dict_regexp.c

[詳解]

/*++
/* NAME
/*  dict_regexp 3
/* SUMMARY
/*  dictionary manager interface to REGEXP regular expression library
/* SYNOPSIS
/*  #include <dict_regexp.h>
/*
/*  DICT    *dict_regexp_open(name, dummy, dict_flags)
/*  const char *name;
/*  int dummy;
/*  int dict_flags;
/* DESCRIPTION
/*  dict_regexp_open() opens the named file and compiles the contained
/*  regular expressions. The result object can be used to match strings
/*  against the table.
/* SEE ALSO
/*  dict(3) generic dictionary manager
/*  regexp_table(5) format of Postfix regular expression tables
/* AUTHOR(S)
/*  LaMont Jones
/*  lamont@hp.com
/*
/*  Based on PCRE dictionary contributed by Andrew McNamara
/*  andrewm@connect.com.au
/*  connect.com.au Pty. Ltd.
/*  Level 3, 213 Miller St
/*  North Sydney, NSW, Australia
/*
/*  Heavily rewritten by Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*
/*  Wietse Venema
/*  Google, Inc.
/*  111 8th Avenue
/*  New York, NY 10011, USA
/*--*/

/* System library. */

#include "sys_defs.h"

#ifdef HAS_POSIX_REGEXP

#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <regex.h>
#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif

/* Utility library. */

#include "mymalloc.h"
#include "msg.h"
#include "safe.h"
#include "vstream.h"
#include "vstring.h"
#include "stringops.h"
#include "readlline.h"
#include "dict.h"
#include "dict_regexp.h"
#include "mac_parse.h"
#include "warn_stat.h"
#include "mvect.h"

 /*
  * Support for IF/ENDIF based on an idea by Bert Driehuis.
  */
#define DICT_REGEXP_OP_MATCH    1   /* Match this regexp */
#define DICT_REGEXP_OP_IF   2   /* Increase if/endif nesting on match */
#define DICT_REGEXP_OP_ENDIF    3   /* Decrease if/endif nesting on match */

 /*
  * Regular expression before compiling.
  */
typedef struct {
    char   *regexp;         /* regular expression */
    int     options;            /* regcomp() options */
    int     match;          /* positive or negative match */
} DICT_REGEXP_PATTERN;

 /*
  * Compiled generic rule, and subclasses that derive from it.
  */
typedef struct DICT_REGEXP_RULE {
    int     op;             /* DICT_REGEXP_OP_MATCH/IF/ENDIF */
    int     lineno;         /* source file line number */
    struct DICT_REGEXP_RULE *next;  /* next rule in dict */
} DICT_REGEXP_RULE;

typedef struct {
    DICT_REGEXP_RULE rule;      /* generic part */
    regex_t *first_exp;         /* compiled primary pattern */
    int     first_match;        /* positive or negative match */
    regex_t *second_exp;        /* compiled secondary pattern */
    int     second_match;       /* positive or negative match */
    char   *replacement;        /* replacement text */
    size_t  max_sub;            /* largest $number in replacement */
} DICT_REGEXP_MATCH_RULE;

typedef struct {
    DICT_REGEXP_RULE rule;      /* generic members */
    regex_t *expr;          /* the condition */
    int     match;          /* positive or negative match */
    struct DICT_REGEXP_RULE *endif_rule;/* matching endif rule */
} DICT_REGEXP_IF_RULE;

 /*
  * Regexp map.
  */
typedef struct {
    DICT    dict;           /* generic members */
    regmatch_t *pmatch;         /* matched substring info */
    DICT_REGEXP_RULE *head;     /* first rule */
    VSTRING *expansion_buf;     /* lookup result */
} DICT_REGEXP;

 /*
  * Macros to make dense code more readable.
  */
#define NULL_SUBSTITUTIONS  (0)
#define NULL_MATCH_RESULT   ((regmatch_t *) 0)

 /*
  * Context for $number expansion callback.
  */
typedef struct {
    DICT_REGEXP *dict_regexp;       /* the dictionary handle */
    DICT_REGEXP_MATCH_RULE *match_rule; /* the rule we matched */
    const char *lookup_string;      /* matched text */
} DICT_REGEXP_EXPAND_CONTEXT;

