对xml格式的字符串解析

源码：https://github.com/leethomason/tinyxml2.git

简单实例：

static const char* xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\r\n"

        "<file xmlns=\"urn:gsma:params:xml:ns:rcs:rcs:fthttp\" xmlns:am=\"urn:gsma:params:xml:ns:rcs:rcs:rram\">\r\n"

        "<file-info type=\"thumbnail\">\r\n"

        "<file-size>4800</file-size>\r\n"

        "<content-type>image/jpeg</content-type>\r\n"

        "<data url=\"http://10.9.119.33/s/3/0045730523.jpg\" until=\"2020-07-16T20:00:44+08:00\" />\r\n"

        "</file-info>\r\n"

        "<file-info type=\"file\" file-disposition=\"attachment\">\r\n"

        "<file-size>4971</file-size>\r\n"

        "<file-hash-algorithm>md5</file-hash-algorithm>\r\n"

        "<file-hash-value>90:3D:3A:82:70:65:57:69:DE:4E:06:5B:7E:06:34:16</file-hash-value>\r\n"

        "<file-name>151bf0195d0ed250b202bd7231a7c509.jpeg</file-name>\r\n"

        "<content-type>image/jpeg</content-type>\r\n"

        "<data url=\"http://10.9.119.33/s/3/2b681b67-a40a-1038-a6ae-611c59a959a3.jpeg\" until=\"2020-07-16T20:00:44+08:00\" />\r\n"

        "</file-info>\r\n"

        "</file>\r\n";

int parse_xml_info()
{

    XMLDocument doc;

    XMLElement* file;

    const char *type = 0;

    const XMLElement* p;

    XMLError err;

    XMLError queryResult;

    unsigned long long file_size = 0;

    const char *origFileName = 0;
    const char *contentType = 0;

    bool found = false;

    err = doc.Parse(xml);

    if (err){
        printf("parse_xml_info: Parse err\n");
        return -1;
    }

    file = doc.FirstChildElement("file");

    if (!file){
        printf("parse_xml_info: FirstChildElement file err\n");
        return -1;

    }

    for (p = file->FirstChildElement("file-info"); p; p = p->NextSiblingElement("file-info")) {

        queryResult = p->QueryStringAttribute("type", &type);

        if (queryResult == XML_SUCCESS){

            if (strncmp("file", type, 4) == 0){

                p->FirstChildElement("file-size")->QueryUnsigned64Text(&file_size);

                contentType = p->FirstChildElement("content-type")->GetText();

                p->FirstChildElement("data")->QueryStringAttribute("url", &origFileName);

                found = true;

                break;

            }

        }

    }

    if (!found){
        printf("parse_xml_info: file-info Attribute(type) not found \'file\' \n");
        return -1;
    }

    printf("parse_xml_info: file_size:%u content_type:%s  origFileName:%s",
        file_size, contentType, origFileName);

    return 0;

}