/*

 * symlink.c --- make a symlink in the filesystem, based on mkdir.c

 *

 * Copyright (c) 2012, Intel Corporation.

 * All Rights Reserved.

 *

 * %Begin-Header%

 * This file may be redistributed under the terms of the GNU Library

 * General Public License, version 2.

 * %End-Header%

 */

#include "config.h"

#include <stdio.h>

#include <string.h>

#if HAVE_UNISTD_H

#include <unistd.h>

#endif

#include <fcntl.h>

#include <time.h>

#if HAVE_SYS_STAT_H

#include <sys/stat.h>

#endif

#if HAVE_SYS_TYPES_H

#include <sys/types.h>

#endif

#include "ext2_fs.h"

#include "ext2fs.h"

#ifndef HAVE_STRNLEN

/*

 * Incredibly, libc5 doesn't appear to have strnlen.  So we have to

 * provide our own.

 */

static int my_strnlen(const char * s, int count)

{

  const char *cp = s;

  while (count-- && *cp)

    cp++;

  return cp - s;

}

#define strnlen(str, x) my_strnlen((str),(x))

#endif

errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino,

       const char *name, const char *target)

{

  errcode_t   retval;

  struct ext2_inode inode;

  ext2_ino_t    scratch_ino;

  blk64_t     blk;

  int     fastlink, inlinelink;

  unsigned int    target_len;

  char      *block_buf = 0;

  int     drop_refcount = 0;

  EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

  /*

   * The Linux kernel doesn't allow for links longer than a block

   * (counting the NUL terminator)

   */

  target_len = strnlen(target, fs->blocksize + 1);

  if (target_len >= fs->blocksize) {

    retval = EXT2_ET_INVALID_ARGUMENT;

    goto cleanup;

  }

  /*

   * Allocate a data block for slow links

   */

  retval = ext2fs_get_mem(fs->blocksize, &block_buf);

  if (retval)

    goto cleanup;

  memset(block_buf, 0, fs->blocksize);

  strncpy(block_buf, target, fs->blocksize);

  memset(&inode, 0, sizeof(struct ext2_inode));

  fastlink = (target_len < sizeof(inode.i_block));

  if (!fastlink) {

    retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino,

                      &inode,

                      0),

             NULL, &blk);

    if (retval)

      goto cleanup;

  }

  /*

   * Allocate an inode, if necessary

   */

  if (!ino) {

    retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,

            0, &ino);

    if (retval)

      goto cleanup;

  }

  /*

   * Create the inode structure....

   */

  inode.i_mode = LINUX_S_IFLNK | 0777;

  inode.i_uid = inode.i_gid = 0;

  inode.i_links_count = 1;

  ext2fs_inode_size_set(fs, &inode, target_len);

  /* The time fields are set by ext2fs_write_new_inode() */

  inlinelink = !fastlink && ext2fs_has_feature_inline_data(fs->super);

  if (fastlink) {

    /* Fast symlinks, target stored in inode */

    strcpy((char *)&inode.i_block, target);

  } else if (inlinelink) {

    /* Try inserting an inline data symlink */

    inode.i_flags |= EXT4_INLINE_DATA_FL;

    retval = ext2fs_write_new_inode(fs, ino, &inode);

    if (retval)

      goto cleanup;

    retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf,

            target_len);

    if (retval) {

      inode.i_flags &= ~EXT4_INLINE_DATA_FL;

      inlinelink = 0;

      goto need_block;

    }

    retval = ext2fs_read_inode(fs, ino, &inode);

    if (retval)

      goto cleanup;

  } else {

need_block:

    /* Slow symlinks, target stored in the first block */

    ext2fs_iblk_set(fs, &inode, 1);

    if (ext2fs_has_feature_extents(fs->super)) {

      /*

       * The extent bmap is setup after the inode and block

       * have been written out below.

       */

      inode.i_flags |= EXT4_EXTENTS_FL;

    }

  }

  /*

   * Write out the inode and inode data block.  The inode generation

   * number is assigned by write_new_inode, which means that the

   * operations using ino must come after it.

   */

  if (inlinelink)

    retval = ext2fs_write_inode(fs, ino, &inode);

  else

    retval = ext2fs_write_new_inode(fs, ino, &inode);

  if (retval)

    goto cleanup;

  if (!fastlink && !inlinelink) {

    retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,

              &blk);

    if (retval)

      goto cleanup;

    retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);

    if (retval)

      goto cleanup;

  }

  /*

   * Update accounting....

   */

  if (!fastlink && !inlinelink)

    ext2fs_block_alloc_stats2(fs, blk, +1);

  ext2fs_inode_alloc_stats2(fs, ino, +1, 0);

  drop_refcount = 1;

  /*

   * Link the symlink into the filesystem hierarchy

   */

  if (name) {

    retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,

               &scratch_ino);

    if (!retval) {

      retval = EXT2_ET_FILE_EXISTS;

      goto cleanup;

    }

    if (retval != EXT2_ET_FILE_NOT_FOUND)

      goto cleanup;

    retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);

    if (retval)

      goto cleanup;

  }

  drop_refcount = 0;

cleanup:

  if (block_buf)

    ext2fs_free_mem(&block_buf);

  if (drop_refcount) {

    if (!fastlink && !inlinelink)

      ext2fs_block_alloc_stats2(fs, blk, -1);

    ext2fs_inode_alloc_stats2(fs, ino, -1, 0);

  }

  return retval;

}

/*

 * Test whether an inode is a fast symlink.

 *

 * A fast symlink has its symlink data stored in inode->i_block.

 */

int ext2fs_is_fast_symlink(struct ext2_inode *inode)

{

  return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) &&

         EXT2_I_SIZE(inode) < sizeof(inode->i_block);

}