C函数计算相对路径

Question

输入:两条路径，如

• 来自:/usr/share/lib
• inTo:/usr/bin

关于输出:像

这样的路径

• oRelPath == ../../bin

是否有任何标准或接近标准的功能？感兴趣的操作系统是:windows、mac、linux看起来很奇怪，对于这样的标准琐碎任务，似乎没有任何标准函数(或者它们以不明显的方式调用)

Answer 1

我将@Armali 发布的 C# 代码转换为 C++:

#include <vector>
#include <string>
#include <algorithm>

std::vector<std::string> str_split(const std::string& in,  const std::string& delim=" \t\r\n") {
    std::vector<std::string> out;
    auto firstPos = in.find_first_not_of(delim);
    auto secondPos = in.find_first_of(delim, firstPos);
    out.clear();
    if(firstPos != std::string::npos)
    { out.push_back( in.substr( firstPos, secondPos - firstPos ) ); }
    while( secondPos != std::string::npos ) {
        firstPos = in.find_first_not_of(delim, secondPos);
        if(firstPos == std::string::npos)
        { break; }
        secondPos = in.find_first_of( delim, firstPos );
        out.push_back( in.substr( firstPos, secondPos - firstPos ) );
    }
    return out;
}

int str_compare_no_case(std::string a, std::string b) {
    std::transform(a.begin(), a.end(), a.begin(), ::tolower);
    std::transform(b.begin(), b.end(), b.begin(), ::tolower);
    return a.compare(b);
}

static std::string MakeRelativePath(std::string absPath, std::string relTo) {
#ifdef _WIN32
    const char directorySeparator = '\\';
#else
    const char directorySeparator = '/';
#endif
    std::string DirectorySeparatorChars = {directorySeparator, '\0'};
    auto absParts = str_split(absPath, DirectorySeparatorChars);
    auto relParts = str_split(relTo, DirectorySeparatorChars);

    // Get the shortest of the two paths
    size_t len = std::min(absParts.size(), relParts.size());

    // Use to determine where in the loop we exited
    int lastCommonRoot = -1;
    int index;

    // Find common root
    for (size_t index = 0; index < len; index++) {
        if (str_compare_no_case(absParts[index], relParts[index])==0) {
            lastCommonRoot = index;
        } else {
            break;
        }
    }

    // If we didn't find a common prefix "c:\xx", "D:\"
    if (lastCommonRoot == -1) {
        // The path of the two files doesn't have any common base.
        return absPath;
    }

    // Build up the relative path
    std::string relativePath;

    // Add on the ..
    for (size_t index = lastCommonRoot + 1; index < relParts.size(); index++) {
        relativePath += "..";
        relativePath += directorySeparator;
    }

    // Add on the folders
    for (size_t index = lastCommonRoot + 1; index+1 < absParts.size(); index++) {
        relativePath += absParts[index];
        relativePath += directorySeparator;
    }
    if(!absParts.empty()) {
        relativePath += absParts[absParts.size() - 1];
    }
    return relativePath;
}