dict_pcre.c

[詳解]

/*++
/* NAME
/*  dict_pcre 3
/* SUMMARY
/*  dictionary manager interface to PCRE regular expression library
/* SYNOPSIS
/*  #include <dict_pcre.h>
/*
/*  DICT    *dict_pcre_open(name, dummy, dict_flags)
/*  const char *name;
/*  int dummy;
/*  int dict_flags;
/* DESCRIPTION
/*  dict_pcre_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
/* AUTHOR(S)
/*  Andrew McNamara
/*  andrewm@connect.com.au
/*  connect.com.au Pty. Ltd.
/*  Level 3, 213 Miller St
/*  North Sydney, NSW, Australia
/*
/*  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
/*--*/

#include "sys_defs.h"

#ifdef HAS_PCRE

/* System library. */

#include <sys/stat.h>
#include <stdio.h>          /* sprintf() prototype */
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.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_pcre.h"
#include "mac_parse.h"
#include "pcre.h"
#include "warn_stat.h"
#include "mvect.h"

 /*
  * Backwards compatibility.
  */
#ifdef PCRE_STUDY_JIT_COMPILE
#define DICT_PCRE_FREE_STUDY(x) pcre_free_study(x)
#else
#define DICT_PCRE_FREE_STUDY(x) pcre_free((char *) (x))
#endif

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

 /*
  * Max strings captured by regexp - essentially the max number of (..)
  */
#define PCRE_MAX_CAPTURE    99

 /*
  * Regular expression before and after compilation.
  */
typedef struct {
    char   *regexp;         /* regular expression */
    int     options;            /* options */
    int     match;          /* positive or negative match */
} DICT_PCRE_REGEXP;

typedef struct {
    pcre   *pattern;            /* the compiled pattern */
    pcre_extra *hints;          /* hints to speed pattern execution */
} DICT_PCRE_ENGINE;

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

typedef struct {
    DICT_PCRE_RULE rule;        /* generic part */
    pcre   *pattern;            /* compiled pattern */
    pcre_extra *hints;          /* hints to speed pattern execution */
    char   *replacement;        /* replacement string */
    int     match;          /* positive or negative match */
    size_t  max_sub;            /* largest $number in replacement */
} DICT_PCRE_MATCH_RULE;

typedef struct {
    DICT_PCRE_RULE rule;        /* generic members */
    pcre   *pattern;            /* compiled pattern */
    pcre_extra *hints;          /* hints to speed pattern execution */
    int     match;          /* positive or negative match */
    struct DICT_PCRE_RULE *endif_rule;  /* matching endif rule */
} DICT_PCRE_IF_RULE;

 /*
  * PCRE map.
  */
typedef struct {
    DICT    dict;           /* generic members */
    DICT_PCRE_RULE *head;
    VSTRING *expansion_buf;     /* lookup result */
} DICT_PCRE;

static int dict_pcre_init = 0;      /* flag need to init pcre library */

/*
 * Context for $number expansion callback.
 */
typedef struct {
    DICT_PCRE *dict_pcre;       /* the dictionary handle */
    DICT_PCRE_MATCH_RULE *match_rule;   /* the rule we matched */
    const char *lookup_string;      /* string against which we match */
    int     offsets[PCRE_MAX_CAPTURE * 3];  /* Cut substrings */
    int     matches;            /* Count of cuts */
} DICT_PCRE_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 $n seen */
    char   *literal;            /* constant result, $$ -> $ */
} DICT_PCRE_PRESCAN_CONTEXT;

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

 /*
  * Macros to make dense code more accessible.
  */
#define NULL_STARTOFFSET    (0)
#define NULL_EXEC_OPTIONS   (0)
#define NULL_OVECTOR        ((int *) 0)
#define NULL_OVECTOR_LENGTH (0)

/* dict_pcre_expand - replace $number with matched text */

static int dict_pcre_expand(int type, VSTRING *buf, void *ptr)
{
    DICT_PCRE_EXPAND_CONTEXT *ctxt = (DICT_PCRE_EXPAND_CONTEXT *) ptr;
    DICT_PCRE_MATCH_RULE *match_rule = ctxt->match_rule;
    DICT_PCRE *dict_pcre = ctxt->dict_pcre;
    const char *pp;
    int     n;
    int     ret;

