host/libs/location/GpxParser.cpp

/*
 * Copyright (C) 2015-2022 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "GpxParser.h"
#include <libxml/parser.h>
#include <string.h>
#include <time.h>
#include <algorithm>
#include "StringParse.h"

using std::string;

// format an error message
template <class... Args>
static string formatError(const char *format, Args &&...args) {
  char buf[100] = {};
  snprintf(buf, sizeof(buf) - 1, format, std::forward<Args>(args)...);
  return buf;
}

static void cleanupXmlDoc(xmlDoc *doc) {
  xmlFreeDoc(doc);
  xmlCleanupParser();
}

static bool parseLocation(xmlNode *ptNode, xmlDoc *doc, GpsFix *result,
                          string *error) {
  float latitude;
  float longitude;

  xmlAttrPtr attr;
  xmlChar *tmpStr;

  // Check for and get the latitude attribute
  attr = xmlHasProp(ptNode, (const xmlChar *)"lat");
  if (!attr || !(tmpStr = xmlGetProp(ptNode, (const xmlChar *)"lat"))) {
    *error = formatError("Point missing a latitude on line %d.", ptNode->line);
    return false;  // Return error since a point *must* have a latitude
  } else {
    int read = SscanfWithCLocale(reinterpret_cast<const char *>(tmpStr), "%f",
                                 &latitude);
    xmlFree(tmpStr);  // Caller-freed
    if (read != 1) {
      return false;
    }
  }

  // Check for and get the longitude attribute
  attr = xmlHasProp(ptNode, (const xmlChar *)"lon");
  if (!attr || !(tmpStr = xmlGetProp(ptNode, (const xmlChar *)"lon"))) {
    *error = formatError("Point missing a longitude on line %d.", ptNode->line);
    return false;  // Return error since a point *must* have a longitude
  } else {
    int read = SscanfWithCLocale(reinterpret_cast<const char *>(tmpStr), "%f",
                                 &longitude);
    xmlFree(tmpStr);  // Caller-freed
    if (read != 1) {
      return false;
    }
  }

  // The result will be valid if this point is reached
  result->latitude = latitude;
  result->longitude = longitude;

  // Check for potential children nodes (including time, elevation, name, and
  // description) Note that none are actually required according to the GPX
  // format.
  int childCount = 0;
  for (xmlNode *field = ptNode->children; field; field = field->next) {
    tmpStr = nullptr;

    if (!strcmp((const char *)field->name, "time")) {
      if ((tmpStr = xmlNodeListGetString(doc, field->children, 1))) {
        // Convert to a number
        struct tm time = {};
        time.tm_isdst = -1;
        int results = sscanf((const char *)tmpStr, "%u-%u-%uT%u:%u:%u",
                             &time.tm_year, &time.tm_mon, &time.tm_mday,
                             &time.tm_hour, &time.tm_min, &time.tm_sec);
        if (results != 6) {
          *error = formatError(
              "Improperly formatted time on line %d.<br/>"
              "Times must be in ISO format.",
              ptNode->line);
          return false;
        }

        // Correct according to the struct tm specification
        time.tm_year -= 1900;  // Years since 1900
        time.tm_mon -= 1;      // Months since January, 0-11

        result->time = mktime(&time);
        xmlFree(tmpStr);  // Caller-freed
        childCount++;
      }
    } else if (!strcmp((const char *)field->name, "ele")) {
      if ((tmpStr = xmlNodeListGetString(doc, field->children, 1))) {
        int read = SscanfWithCLocale(reinterpret_cast<const char *>(tmpStr),
                                     "%f", &result->elevation);
        xmlFree(tmpStr);  // Caller-freed
        if (read != 1) {
          return false;
        }
        childCount++;
      }
    } else if (!strcmp((const char *)field->name, "name")) {
      if ((tmpStr = xmlNodeListGetString(doc, field->children, 1))) {
        result->name = reinterpret_cast<const char *>(tmpStr);
        xmlFree(tmpStr);  // Caller-freed
        childCount++;
      }
    } else if (!strcmp((const char *)field->name, "desc")) {
      if ((tmpStr = xmlNodeListGetString(doc, field->children, 1))) {
        result->description = reinterpret_cast<const char *>(tmpStr);
        xmlFree(tmpStr);  // Caller-freed
        childCount++;
      }
    }

    // We only care about 4 potential child fields, so quit after finding those
    if (childCount == 4) {
      break;
    }
  }

  return true;
}

static bool parse(xmlDoc *doc, GpsFixArray *fixes, string *error) {
  xmlNode *root = xmlDocGetRootElement(doc);
  GpsFix location;
  bool isOk;

  for (xmlNode *child = root->children; child; child = child->next) {
    // Individual <wpt> elements are parsed on their own
    if (!strcmp((const char *)child->name, "wpt")) {
      isOk = parseLocation(child, doc, &location, error);
      if (!isOk) {
        cleanupXmlDoc(doc);
        return false;
      }
      fixes->push_back(location);
    }

    // <rte> elements require an additional depth of parsing
    else if (!strcmp((const char *)child->name, "rte")) {
      for (xmlNode *rtept = child->children; rtept; rtept = rtept->next) {
        // <rtept> elements are parsed just like <wpt> elements
        if (!strcmp((const char *)rtept->name, "rtept")) {
          isOk = parseLocation(rtept, doc, &location, error);
          if (!isOk) {
            cleanupXmlDoc(doc);
            return false;
          }
          fixes->push_back(location);
        }
      }
    }

    // <trk> elements require two additional depths of parsing
    else if (!strcmp((const char *)child->name, "trk")) {
      for (xmlNode *trkseg = child->children; trkseg; trkseg = trkseg->next) {
        // Skip non <trkseg> elements
        if (!strcmp((const char *)trkseg->name, "trkseg")) {
          // <trkseg> elements an additional depth of parsing
          for (xmlNode *trkpt = trkseg->children; trkpt; trkpt = trkpt->next) {
            // <trkpt> elements are parsed just like <wpt> elements
            if (!strcmp((const char *)trkpt->name, "trkpt")) {
              isOk = parseLocation(trkpt, doc, &location, error);
              if (!isOk) {
                cleanupXmlDoc(doc);
                return false;
              }
              fixes->push_back(location);
            }
          }
        }
      }
    }
  }

  // Sort the values by timestamp
  std::sort(fixes->begin(), fixes->end());

  cleanupXmlDoc(doc);
  return true;
}

bool GpxParser::parseFile(const char *filePath, GpsFixArray *fixes,
                          string *error) {
  xmlDocPtr doc = xmlReadFile(filePath, nullptr, 0);
  if (doc == nullptr) {
    cleanupXmlDoc(doc);
    *error = "GPX document not parsed successfully.";
    return false;
  }
  return parse(doc, fixes, error);
}

bool GpxParser::parseString(const char *str, int len, GpsFixArray *fixes,
                            string *error) {
  xmlDocPtr doc = xmlReadMemory(str, len, NULL, NULL, 0);
  if (doc == nullptr) {
    cleanupXmlDoc(doc);
    *error = "GPX document not parsed successfully.";
    return false;
  }
  return parse(doc, fixes, error);
}