 /*
  * Context for $number pre-scan callback.
  */
typedef struct {
    const char *mapname;        /* name of regexp map */
    int     lineno;         /* where in file */
    size_t  max_sub;            /* largest $number seen */
    char   *literal;            /* constant result, $$ -> $ */
} DICT_REGEXP_PRESCAN_CONTEXT;

 /*
  * Compatibility.
  */
#ifndef MAC_PARSE_OK
#define MAC_PARSE_OK 0
#endif

/* dict_regexp_expand - replace $number with substring from matched text */

static int dict_regexp_expand(int type, VSTRING *buf, void *ptr)
{
    DICT_REGEXP_EXPAND_CONTEXT *ctxt = (DICT_REGEXP_EXPAND_CONTEXT *) ptr;
    DICT_REGEXP_MATCH_RULE *match_rule = ctxt->match_rule;
    DICT_REGEXP *dict_regexp = ctxt->dict_regexp;
    regmatch_t *pmatch;
    size_t  n;

    /*
     * Replace $number by the corresponding substring from the matched text.
     * We pre-scanned the replacement text at compile time, so any out of
     * range $number means that something impossible has happened.
     */
    if (type == MAC_PARSE_VARNAME) {
    n = atoi(vstring_str(buf));
    if (n < 1 || n > match_rule->max_sub)
        msg_panic("regexp map %s, line %d: out of range replacement index \"%s\"",
              dict_regexp->dict.name, match_rule->rule.lineno,
              vstring_str(buf));
    pmatch = dict_regexp->pmatch + n;
    if (pmatch->rm_so < 0 || pmatch->rm_so == pmatch->rm_eo)
        return (MAC_PARSE_UNDEF);       /* empty or not matched */
    vstring_strncat(dict_regexp->expansion_buf,
            ctxt->lookup_string + pmatch->rm_so,
            pmatch->rm_eo - pmatch->rm_so);
    return (MAC_PARSE_OK);
    }

    /*
     * Straight text - duplicate with no substitution.
     */
    else {
    vstring_strcat(dict_regexp->expansion_buf, vstring_str(buf));
    return (MAC_PARSE_OK);
    }
}

/* dict_regexp_regerror - report regexp compile/execute error */

static void dict_regexp_regerror(const char *mapname, int lineno, int error,
                         const regex_t *expr)
{
    char    errbuf[256];

    (void) regerror(error, expr, errbuf, sizeof(errbuf));
    msg_warn("regexp map %s, line %d: %s", mapname, lineno, errbuf);
}

 /*
  * Inlined to reduce function call overhead in the time-critical loop.
  */
#define DICT_REGEXP_REGEXEC(err, map, line, expr, match, str, nsub, pmatch) \
    ((err) = regexec((expr), (str), (nsub), (pmatch), 0), \
     ((err) == REG_NOMATCH ? !(match) : \
      (err) == 0 ? (match) : \
      (dict_regexp_regerror((map), (line), (err), (expr)), 0)))

/* dict_regexp_lookup - match string and perform optional substitution */

static const char *dict_regexp_lookup(DICT *dict, const char *lookup_string)
{
    DICT_REGEXP *dict_regexp = (DICT_REGEXP *) dict;
    DICT_REGEXP_RULE *rule;
    DICT_REGEXP_IF_RULE *if_rule;
    DICT_REGEXP_MATCH_RULE *match_rule;
    DICT_REGEXP_EXPAND_CONTEXT expand_context;
    int     error;

    dict->error = 0;

    if (msg_verbose)
    msg_info("dict_regexp_lookup: %s: %s", dict->name, lookup_string);

    /*
     * Optionally fold the key.
     */
    if (dict->flags & DICT_FLAG_FOLD_MUL) {
    if (dict->fold_buf == 0)
        dict->fold_buf = vstring_alloc(10);
    vstring_strcpy(dict->fold_buf, lookup_string);
    lookup_string = lowercase(vstring_str(dict->fold_buf));
    }
    for (rule = dict_regexp->head; rule; rule = rule->next) {

    switch (rule->op) {

        /*
         * Search for the first matching primary expression. Limit the
         * overhead for substring substitution to the bare minimum.
         */
    case DICT_REGEXP_OP_MATCH:
        match_rule = (DICT_REGEXP_MATCH_RULE *) rule;
        if (!DICT_REGEXP_REGEXEC(error, dict->name, rule->lineno,
                     match_rule->first_exp,
                     match_rule->first_match,
                     lookup_string,
                     match_rule->max_sub > 0 ?
                     match_rule->max_sub + 1 : 0,
                     dict_regexp->pmatch))
        continue;
        if (match_rule->second_exp
        && !DICT_REGEXP_REGEXEC(error, dict->name, rule->lineno,
                    match_rule->second_exp,
                    match_rule->second_match,
                    lookup_string,
                    NULL_SUBSTITUTIONS,
                    NULL_MATCH_RESULT))
        continue;