    /*
     * Replace $0-${99} with strings cut from matched text.
     */
    if (type == MAC_PARSE_VARNAME) {
    n = atoi(vstring_str(buf));
    ret = pcre_get_substring(ctxt->lookup_string, ctxt->offsets,
                 ctxt->matches, n, &pp);
    if (ret < 0) {
        if (ret == PCRE_ERROR_NOSUBSTRING)
        return (MAC_PARSE_UNDEF);
        else
        msg_fatal("pcre map %s, line %d: pcre_get_substring error: %d",
            dict_pcre->dict.name, match_rule->rule.lineno, ret);
    }
    if (*pp == 0) {
        myfree((void *) pp);
        return (MAC_PARSE_UNDEF);
    }
    vstring_strcat(dict_pcre->expansion_buf, pp);
    myfree((void *) pp);
    return (MAC_PARSE_OK);
    }

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

/* dict_pcre_exec_error - report matching error */

static void dict_pcre_exec_error(const char *mapname, int lineno, int errval)
{
    switch (errval) {
    case 0:
    msg_warn("pcre map %s, line %d: too many (...)",
         mapname, lineno);
    return;
    case PCRE_ERROR_NULL:
    case PCRE_ERROR_BADOPTION:
    msg_warn("pcre map %s, line %d: bad args to re_exec",
         mapname, lineno);
    return;
    case PCRE_ERROR_BADMAGIC:
    case PCRE_ERROR_UNKNOWN_NODE:
    msg_warn("pcre map %s, line %d: corrupt compiled regexp",
         mapname, lineno);
    return;
#ifdef PCRE_ERROR_NOMEMORY
    case PCRE_ERROR_NOMEMORY:
    msg_warn("pcre map %s, line %d: out of memory",
         mapname, lineno);
    return;
#endif
#ifdef PCRE_ERROR_MATCHLIMIT
    case PCRE_ERROR_MATCHLIMIT:
    msg_warn("pcre map %s, line %d: backtracking limit exceeded",
         mapname, lineno);
    return;
#endif
#ifdef PCRE_ERROR_BADUTF8
    case PCRE_ERROR_BADUTF8:
    msg_warn("pcre map %s, line %d: bad UTF-8 sequence in search string",
         mapname, lineno);
    return;
#endif
#ifdef PCRE_ERROR_BADUTF8_OFFSET
    case PCRE_ERROR_BADUTF8_OFFSET:
    msg_warn("pcre map %s, line %d: bad UTF-8 start offset in search string",
         mapname, lineno);
    return;
#endif
    default:
    msg_warn("pcre map %s, line %d: unknown pcre_exec error: %d",
         mapname, lineno, errval);
    return;
    }
}

 /*
  * Inlined to reduce function call overhead in the time-critical loop.
  */
#define DICT_PCRE_EXEC(ctxt, map, line, pattern, hints, match, str, len) \
    ((ctxt).matches = pcre_exec((pattern), (hints), (str), (len), \
                NULL_STARTOFFSET, NULL_EXEC_OPTIONS, \
                (ctxt).offsets, PCRE_MAX_CAPTURE * 3), \
     (ctxt).matches > 0 ? (match) : \
     (ctxt).matches == PCRE_ERROR_NOMATCH ? !(match) : \
     (dict_pcre_exec_error((map), (line), (ctxt).matches), 0))

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

static const char *dict_pcre_lookup(DICT *dict, const char *lookup_string)
{
    DICT_PCRE *dict_pcre = (DICT_PCRE *) dict;
    DICT_PCRE_RULE *rule;
    DICT_PCRE_IF_RULE *if_rule;
    DICT_PCRE_MATCH_RULE *match_rule;
    int     lookup_len = strlen(lookup_string);
    DICT_PCRE_EXPAND_CONTEXT ctxt;

    dict->error = 0;

    if (msg_verbose)
    msg_info("dict_pcre_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_pcre->head; rule; rule = rule->next) {

    switch (rule->op) {

        /*
         * Search for a matching expression.
         */
    case DICT_PCRE_OP_MATCH:
        match_rule = (DICT_PCRE_MATCH_RULE *) rule;
        if (!DICT_PCRE_EXEC(ctxt, dict->name, rule->lineno,
                match_rule->pattern, match_rule->hints,
                  match_rule->match, lookup_string, lookup_len))
        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;

        /*
         * We've got a match. Perform substitution on replacement string.
         */
        if (dict_pcre->expansion_buf == 0)
        dict_pcre->expansion_buf = vstring_alloc(10);
        VSTRING_RESET(dict_pcre->expansion_buf);
        ctxt.dict_pcre = dict_pcre;
        ctxt.match_rule = match_rule;
        ctxt.lookup_string = lookup_string;

        if (mac_parse(match_rule->replacement, dict_pcre_expand,
              (void *) &ctxt) & MAC_PARSE_ERROR)
        msg_fatal("pcre map %s, line %d: bad replacement syntax",
              dict->name, rule->lineno);

