main.cpp

#include "process.h"
#include <iostream>
#include <string>
#include <glob.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#ifndef JARFILE
#error No JARFILE defined!
#endif

using namespace std;

#ifdef EMBEDDED_JAR_FILE
// see http://stackoverflow.com/questions/6785214/how-to-embed-a-file-into-an-executable-file and http://gareus.org/wiki/embedding_resources_in_executables
extern const unsigned char _binary_embedded_jar_file_start[];
extern const unsigned char _binary_embedded_jar_file_end[];
#endif

int runJava(string &javaBin, string &jarfile) {
  char * const args[] = { (char *)javaBin.c_str(),
                          (char *)"-jar",
                          (char *)jarfile.c_str(),
                          NULL };
#ifndef QUIET
  cerr << "Trying " << javaBin << endl;
#endif
  Process p(args[0], args, false);
  return p.wait();
}

bool fileExists(string &file) {
  struct stat buf;
  if (stat(file.c_str(), &buf) == -1) {
    return false;
  }
  return true;
}

char *tmpjar = NULL;

static pid_t parentpid = getpid();
void cleanup(void) {
  if (getpid() != parentpid) {
    return;
  }
  if (tmpjar != NULL) {
    cerr << "deleting " << tmpjar << endl;
    unlink(tmpjar);
  }
}

int main(int argc, char *argv[])
{
#ifdef EMBEDDED_JAR_FILE
  tmpjar = strdup("/tmp/tmpjarfileXXXXXX");
  int fd = mkstemp(tmpjar);
  size_t len = _binary_embedded_jar_file_end - _binary_embedded_jar_file_start;
  cerr << "creating " << tmpjar << " with " << len << " bytes" << endl;
  write(fd, _binary_embedded_jar_file_start, len);
  fsync(fd);
  atexit(cleanup);

  string jarfile = tmpjar;
#else
  string jarfile = JARFILE;
#endif

  int numJREs = 0;

  // if the environment variable JAVA_HOME is set, we try this jvm 
  char *java_home = getenv("JAVA_HOME");
  if (java_home != NULL)
  {
    string javaBin = java_home;
    javaBin += "/bin/java";
    if (fileExists(javaBin)) {
      ++numJREs;
      if (runJava(javaBin, jarfile) == 0) {
        return 0;
      }
    }
  }

  // then, we'll try the PATH
  char *paths = getenv("PATH");
  if (paths != NULL) {
    paths = strdup(paths);
    char *path = strtok(paths, ":");
    while (path != NULL) {
      string javaBin = path;
      javaBin += "java";
      if (fileExists(javaBin)) {
        ++numJREs;
        if (runJava(javaBin, jarfile) == 0) {
          return 0;
        }
      }
      path = strtok(NULL, ":");
    }
    free(paths);
  }


  // try any jvm in /usr/lib/jvm/*/bin/java
  glob_t globbuf = { 0, NULL, 0};
  if (glob("/usr/lib/jvm/*/bin/java", 0, NULL, &globbuf) == 0) {
    for (int i=0; i<globbuf.gl_pathc; ++i) {
      string javaBin = globbuf.gl_pathv[i];
      if (fileExists(javaBin)) {
        ++numJREs;
        if (runJava(javaBin, jarfile) == 0) {
          return 0;
        }
      }
    }
  }
  globfree(&globbuf);

  // see if we can find the jvm via update-alternatives
  char *args[] = { (char *)"/usr/bin/update-alternatives",
                   (char *)"--list",
                   (char *)"java",
                   NULL };
  Process p(args[0], args);
  string javaBin;
  while (p.getline(javaBin) > 0) {
    if (fileExists(javaBin)) {
      ++numJREs;
      if (runJava(javaBin, jarfile) == 0) {
        return 0;
      }
    }
  }

  char *errmsg = (char *)"Could not launch "JARFILE;

  if (numJREs == 0)
  {
    errmsg = (char *)"Java is not installed!";
  }

  cerr << errmsg << endl;

  if (getenv("DISPLAY") != NULL)
  {
    char *args[] = { (char *)"/usr/bin/xmessage",
                     (char *)"-center",
                     errmsg,
                   NULL };
    Process p(args[0], args);
    p.wait();
  }

  return 1;
}