        /*
         * Skip $number substitutions when the replacement text contains
         * no $number strings, as learned during the compile time
         * pre-scan. The pre-scan already replaced $$ by $.
         */
        if (match_rule->max_sub == 0)
        return (match_rule->replacement);

        /*
         * Perform $number substitutions on the replacement text. We
         * pre-scanned the replacement text at compile time. Any macro
         * expansion errors at this point mean something impossible has
         * happened.
         */
        if (!dict_regexp->expansion_buf)
        dict_regexp->expansion_buf = vstring_alloc(10);
        VSTRING_RESET(dict_regexp->expansion_buf);
        expand_context.lookup_string = lookup_string;
        expand_context.match_rule = match_rule;
        expand_context.dict_regexp = dict_regexp;

        if (mac_parse(match_rule->replacement, dict_regexp_expand,
              (void *) &expand_context) & MAC_PARSE_ERROR)
        msg_panic("regexp map %s, line %d: bad replacement syntax",
              dict->name, rule->lineno);
        VSTRING_TERMINATE(dict_regexp->expansion_buf);
        return (vstring_str(dict_regexp->expansion_buf));

        /*
         * Conditional.
         */
    case DICT_REGEXP_OP_IF:
        if_rule = (DICT_REGEXP_IF_RULE *) rule;
        if (DICT_REGEXP_REGEXEC(error, dict->name, rule->lineno,
                   if_rule->expr, if_rule->match, lookup_string,
                    NULL_SUBSTITUTIONS, NULL_MATCH_RESULT))
        continue;
        /* An IF without matching ENDIF has no "endif" rule. */
        if ((rule = if_rule->endif_rule) == 0)
        return (0);
        /* FALLTHROUGH */

        /*
         * ENDIF after IF.
         */
    case DICT_REGEXP_OP_ENDIF:
        continue;

    default:
        msg_panic("dict_regexp_lookup: impossible operation %d", rule->op);
    }
    }
    return (0);
}

/* dict_regexp_close - close regexp dictionary */

static void dict_regexp_close(DICT *dict)
{
    DICT_REGEXP *dict_regexp = (DICT_REGEXP *) dict;
    DICT_REGEXP_RULE *rule;
    DICT_REGEXP_RULE *next;
    DICT_REGEXP_MATCH_RULE *match_rule;
    DICT_REGEXP_IF_RULE *if_rule;

    for (rule = dict_regexp->head; rule; rule = next) {
    next = rule->next;
    switch (rule->op) {
    case DICT_REGEXP_OP_MATCH:
        match_rule = (DICT_REGEXP_MATCH_RULE *) rule;
        if (match_rule->first_exp) {
        regfree(match_rule->first_exp);
        myfree((void *) match_rule->first_exp);
        }
        if (match_rule->second_exp) {
        regfree(match_rule->second_exp);
        myfree((void *) match_rule->second_exp);
        }
        if (match_rule->replacement)
        myfree((void *) match_rule->replacement);
        break;
    case DICT_REGEXP_OP_IF:
        if_rule = (DICT_REGEXP_IF_RULE *) rule;
        if (if_rule->expr) {
        regfree(if_rule->expr);
        myfree((void *) if_rule->expr);
        }
        break;
    case DICT_REGEXP_OP_ENDIF:
        break;
    default:
        msg_panic("dict_regexp_close: unknown operation %d", rule->op);
    }
    myfree((void *) rule);
    }
    if (dict_regexp->pmatch)
    myfree((void *) dict_regexp->pmatch);
    if (dict_regexp->expansion_buf)
    vstring_free(dict_regexp->expansion_buf);
    if (dict->fold_buf)
    vstring_free(dict->fold_buf);
    dict_free(dict);
}

