/*      $OpenBSD: walk.c,v 1.12 2023/08/19 04:21:06 guenther Exp $      */
/*      $NetBSD: walk.c,v 1.29 2015/11/25 00:48:49 christos Exp $       */

/*
 * Copyright (c) 2001 Wasabi Systems, Inc.
 * All rights reserved.
 *
 * Written by Luke Mewburn for Wasabi Systems, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed for the NetBSD Project by
 *      Wasabi Systems, Inc.
 * 4. The name of Wasabi Systems, Inc. may not be used to endorse
 *    or promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <stdio.h>
#include <dirent.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <unistd.h>

#include "makefs.h"

static  fsnode  *create_fsnode(const char *, const char *, const char *,
                               struct stat *);
static  fsinode *link_check(fsinode *);


/*
 * walk_dir --
 *      build a tree of fsnodes from `root' and `dir', with a parent
 *      fsnode of `parent' (which may be NULL for the root of the tree).
 *      append the tree to a fsnode of `join' if it is not NULL.
 *      each "level" is a directory, with the "." entry guaranteed to be
 *      at the start of the list, and without ".." entries.
 */
fsnode *
walk_dir(const char *root, const char *dir, fsnode *parent, fsnode *join)
{
        fsnode          *first, *cur, *prev, *last;
        DIR             *dirp;
        struct dirent   *dent;
        char            path[PATH_MAX+1];
        struct stat     stbuf;
        char            *name, *rp;
        int             dot, len;

        assert(root != NULL);
        assert(dir != NULL);

        len = snprintf(path, sizeof(path), "%s/%s", root, dir);
        if (len >= (int)sizeof(path))
                errx(1, "Pathname too long.");
        if ((dirp = opendir(path)) == NULL)
                err(1, "Can't opendir `%s'", path);
        rp = path + strlen(root) + 1;
        if (join != NULL) {
                first = cur = join;
                while (cur->next != NULL)
                        cur = cur->next;
                prev = last = cur;
        } else
                last = first = prev = NULL;
        while ((dent = readdir(dirp)) != NULL) {
                name = dent->d_name;
                dot = 0;
                if (name[0] == '.')
                        switch (name[1]) {
                        case '\0':      /* "." */
                                if (join != NULL)
                                        continue;
                                dot = 1;
                                break;
                        case '.':       /* ".." */
                                if (name[2] == '\0')
                                        continue;
                                /* FALLTHROUGH */
                        default:
                                dot = 0;
                        }
                if (snprintf(path + len, sizeof(path) - len, "/%s", name) >=
                    (int)sizeof(path) - len)
                        errx(1, "Pathname too long.");
                if (lstat(path, &stbuf) == -1)
                        err(1, "Can't lstat `%s'", path);
                if (S_ISSOCK(stbuf.st_mode & S_IFMT))
                        continue;

                if (join != NULL) {
                        cur = join->next;
                        for (;;) {
                                if (cur == NULL || strcmp(cur->name, name) == 0)
                                        break;
                                if (cur == last) {
                                        cur = NULL;
                                        break;
                                }
                                cur = cur->next;
                        }
                        if (cur != NULL) {
                                if (S_ISDIR(cur->type) &&
                                    S_ISDIR(stbuf.st_mode)) {
                                        cur->child = walk_dir(root, rp, cur,
                                            cur->child);
                                        continue;
                                }
                                errx(1, "Can't merge %s `%s' with "
                                    "existing %s",
                                    inode_type(stbuf.st_mode), path,
                                    inode_type(cur->type));
                        }
                }

                cur = create_fsnode(root, dir, name, &stbuf);
                cur->parent = parent;
                if (dot) {
                                /* ensure "." is at the start of the list */
                        cur->next = first;
                        first = cur;
                        if (! prev)
                                prev = cur;
                        cur->first = first;
                } else {                        /* not "." */
                        if (prev)
                                prev->next = cur;
                        prev = cur;
                        if (!first)
                                first = cur;
                        cur->first = first;
                        if (S_ISDIR(cur->type)) {
                                cur->child = walk_dir(root, rp, cur, NULL);
                                continue;
                        }
                }
                if (stbuf.st_nlink > 1) {
                        fsinode *curino;

                        curino = link_check(cur->inode);
                        if (curino != NULL) {
                                free(cur->inode);
                                cur->inode = curino;
                                cur->inode->nlink++;
                        }
                }
                if (S_ISLNK(cur->type)) {
                        char    slink[PATH_MAX+1];
                        int     llen;

