htable.c

[詳解]

/*++
/* NAME
/*  htable 3
/* SUMMARY
/*  hash table manager
/* SYNOPSIS
/*  #include <htable.h>
/*
/*  typedef struct {
/* .in +4
/*      char    *key;
/*      void    *value;
/*      /* private fields... */
/* .in -4
/*  } HTABLE_INFO;
/*
/*  HTABLE  *htable_create(size)
/*  int size;
/*
/*  HTABLE_INFO *htable_enter(table, key, value)
/*  HTABLE  *table;
/*  const char *key;
/*  void    *value;
/*
/*  char    *htable_find(table, key)
/*  HTABLE  *table;
/*  const char *key;
/*
/*  HTABLE_INFO *htable_locate(table, key)
/*  HTABLE  *table;
/*  const char *key;
/*
/*  void    htable_delete(table, key, free_fn)
/*  HTABLE  *table;
/*  const char *key;
/*  void    (*free_fn)(void *);
/*
/*  void    htable_free(table, free_fn)
/*  HTABLE  *table;
/*  void    (*free_fn)(void *);
/*
/*  void    htable_walk(table, action, ptr)
/*  HTABLE  *table;
/*  void    (*action)(HTABLE_INFO *, void *ptr);
/*  void    *ptr;
/*
/*  HTABLE_INFO **htable_list(table)
/*  HTABLE  *table;
/*
/*  HTABLE_INFO *htable_sequence(table, how)
/*  HTABLE  *table;
/*  int how;
/* DESCRIPTION
/*  This module maintains one or more hash tables. Each table entry
/*  consists of a unique string-valued lookup key and a generic
/*  character-pointer value.
/*  The tables are automatically resized when they fill up. When the
/*  values to be remembered are not character pointers, proper casts
/*  should be used or the code will not be portable.
/*
/*  htable_create() creates a table of the specified size and returns a
/*  pointer to the result. The lookup keys are saved with mystrdup().
/*  htable_enter() stores a (key, value) pair into the specified table
/*  and returns a pointer to the resulting entry. The code does not
/*  check if an entry with that key already exists: use htable_locate()
/*  for updating an existing entry.
/*
/*  htable_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 htable_locate().
/*
/*  htable_locate() returns a pointer to the entry that was stored
/*  for the given key, or a null pointer if it was not found.
/*
/*  htable_delete() removes one entry that was stored under the given key.
/*  If the free_fn argument is not a null pointer, the corresponding
/*  function is called with as argument the non-zero value stored under
/*  the key.
/*
/*  htable_free() destroys a hash table, including contents. If the free_fn
/*  argument is not a null pointer, the corresponding function is called
/*  for each table entry, with as argument the non-zero value stored
/*  with the entry.
/*
/*  htable_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.
/*
/*  htable_list() returns a null-terminated list of pointers to
/*  all elements in the named table. The list should be passed to
/*  myfree().
/*
/*  htable_sequence() returns the first or next element depending
/*  on the value of the "how" argument.  Specify HTABLE_SEQ_FIRST
/*  to start a new sequence, HTABLE_SEQ_NEXT to continue, and
/*  HTABLE_SEQ_STOP to terminate a sequence early.  The caller
/*  must not delete an element before it is visited.
/* RESTRICTIONS
/*  A callback function should not modify the hash table 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
/* 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>
#include <string.h>

/* Local stuff */

#include "mymalloc.h"
#include "msg.h"
#include "htable.h"

/* htable_hash - hash a string */

static size_t htable_hash(const char *s, size_t size)
{
    size_t  h = 0;
    size_t  g;

    /*
     * From the "Dragon" book by Aho, Sethi and Ullman.
     */

    while (*s) {
    h = (h << 4U) + *(unsigned const char *) s++;
    if ((g = (h & 0xf0000000)) != 0) {
        h ^= (g >> 24U);
        h ^= g;
    }
    }
    return (h % size);
}

