/*
 *  linux/fs/adfs/dir_f.c
 *
 * Copyright (C) 1997-1999 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  E and F format directory handling
 */
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/adfs_fs.h>
#include <linux/time.h>
#include <linux/stat.h>
#include <linux/spinlock.h>
#include <linux/buffer_head.h>
#include <linux/string.h>

#include "adfs.h"
#include "dir_f.h"

static void adfs_f_free(struct adfs_dir *dir);

/*
 * Read an (unaligned) value of length 1..4 bytes
 */
static inline unsigned int adfs_readval(unsigned char *p, int len)
{
        unsigned int val = 0;

        switch (len) {
        case 4:         val |= p[3] << 24;
        case 3:         val |= p[2] << 16;
        case 2:         val |= p[1] << 8;
        default:        val |= p[0];
        }
        return val;
}

static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
{
        switch (len) {
        case 4:         p[3] = val >> 24;
        case 3:         p[2] = val >> 16;
        case 2:         p[1] = val >> 8;
        default:        p[0] = val;
        }
}

static inline int adfs_readname(char *buf, char *ptr, int maxlen)
{
        char *old_buf = buf;

        while ((unsigned char)*ptr >= ' ' && maxlen--) {
                if (*ptr == '/')
                        *buf++ = '.';
                else
                        *buf++ = *ptr;
                ptr++;
        }
        *buf = '\0';

        return buf - old_buf;
}

#define ror13(v) ((v >> 13) | (v << 19))

#define dir_u8(idx)                             \
        ({ int _buf = idx >> blocksize_bits;    \
           int _off = idx - (_buf << blocksize_bits);\
          *(u8 *)(bh[_buf]->b_data + _off);     \
        })

#define dir_u32(idx)                            \
        ({ int _buf = idx >> blocksize_bits;    \
           int _off = idx - (_buf << blocksize_bits);\
          *(__le32 *)(bh[_buf]->b_data + _off); \
        })

#define bufoff(_bh,_idx)                        \
        ({ int _buf = _idx >> blocksize_bits;   \
           int _off = _idx - (_buf << blocksize_bits);\
          (u8 *)(_bh[_buf]->b_data + _off);     \
        })

/*
 * There are some algorithms that are nice in
 * assembler, but a bitch in C...  This is one
 * of them.
 */
static u8
adfs_dir_checkbyte(const struct adfs_dir *dir)
{
        struct buffer_head * const *bh = dir->bh;
        const int blocksize_bits = dir->sb->s_blocksize_bits;
        union { __le32 *ptr32; u8 *ptr8; } ptr, end;
        u32 dircheck = 0;
        int last = 5 - 26;
        int i = 0;

        /*
         * Accumulate each word up to the last whole
         * word of the last directory entry.  This
         * can spread across several buffer heads.
         */
        do {
                last += 26;
                do {
                        dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);

                        i += sizeof(u32);
                } while (i < (last & ~3));
        } while (dir_u8(last) != 0);

        /*
         * Accumulate the last few bytes.  These
         * bytes will be within the same bh.
         */
        if (i != last) {
                ptr.ptr8 = bufoff(bh, i);
                end.ptr8 = ptr.ptr8 + last - i;

                do
                        dircheck = *ptr.ptr8++ ^ ror13(dircheck);
                while (ptr.ptr8 < end.ptr8);
        }

        /*
         * The directory tail is in the final bh
         * Note that contary to the RISC OS PRMs,
         * the first few bytes are NOT included
         * in the check.  All bytes are in the
         * same bh.
         */
        ptr.ptr8 = bufoff(bh, 2008);
        end.ptr8 = ptr.ptr8 + 36;

        do {
                __le32 v = *ptr.ptr32++;
                dircheck = le32_to_cpu(v) ^ ror13(dircheck);
        } while (ptr.ptr32 < end.ptr32);

        return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
}

/*
 * Read and check that a directory is valid
 */
static int
adfs_dir_read(struct super_block *sb, unsigned long object_id,
              unsigned int size, struct adfs_dir *dir)
{
        const unsigned int blocksize_bits = sb->s_blocksize_bits;
        int blk = 0;

        /*
         * Directories which are not a multiple of 2048 bytes
         * are considered bad v2 [3.6]
         */
        if (size & 2047)
                goto bad_dir;

        size >>= blocksize_bits;

        dir->nr_buffers = 0;
        dir->sb = sb;

        for (blk = 0; blk < size; blk++) {
                int phys;

                phys = __adfs_block_map(sb, object_id, blk);
                if (!phys) {
                        adfs_error(sb, "dir object %lX has a hole at offset %d",
                                   object_id, blk);
                        goto release_buffers;
                }

                dir->bh[blk] = sb_bread(sb, phys);
                if (!dir->bh[blk])
                        goto release_buffers;
        }

        memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
        memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));

        if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
            memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
                goto bad_dir;

        if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
            memcmp(&dir->dirhead.startname, "Hugo", 4))
                goto bad_dir;

        if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
                goto bad_dir;

        dir->nr_buffers = blk;

        return 0;

bad_dir:
        adfs_error(sb, "corrupted directory fragment %lX",
                   object_id);
release_buffers:
        for (blk -= 1; blk >= 0; blk -= 1)
                brelse(dir->bh[blk]);

        dir->sb = NULL;

        return -EIO;
}

/*
 * convert a disk-based directory entry to a Linux ADFS directory entry
 */
static inline void
adfs_dir2obj(struct object_info *obj, struct adfs_direntry *de)
{
        obj->name_len = adfs_readname(obj->name, de->dirobname, ADFS_F_NAME_LEN);
        obj->file_id  = adfs_readval(de->dirinddiscadd, 3);
        obj->loadaddr = adfs_readval(de->dirload, 4);
        obj->execaddr = adfs_readval(de->direxec, 4);
        obj->size     = adfs_readval(de->dirlen,  4);
        obj->attr     = de->newdiratts;
}