/* dict_regexp_get_pat - extract one pattern with options from rule */

static int dict_regexp_get_pat(const char *mapname, int lineno, char **bufp,
                           DICT_REGEXP_PATTERN *pat)
{
    char   *p = *bufp;
    char    re_delim;

    /*
     * Process negation operators.
     */
    pat->match = 1;
    for (;;) {
    if (*p == '!')
        pat->match = !pat->match;
    else if (!ISSPACE(*p))
        break;
    p++;
    }
    if (*p == 0) {
    msg_warn("regexp map %s, line %d: no regexp: skipping this rule",
         mapname, lineno);
    return (0);
    }

    /*
     * Search for the closing delimiter, handling backslash escape.
     */
    re_delim = *p++;
    pat->regexp = p;
    while (*p) {
    if (*p == '\\') {
        if (p[1])
        p++;
        else
        break;
    } else if (*p == re_delim) {
        break;
    }
    ++p;
    }
    if (!*p) {
    msg_warn("regexp map %s, line %d: no closing regexp delimiter \"%c\": "
         "skipping this rule", mapname, lineno, re_delim);
    return (0);
    }
    *p++ = 0;                   /* null terminate */

    /*
     * Search for options.
     */
    pat->options = REG_EXTENDED | REG_ICASE;
    while (*p && !ISSPACE(*p) && *p != '!') {
    switch (*p) {
    case 'i':
        pat->options ^= REG_ICASE;
        break;
    case 'm':
        pat->options ^= REG_NEWLINE;
        break;
    case 'x':
        pat->options ^= REG_EXTENDED;
        break;
    default:
        msg_warn("regexp map %s, line %d: unknown regexp option \"%c\": "
             "skipping this rule", mapname, lineno, *p);
        return (0);
    }
    ++p;
    }
    *bufp = p;
    return (1);
}

/* dict_regexp_get_pats - get the primary and second patterns and flags */

static int dict_regexp_get_pats(const char *mapname, int lineno, char **p,
                        DICT_REGEXP_PATTERN *first_pat,
                        DICT_REGEXP_PATTERN *second_pat)
{

    /*
     * Get the primary and optional secondary patterns and their flags.
     */
    if (dict_regexp_get_pat(mapname, lineno, p, first_pat) == 0)
    return (0);
    if (**p == '!') {
#if 0
    static int bitrot_warned = 0;

    if (bitrot_warned == 0) {
        msg_warn("regexp file %s, line %d: /pattern1/!/pattern2/ goes away,"
         " use \"if !/pattern2/ ... /pattern1/ ... endif\" instead",
             mapname, lineno);
        bitrot_warned = 1;
    }
#endif
    if (dict_regexp_get_pat(mapname, lineno, p, second_pat) == 0)
        return (0);
    } else {
    second_pat->regexp = 0;
    }
    return (1);
}

/* dict_regexp_prescan - find largest $number in replacement text */

static int dict_regexp_prescan(int type, VSTRING *buf, void *context)
{
    DICT_REGEXP_PRESCAN_CONTEXT *ctxt = (DICT_REGEXP_PRESCAN_CONTEXT *) context;
    size_t  n;

    /*
     * Keep a copy of literal text (with $$ already replaced by $) if and
     * only if the replacement text contains no $number expression. This way
     * we can avoid having to scan the replacement text at lookup time.
     */
    if (type == MAC_PARSE_VARNAME) {
    if (ctxt->literal) {
        myfree(ctxt->literal);
        ctxt->literal = 0;
    }
    if (!alldig(vstring_str(buf))) {
        msg_warn("regexp map %s, line %d: non-numeric replacement index \"%s\"",
             ctxt->mapname, ctxt->lineno, vstring_str(buf));
        return (MAC_PARSE_ERROR);
    }
    n = atoi(vstring_str(buf));
    if (n < 1) {
        msg_warn("regexp map %s, line %d: out-of-range replacement index \"%s\"",
             ctxt->mapname, ctxt->lineno, vstring_str(buf));
        return (MAC_PARSE_ERROR);
    }
    if (n > ctxt->max_sub)
        ctxt->max_sub = n;
    } else if (type == MAC_PARSE_LITERAL && ctxt->max_sub == 0) {
    if (ctxt->literal)
        msg_panic("regexp map %s, line %d: multiple literals but no $number",
              ctxt->mapname, ctxt->lineno);
    ctxt->literal = mystrdup(vstring_str(buf));
    }
    return (MAC_PARSE_OK);
}

