c++ program for adding build tag section to a elf file

elftagger.cpp

#include <elfio/elfio.hpp>
#include <libxml/parser.h>
#include <libxml/tree.h>
#include <iostream>
#include <time.h>
#include <string.h>

using namespace ELFIO;

static const char* xmlConfigFile = "buildtag.xml";
static const char* DATETIME_STR = "datetime";
static const int DATETIME_OPT = 0;
static const char* BUILDER_STR = "builder";
static const int BUILDER_OPT = 1;
static const char* GUID_STR = "guid";
static const int GUID_OPT = 2;
static const char* GIT_DESC = "git-describe";
static const int GIT_OPT = 3;

static struct {
    bool isSet;
    std::string formetStr;
} options[4] = {};

bool readConfig(const char *filename) {
    LIBXML_TEST_VERSION
    xmlDocPtr doc;

    doc = xmlReadFile(filename, NULL, 0);
    if (doc == NULL) {
        fprintf(stderr, "Failed to parse %s\n", filename);
        return false;
    }
    for (xmlNode *cur_node = xmlDocGetRootElement(doc)->children->next; cur_node; cur_node = cur_node->next) {
        std::cout << (const char*)(cur_node->name) << std::endl;
       if (cur_node->type == XML_ELEMENT_NODE) {
          if (strstr(reinterpret_cast<const char*>(cur_node->name),DATETIME_STR) != NULL) {
              options[DATETIME_OPT].isSet = true;
              options[DATETIME_OPT].formetStr = std::string(reinterpret_cast<const char*>(cur_node->children->content));
          } else if (strstr(reinterpret_cast<const char*>(cur_node->name),BUILDER_STR) != NULL) {
              options[BUILDER_OPT].isSet = true;
          } else if (strstr(reinterpret_cast<const char*>(cur_node->name),GUID_STR) != NULL) {
              options[GUID_OPT].isSet = true;
          } else if (strstr(reinterpret_cast<const char*>(cur_node->name),GIT_DESC) != NULL) {
              options[GIT_OPT].isSet = true;
          }
       }
    }
    xmlFreeDoc(doc);
    xmlCleanupParser();
    return true;
}

int getNoteSection(elfio& reader) {
    Elf_Half sec_num = reader.sections.size();
    for(int i=static_cast<int>(sec_num); i--; i>0) {
        if ((reader.sections[i]->get_type() == SHT_NOTE) && 
                (reader.sections[i]->get_name() == ".note.gnu.build-id")) {
            return i;
        }
    }
    return 0;
}

void createTags(elfio& tagger, section*& noteSection) {
    ELFIO::note_section_accessor noteAcc(tagger,noteSection);
    char buffer[512] = {};
    if (options[DATETIME_OPT].isSet) {
        time_t rawtime;
        struct tm* now;
        time(&rawtime);
        now = gmtime(&rawtime);
        size_t nowLen = strftime(buffer,sizeof(buffer),options[DATETIME_OPT].formetStr.c_str(), now);
        noteAcc.add_note(SHT_NOTE, "BuildTime", buffer, nowLen);
    }
}

int main (int argc, char* argv[]) {
    elfio tagger;
    readConfig(xmlConfigFile);
    tagger.load("a.out");
    int noteSectionId = getNoteSection(tagger);
    section* noteSection;
    if (noteSectionId == 0) {
        noteSection = tagger.sections.add("note.applicationid");
        noteSection->set_type(SHT_NOTE);
        noteSection->set_addr_align(1);
        std::cout << "Adding new section\n";
    } else {
        std::cout << "Getting existing section " << noteSectionId << " \n";
        noteSection = tagger.sections[noteSectionId];
    }
    createTags(tagger,noteSection);
    tagger.set_entry( 0x08048000 );    
    tagger.save("a.1.out");
    return 0;
}