14.Quản lý IO

Khái quát

Quản lý IO là việc đọc các luồng dữ liệu (stream), gồm:

• File stream
• Buffer stream (luồng dữ liệu trong bộ nhớ)

Về phương thức hoạt động, các luồng chia làm 2 loại:

• Luồng đọc
• Luồng ghi

Với luồng chỉ đọc, ta định nghĩa interface:

IReadableStream

class IReadableStream { public: virtual void Read(__UINT8* buffer, int offset, int length) = 0; virtual void ReadInt8(__INT8 &val) = 0; virtual void ReadUInt8(__UINT8 &val) = 0; virtual void ReadInt16(__INT16 &val) = 0; virtual void ReadUInt16(__UINT16 &val) = 0; virtual void ReadInt32(__INT32 &val) = 0; virtual void ReadUInt32(__UINT32 &val) = 0; virtual void ReadInt64(__INT64 &val) = 0; virtual void ReadUInt64(__UINT64 &val) = 0; virtual void Skip(__UINT32 n) = 0; virtual void Goto(__UINT32 pos) = 0; };

Với luồng ghi, ta định nghĩa interface:

IWriteableStream

class IWriteableStream { public: virtual void Write(__UINT8* buffer, int offset, int length) = 0; virtual void WriteInt8(__INT8 val) = 0; virtual void WriteUInt8(__UINT8 val) = 0; virtual void WriteInt16(__INT16 val) = 0; virtual void WriteUInt16(__UINT16 val) = 0; virtual void WriteInt32(__INT32 val) = 0; virtual void WriteUInt32(__UINT32 val) = 0; virtual void WriteInt64(__INT64 val) = 0; virtual void WriteUInt64(__UINT64 val) = 0; virtual void WriteSeq(__UINT8 val, int length) = 0; };

Tiếp theo, ta định nghĩa tổng quát một stream buffer có cấu trúc sau:

IStreamBuffer

enum EStreamStatus { ESTREAM_READY, ESTREAM_ERROR, ESTREAM_OPEN, ESTREAM_CLOSE };

class IStreamBuffer { public: IStreamBuffer(const char* name):m_eStreamStatus(ESTREAM_READY) { m_strName = new char[strlen(name) + 1]; memcpy(m_strName, name, strlen(name) + 1); } virtual ~IStreamBuffer() { SAFE_DEL(m_strName); } virtual void Open() {m_eStreamStatus = ESTREAM_OPEN;} virtual void Close() {m_eStreamStatus = ESTREAM_CLOSE;} virtual __UINT32 GetLength() = 0; virtual char* GetName() {return m_strName;} virtual EStreamStatus GetStatus() {return m_eStreamStatus;} protected: EStreamStatus m_eStreamStatus; char* m_strName; };

Mô hình xây dựng

Từ 3 lớp khái quát trên, ta xây dựng tập lớp phục vụ cho các mục đích như: luồng ghi file, luồng đọc file, luồng ghi buffer, luồng đọc buffer, ... Trong đó, với file, ta lại phân ra file cho WIN32, file cho Android, ....

Ta chia mỗi phương pháp đọc/ghi (file-win32, file-android, buffer, ...) thành các tập giao thức riêng, tạm gọi là các IO driver. Vậy ta có các driver:

• CFileWin32Driver: driver dùng cho đọc/ghi file Win32 little endian
• CFileAndroidDriver: driver dùng cho đọc/ghi file trên Android
• CBufferDriver: driver dùng cho đọc/ghi buffer
• ....

Ví dụ CFileWin32Driver

CFileWin32Driver

class CFileWin32Driver: public CSingleton<CFileWin32Driver> { friend class CSingleton<CFileWin32Driver>; protected: CFileWin32Driver() {} public: void Read(FILE*F, __UINT8* buffer, int offset, int length) { fread(buffer + offset, 1, length, F); } void Write(FILE*F, __UINT8* buffer, int offset, int length) { fwrite(buffer + offset, 1, length, F); } void Seek(FILE*F, int offset) { fseek(F, offset, SEEK_CUR); } void Goto(FILE*F, int offsetFromTop) { if (offsetFromTop==-1) { fseek(F, 0, SEEK_END); } else { fseek(F, offsetFromTop, SEEK_SET); } } void Rewind(FILE*F) { rewind(F); } void Open(FILE*& f, const char* filename, const char* mode) { fopen_s(&f, filename, mode); } void Close(FILE*& f) { fclose(f); } __UINT32 GetLength(FILE*& f) { fpos_t curpos; fgetpos(f, &curpos); fseek (f, 0, SEEK_END); __UINT32 size = ftell (f); fseek(f, __UINT32(curpos), SEEK_SET); return size; } void TestError() { if (errno) { char buf[1024]; strerror_s(buf, errno); Log("CFileWin32Driver Error: %s",buf); } } };

