/*
   * linux/fs/befs/btree.c
   *
   * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
   *
   * Licensed under the GNU GPL. See the file COPYING for details.
   *
   * 2002-02-05: Sergey S. Kostyliov added binary search within
   * 		btree nodes.
   *
   * Many thanks to:
   *
   * Dominic Giampaolo, author of "Practical File System
   * Design with the Be File System", for such a helpful book.
   * 
   * Marcus J. Ranum, author of the b+tree package in 
   * comp.sources.misc volume 10. This code is not copied from that
   * work, but it is partially based on it.
   *
   * Makoto Kato, author of the original BeFS for linux filesystem
   * driver.
   */
  
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/slab.h>
  #include <linux/mm.h>
  #include <linux/buffer_head.h>
  
  #include "befs.h"
  #include "btree.h"
  #include "datastream.h"
  
  /*
   * The btree functions in this file are built on top of the
   * datastream.c interface, which is in turn built on top of the
   * io.c interface.
   */
  
  /* Befs B+tree structure:
   * 
   * The first thing in the tree is the tree superblock. It tells you
   * all kinds of useful things about the tree, like where the rootnode
   * is located, and the size of the nodes (always 1024 with current version
   * of BeOS).
   *
   * The rest of the tree consists of a series of nodes. Nodes contain a header
   * (struct befs_btree_nodehead), the packed key data, an array of shorts 
   * containing the ending offsets for each of the keys, and an array of
   * befs_off_t values. In interior nodes, the keys are the ending keys for 
   * the childnode they point to, and the values are offsets into the 
   * datastream containing the tree. 
   */
  
  /* Note:
   * 
   * The book states 2 confusing things about befs b+trees. First, 
   * it states that the overflow field of node headers is used by internal nodes
   * to point to another node that "effectively continues this one". Here is what
   * I believe that means. Each key in internal nodes points to another node that
   * contains key values less than itself. Inspection reveals that the last key 
   * in the internal node is not the last key in the index. Keys that are 
   * greater than the last key in the internal node go into the overflow node. 
   * I imagine there is a performance reason for this.
   *
   * Second, it states that the header of a btree node is sufficient to 
   * distinguish internal nodes from leaf nodes. Without saying exactly how. 
   * After figuring out the first, it becomes obvious that internal nodes have
   * overflow nodes and leafnodes do not.
   */
  
  /* 
   * Currently, this code is only good for directory B+trees.
   * In order to be used for other BFS indexes, it needs to be extended to handle
   * duplicate keys and non-string keytypes (int32, int64, float, double).
   */
  
  /*
   * In memory structure of each btree node
   */
  typedef struct {
  	befs_host_btree_nodehead head;	/* head of node converted to cpu byteorder */
  	struct buffer_head *bh;
  	befs_btree_nodehead *od_node;	/* on disk node */
  } befs_btree_node;
  
  /* local constants */
  static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
  
  /* local functions */
  static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
  			       befs_btree_super * bt_super,
  			       befs_btree_node * this_node,
  			       befs_off_t * node_off);
  
  static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
  			      befs_btree_super * sup);
  
  static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
  			     befs_btree_node * node, befs_off_t node_off);
  
  static int befs_leafnode(befs_btree_node * node);
  
  static fs16 *befs_bt_keylen_index(befs_btree_node * node);
  
  static fs64 *befs_bt_valarray(befs_btree_node * node);
  
  static char *befs_bt_keydata(befs_btree_node * node);
  
  static int befs_find_key(struct super_block *sb, befs_btree_node * node,
  			 const char *findkey, befs_off_t * value);
  
  static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
  			     int index, u16 * keylen);
  
  static int befs_compare_strings(const void *key1, int keylen1,
  				const void *key2, int keylen2);
  
