dict_random.c

[詳解]

/*++
/* NAME
/*  dict_random 3
/* SUMMARY
/*  dictionary manager interface for randomized tables
/* SYNOPSIS
/*  #include <dict_random.h>
/*
/*  DICT    *dict_random_open(name, open_flags, dict_flags)
/*  const char *name;
/*  int open_flags;
/*  int dict_flags;
/* DESCRIPTION
/*  dict_random_open() opens an in-memory, read-only, table.
/*  Example: "\fBrandmap:{\fIresult_1, ... ,result_n}\fR".
/*
/*  Each table query returns a random choice from the specified
/*  results. Other table access methods are not supported.
/*
/*  The first and last characters of the "randmap:" table name
/*  must be '{' and '}'. Within these, individual maps are
/*  separated with comma or whitespace.
/* SEE ALSO
/*  dict(3) generic dictionary 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
/*--*/

/* System library. */

#include <sys_defs.h>
#include <string.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <myrand.h>
#include <stringops.h>
#include <dict_random.h>

/* Application-specific. */

typedef struct {
    DICT    dict;           /* generic members */
    ARGV   *replies;            /* reply values */
} DICT_RANDOM;

#define STR(x) vstring_str(x)

/* dict_random_lookup - find randomized-table entry */

static const char *dict_random_lookup(DICT *dict, const char *unused_query)
{
    DICT_RANDOM *dict_random = (DICT_RANDOM *) dict;

    DICT_ERR_VAL_RETURN(dict, DICT_ERR_NONE,
     dict_random->replies->argv[myrand() % dict_random->replies->argc]);
}

/* dict_random_close - disassociate from randomized table */

static void dict_random_close(DICT *dict)
{
    DICT_RANDOM *dict_random = (DICT_RANDOM *) dict;

    argv_free(dict_random->replies);
    dict_free(dict);
}

/* dict_random_open - open a randomized table */

DICT   *dict_random_open(const char *name, int open_flags, int dict_flags)
{
    DICT_RANDOM *dict_random;
    char   *saved_name = 0;
    ARGV   *argv;
    size_t  len;

    /*
     * Clarity first. Let the optimizer worry about redundant code.
     */
#define DICT_RANDOM_RETURN(x) do { \
    if (saved_name != 0) \
        myfree(saved_name); \
    return (x); \
    } while (0)

    /*
     * Sanity checks.
     */
    if (open_flags != O_RDONLY)
    DICT_RANDOM_RETURN(dict_surrogate(DICT_TYPE_RANDOM, name,
                      open_flags, dict_flags,
                  "%s:%s map requires O_RDONLY access mode",
                      DICT_TYPE_RANDOM, name));

    /*
     * Split the name name into its constituent parts.
     */
    if ((len = balpar(name, CHARS_BRACE)) == 0 || name[len] != 0
    || *(saved_name = mystrndup(name + 1, len - 2)) == 0
    || ((argv = argv_splitq(saved_name, CHARS_COMMA_SP, CHARS_BRACE)),
        (argv->argc == 0)))
    DICT_RANDOM_RETURN(dict_surrogate(DICT_TYPE_RANDOM, name,
                      open_flags, dict_flags,
                      "bad syntax: \"%s:%s\"; "
                      "need \"%s:{value...}\"",
                      DICT_TYPE_RANDOM, name,
                      DICT_TYPE_RANDOM));

    /*
     * Bundle up the result.
     */
    dict_random =
    (DICT_RANDOM *) dict_alloc(DICT_TYPE_RANDOM, name, sizeof(*dict_random));
    dict_random->dict.lookup = dict_random_lookup;
    dict_random->dict.close = dict_random_close;
    dict_random->dict.flags = dict_flags | DICT_FLAG_PATTERN;
    dict_random->replies = argv;
    dict_random->dict.owner.status = DICT_OWNER_TRUSTED;
    dict_random->dict.owner.uid = 0;

    DICT_RANDOM_RETURN(DICT_DEBUG (&dict_random->dict));
}