Từ các lớp driver, ta xây dựng 2 lớp chính

• CReadStream
• CWriteStream

Ví dụ:

CReadStream & CWriteStream

template <class StreamDriver> class CReaderStream: public IReadableStream, IStreamBuffer { public: CReaderStream(const char* name): IStreamBuffer(name) {} virtual ~CReaderStream(){} virtual void Read(__UINT8* buffer, int offset, int length) {} virtual void ReadInt8(__INT8 &val) {} virtual void ReadUInt8(__UINT8 &val) {} virtual void ReadInt16(__INT16 &val) {} virtual void ReadUInt16(__UINT16 &val) {} virtual void ReadInt32(__INT32 &val) {} virtual void ReadUInt32(__UINT32 &val) {} virtual void ReadInt64(__INT64 &val) {} virtual void ReadUInt64(__UINT64 &val) {} virtual void Skip(__UINT32 n) {} virtual void Goto(__UINT32 pos) {} virtual void Open() {IStreamBuffer::Open();} virtual void Close() {IStreamBuffer::Close();} virtual __UINT32 GetLength() {return 0;} }; template <class StreamDriver> class CWriteStream: public IWriteableStream, IStreamBuffer { public: CWriteStream(const char* name): IStreamBuffer(name) {} virtual ~CWriteStream(){} virtual void Write(__UINT8* buffer, int offset, int length) {} virtual void WriteInt8(__INT8 val) {} virtual void WriteUInt8(__UINT8 val) {} virtual void WriteInt16(__INT16 val) {} virtual void WriteUInt16(__UINT16 val) {} virtual void WriteInt32(__INT32 val) {} virtual void WriteUInt32(__UINT32 val) {} virtual void WriteInt64(__INT64 val) {} virtual void WriteUInt64(__UINT64 val) {} virtual void WriteSeq(__UINT8 val, int length) {} virtual void Open() {IStreamBuffer::Open();} virtual void Close() {IStreamBuffer::Close();} virtual __UINT32 GetLength() {return 0;} };

Ứng với từng driver, ta implement các trường hợp của CReadStream và CWriteStream. Ví dụ với Win32

CReaderStream & CWriteStream cho CFileWin32Driver

enum EFileWin32Mode { EFILEWIN32_READ, EFILEWIN32_WRITE };