                        llen = readlink(path, slink, sizeof(slink) - 1);
                        if (llen == -1)
                                err(1, "Readlink `%s'", path);
                        slink[llen] = '\0';
                        cur->symlink = estrdup(slink);
                }
        }
        assert(first != NULL);
        if (join == NULL)
                for (cur = first->next; cur != NULL; cur = cur->next)
                        cur->first = first;
        if (closedir(dirp) == -1)
                err(1, "Can't closedir `%s/%s'", root, dir);
        return (first);
}

static fsnode *
create_fsnode(const char *root, const char *path, const char *name,
    struct stat *stbuf)
{
        fsnode *cur;

        cur = ecalloc(1, sizeof(*cur));
        cur->path = estrdup(path);
        cur->name = estrdup(name);
        cur->inode = ecalloc(1, sizeof(*cur->inode));
        cur->root = root;
        cur->type = stbuf->st_mode & S_IFMT;
        cur->inode->nlink = 1;
        cur->inode->st = *stbuf;
        if (Tflag) {
                cur->inode->st.st_atim.tv_sec = stampts;
                cur->inode->st.st_atim.tv_nsec = 0;
                cur->inode->st.st_mtim = cur->inode->st.st_ctim =
                    cur->inode->st.st_atim;
        }
        return (cur);
}

/*
 * free_fsnodes --
 *      Removes node from tree and frees it and all of
 *   its descendants.
 */
void
free_fsnodes(fsnode *node)
{
        fsnode  *cur, *next;

        assert(node != NULL);

        /* for ".", start with actual parent node */
        if (node->first == node) {
                assert(node->name[0] == '.' && node->name[1] == '\0');
                if (node->parent) {
                        assert(node->parent->child == node);
                        node = node->parent;
                }
        }

        /* Find ourselves in our sibling list and unlink */
        if (node->first != node) {
                for (cur = node->first; cur->next; cur = cur->next) {
                        if (cur->next == node) {
                                cur->next = node->next;
                                node->next = NULL;
                                break;
                        }
                }
        }

        for (cur = node; cur != NULL; cur = next) {
                next = cur->next;
                if (cur->child) {
                        cur->child->parent = NULL;
                        free_fsnodes(cur->child);
                }
                if (cur->inode->nlink-- == 1)
                        free(cur->inode);
                if (cur->symlink)
                        free(cur->symlink);
                free(cur->path);
                free(cur->name);
                free(cur);
        }
}


/*
 * inode_type --
 *      for a given inode type `mode', return a descriptive string.
 *      for most cases, uses inotype() from mtree/misc.c
 */
const char *
inode_type(mode_t mode)
{
        switch (mode & S_IFMT) {
        case S_IFBLK:
                return ("block");
        case S_IFCHR:
                return ("char");
        case S_IFDIR:
                return ("dir");
        case S_IFIFO:
                return ("fifo");
        case S_IFREG:
                return ("file");
        case S_IFLNK:
                return ("symlink");
        case S_IFSOCK:
                return ("socket");
        default:
                return ("unknown");
        }
}


/*
 * link_check --
 *      return pointer to fsinode matching `entry's st_ino & st_dev if it exists,
 *      otherwise add `entry' to table and return NULL
 */
/* This was borrowed from du.c and tweaked to keep an fsnode
 * pointer instead. -- dbj@netbsd.org
 */
static fsinode *
link_check(fsinode *entry)
{
        static struct entry {
                fsinode *data;
        } *htable;
        static int htshift;  /* log(allocated size) */
        static int htmask;   /* allocated size - 1 */
        static int htused;   /* 2*number of insertions */
        int h, h2;
        uint64_t tmp;
        /* this constant is (1<<64)/((1+sqrt(5))/2)
         * aka (word size)/(golden ratio)
         */
        const uint64_t HTCONST = 11400714819323198485ULL;
        const int HTBITS = 64;

        /* Never store zero in hashtable */
        assert(entry);

        /* Extend hash table if necessary, keep load under 0.5 */
        if (htused<<1 >= htmask) {
                struct entry *ohtable;

                if (!htable)
                        htshift = 10;   /* starting hashtable size */
                else
                        htshift++;   /* exponential hashtable growth */

                htmask  = (1 << htshift) - 1;
                htused = 0;

                ohtable = htable;
                htable = ecalloc(htmask+1, sizeof(*htable));
                /* populate newly allocated hashtable */
                if (ohtable) {
                        int i;
                        for (i = 0; i <= htmask>>1; i++)
                                if (ohtable[i].data)
                                        link_check(ohtable[i].data);
                        free(ohtable);
                }
        }

        /* multiplicative hashing */
        tmp = entry->st.st_dev;
        tmp <<= HTBITS>>1;
        tmp |=  entry->st.st_ino;
        tmp *= HTCONST;
        h  = tmp >> (HTBITS - htshift);
        h2 = 1 | ( tmp >> (HTBITS - (htshift<<1) - 1)); /* must be odd */

        /* open address hashtable search with double hash probing */
        while (htable[h].data) {
                if ((htable[h].data->st.st_ino == entry->st.st_ino) &&
                    (htable[h].data->st.st_dev == entry->st.st_dev)) {
                        return htable[h].data;
                }
                h = (h + h2) & htmask;
        }

        /* Insert the current entry into hashtable */
        htable[h].data = entry;
        htused++;
        return NULL;
}