  /**
   * befs_bt_read_super - read in btree superblock convert to cpu byteorder
   * @sb: Filesystem superblock
   * @ds: Datastream to read from
   * @sup: Buffer in which to place the btree superblock
   *
   * Calls befs_read_datastream to read in the btree superblock and
   * makes sure it is in cpu byteorder, byteswapping if necessary.
   *
   * On success, returns BEFS_OK and *@sup contains the btree superblock,
   * in cpu byte order.
   *
   * On failure, BEFS_ERR is returned.
   */
  static int
  befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
  		   befs_btree_super * sup)
  {
  	struct buffer_head *bh = NULL;
  	befs_disk_btree_super *od_sup = NULL;
  
  	befs_debug(sb, "---> befs_btree_read_super()");
  
  	bh = befs_read_datastream(sb, ds, 0, NULL);
  
  	if (!bh) {
  		befs_error(sb, "Couldn't read index header.");
  		goto error;
  	}
  	od_sup = (befs_disk_btree_super *) bh->b_data;
  	befs_dump_index_entry(sb, od_sup);
  
  	sup->magic = fs32_to_cpu(sb, od_sup->magic);
  	sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
  	sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
  	sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
  	sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
  	sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
  	sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
  
  	brelse(bh);
  	if (sup->magic != BEFS_BTREE_MAGIC) {
  		befs_error(sb, "Index header has bad magic.");
  		goto error;
  	}
  
  	befs_debug(sb, "<--- befs_btree_read_super()");
  	return BEFS_OK;
  
        error:
  	befs_debug(sb, "<--- befs_btree_read_super() ERROR");
  	return BEFS_ERR;
  }
  
  /**
   * befs_bt_read_node - read in btree node and convert to cpu byteorder
   * @sb: Filesystem superblock
   * @ds: Datastream to read from
   * @node: Buffer in which to place the btree node
   * @node_off: Starting offset (in bytes) of the node in @ds
   *
   * Calls befs_read_datastream to read in the indicated btree node and
   * makes sure its header fields are in cpu byteorder, byteswapping if
   * necessary.
   * Note: node->bh must be NULL when this function called first
   * time. Don't forget brelse(node->bh) after last call.
   *
   * On success, returns BEFS_OK and *@node contains the btree node that
   * starts at @node_off, with the node->head fields in cpu byte order.
   *
   * On failure, BEFS_ERR is returned.
   */
  
  static int
  befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
  		  befs_btree_node * node, befs_off_t node_off)
  {
  	uint off = 0;
  
  	befs_debug(sb, "---> befs_bt_read_node()");
  
  	if (node->bh)
  		brelse(node->bh);
  
  	node->bh = befs_read_datastream(sb, ds, node_off, &off);
  	if (!node->bh) {
  		befs_error(sb, "befs_bt_read_node() failed to read "
  			   "node at %Lu", node_off);
  		befs_debug(sb, "<--- befs_bt_read_node() ERROR");
  
  		return BEFS_ERR;
  	}
  	node->od_node =
  	    (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
  
  	befs_dump_index_node(sb, node->od_node);
  
  	node->head.left = fs64_to_cpu(sb, node->od_node->left);
  	node->head.right = fs64_to_cpu(sb, node->od_node->right);
  	node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
  	node->head.all_key_count =
  	    fs16_to_cpu(sb, node->od_node->all_key_count);
  	node->head.all_key_length =
  	    fs16_to_cpu(sb, node->od_node->all_key_length);
  
  	befs_debug(sb, "<--- befs_btree_read_node()");
  	return BEFS_OK;
  }
  
  /**
   * befs_btree_find - Find a key in a befs B+tree
   * @sb: Filesystem superblock
   * @ds: Datastream containing btree
   * @key: Key string to lookup in btree
   * @value: Value stored with @key
   *
   * On success, returns BEFS_OK and sets *@value to the value stored
   * with @key (usually the disk block number of an inode).
   *
   * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
   * 
   * Algorithm: 
   *   Read the superblock and rootnode of the b+tree.
   *   Drill down through the interior nodes using befs_find_key().
   *   Once at the correct leaf node, use befs_find_key() again to get the
   *   actuall value stored with the key.
   */
  int
  befs_btree_find(struct super_block *sb, befs_data_stream * ds,
  		const char *key, befs_off_t * value)
  {
  	befs_btree_node *this_node = NULL;
  	befs_btree_super bt_super;
  	befs_off_t node_off;
  	int res;
  
  	befs_debug(sb, "---> befs_btree_find() Key: %s", key);
  
  	if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
  		befs_error(sb,
  			   "befs_btree_find() failed to read index superblock");
  		goto error;
  	}
  
  	this_node = kmalloc(sizeof (befs_btree_node),
  						GFP_NOFS);
  	if (!this_node) {
  		befs_error(sb, "befs_btree_find() failed to allocate %u "
  			   "bytes of memory", sizeof (befs_btree_node));
  		goto error;
  	}
  
  	this_node->bh = NULL;
  