        VSTRING_TERMINATE(dict_pcre->expansion_buf);
        return (vstring_str(dict_pcre->expansion_buf));

        /*
         * Conditional. XXX We provide space for matched substring info
         * because PCRE uses part of it as workspace for backtracking.
         * PCRE will allocate memory if it runs out of backtracking
         * storage.
         */
    case DICT_PCRE_OP_IF:
        if_rule = (DICT_PCRE_IF_RULE *) rule;
        if (DICT_PCRE_EXEC(ctxt, dict->name, rule->lineno,
                   if_rule->pattern, if_rule->hints,
                   if_rule->match, lookup_string, lookup_len))
        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_PCRE_OP_ENDIF:
        continue;

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

/* dict_pcre_close - close pcre dictionary */

static void dict_pcre_close(DICT *dict)
{
    DICT_PCRE *dict_pcre = (DICT_PCRE *) dict;
    DICT_PCRE_RULE *rule;
    DICT_PCRE_RULE *next;
    DICT_PCRE_MATCH_RULE *match_rule;
    DICT_PCRE_IF_RULE *if_rule;

    for (rule = dict_pcre->head; rule; rule = next) {
    next = rule->next;
    switch (rule->op) {
    case DICT_PCRE_OP_MATCH:
        match_rule = (DICT_PCRE_MATCH_RULE *) rule;
        if (match_rule->pattern)
        myfree((void *) match_rule->pattern);
        if (match_rule->hints)
        DICT_PCRE_FREE_STUDY(match_rule->hints);
        if (match_rule->replacement)
        myfree((void *) match_rule->replacement);
        break;
    case DICT_PCRE_OP_IF:
        if_rule = (DICT_PCRE_IF_RULE *) rule;
        if (if_rule->pattern)
        myfree((void *) if_rule->pattern);
        if (if_rule->hints)
        DICT_PCRE_FREE_STUDY(if_rule->hints);
        break;
    case DICT_PCRE_OP_ENDIF:
        break;
    default:
        msg_panic("dict_pcre_close: unknown operation %d", rule->op);
    }
    myfree((void *) rule);
    }
    if (dict_pcre->expansion_buf)
    vstring_free(dict_pcre->expansion_buf);
    if (dict->fold_buf)
    vstring_free(dict->fold_buf);
    dict_free(dict);
}

/* dict_pcre_get_pattern - extract pattern from rule */

static int dict_pcre_get_pattern(const char *mapname, int lineno, char **bufp,
                         DICT_PCRE_REGEXP *pattern)
{
    char   *p = *bufp;
    char    re_delimiter;

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

    /*
     * Search for second delimiter, handling backslash escape.
     */
    while (*p) {
    if (*p == '\\') {
        ++p;
        if (*p == 0)
        break;
    } else if (*p == re_delimiter)
        break;
    ++p;
    }

    if (!*p) {
    msg_warn("pcre map %s, line %d: no closing regexp delimiter \"%c\": "
         "ignoring this rule", mapname, lineno, re_delimiter);
    return (0);
    }
    *p++ = 0;                   /* Null term the regexp */

    /*
     * Parse any regexp options.
     */
    pattern->options = PCRE_CASELESS | PCRE_DOTALL;
    while (*p && !ISSPACE(*p)) {
    switch (*p) {
    case 'i':
        pattern->options ^= PCRE_CASELESS;
        break;
    case 'm':
        pattern->options ^= PCRE_MULTILINE;
        break;
    case 's':
        pattern->options ^= PCRE_DOTALL;
        break;
    case 'x':
        pattern->options ^= PCRE_EXTENDED;
        break;
    case 'A':
        pattern->options ^= PCRE_ANCHORED;
        break;
    case 'E':
        pattern->options ^= PCRE_DOLLAR_ENDONLY;
        break;
    case 'U':
        pattern->options ^= PCRE_UNGREEDY;
        break;
    case 'X':
        pattern->options ^= PCRE_EXTRA;
        break;
    default:
        msg_warn("pcre map %s, line %d: unknown regexp option \"%c\": "
             "skipping this rule", mapname, lineno, *p);
        return (0);
    }
    ++p;
    }
    *bufp = p;
    return (1);
}

/* dict_pcre_prescan - sanity check $number instances in replacement text */

static int dict_pcre_prescan(int type, VSTRING *buf, void *context)
{
    DICT_PCRE_PRESCAN_CONTEXT *ctxt = (DICT_PCRE_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("pcre 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("pcre 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("pcre map %s, line %d: multiple literals but no $number",
              ctxt->mapname, ctxt->lineno);
    ctxt->literal = mystrdup(vstring_str(buf));
    }
    return (MAC_PARSE_OK);
}

