Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

Back: Memory Management
Forward: Library Implementation
 
FastBack: A Sample Shell Application
Up: Portability Infrastructure
FastForward: Library Implementation
Top: Autoconf, Automake, and Libtool
Contents: Table of Contents
Index: Index
About: About this document

9.2.1.3 Generalised List Data Type

In many C programs you will see various implementations and re-implementations of lists and stacks, each tied to its own particular project. It is surprisingly simple to write a catch-all implementation, as I have done here with a generalised list operation API in `list.h':

 
#ifndef SIC_LIST_H
#define SIC_LIST_H 1

#include <sic/common.h>

BEGIN_C_DECLS

typedef struct list {
  struct list *next;    /* chain forward pointer*/
  void *userdata;       /* incase you want to use raw Lists */
} List;

extern List *list_new       (void *userdata);
extern List *list_cons      (List *head, List *tail);
extern List *list_tail      (List *head);
extern size_t list_length   (List *head);

END_C_DECLS

#endif /* !SIC_LIST_H */

The trick is to ensure that any structures you want to chain together have their forward pointer in the first field. Having done that, the generic functions declared above can be used to manipulate any such chain by casting it to List * and back again as necessary.

For example:

 
struct foo {
  struct foo *next;

  char *bar;
  struct baz *qux;
  ...
};

...
  struct foo *foo_list = NULL;

  foo_list = (struct foo *) list_cons ((List *) new_foo (),
                                       (List *) foo_list);
...

The implementation of the list manipulation functions is in `list.c':

 
#include "list.h"

List *
list_new (void *userdata)
{
  List *new = XMALLOC (List, 1);

  new->next = NULL;
  new->userdata = userdata;

  return new;
}

List *
list_cons (List *head, List *tail)
{
  head->next = tail;
  return head;
}

List *
list_tail (List *head)
{
  return head->next;
}

size_t
list_length (List *head)
{
  size_t n;
  
  for (n = 0; head; ++n)
    head = head->next;

  return n;
}


This document was generated by Gary V. Vaughan on February, 8 2006 using texi2html

 
 
  Published under the terms of the Open Publication License Design by Interspire