  	/* read in root node */
  	node_off = bt_super.root_node_ptr;
  	if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
  		befs_error(sb, "befs_btree_find() failed to read "
  			   "node at %Lu", node_off);
  		goto error_alloc;
  	}
  
  	while (!befs_leafnode(this_node)) {
  		res = befs_find_key(sb, this_node, key, &node_off);
  		if (res == BEFS_BT_NOT_FOUND)
  			node_off = this_node->head.overflow;
  		/* if no match, go to overflow node */
  		if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
  			befs_error(sb, "befs_btree_find() failed to read "
  				   "node at %Lu", node_off);
  			goto error_alloc;
  		}
  	}
  
  	/* at the correct leaf node now */
  
  	res = befs_find_key(sb, this_node, key, value);
  
  	brelse(this_node->bh);
  	kfree(this_node);
  
  	if (res != BEFS_BT_MATCH) {
  		befs_debug(sb, "<--- befs_btree_find() Key %s not found", key);
  		*value = 0;
  		return BEFS_BT_NOT_FOUND;
  	}
  	befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu",
  		   key, *value);
  	return BEFS_OK;
  
        error_alloc:
  	kfree(this_node);
        error:
  	*value = 0;
  	befs_debug(sb, "<--- befs_btree_find() ERROR");
  	return BEFS_ERR;
  }
  
  /**
   * befs_find_key - Search for a key within a node
   * @sb: Filesystem superblock
   * @node: Node to find the key within
   * @key: Keystring to search for
   * @value: If key is found, the value stored with the key is put here
   *
   * finds exact match if one exists, and returns BEFS_BT_MATCH
   * If no exact match, finds first key in node that is greater
   * (alphabetically) than the search key and returns BEFS_BT_PARMATCH
   * (for partial match, I guess). Can you think of something better to
   * call it?
   *
   * If no key was a match or greater than the search key, return
   * BEFS_BT_NOT_FOUND.
   *
   * Use binary search instead of a linear.
   */
  static int
  befs_find_key(struct super_block *sb, befs_btree_node * node,
  	      const char *findkey, befs_off_t * value)
  {
  	int first, last, mid;
  	int eq;
  	u16 keylen;
  	int findkey_len;
  	char *thiskey;
  	fs64 *valarray;
  
  	befs_debug(sb, "---> befs_find_key() %s", findkey);
  
  	*value = 0;
  
  	findkey_len = strlen(findkey);
  
  	/* if node can not contain key, just skeep this node */
  	last = node->head.all_key_count - 1;
  	thiskey = befs_bt_get_key(sb, node, last, &keylen);
  
  	eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
  	if (eq < 0) {
  		befs_debug(sb, "<--- befs_find_key() %s not found", findkey);
  		return BEFS_BT_NOT_FOUND;
  	}
  
  	valarray = befs_bt_valarray(node);
  
  	/* simple binary search */
  	first = 0;
  	mid = 0;
  	while (last >= first) {
  		mid = (last + first) / 2;
  		befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
  			   mid);
  		thiskey = befs_bt_get_key(sb, node, mid, &keylen);
  		eq = befs_compare_strings(thiskey, keylen, findkey,
  					  findkey_len);
  
  		if (eq == 0) {
  			befs_debug(sb, "<--- befs_find_key() found %s at %d",
  				   thiskey, mid);
  
  			*value = fs64_to_cpu(sb, valarray[mid]);
  			return BEFS_BT_MATCH;
  		}
  		if (eq > 0)
  			last = mid - 1;
  		else
  			first = mid + 1;
  	}
  	if (eq < 0)
  		*value = fs64_to_cpu(sb, valarray[mid + 1]);
  	else
  		*value = fs64_to_cpu(sb, valarray[mid]);
  	befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid);
  	return BEFS_BT_PARMATCH;
  }
  