/* htable_link - insert element into table */

#define htable_link(table, element) { \
     HTABLE_INFO **_h = table->data + htable_hash(element->key, table->size);\
    element->prev = 0; \
    if ((element->next = *_h) != 0) \
    (*_h)->prev = element; \
    *_h = element; \
    table->used++; \
}

/* htable_size - allocate and initialize hash table */

static void htable_size(HTABLE *table, size_t size)
{
    HTABLE_INFO **h;

    size |= 1;

    table->data = h = (HTABLE_INFO **) mymalloc(size * sizeof(HTABLE_INFO *));
    table->size = size;
    table->used = 0;

    while (size-- > 0)
    *h++ = 0;
}

/* htable_create - create initial hash table */

HTABLE *htable_create(ssize_t size)
{
    HTABLE *table;

    table = (HTABLE *) mymalloc(sizeof(HTABLE));
    htable_size(table, size < 13 ? 13 : size);
    table->seq_bucket = table->seq_element = 0;
    return (table);
}

/* htable_grow - extend existing table */

static void htable_grow(HTABLE *table)
{
    HTABLE_INFO *ht;
    HTABLE_INFO *next;
    size_t  old_size = table->size;
    HTABLE_INFO **h = table->data;
    HTABLE_INFO **old_entries = h;

    htable_size(table, 2 * old_size);

    while (old_size-- > 0) {
    for (ht = *h++; ht; ht = next) {
        next = ht->next;
        htable_link(table, ht);
    }
    }
    myfree((void *) old_entries);
}

/* htable_enter - enter (key, value) pair */

HTABLE_INFO *htable_enter(HTABLE *table, const char *key, void *value)
{
    HTABLE_INFO *ht;

    if (table->used >= table->size)
    htable_grow(table);
    ht = (HTABLE_INFO *) mymalloc(sizeof(HTABLE_INFO));
    ht->key = mystrdup(key);
    ht->value = value;
    htable_link(table, ht);
    return (ht);
}

/* htable_find - lookup value */

void   *htable_find(HTABLE *table, const char *key)
{
    HTABLE_INFO *ht;

#define STREQ(x,y) (x == y || (x[0] == y[0] && strcmp(x,y) == 0))

    if (table)
    for (ht = table->data[htable_hash(key, table->size)]; ht; ht = ht->next)
        if (STREQ(key, ht->key))
        return (ht->value);
    return (0);
}

/* htable_locate - lookup entry */

HTABLE_INFO *htable_locate(HTABLE *table, const char *key)
{
    HTABLE_INFO *ht;

#define STREQ(x,y) (x == y || (x[0] == y[0] && strcmp(x,y) == 0))

    if (table)
    for (ht = table->data[htable_hash(key, table->size)]; ht; ht = ht->next)
        if (STREQ(key, ht->key))
        return (ht);
    return (0);
}

/* htable_delete - delete one entry */

void    htable_delete(HTABLE *table, const char *key, void (*free_fn) (void *))
{
    if (table) {
    HTABLE_INFO *ht;
    HTABLE_INFO **h = table->data + htable_hash(key, table->size);

#define STREQ(x,y) (x == y || (x[0] == y[0] && strcmp(x,y) == 0))

    for (ht = *h; ht; ht = ht->next) {
        if (STREQ(key, ht->key)) {
        if (ht->next)
            ht->next->prev = ht->prev;
        if (ht->prev)
            ht->prev->next = ht->next;
        else
            *h = ht->next;
        table->used--;
        myfree(ht->key);
        if (free_fn && ht->value)
            (*free_fn) (ht->value);
        myfree((void *) ht);
        return;
        }
    }
    msg_panic("htable_delete: unknown_key: \"%s\"", key);
    }
}

