c++ - 如果从文件流读取数据，为什么 gSOAP 将标准输入模式设置为二进制？

Question

我一直在玩 gSOAP XML 数据绑定(bind)，方法是将 XML 文档加载到 C++ 类中，修改数据并将其序列化回 XML。

这是 XML 的片段 - library.xml:

<?xml version="1.0" encoding="UTF-8"?>    
<gt:Library xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:gt="http://www.bk.com/gSOAP/test">
    <gt:Books>
        <gt:Book isbn="0132350882" author="Robert C. Martin" title="Clean Code">
            <gt:CopiesAvailable>2</gt:CopiesAvailable>
        </gt:Book>
        <gt:Book isbn="020161622X" author="Andrew Hunt" title="The Pragmatic Programmer">
            <gt:CopiesAvailable>0</gt:CopiesAvailable>
        </gt:Book>
        <gt:Book isbn="0201633612" author="Erich Gamma" title="Design patterns">
            <gt:CopiesAvailable>1</gt:CopiesAvailable>
        </gt:Book>      
    </gt:Books>
    ...
</gt:Library>

以下代码将 XML 加载到对象中，修改对象并将其序列化回 XML。请注意，XML 是通过文件流从文件中加载的，要添加的数据是通过标准输入 (cin) 从用户处获取的。

主要.cpp:

#include "soapH.h"
#include "gt.nsmap"
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
using std::cin;
using std::cout;
using std::endl;
using std::ifstream;
using std::ofstream;
using std::fstream;
using std::string;
using std::stringstream;

void DisplayAllBooks(const _gt__Library& library)
{
    cout << "\n\nDisplaying all books in the library:" << endl;

    std::vector<_gt__Library_Books_Book>::const_iterator it = library.Books.Book.begin();
    for(;it != library.Books.Book.end(); it++)
    {
        cout << "\nBook:\n" << "\tTitle:" << (*it).title << "\n\tAuthor:" << (*it).author <<"\n\tISBN: " << (*it).isbn << "\n\tCopies available: " << static_cast<int>((*it).CopiesAvailable) << endl;
    }
}

void AddBook(_gt__Library& library)
{
    cout << "\n\nAdding a new book:" << endl;

    _gt__Library_Books_Book book;

    cout << "\tTitle: " << std::flush;
    getline(cin, book.title);

    cout << "\tAuthor: " << std::flush;
    getline(cin, book.author);

    cout << "\tISBN:" << std::flush;
    getline(cin, book.isbn);

    cout << "\tCopies available: " << std::flush;
    string strCopiesAvailable;
    getline(cin, strCopiesAvailable);
    stringstream ss(strCopiesAvailable);
    ss >> book.CopiesAvailable;

    library.Books.Book.push_back(book);
}

// Terminate and destroy soap
void DestroySoap(struct soap* pSoap)
{
    // remove deserialized class instances (C++ objects) 
    soap_destroy(pSoap); 

    // clean up and remove deserialized data 
    soap_end(pSoap);  

    // detach context (last use and no longer in scope)
    soap_done(pSoap);
}

int main()
{

    //
    // Create and intialize soap
    //

    // gSOAP runtime context
    struct soap soap; 

    // initialize runtime context 
    soap_init(&soap); 

    // Set input mode
    soap_imode(&soap, SOAP_ENC_XML);

    // reset deserializers; start new (de)serialization phase 
    soap_begin(&soap); 

    //
    // Load XML (Deserialize)
    //

    _gt__Library library;   
    string strXML = "library.xml";

    ifstream fstreamIN(strXML);
    soap.is = &fstreamIN;                               

    // calls soap_begin_recv, soap_get__gt__Library and soap_end_recv
    if(soap_read__gt__Library(&soap, &library) != SOAP_OK)
    {
        std::cout << "soap_read__gt__Library() failed" << std::endl;
        DestroySoap(&soap);
        return 1;
    }

    fstreamIN.close();

    //
    // Display books before and after adding a new book
    //

    DisplayAllBooks(library);
    AddBook(library);
    DisplayAllBooks(library);

    //
    // Serialize
    //

    soap_set_omode(&soap, SOAP_XML_INDENT); 

    ofstream fstreamOUT("library.xml");
    soap.os = &fstreamOUT;

    // calls soap_begin_send, soap_serialize, soap_put and soap_end_send
    if(soap_write__gt__Library(&soap, &library) != SOAP_OK) 
    {
        std::cout << "soap_write__gt__Library() failed" << std::endl;
        DestroySoap(&soap);
        return 1;
    }

    fstreamOUT.close();

    DestroySoap(&soap);

    return 0;
}

运行此测试应用程序后，一切正常，除了所有新添加的元素都有以回车符结尾的字符串(CR - ):

修改后的 XML 如下所示:

<?xml version="1.0" encoding="UTF-8"?>
<gt:Library xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:gt="http://www.bk.com/gSOAP/test">
    <gt:Books>
        <gt:Book isbn="0132350882" author="Robert C. Martin" title="Clean Code">
            <gt:CopiesAvailable>2</gt:CopiesAvailable>
        </gt:Book>
        <gt:Book isbn="020161622X" author="Andrew Hunt" title="The Pragmatic Programmer">
            <gt:CopiesAvailable>0</gt:CopiesAvailable>
        </gt:Book>
        <gt:Book isbn="0201633612" author="Erich Gamma" title="Design patterns">
            <gt:CopiesAvailable>1</gt:CopiesAvailable>
        </gt:Book>
        <gt:Book isbn="12345678&#xD;" author="Scott Meyers&#xD;" title="Effective C++&#xD;">
            <gt:CopiesAvailable>123</gt:CopiesAvailable>
        </gt:Book>
    </gt:Books>
    ...
</gt:Library>

我追查了错误的来源，发现了以下内容:

soap_read__gt__Library() 调用 soap_begin_send() 执行以下行:

_setmode(soap->recvfd, _O_BINARY);

soap->recvfd 在 soap_init() 中设置为 0 并且 0 是文件的值stdin 的描述符。

一旦 stdin 的模式更改为二进制，STL 库不会将 \r\n 解析为单个 \n读取操作和 getline(cin, str) 像往常一样读取所有内容直到 \n，将 \r 复制到输出字符串中。这正是出现在最终 XML 中的新字符串中的回车符。

我的问题是:如果数据源是文件流，为什么 gSOAP 会修改 stdin 模式？这是 gSOAP 中的错误吗？

注意:

正如预期的那样，如果 stdio 的模式在 soap_begin_send() 之后但在从 std 读取数据之前恢复为 _O_TEXT::cin、getline() 工作正常。这是补丁:

_setmode(_fileno(stdin), _O_TEXT)

Answer 1

这是为了避免在读写 Unicode 和 UTF-8 编码的 XML 时出现编码问题。