROR(Status)) {
        Print(L"Failed to read file %s: %r\n", FileName, Status);
        return Status;
    }

    // Search for the string
    CHAR8 *SearchString = "hello";
    if (StrStr(Buffer, SearchString) != NULL) {
        Print(L"Found \"%a\" in file %s\n", SearchString, FileName);
    } else {
        Print(L"Could not find \"%a\" in file %s\n", SearchString, FileName);
    }

    // Clean up
    File->Close(File);
    Root->Close(Root);

    return EFI_SUCCESS;
}

该代码首先打开文件系统的根目录，然后打开指定的文件。它将文件内容读入缓冲区，然后在该缓冲区中搜索特定字符串。如果找到了该字符串，则输出一条消息，否则输出另一条消息。最后，文件和根目录被关闭以释放资源。