/* dict_regexp_compile_pat - compile one pattern */

static regex_t *dict_regexp_compile_pat(const char *mapname, int lineno,
                            DICT_REGEXP_PATTERN *pat)
{
    int     error;
    regex_t *expr;

    expr = (regex_t *) mymalloc(sizeof(*expr));
    error = regcomp(expr, pat->regexp, pat->options);
    if (error != 0) {
    dict_regexp_regerror(mapname, lineno, error, expr);
    myfree((void *) expr);
    return (0);
    }
    return (expr);
}

/* dict_regexp_rule_alloc - fill in a generic rule structure */

static DICT_REGEXP_RULE *dict_regexp_rule_alloc(int op, int lineno, size_t size)
{
    DICT_REGEXP_RULE *rule;

    rule = (DICT_REGEXP_RULE *) mymalloc(size);
    rule->op = op;
    rule->lineno = lineno;
    rule->next = 0;

    return (rule);
}

/* dict_regexp_parseline - parse one rule */

static DICT_REGEXP_RULE *dict_regexp_parseline(const char *mapname, int lineno,
                                char *line, int nesting,
                                   int dict_flags)
{
    char   *p;

    p = line;

    /*
     * An ordinary rule takes one or two patterns and replacement text.
     */
    if (!ISALNUM(*p)) {
    DICT_REGEXP_PATTERN first_pat;
    DICT_REGEXP_PATTERN second_pat;
    DICT_REGEXP_PRESCAN_CONTEXT prescan_context;
    regex_t *first_exp = 0;
    regex_t *second_exp;
    DICT_REGEXP_MATCH_RULE *match_rule;

    /*
     * Get the primary and the optional secondary patterns.
     */
    if (!dict_regexp_get_pats(mapname, lineno, &p, &first_pat, &second_pat))
        return (0);

    /*
     * Get the replacement text.
     */
    while (*p && ISSPACE(*p))
        ++p;
    if (!*p) {
        msg_warn("regexp map %s, line %d: no replacement text: "
             "using empty string", mapname, lineno);
    }

    /*
     * Find the highest-numbered $number in the replacement text. We can
     * speed up pattern matching 1) by passing hints to the regexp
     * compiler, setting the REG_NOSUB flag when the replacement text
     * contains no $number string; 2) by passing hints to the regexp
     * execution code, limiting the amount of text that is made available
     * for substitution.
     */
    prescan_context.mapname = mapname;
    prescan_context.lineno = lineno;
    prescan_context.max_sub = 0;
    prescan_context.literal = 0;

    /*
     * The optimizer will eliminate code duplication and/or dead code.
     */
#define CREATE_MATCHOP_ERROR_RETURN(rval) do { \
    if (first_exp) { \
        regfree(first_exp); \
        myfree((void *) first_exp); \
    } \
    if (prescan_context.literal) \
        myfree(prescan_context.literal); \
    return (rval); \
    } while (0)

    if (mac_parse(p, dict_regexp_prescan, (void *) &prescan_context)
        & MAC_PARSE_ERROR) {
        msg_warn("regexp map %s, line %d: bad replacement syntax: "
             "skipping this rule", mapname, lineno);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }

    /*
     * Compile the primary and the optional secondary pattern. Speed up
     * execution when no matched text needs to be substituted into the
     * result string, or when the highest numbered substring is less than
     * the total number of () subpatterns.
     */
    if (prescan_context.max_sub == 0)
        first_pat.options |= REG_NOSUB;
    if (prescan_context.max_sub > 0 && first_pat.match == 0) {
        msg_warn("regexp map %s, line %d: $number found in negative match "
           "replacement text: skipping this rule", mapname, lineno);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }
    if (prescan_context.max_sub > 0 && (dict_flags & DICT_FLAG_NO_REGSUB)) {
        msg_warn("regexp map %s, line %d: "
             "regular expression substitution is not allowed: "
             "skipping this rule", mapname, lineno);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }
    if ((first_exp = dict_regexp_compile_pat(mapname, lineno,
                         &first_pat)) == 0)
        CREATE_MATCHOP_ERROR_RETURN(0);
    if (prescan_context.max_sub > first_exp->re_nsub) {
        msg_warn("regexp map %s, line %d: out of range replacement index \"%d\": "
             "skipping this rule", mapname, lineno,
             (int) prescan_context.max_sub);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }
    if (second_pat.regexp != 0) {
        second_pat.options |= REG_NOSUB;
        if ((second_exp = dict_regexp_compile_pat(mapname, lineno,
                              &second_pat)) == 0)
        CREATE_MATCHOP_ERROR_RETURN(0);
    } else {
        second_exp = 0;
    }
    match_rule = (DICT_REGEXP_MATCH_RULE *)
        dict_regexp_rule_alloc(DICT_REGEXP_OP_MATCH, lineno,
                   sizeof(DICT_REGEXP_MATCH_RULE));
    match_rule->first_exp = first_exp;
    match_rule->first_match = first_pat.match;
    match_rule->max_sub = prescan_context.max_sub;
    match_rule->second_exp = second_exp;
    match_rule->second_match = second_pat.match;
    if (prescan_context.literal)
        match_rule->replacement = prescan_context.literal;
    else
        match_rule->replacement = mystrdup(p);
    return ((DICT_REGEXP_RULE *) match_rule);
    }

    /*
     * The IF operator takes one pattern but no replacement text.
     */
    else if (strncasecmp(p, "IF", 2) == 0 && !ISALNUM(p[2])) {
    DICT_REGEXP_PATTERN pattern;
    regex_t *expr;
    DICT_REGEXP_IF_RULE *if_rule;

    p += 2;
    while (*p && ISSPACE(*p))
        p++;
    if (!dict_regexp_get_pat(mapname, lineno, &p, &pattern))
        return (0);
    while (*p && ISSPACE(*p))
        ++p;
    if (*p) {
        msg_warn("regexp map %s, line %d: ignoring extra text after"
             " IF statement: \"%s\"", mapname, lineno, p);
        msg_warn("regexp map %s, line %d: do not prepend whitespace"
             " to statements between IF and ENDIF", mapname, lineno);
    }
    if ((expr = dict_regexp_compile_pat(mapname, lineno, &pattern)) == 0)
        return (0);
    if_rule = (DICT_REGEXP_IF_RULE *)
        dict_regexp_rule_alloc(DICT_REGEXP_OP_IF, lineno,
                   sizeof(DICT_REGEXP_IF_RULE));
    if_rule->expr = expr;
    if_rule->match = pattern.match;
    if_rule->endif_rule = 0;
    return ((DICT_REGEXP_RULE *) if_rule);
    }

    /*
     * The ENDIF operator takes no patterns and no replacement text.
     */
    else if (strncasecmp(p, "ENDIF", 5) == 0 && !ISALNUM(p[5])) {
    DICT_REGEXP_RULE *rule;

    p += 5;
    if (nesting == 0) {
        msg_warn("regexp map %s, line %d: ignoring ENDIF without matching IF",
             mapname, lineno);
        return (0);
    }
    while (*p && ISSPACE(*p))
        ++p;
    if (*p)
        msg_warn("regexp map %s, line %d: ignoring extra text after ENDIF",
             mapname, lineno);
    rule = dict_regexp_rule_alloc(DICT_REGEXP_OP_ENDIF, lineno,
                      sizeof(DICT_REGEXP_RULE));
    return (rule);
    }

    /*
     * Unrecognized input.
     */
    else {
    msg_warn("regexp map %s, line %d: ignoring unrecognized request",
         mapname, lineno);
    return (0);
    }
}

/* dict_regexp_open - load and compile a file containing regular expressions */

DICT   *dict_regexp_open(const char *mapname, int open_flags, int dict_flags)
{
    const char myname[] = "dict_regexp_open";
    DICT_REGEXP *dict_regexp;
    VSTREAM *map_fp = 0;
    struct stat st;
    VSTRING *line_buffer = 0;
    DICT_REGEXP_RULE *rule;
    DICT_REGEXP_RULE *last_rule = 0;
    int     lineno;
    int     last_line = 0;
    size_t  max_sub = 0;
    int     nesting = 0;
    char   *p;
    DICT_REGEXP_RULE **rule_stack = 0;
    MVECT   mvect;