/*
 * convert a Linux ADFS directory entry to a disk-based directory entry
 */
static inline void
adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
{
        adfs_writeval(de->dirinddiscadd, 3, obj->file_id);
        adfs_writeval(de->dirload, 4, obj->loadaddr);
        adfs_writeval(de->direxec, 4, obj->execaddr);
        adfs_writeval(de->dirlen,  4, obj->size);
        de->newdiratts = obj->attr;
}

/*
 * get a directory entry.  Note that the caller is responsible
 * for holding the relevant locks.
 */
static int
__adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
{
        struct super_block *sb = dir->sb;
        struct adfs_direntry de;
        int thissize, buffer, offset;

        buffer = pos >> sb->s_blocksize_bits;

        if (buffer > dir->nr_buffers)
                return -EINVAL;

        offset = pos & (sb->s_blocksize - 1);
        thissize = sb->s_blocksize - offset;
        if (thissize > 26)
                thissize = 26;

        memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
        if (thissize != 26)
                memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
                       26 - thissize);

        if (!de.dirobname[0])
                return -ENOENT;

        adfs_dir2obj(obj, &de);

        return 0;
}

static int
__adfs_dir_put(struct adfs_dir *dir, int pos, struct object_info *obj)
{
        struct super_block *sb = dir->sb;
        struct adfs_direntry de;
        int thissize, buffer, offset;

        buffer = pos >> sb->s_blocksize_bits;

        if (buffer > dir->nr_buffers)
                return -EINVAL;

        offset = pos & (sb->s_blocksize - 1);
        thissize = sb->s_blocksize - offset;
        if (thissize > 26)
                thissize = 26;

        /*
         * Get the entry in total
         */
        memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
        if (thissize != 26)
                memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
                       26 - thissize);

        /*
         * update it
         */
        adfs_obj2dir(&de, obj);

        /*
         * Put the new entry back
         */
        memcpy(dir->bh[buffer]->b_data + offset, &de, thissize);
        if (thissize != 26)
                memcpy(dir->bh[buffer + 1]->b_data, ((char *)&de) + thissize,
                       26 - thissize);

        return 0;
}

/*
 * the caller is responsible for holding the necessary
 * locks.
 */
static int
adfs_dir_find_entry(struct adfs_dir *dir, unsigned long object_id)
{
        int pos, ret;

        ret = -ENOENT;

        for (pos = 5; pos < ADFS_NUM_DIR_ENTRIES * 26 + 5; pos += 26) {
                struct object_info obj;

                if (!__adfs_dir_get(dir, pos, &obj))
                        break;

                if (obj.file_id == object_id) {
                        ret = pos;
                        break;
                }
        }

        return ret;
}

static int
adfs_f_read(struct super_block *sb, unsigned int id, unsigned int sz, struct adfs_dir *dir)
{
        int ret;

        if (sz != ADFS_NEWDIR_SIZE)
                return -EIO;

        ret = adfs_dir_read(sb, id, sz, dir);
        if (ret)
                adfs_error(sb, "unable to read directory");
        else
                dir->parent_id = adfs_readval(dir->dirtail.new.dirparent, 3);

        return ret;
}

static int
adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
{
        if (fpos >= ADFS_NUM_DIR_ENTRIES)
                return -ENOENT;

        dir->pos = 5 + fpos * 26;
        return 0;
}

static int
adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
{
        unsigned int ret;

        ret = __adfs_dir_get(dir, dir->pos, obj);
        if (ret == 0)
                dir->pos += 26;

        return ret;
}

static int
adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
{
        struct super_block *sb = dir->sb;
        int ret, i;

        ret = adfs_dir_find_entry(dir, obj->file_id);
        if (ret < 0) {
                adfs_error(dir->sb, "unable to locate entry to update");
                goto out;
        }

        __adfs_dir_put(dir, ret, obj);
 
        /*
         * Increment directory sequence number
         */
        dir->bh[0]->b_data[0] += 1;
        dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 6] += 1;

        ret = adfs_dir_checkbyte(dir);
        /*
         * Update directory check byte
         */
        dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 1] = ret;

#if 1
        {
        const unsigned int blocksize_bits = sb->s_blocksize_bits;

        memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
        memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));

        if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
            memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
                goto bad_dir;

        if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
            memcmp(&dir->dirhead.startname, "Hugo", 4))
                goto bad_dir;

        if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
                goto bad_dir;
        }
#endif
        for (i = dir->nr_buffers - 1; i >= 0; i--)
                mark_buffer_dirty(dir->bh[i]);

        ret = 0;
out:
        return ret;
#if 1
bad_dir:
        adfs_error(dir->sb, "whoops!  I broke a directory!");
        return -EIO;
#endif
}

static void
adfs_f_free(struct adfs_dir *dir)
{
        int i;

        for (i = dir->nr_buffers - 1; i >= 0; i--) {
                brelse(dir->bh[i]);
                dir->bh[i] = NULL;
        }

        dir->nr_buffers = 0;
        dir->sb = NULL;
}

struct adfs_dir_ops adfs_f_dir_ops = {
        .read           = adfs_f_read,
        .setpos         = adfs_f_setpos,
        .getnext        = adfs_f_getnext,
        .update         = adfs_f_update,
        .free           = adfs_f_free
};