core/vil1/vil1_open.cxx

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// This is core/vil1/vil1_open.cxx
#ifdef VCL_NEEDS_PRAGMA_INTERFACE
#pragma implementation
#endif
//:
// \file
// \author fsm

#include "vil1_open.h"

#include <vcl_cstring.h>  // strncmp()

#include <vil1/vil1_stream_fstream.h>
#include <vil1/vil1_stream_core.h>
#include <vil1/vil1_stream_url.h>

vil1_stream *vil1_open(char const* what, char const* how)
{
  // check for null pointer or empty strings.
  if (!what || !*what)
    return 0;

  // try to open as file first.
  vil1_stream *is = new vil1_stream_fstream(what, how);
#if 0
  // unfortunately, the following doesn't work because (note typo)
  //    vil1_open("/tmp/foo.jgp")
  // will create a new file, permissions allowing, instead of opening
  // the intended file /tmp/foo.jpg. suggest long-term solution is to
  // make a new vil1_open*() set of functions which can open an image
  // for reading and/or writing depending on the caller's need and that
  // vil1_load() just does a vil1_open() for reading. i do not think people
  // expect "loading an image" to open the disk file for writing by
  // default. -- fsm
  vil1_stream *is = new vil1_stream_fstream(what, "r+");
#endif
  if (!is->ok()) {
    // this will delete the stream object.
    is->ref();
    is->unref();
    is = 0;
  }

  if (!is) {
    // hacked check for filenames beginning "gen:".
    int l = vcl_strlen(what);
    if (l > 4 && vcl_strncmp(what, "gen:", 4) == 0) {
      if (vcl_strcmp(how, "r") == 0) {
        // Make an in-core stream...
        vil1_stream_core *cis = new vil1_stream_core();
        cis->write(what, l+1);
        is = cis;
      }
      else {
        vcl_cerr << __FILE__ ": cannot open gen:* for writing\n";
      }
    }
  }
  if (is && !is->ok()) {
    // this will delete the stream object.
    is->ref();
    is->unref();
    is = 0;
  }

  if (!is) {
    // maybe it's a URL?
    int l = vcl_strlen(what);
    if (l > 4 && vcl_strncmp(what, "http://", 7) == 0) {
#ifdef __APPLE__
      vcl_cerr << __FILE__ ": cannot open URL for writing (yet)\n";
#else
      if (vcl_strcmp(how, "r") == 0) {
        is = new vil1_stream_url(what);
      }
      else vcl_cerr << __FILE__ ": cannot open URL for writing (yet)\n";
#endif
    }
  }
  if (is && !is->ok()) {
    // this will delete the stream object.
    is->ref();
    is->unref();
    is = 0;
  }

  return is;
}

---