nvtable.c

[詳解]

/*++
/* NAME
/*  nvtable 3
/* SUMMARY
/*  attribute list manager
/* SYNOPSIS
/*  #include <nvtable.h>
/*
/*  typedef struct {
/* .in +4
/*      char    *key;
/*      char    *value;
/*      /* private fields... */
/* .in -4
/*  } NVTABLE_INFO;
/*
/*  NVTABLE *nvtable_create(size)
/*  int size;
/*
/*  NVTABLE_INFO *nvtable_update(table, key, value)
/*  NVTABLE *table;
/*  const char *key;
/*  const char *value;
/*
/*  char    *nvtable_find(table, key)
/*  NVTABLE *table;
/*  const char *key;
/*
/*  NVTABLE_INFO *nvtable_locate(table, key)
/*  NVTABLE *table;
/*  const char *key;
/*
/*  void    nvtable_delete(table, key)
/*  NVTABLE *table;
/*  const char *key;
/*
/*  void    nvtable_free(table)
/*  NVTABLE *table;
/*
/*  void    nvtable_walk(table, action, ptr)
/*  NVTABLE *table;
/*  void    (*action)(NVTABLE_INFO *, char *ptr);
/*  char    *ptr;
/*
/*  NVTABLE_INFO **nvtable_list(table)
/*  NVTABLE *table;
/* DESCRIPTION
/*  This module maintains one or more attribute lists. It provides a
/*  more convenient interface than hash tables, although it uses the
/*  same underlying implementation. Each attribute list entry consists
/*  of a unique string-valued lookup key and a string value.
/*
/*  nvtable_create() creates a table of the specified size and returns a
/*  pointer to the result.
/*
/*  nvtable_update() stores or updates a (key, value) pair in the specified
/*  table and returns a pointer to the resulting entry. The key and the
/*  value are copied.
/*
/*  nvtable_find() returns the value that was stored under the given key,
/*  or a null pointer if it was not found. In order to distinguish
/*  a null value from a non-existent value, use nvtable_locate().
/*
/*  nvtable_locate() returns a pointer to the entry that was stored
/*  for the given key, or a null pointer if it was not found.
/*
/*  nvtable_delete() removes one entry that was stored under the given key.
/*
/*  nvtable_free() destroys a hash table, including contents.
/*
/*  nvtable_walk() invokes the action function for each table entry, with
/*  a pointer to the entry as its argument. The ptr argument is passed
/*  on to the action function.
/*
/*  nvtable_list() returns a null-terminated list of pointers to
/*  all elements in the named table. The list should be passed to
/*  myfree().
/* RESTRICTIONS
/*  A callback function should not modify the attribute list that is
/*  specified to its caller.
/* DIAGNOSTICS
/*  The following conditions are reported and cause the program to
/*  terminate immediately: memory allocation failure; an attempt
/*  to delete a non-existent entry.
/* SEE ALSO
/*  mymalloc(3) memory management wrapper
/*  htable(3) hash table manager
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* C library */

#include <sys_defs.h>

/* Utility library. */

#include <mymalloc.h>
#include <htable.h>
#include <nvtable.h>

/* nvtable_update - update or enter (key, value) pair */

NVTABLE_INFO *nvtable_update(NVTABLE * table, const char *key, const char *value)
{
    NVTABLE_INFO *ht;

    if ((ht = htable_locate(table, key)) != 0) {
    myfree(ht->value);
    } else {
    ht = htable_enter(table, key, (void *) 0);
    }
    ht->value = mystrdup(value);
    return (ht);
}