daemon: Fix possible use-after-free.

[jackhill/guix/guix.git] / nix / libutil / xml-writer.cc

#include <assert.h>

#include "xml-writer.hh"


namespace nix {
    

XMLWriter::XMLWriter(bool indent, std::ostream & output)
    : output(output), indent(indent)
{
    output << "<?xml version='1.0' encoding='utf-8'?>" << std::endl;
    closed = false;
}


XMLWriter::~XMLWriter()
{
    close();
}


void XMLWriter::close()
{
    if (closed) return;
    while (!pendingElems.empty()) closeElement();
    closed = true;
}


void XMLWriter::indent_(unsigned int depth)
{
    if (!indent) return;
    output << string(depth * 2, ' ');
}


void XMLWriter::openElement(const string & name,
    const XMLAttrs & attrs)
{
    assert(!closed);
    indent_(pendingElems.size());
    output << "<" << name;
    writeAttrs(attrs);
    output << ">";
    if (indent) output << std::endl;
    pendingElems.push_back(name);
}


void XMLWriter::closeElement()
{
    assert(!pendingElems.empty());
    indent_(pendingElems.size() - 1);
    output << "</" << pendingElems.back() << ">";
    if (indent) output << std::endl;
    pendingElems.pop_back();
    if (pendingElems.empty()) closed = true;
}


void XMLWriter::writeEmptyElement(const string & name,
    const XMLAttrs & attrs)
{
    assert(!closed);
    indent_(pendingElems.size());
    output << "<" << name;
    writeAttrs(attrs);
    output << " />";
    if (indent) output << std::endl;
}


void XMLWriter::writeAttrs(const XMLAttrs & attrs)
{
    for (XMLAttrs::const_iterator i = attrs.begin(); i != attrs.end(); ++i) {
        output << " " << i->first << "=\"";
        for (unsigned int j = 0; j < i->second.size(); ++j) {
            char c = i->second[j];
            if (c == '"') output << "&quot;";
            else if (c == '<') output << "&lt;";
            else if (c == '>') output << "&gt;";
            else if (c == '&') output << "&amp;";
            /* Escape newlines to prevent attribute normalisation (see
               XML spec, section 3.3.3. */
            else if (c == '\n') output << "&#xA;";
            else output << c;
        }
        output << "\"";
    }
}


}