class CFileWin32Base: public IStreamBuffer { public: CFileWin32Base(const char* name, EFileWin32Mode mode): IStreamBuffer(name) , m_pFile(0), m_iLength(0), e_Mode(mode) { m_pDriver = CFileWin32Driver::GetInstance(); Open(); } virtual ~CFileWin32Base() { Close(); } void Open() { if (m_eStreamStatus == ESTREAM_OPEN) { return; } m_pDriver->Open(m_pFile, this->GetName(), (e_Mode == EFILEWIN32_READ)?"rb":"wb"); IStreamBuffer::Open(); if (!m_pFile) { m_eStreamStatus = ESTREAM_ERROR; } else { m_iLength = m_pDriver->GetLength(m_pFile); } m_pDriver->TestError(); } void Close() { if ((m_eStreamStatus != ESTREAM_CLOSE) && m_pFile) { m_pDriver->Close(m_pFile); m_pFile = 0; } IStreamBuffer::Close(); m_pDriver->TestError(); } __UINT32 GetLength() { return m_iLength; } protected: FILE* m_pFile; CFileWin32Driver* m_pDriver; __UINT32 m_iLength; EFileWin32Mode e_Mode; }; template <> class CReaderStream<CFileWin32Driver>: public IReadableStream, public CFileWin32Base { public: CReaderStream(const char* name): CFileWin32Base(name, EFILEWIN32_READ) {} virtual ~CReaderStream() {} void Read(__UINT8* buffer, int offset, int length) { if (m_eStreamStatus == ESTREAM_OPEN) { m_pDriver->Read(m_pFile, buffer, offset, length); } } void ReadInt8(__INT8 &val) { val = 0; if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buf[1]; m_pDriver->Read(m_pFile, buf, 0, 1); val = __INT8(buf[0]); } } void ReadUInt8(__UINT8 &val) { val = 0; if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buf[1]; m_pDriver->Read(m_pFile, buf, 0, 1); val = __UINT8(buf[0]); } } void ReadInt16(__INT16 &val) { val = 0; if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buf[2]; m_pDriver->Read(m_pFile, buf, 0, 2); val = __UINT16(buf[1]); val <<= 8; val |= __UINT16(buf[0]); } } void ReadUInt16(__UINT16 &val) { val = 0; __INT16 tmp = 0; ReadInt16(tmp); val = __UINT16(tmp); } void ReadInt32(__INT32 &val) { val = 0; if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buf[4]; m_pDriver->Read(m_pFile, buf, 0, 4); val = __UINT16(buf[3]); val <<= 8; val |= __UINT16(buf[2]); val <<= 8; val |= __UINT16(buf[1]); val <<= 8; val |= __UINT16(buf[0]); } } void ReadUInt32(__UINT32 &val) { val = 0; __INT32 tmp = 0; ReadInt32(tmp); val = __UINT32(tmp); } void ReadInt64(__INT64 &val) { val = 0; if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buf[8]; m_pDriver->Read(m_pFile, buf, 0, 8); val = __UINT16(buf[7]); val <<= 8; val |= __UINT16(buf[6]); val <<= 8; val |= __UINT16(buf[5]); val <<= 8; val |= __UINT16(buf[4]); val <<= 8; val |= __UINT16(buf[3]); val <<= 8; val |= __UINT16(buf[2]); val <<= 8; val |= __UINT16(buf[1]); val <<= 8; val |= __UINT16(buf[0]); } } void ReadUInt64(__UINT64 &val) { val = 0; __INT64 tmp = 0; ReadInt64(tmp); val = __UINT64(tmp); } void Skip(__UINT32 n) { m_pDriver->Seek(m_pFile, n); } void Goto(__UINT32 n) { m_pDriver->Goto(m_pFile, n); } }; template <> class CWriteStream<CFileWin32Driver>: public IWriteableStream, public CFileWin32Base { public: CWriteStream(const char* name): CFileWin32Base(name, EFILEWIN32_WRITE) {} virtual ~CWriteStream() {} void Write(__UINT8* buffer, int offset, int length) { if (m_eStreamStatus == ESTREAM_OPEN) { m_pDriver->Write(m_pFile, buffer , 0, length); } } void WriteInt8(__INT8 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val)}; m_pDriver->Write(m_pFile, buffer , 0, 1); } } void WriteUInt8(__UINT8 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val)}; m_pDriver->Write(m_pFile, buffer , 0, 1); } } void WriteInt16(__INT16 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val&0xFF), __UINT8(val>>8)}; m_pDriver->Write(m_pFile, buffer , 0, 2); } } void WriteUInt16(__UINT16 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val&0xFF), __UINT8((val>>8)&0xFF)}; m_pDriver->Write(m_pFile, buffer , 0, 2); } } void WriteInt32(__INT32 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val&0xFF), __UINT8((val>>8)&0xFF), __UINT8((val>>16)&0xFF), __UINT8((val>>24)&0xFF)}; m_pDriver->Write(m_pFile, buffer , 0, 4); } } void WriteUInt32(__UINT32 val) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 buffer[] = {__UINT8(val&0xFF), __UINT8((val>>8)&0xFF), __UINT8((val>>16)&0xFF), __UINT8((val>>24)&0xFF)}; m_pDriver->Write(m_pFile, buffer , 0, 4); } } void WriteInt64(__INT64 val) { TODO("WriteInt64 is not implemented"); } void WriteUInt64(__UINT64 val) { TODO("WriteUInt64 is not implemented"); } void WriteSeq(__UINT8 val, int length) { if (m_eStreamStatus == ESTREAM_OPEN) { __UINT8 *buffer = new __UINT8[length]; memset(buffer, 0, length); m_pDriver->Write(m_pFile, buffer , 0, length); SAFE_DEL(buffer); } } };

Trong ví dụ trên, CFileWin32Base được xây dựng như một trường hợp đặc biệt của IStreamBuffer.

Class diagram

Source code

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