    /*
     * Let the optimizer worry about eliminating redundant code.
     */
#define DICT_REGEXP_OPEN_RETURN(d) do { \
    DICT *__d = (d); \
    if (line_buffer != 0) \
        vstring_free(line_buffer); \
    if (map_fp != 0) \
        vstream_fclose(map_fp); \
    return (__d); \
    } while (0)

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

    /*
     * Open the configuration file.
     */
    if ((map_fp = vstream_fopen(mapname, O_RDONLY, 0)) == 0)
    DICT_REGEXP_OPEN_RETURN(dict_surrogate(DICT_TYPE_REGEXP, mapname,
                           open_flags, dict_flags,
                           "open %s: %m", mapname));
    if (fstat(vstream_fileno(map_fp), &st) < 0)
    msg_fatal("fstat %s: %m", mapname);

    line_buffer = vstring_alloc(100);

    dict_regexp = (DICT_REGEXP *) dict_alloc(DICT_TYPE_REGEXP, mapname,
                         sizeof(*dict_regexp));
    dict_regexp->dict.lookup = dict_regexp_lookup;
    dict_regexp->dict.close = dict_regexp_close;
    dict_regexp->dict.flags = dict_flags | DICT_FLAG_PATTERN;
    if (dict_flags & DICT_FLAG_FOLD_MUL)
    dict_regexp->dict.fold_buf = vstring_alloc(10);
    dict_regexp->head = 0;
    dict_regexp->pmatch = 0;
    dict_regexp->expansion_buf = 0;
    dict_regexp->dict.owner.uid = st.st_uid;
    dict_regexp->dict.owner.status = (st.st_uid != 0);

    /*
     * Parse the regexp table.
     */
    while (readllines(line_buffer, map_fp, &last_line, &lineno)) {
    p = vstring_str(line_buffer);
    trimblanks(p, 0)[0] = 0;
    if (*p == 0)
        continue;
    rule = dict_regexp_parseline(mapname, lineno, p, nesting, dict_flags);
    if (rule == 0)
        continue;
    if (rule->op == DICT_REGEXP_OP_MATCH) {
        if (((DICT_REGEXP_MATCH_RULE *) rule)->max_sub > max_sub)
        max_sub = ((DICT_REGEXP_MATCH_RULE *) rule)->max_sub;
    } else if (rule->op == DICT_REGEXP_OP_IF) {
        if (rule_stack == 0)
        rule_stack = (DICT_REGEXP_RULE **) mvect_alloc(&mvect,
                       sizeof(*rule_stack), nesting + 1,
                        (MVECT_FN) 0, (MVECT_FN) 0);
        else
        rule_stack =
            (DICT_REGEXP_RULE **) mvect_realloc(&mvect, nesting + 1);
        rule_stack[nesting] = rule;
        nesting++;
    } else if (rule->op == DICT_REGEXP_OP_ENDIF) {
        DICT_REGEXP_IF_RULE *if_rule;

        if (nesting-- <= 0)
        /* Already handled in dict_regexp_parseline(). */
        msg_panic("%s: ENDIF without IF", myname);
        if (rule_stack[nesting]->op != DICT_REGEXP_OP_IF)
        msg_panic("%s: unexpected rule stack element type %d",
              myname, rule_stack[nesting]->op);
        if_rule = (DICT_REGEXP_IF_RULE *) rule_stack[nesting];
        if_rule->endif_rule = rule;
    }
    if (last_rule == 0)
        dict_regexp->head = rule;
    else
        last_rule->next = rule;
    last_rule = rule;
    }

    while (nesting-- > 0)
    msg_warn("regexp map %s, line %d: IF has no matching ENDIF",
         mapname, rule_stack[nesting]->lineno);

    if (rule_stack)
    (void) mvect_free(&mvect);

    /*
     * Allocate space for only as many matched substrings as used in the
     * replacement text.
     */
    if (max_sub > 0)
    dict_regexp->pmatch =
        (regmatch_t *) mymalloc(sizeof(regmatch_t) * (max_sub + 1));

    DICT_REGEXP_OPEN_RETURN(DICT_DEBUG (&dict_regexp->dict));
}

#endif