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