2.1.ReactOS源码分析ReadFile函数分解

2.1.ReactOS源码分析ReadFile函数分解

2.1.ReactOS源码分析ReadFile函数分解

ReadFile函数的分析

BOOL WINAPI ReadFile(HANDLE,PVOID,DWORD,PDWORD,LPOVERLAPPED);

ReadFile函数的声明

BOOL STDCALL
ReadFile(IN HANDLE hFile,
         IN LPVOID lpBuffer,
         IN DWORD nNumberOfBytesToRead,
         OUT LPDWORD lpNumberOfBytesRead  OPTIONAL,
         IN LPOVERLAPPED lpOverlapped  OPTIONAL)
{
   NTSTATUS Status;

   DPRINT("ReadFile(hFile %x)\n", hFile);

   if (lpNumberOfBytesRead != NULL)
     {
        *lpNumberOfBytesRead = 0;
     }

   if (IsConsoleHandle(hFile))
     {
	return ReadConsoleA(hFile,
                            lpBuffer,
                            nNumberOfBytesToRead,
                            lpNumberOfBytesRead,
                            NULL);
     }

   if (lpOverlapped != NULL)
     {
        LARGE_INTEGER Offset;
        PVOID ApcContext;

        Offset.u.LowPart = lpOverlapped->Offset;
        Offset.u.HighPart = lpOverlapped->OffsetHigh;
	lpOverlapped->Internal = STATUS_PENDING;
	ApcContext = (((ULONG_PTR)lpOverlapped->hEvent & 0x1) ? NULL : lpOverlapped);

	Status = NtReadFile(hFile,
                            lpOverlapped->hEvent,
                            NULL,
                            ApcContext,
                            (PIO_STATUS_BLOCK)lpOverlapped,
                            lpBuffer,
                            nNumberOfBytesToRead,
                            &Offset,
                            NULL);

        /* return FALSE in case of failure and pending operations! */
        if (!NT_SUCCESS(Status) || Status == STATUS_PENDING)
          {
             if (Status == STATUS_END_OF_FILE &&
                 lpNumberOfBytesRead != NULL)
               {
                  *lpNumberOfBytesRead = 0;
               }

             SetLastErrorByStatus(Status);
             return FALSE;
          }

        if (lpNumberOfBytesRead != NULL)
          {
             *lpNumberOfBytesRead = lpOverlapped->InternalHigh;
          }
     }
   else
     {
        IO_STATUS_BLOCK Iosb;

        Status = NtReadFile(hFile,
                            NULL,
                            NULL,
                            NULL,
                            &Iosb,
                            lpBuffer,
                            nNumberOfBytesToRead,
                            NULL,
                            NULL);

        /* wait in case operation is pending */
        if (Status == STATUS_PENDING)
          {
             Status = NtWaitForSingleObject(hFile,
                                            FALSE,
                                            NULL);
             if (NT_SUCCESS(Status))
               {
                  Status = Iosb.Status;
               }
          }

        if (Status == STATUS_END_OF_FILE)
          {
             /* lpNumberOfBytesRead must not be NULL here, in fact Win doesn't
                check that case either and crashes (only after the operation
                completed) */
             *lpNumberOfBytesRead = 0;
             return TRUE;
          }

        if (NT_SUCCESS(Status))
          {
             /* lpNumberOfBytesRead must not be NULL here, in fact Win doesn't
                check that case either and crashes (only after the operation
                completed) */
             *lpNumberOfBytesRead = Iosb.Information;
          }
        else
          {
             SetLastErrorByStatus(Status);
             return FALSE;
          }
     }

   DPRINT("ReadFile() succeeded\n");
   return TRUE;
}

ReadFile函数的核心代码

BOOL STDCALL
ReadFile(IN HANDLE hFile,
         IN LPVOID lpBuffer,
         IN DWORD nNumberOfBytesToRead,
         OUT LPDWORD lpNumberOfBytesRead  OPTIONAL,
         IN LPOVERLAPPED lpOverlapped  OPTIONAL)
{
   NTSTATUS Status;

 // ...

      Status = NtReadFile(hFile,
                            NULL,
                            NULL,
                            NULL,
                            &Iosb,
                            lpBuffer,
                            nNumberOfBytesToRead,
                            NULL,
                            NULL);

    //...
   return TRUE;
}

1，ReadFile函数的分析，转变为对函数NtReadFile函数的分析。
NtReadFile函数的分析请看本专栏NtReadFile函数的分析