/* dict_pcre_compile - compile pattern */

static int dict_pcre_compile(const char *mapname, int lineno,
                         DICT_PCRE_REGEXP *pattern,
                         DICT_PCRE_ENGINE *engine)
{
    const char *error;
    int     errptr;

    engine->pattern = pcre_compile(pattern->regexp, pattern->options,
                   &error, &errptr, NULL);
    if (engine->pattern == 0) {
    msg_warn("pcre map %s, line %d: error in regex at offset %d: %s",
         mapname, lineno, errptr, error);
    return (0);
    }
    engine->hints = pcre_study(engine->pattern, 0, &error);
    if (error != 0) {
    msg_warn("pcre map %s, line %d: error while studying regex: %s",
         mapname, lineno, error);
    myfree((void *) engine->pattern);
    return (0);
    }
    return (1);
}

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

static DICT_PCRE_RULE *dict_pcre_rule_alloc(int op, int lineno, size_t size)
{
    DICT_PCRE_RULE *rule;

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

    return (rule);
}

/* dict_pcre_parse_rule - parse and compile one rule */

static DICT_PCRE_RULE *dict_pcre_parse_rule(const char *mapname, int lineno,
                                char *line, int nesting,
                                int dict_flags)
{
    char   *p;
    int     actual_sub;

    p = line;

    /*
     * An ordinary match rule takes one pattern and replacement text.
     */
    if (!ISALNUM(*p)) {
    DICT_PCRE_REGEXP regexp;
    DICT_PCRE_ENGINE engine;
    DICT_PCRE_PRESCAN_CONTEXT prescan_context;
    DICT_PCRE_MATCH_RULE *match_rule;

    /*
     * Get the pattern string and options.
     */
    if (dict_pcre_get_pattern(mapname, lineno, &p, &regexp) == 0)
        return (0);

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

    /*
     * Sanity check the $number instances in the replacement text.
     */
    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 (prescan_context.literal) \
        myfree(prescan_context.literal); \
    return (rval); \
    } while (0)

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

    /*
     * Substring replacement not possible with negative regexps.
     */
    if (prescan_context.max_sub > 0 && regexp.match == 0) {
        msg_warn("pcre 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("pcre map %s, line %d: "
             "regular expression substitution is not allowed: "
             "skipping this rule", mapname, lineno);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }

    /*
     * Compile the pattern.
     */
    if (dict_pcre_compile(mapname, lineno, &regexp, &engine) == 0)
        CREATE_MATCHOP_ERROR_RETURN(0);
#ifdef PCRE_INFO_CAPTURECOUNT
    if (pcre_fullinfo(engine.pattern, engine.hints,
              PCRE_INFO_CAPTURECOUNT,
              (void *) &actual_sub) != 0)
        msg_panic("pcre map %s, line %d: pcre_fullinfo failed",
              mapname, lineno);
    if (prescan_context.max_sub > actual_sub) {
        msg_warn("pcre map %s, line %d: out of range replacement index \"%d\": "
             "skipping this rule", mapname, lineno,
             (int) prescan_context.max_sub);
        if (engine.pattern)
        myfree((void *) engine.pattern);
        if (engine.hints)
        DICT_PCRE_FREE_STUDY(engine.hints);
        CREATE_MATCHOP_ERROR_RETURN(0);
    }
#endif

    /*
     * Save the result.
     */
    match_rule = (DICT_PCRE_MATCH_RULE *)
        dict_pcre_rule_alloc(DICT_PCRE_OP_MATCH, lineno,
                 sizeof(DICT_PCRE_MATCH_RULE));
    match_rule->match = regexp.match;
    match_rule->max_sub = prescan_context.max_sub;
    if (prescan_context.literal)
        match_rule->replacement = prescan_context.literal;
    else
        match_rule->replacement = mystrdup(p);
    match_rule->pattern = engine.pattern;
    match_rule->hints = engine.hints;
    return ((DICT_PCRE_RULE *) match_rule);
    }

    /*
     * The IF operator takes one pattern but no replacement text.
     */
    else if (strncasecmp(p, "IF", 2) == 0 && !ISALNUM(p[2])) {
    DICT_PCRE_REGEXP regexp;
    DICT_PCRE_ENGINE engine;
    DICT_PCRE_IF_RULE *if_rule;

    p += 2;

    /*
     * Get the pattern.
     */
    while (*p && ISSPACE(*p))
        p++;
    if (!dict_pcre_get_pattern(mapname, lineno, &p, &regexp))
        return (0);

    /*
     * Warn about out-of-place text.
     */
    while (*p && ISSPACE(*p))
        ++p;
    if (*p) {
        msg_warn("pcre map %s, line %d: ignoring extra text after "
             "IF statement: \"%s\"", mapname, lineno, p);
        msg_warn("pcre map %s, line %d: do not prepend whitespace"
             " to statements between IF and ENDIF", mapname, lineno);
    }

    /*
     * Compile the pattern.
     */
    if (dict_pcre_compile(mapname, lineno, &regexp, &engine) == 0)
        return (0);

    /*
     * Save the result.
     */
    if_rule = (DICT_PCRE_IF_RULE *)
        dict_pcre_rule_alloc(DICT_PCRE_OP_IF, lineno,
                 sizeof(DICT_PCRE_IF_RULE));
    if_rule->match = regexp.match;
    if_rule->pattern = engine.pattern;
    if_rule->hints = engine.hints;
    if_rule->endif_rule = 0;
    return ((DICT_PCRE_RULE *) if_rule);
    }

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

    p += 5;

    /*
     * Warn about out-of-place ENDIFs.
     */
    if (nesting == 0) {
        msg_warn("pcre map %s, line %d: ignoring ENDIF without matching IF",
             mapname, lineno);
        return (0);
    }

    /*
     * Warn about out-of-place text.
     */
    while (*p && ISSPACE(*p))
        ++p;
    if (*p)
        msg_warn("pcre map %s, line %d: ignoring extra text after ENDIF",
             mapname, lineno);

    /*
     * Save the result.
     */
    rule = dict_pcre_rule_alloc(DICT_PCRE_OP_ENDIF, lineno,
                    sizeof(DICT_PCRE_RULE));
    return (rule);
    }

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

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

DICT   *dict_pcre_open(const char *mapname, int open_flags, int dict_flags)
{
    const char myname[] = "dict_pcre_open";
    DICT_PCRE *dict_pcre;
    VSTREAM *map_fp = 0;
    struct stat st;
    VSTRING *line_buffer = 0;
    DICT_PCRE_RULE *last_rule = 0;
    DICT_PCRE_RULE *rule;
    int     last_line = 0;
    int     lineno;
    int     nesting = 0;
    char   *p;
    DICT_PCRE_RULE **rule_stack = 0;
    MVECT   mvect;

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

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

    /*
     * Open the configuration file.
     */
    if ((map_fp = vstream_fopen(mapname, O_RDONLY, 0)) == 0)
    DICT_PCRE_OPEN_RETURN(dict_surrogate(DICT_TYPE_PCRE, 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_pcre = (DICT_PCRE *) dict_alloc(DICT_TYPE_PCRE, mapname,
                     sizeof(*dict_pcre));
    dict_pcre->dict.lookup = dict_pcre_lookup;
    dict_pcre->dict.close = dict_pcre_close;
    dict_pcre->dict.flags = dict_flags | DICT_FLAG_PATTERN;
    if (dict_flags & DICT_FLAG_FOLD_MUL)
    dict_pcre->dict.fold_buf = vstring_alloc(10);
    dict_pcre->head = 0;
    dict_pcre->expansion_buf = 0;

    if (dict_pcre_init == 0) {
    pcre_malloc = (void *(*) (size_t)) mymalloc;
    pcre_free = (void (*) (void *)) myfree;
    dict_pcre_init = 1;
    }
    dict_pcre->dict.owner.uid = st.st_uid;
    dict_pcre->dict.owner.status = (st.st_uid != 0);

    /*
     * Parse the pcre table.
     */
    while (readllines(line_buffer, map_fp, &last_line, &lineno)) {
    p = vstring_str(line_buffer);
    trimblanks(p, 0)[0] = 0;        /* Trim space at end */
    if (*p == 0)
        continue;
    rule = dict_pcre_parse_rule(mapname, lineno, p, nesting, dict_flags);
    if (rule == 0)
        continue;
    if (rule->op == DICT_PCRE_OP_IF) {
        if (rule_stack == 0)
        rule_stack = (DICT_PCRE_RULE **) mvect_alloc(&mvect,
                       sizeof(*rule_stack), nesting + 1,
                        (MVECT_FN) 0, (MVECT_FN) 0);
        else
        rule_stack =
            (DICT_PCRE_RULE **) mvect_realloc(&mvect, nesting + 1);
        rule_stack[nesting] = rule;
        nesting++;
    } else if (rule->op == DICT_PCRE_OP_ENDIF) {
        DICT_PCRE_IF_RULE *if_rule;

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

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

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

    DICT_PCRE_OPEN_RETURN(DICT_DEBUG (&dict_pcre->dict));
}

#endif                  /* HAS_PCRE */