srchpath.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

//
//  Visopsys
//  Copyright (C) 1998-2007 J. Andrew McLaughlin
// 
//  This program is free software; you can redistribute it and/or modify it
//  under the terms of the GNU General Public License as published by the Free
//  Software Foundation; either version 2 of the License, or (at your option)
//  any later version.
// 
//  This program is distributed in the hope that it will be useful, but
//  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
//  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
//  for more details.
//  
//  You should have received a copy of the GNU General Public License along
//  with this program; if not, write to the Free Software Foundation, Inc.,
//  59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
//  srchpath.c
//

// This is code that can be shared between multiple libraries.  It won't
// compile on its own; it needs to be #included inside a function
// definition.


// Prototype:
//   int srchpath(const char *orig, char *new)
{
  // Search the PATH specified in the environment variable for the specified
  // filename

  int status = 0;
  char *path = NULL;
  int pathCount = 0;
  char *pathElement = NULL;
  int pathElementCount = 0;
  file theFile;

  // Check params
  if ((orig == NULL) || (new == NULL))
    return (errno = ERR_NULLPARAMETER);

  if ((orig[0] == '/') || (orig[0] == '\\'))
    return (errno = ERR_NOSUCHFILE);

  path = malloc(MAX_PATH_LENGTH);
  pathElement = malloc(MAX_PATH_NAME_LENGTH);
  if ((path == NULL) || (pathElement == NULL))
    return (errno = ERR_MEMORY);

  // Get the value of the PATH environment variable
  status = environmentGet("PATH", path, MAX_PATH_LENGTH);
  if (status < 0)
    {
      free(path);
      free(pathElement);
      return (errno = status);
    }

  pathCount = 0;

  // We need to loop once for each element in the PATH.  Elements are
  // separated by colon characters.  When we hit a NULL character we are
  // at the end.

  while (path[pathCount] != '\0')
    {
      pathElementCount = 0;

      // Copy characters from the path until we hit either a ':' or a NULL
      while ((path[pathCount] != ':') && (path[pathCount] != '\0'))
        {
          pathElement[pathElementCount++] = path[pathCount++];
          pathElement[pathElementCount] = '\0';
        }

      if (path[pathCount] == ':')
        pathCount++;

      // Append the name to the path
      strncat(pathElement, "/", 1);
      strcat(pathElement, orig);

      // Does the file exist in the PATH directory?
      bzero(&theFile, sizeof(file));
      status = fileFind(pathElement, &theFile);
      if (status >= 0)
        {
          // Copy the full path into the buffer supplied
          strcpy(new, pathElement);

          // Return success
	  free(path);
	  free(pathElement);
          return (status = 0);
        }
    }

  // If we fall through, no dice
  free(path);
  free(pathElement);
  return (errno = ERR_NOSUCHFILE);
}