/* htable_free - destroy hash table */

void    htable_free(HTABLE *table, void (*free_fn) (void *))
{
    if (table) {
    ssize_t i = table->size;
    HTABLE_INFO *ht;
    HTABLE_INFO *next;
    HTABLE_INFO **h = table->data;

    while (i-- > 0) {
        for (ht = *h++; ht; ht = next) {
        next = ht->next;
        myfree(ht->key);
        if (free_fn && ht->value)
            (*free_fn) (ht->value);
        myfree((void *) ht);
        }
    }
    myfree((void *) table->data);
    table->data = 0;
    if (table->seq_bucket)
        myfree((void *) table->seq_bucket);
    table->seq_bucket = 0;
    myfree((void *) table);
    }
}

/* htable_walk - iterate over hash table */

void    htable_walk(HTABLE *table, void (*action) (HTABLE_INFO *, void *),
                    void *ptr) {
    if (table) {
    ssize_t i = table->size;
    HTABLE_INFO **h = table->data;
    HTABLE_INFO *ht;

    while (i-- > 0)
        for (ht = *h++; ht; ht = ht->next)
        (*action) (ht, ptr);
    }
}

/* htable_list - list all table members */

HTABLE_INFO **htable_list(HTABLE *table)
{
    HTABLE_INFO **list;
    HTABLE_INFO *member;
    ssize_t count = 0;
    ssize_t i;

    if (table != 0) {
    list = (HTABLE_INFO **) mymalloc(sizeof(*list) * (table->used + 1));
    for (i = 0; i < table->size; i++)
        for (member = table->data[i]; member != 0; member = member->next)
        list[count++] = member;
    } else {
    list = (HTABLE_INFO **) mymalloc(sizeof(*list));
    }
    list[count] = 0;
    return (list);
}

/* htable_sequence - dict(3) compatibility iterator */

HTABLE_INFO *htable_sequence(HTABLE *table, int how)
{
    if (table == 0)
    return (0);

    switch (how) {
    case HTABLE_SEQ_FIRST:          /* start new sequence */
    if (table->seq_bucket)
        myfree((void *) table->seq_bucket);
    table->seq_bucket = htable_list(table);
    table->seq_element = table->seq_bucket;
    return (*(table->seq_element)++);
    case HTABLE_SEQ_NEXT:           /* next element */
    if (table->seq_element && *table->seq_element)
        return (*(table->seq_element)++);
    /* FALLTHROUGH */
    default:                    /* terminate sequence */
    if (table->seq_bucket) {
        myfree((void *) table->seq_bucket);
        table->seq_bucket = table->seq_element = 0;
    }
    return (0);
    }
}

#ifdef TEST
#include <vstring_vstream.h>
#include <myrand.h>

int     main(int unused_argc, char **unused_argv)
{
    VSTRING *buf = vstring_alloc(10);
    ssize_t count = 0;
    HTABLE *hash;
    HTABLE_INFO **ht_info;
    HTABLE_INFO **ht;
    HTABLE_INFO *info;
    ssize_t i;
    ssize_t r;
    int     op;

    /*
     * Load a large number of strings and delete them in a random order.
     */
    hash = htable_create(10);
    while (vstring_get(buf, VSTREAM_IN) != VSTREAM_EOF)
    htable_enter(hash, vstring_str(buf), CAST_INT_TO_VOID_PTR(count++));
    for (i = 0, op = HTABLE_SEQ_FIRST; htable_sequence(hash, op) != 0;
     i++, op = HTABLE_SEQ_NEXT)
     /* void */ ;
    if (i != hash->used)
    msg_panic("%ld entries found, but %lu entries exist",
          (long) i, (unsigned long) hash->used);
    ht_info = htable_list(hash);
    for (i = 0; i < hash->used; i++) {
    r = myrand() % hash->used;
    info = ht_info[i];
    ht_info[i] = ht_info[r];
    ht_info[r] = info;
    }
    for (ht = ht_info; *ht; ht++)
    htable_delete(hash, ht[0]->key, (void (*) (void *)) 0);
    if (hash->used > 0)
    msg_panic("%ld entries not deleted", (long) hash->used);
    myfree((void *) ht_info);
    htable_free(hash, (void (*) (void *)) 0);
    vstring_free(buf);
    return (0);
}

#endif