如何在cpp的xmlXPathRegisterNs (libxml2)中添加多个命名空间

#include <libxml/xpath.h>
#include <iostream>

int main() {
    // 初始化libxml2库
    xmlInitParser();

    // 创建XPath上下文
    xmlXPathContextPtr context = xmlXPathNewContext(nullptr);
    if (!context) {
        std::cerr << "Error creating XPath context" << std::endl;
        return 1;
    }

    // 定义命名空间前缀和URI
    const char* prefix1 = "ns1";
    const char* uri1 = "http://example.com/ns1";
    const char* prefix2 = "ns2";
    const char* uri2 = "http://example.com/ns2";

    // 注册命名空间
    int ret1 = xmlXPathRegisterNs(context, reinterpret_cast<const xmlChar*>(prefix1), reinterpret_cast<const xmlChar*>(uri1));
    int ret2 = xmlXPathRegisterNs(context, reinterpret_cast<const xmlChar*>(prefix2), reinterpret_cast<const xmlChar*>(uri2));

    if (ret1 != 0 || ret2 != 0) {
        std::cerr << "Error registering namespaces" << std::endl;
        return 1;
    }

    // 使用XPath表达式
    const char* xpathExpr = "//ns1:element1 | //ns2:element2";
    xmlXPathObjectPtr result = xmlXPathEvalExpression(reinterpret_cast<const xmlChar*>(xpathExpr), context);
    if (!result) {
        std::cerr << "Error evaluating XPath expression" << std::endl;
        return 1;
    }

    // 处理XPath结果
    // ...

    // 清理资源
    xmlXPathFreeObject(result);
    xmlXPathFreeContext(context);
    xmlCleanupParser();

    return 0;
}