/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
#pragma once
#include "bpf_arena_common.h"

__noinline int bpf_arena_strlen(const char __arena *s __arg_arena)
{
        const char __arena *sc;

        for (sc = s; *sc != '\0'; ++sc)
                cond_break;
        return sc - s;
}

/**
 * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
 * @pat: Shell-style pattern to match, e.g. "*.[ch]".
 * @str: String to match.  The pattern must match the entire string.
 *
 * Perform shell-style glob matching, returning true (1) if the match
 * succeeds, or false (0) if it fails.  Equivalent to !fnmatch(@pat, @str, 0).
 *
 * Pattern metacharacters are ?, *, [ and \.
 * (And, inside character classes, !, - and ].)
 *
 * This is small and simple implementation intended for device blacklists
 * where a string is matched against a number of patterns.  Thus, it
 * does not preprocess the patterns.  It is non-recursive, and run-time
 * is at most quadratic: strlen(@str)*strlen(@pat).
 *
 * An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa");
 * it takes 6 passes over the pattern before matching the string.
 *
 * Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT
 * treat / or leading . specially; it isn't actually used for pathnames.
 *
 * Note that according to glob(7) (and unlike bash), character classes
 * are complemented by a leading !; this does not support the regex-style
 * [^a-z] syntax.
 *
 * An opening bracket without a matching close is matched literally.
 */
__noinline bool glob_match(char const __arena *pat __arg_arena, char const __arena *str __arg_arena)
{
        /*
         * Backtrack to previous * on mismatch and retry starting one
         * character later in the string.  Because * matches all characters
         * (no exception for /), it can be easily proved that there's
         * never a need to backtrack multiple levels.
         */
        char const __arena *back_pat = NULL, *back_str;

        /*
         * Loop over each token (character or class) in pat, matching
         * it against the remaining unmatched tail of str.  Return false
         * on mismatch, or true after matching the trailing nul bytes.
         */
        for (;;) {
                unsigned char c = *str++;
                unsigned char d = *pat++;

                switch (d) {
                case '?':       /* Wildcard: anything but nul */
                        if (c == '\0')
                                return false;
                        break;
                case '*':       /* Any-length wildcard */
                        if (*pat == '\0')       /* Optimize trailing * case */
                                return true;
                        back_pat = pat;
                        back_str = --str;       /* Allow zero-length match */
                        break;
                case '[': {     /* Character class */
                        bool match = false, inverted = (*pat == '!');
                        char const __arena *class = pat + inverted;
                        unsigned char a = *class++;

                        /*
                         * Iterate over each span in the character class.
                         * A span is either a single character a, or a
                         * range a-b.  The first span may begin with ']'.
                         */
                        do {
                                unsigned char b = a;

                                if (a == '\0')  /* Malformed */
                                        goto literal;

                                if (class[0] == '-' && class[1] != ']') {
                                        b = class[1];

                                        if (b == '\0')
                                                goto literal;

                                        class += 2;
                                        /* Any special action if a > b? */
                                }
                                match |= (a <= c && c <= b);
                                cond_break;
                        } while ((a = *class++) != ']');

                        if (match == inverted)
                                goto backtrack;
                        pat = class;
                        }
                        break;
                case '\\':
                        d = *pat++;
                        __attribute__((__fallthrough__));
                default:        /* Literal character */
literal:
                        if (c == d) {
                                if (d == '\0')
                                        return true;
                                break;
                        }
backtrack:
                        if (c == '\0' || !back_pat)
                                return false;   /* No point continuing */
                        /* Try again from last *, one character later in str. */
                        pat = back_pat;
                        str = ++back_str;
                        break;
                }
                cond_break;
        }
        return false;
}