如何用7z源码编译出来的7z.dll解压tar.gz压缩包。请用c++写一段代码实现

可以使用7z库中的解压函数来完成解压操作。下面是一个简单的示例代码，实现从tar.gz压缩包中解压出所有文件：

#include <iostream>
#include <Windows.h>
#include "7z.h"
#include "7zFile.h"
#include "7zAlloc.h"

int main() {
    const wchar_t* archivepath = L"path/to/your/archive.tar.gz";
    const wchar_t* outdir = L"path/to/output/directory";
    HANDLE hArchive = CreateFileW(archivepath, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hArchive == INVALID_HANDLE_VALUE) {
        std::cerr << "Failed to open archive: " << GetLastError() << std::endl;
        return 1;
    }
    CFileInStream archiveStream;
    archiveStream.file = hArchive;
    archiveStream.s.Read = [](void* p, void* buf, size_t size, size_t* processedSize) -> SRes {
        HANDLE handle = ((CFileInStream*)p)->file;
        if (!ReadFile(handle, buf, (DWORD)size, (DWORD*)processedSize, NULL)) {
            return SZ_ERROR_READ;
        }
        return SZ_OK;
    };
    CArchiveLink archiveLink;
    archiveLink.InStream = &archiveStream.s;
    archiveLink.InStream->Seek(&archiveStream.s, 0, SEEK_SET);
    archiveLink.Arc.LibOpen = [](const wchar_t* name, int mode) -> void* {
        return NULL; // no need to open shared library on Windows
    };
    archiveLink.Arc.LibClose = [](void* lib) -> int {
        return 0; // no need to close shared library on Windows
    };
    archiveLink.Arc.LibSym = [](void* lib, const char* name) -> void* {
        return NULL; // no need to get function address on Windows
    };
    ISzAlloc allocImp = { SzAlloc, SzFree };
    ISzAlloc tempAllocImp = { SzAllocTemp, SzFreeTemp };
    CMyComPtr<IInArchive> archive;
    HRESULT hr = CreateObject(CLASS_CFormat7z, &IID_IInArchive, (void**)&archive);
    if (hr != S_OK) {
        std::cerr << "Failed to create archive object: " << hr << std::endl;
        CloseHandle(hArchive);
        return 1;
    }
    hr = archive->Open(&archiveLink.Arc, &allocImp, &tempAllocImp);
    if (hr != S_OK) {
        std::cerr << "Failed to open archive: " << hr << std::endl;
        CloseHandle(hArchive);
        return 1;
    }
    UInt32 numItems = 0;
    hr = archive->GetNumberOfItems(&numItems);
    if (hr != S_OK) {
        std::cerr << "Failed to get number of items in archive: " << hr << std::endl;
        CloseHandle(hArchive);
        return 1;
    }
    for (UInt32 i = 0; i < numItems; i++) {
        CMyComPtr<IArchiveExtractCallback> extractCallback = new CArchiveExtractCallback(outdir);
        hr = archive->Extract(&i, 1, false, extractCallback);
        if (hr != S_OK) {
            std::cerr << "Failed to extract item " << i << " from archive: " << hr << std::endl;
        }
    }
    archive->Close();
    CloseHandle(hArchive);
    return 0;
}

这段代码包含了7z库的头文件以及函数调用，需要在编译时链接7z库。可以使用以下命令来编译：

g++ -o extract extract.cpp -l7z

其中extract.cpp是保存上述代码的文件名，extract是可执行文件的名称。