  /**
   * befs_btree_read - Traverse leafnodes of a btree
   * @sb: Filesystem superblock
   * @ds: Datastream containing btree
   * @key_no: Key number (alphabetical order) of key to read
   * @bufsize: Size of the buffer to return key in
   * @keybuf: Pointer to a buffer to put the key in
   * @keysize: Length of the returned key
   * @value: Value stored with the returned key
   *
   * Heres how it works: Key_no is the index of the key/value pair to 
   * return in keybuf/value.
   * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is 
   * the number of charecters in the key (just a convenience).
   *
   * Algorithm:
   *   Get the first leafnode of the tree. See if the requested key is in that
   *   node. If not, follow the node->right link to the next leafnode. Repeat 
   *   until the (key_no)th key is found or the tree is out of keys.
   */
  int
  befs_btree_read(struct super_block *sb, befs_data_stream * ds,
  		loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
  		befs_off_t * value)
  {
  	befs_btree_node *this_node;
  	befs_btree_super bt_super;
  	befs_off_t node_off = 0;
  	int cur_key;
  	fs64 *valarray;
  	char *keystart;
  	u16 keylen;
  	int res;
  
  	uint key_sum = 0;
  
  	befs_debug(sb, "---> befs_btree_read()");
  
  	if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
  		befs_error(sb,
  			   "befs_btree_read() failed to read index superblock");
  		goto error;
  	}
  
  	if ((this_node = kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
  		befs_error(sb, "befs_btree_read() failed to allocate %u "
  			   "bytes of memory", sizeof (befs_btree_node));
  		goto error;
  	}
  
  	node_off = bt_super.root_node_ptr;
  	this_node->bh = NULL;
  
  	/* seeks down to first leafnode, reads it into this_node */
  	res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
  	if (res == BEFS_BT_EMPTY) {
  		brelse(this_node->bh);
  		kfree(this_node);
  		*value = 0;
  		*keysize = 0;
  		befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
  		return BEFS_BT_EMPTY;
  	} else if (res == BEFS_ERR) {
  		goto error_alloc;
  	}
  
  	/* find the leaf node containing the key_no key */
  
  	while (key_sum + this_node->head.all_key_count <= key_no) {
  
  		/* no more nodes to look in: key_no is too large */
  		if (this_node->head.right == befs_bt_inval) {
  			*keysize = 0;
  			*value = 0;
  			befs_debug(sb,
  				   "<--- befs_btree_read() END of keys at %Lu",
  				   key_sum + this_node->head.all_key_count);
  			brelse(this_node->bh);
  			kfree(this_node);
  			return BEFS_BT_END;
  		}
  
  		key_sum += this_node->head.all_key_count;
  		node_off = this_node->head.right;
  
  		if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
  			befs_error(sb, "befs_btree_read() failed to read "
  				   "node at %Lu", node_off);
  			goto error_alloc;
  		}
  	}
  
  	/* how many keys into this_node is key_no */
  	cur_key = key_no - key_sum;
  
  	/* get pointers to datastructures within the node body */
  	valarray = befs_bt_valarray(this_node);
  
  	keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
  
  	befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
  
  	if (bufsize < keylen + 1) {
  		befs_error(sb, "befs_btree_read() keybuf too small (%u) "
  			   "for key of size %d", bufsize, keylen);
  		brelse(this_node->bh);
  		goto error_alloc;
  	};
  
  	strncpy(keybuf, keystart, keylen);
  	*value = fs64_to_cpu(sb, valarray[cur_key]);
  	*keysize = keylen;
  	keybuf[keylen] = '\0';
  
  	befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
  		   cur_key, keylen, keybuf, *value);
  
  	brelse(this_node->bh);
  	kfree(this_node);
  
  	befs_debug(sb, "<--- befs_btree_read()");
  
  	return BEFS_OK;
  
        error_alloc:
  	kfree(this_node);
  
        error:
  	*keysize = 0;
  	*value = 0;
  	befs_debug(sb, "<--- befs_btree_read() ERROR");
  	return BEFS_ERR;
  }
  
  /**
   * befs_btree_seekleaf - