KpiPartialFile.h

#pragma once

#include "kpi.h"
#include "kpi_decoder.h"
#include "kpi_impl.h"

// http://kbmplaybbs.dip.jp/?md=ov&no=5321&pn=5314&ln=1
// IKpiFile の一部分だけを扱う。
// 無圧縮アーカイブなどで使う。
class KpiPartialFile : public KbKpiUnknownImpl<IKpiFile>
{
private:
    IKpiFile* m_pFile;
    UINT64 m_qwCurrentPos;
    UINT64 m_qwStartOffset;
    UINT64 m_qwEndOffset;
    UINT64 m_qwSize;

public:
    KpiPartialFile(IKpiFile* pFile,
        UINT64 qwStartOffset,
        UINT64 qwEndOffset)
    {
        if (qwEndOffset < qwStartOffset) {
            qwEndOffset = qwStartOffset;
        }
        m_pFile = pFile;
        m_qwCurrentPos = m_qwStartOffset = qwStartOffset;
        m_qwEndOffset = qwEndOffset;
        m_qwSize = qwEndOffset - qwStartOffset;
        pFile->Seek(qwStartOffset, FILE_BEGIN);
        pFile->AddRef();
    }
    virtual ~KpiPartialFile(void) override
    {
        m_pFile->Release();
    }

    // IKpiFile 派生
    DWORD WINAPI GetFileName(wchar_t* pszName, DWORD dwSize) override { pszName[0] = 0; return 0; }
    BOOL WINAPI GetRealFileW(const wchar_t** ppszFileName) override { *ppszFileName = nullptr; return FALSE; }
    BOOL WINAPI GetRealFileA(const char** ppszFileName) override { *ppszFileName = nullptr; return FALSE; }
    BOOL WINAPI GetBuffer(const BYTE** ppBuffer, size_t* pstSize) override { *ppBuffer = nullptr; *pstSize = 0; return FALSE; }
    BOOL WINAPI CreateClone(IKpiFile** ppFile) override { *ppFile = nullptr; return FALSE; }
    BOOL WINAPI Abort(void) override { return FALSE; }
    //↑ここまで未対応で OK

    DWORD WINAPI Read(void* pBuffer, DWORD dwSize)
    {
        if (dwSize + m_qwCurrentPos > m_qwEndOffset) {
            dwSize = static_cast<DWORD>(m_qwEndOffset - m_qwCurrentPos);
        }
        dwSize = m_pFile->Read(pBuffer, dwSize);
        m_qwCurrentPos += dwSize;
        return dwSize;
    }

    UINT64 WINAPI Seek(INT64 i64Pos, DWORD dwOrigin) override
    {
        switch (dwOrigin) {
        case FILE_BEGIN:
            i64Pos += m_qwStartOffset;
            break;
        case FILE_CURRENT:
            i64Pos += m_qwCurrentPos;
            break;
        case FILE_END:
            i64Pos += m_qwEndOffset;
            break;
        }
        if (i64Pos < static_cast<INT64>(m_qwStartOffset)) {
            i64Pos = m_qwStartOffset;
        }
        else if (i64Pos > static_cast<INT64>(m_qwEndOffset)) {
            i64Pos = m_qwEndOffset;
        }
        m_qwCurrentPos = i64Pos;
        m_pFile->Seek(i64Pos, FILE_BEGIN);
        return m_qwCurrentPos - m_qwStartOffset;
    }

    UINT64 WINAPI GetSize(void) override
    {
        return m_qwSize;
    }
};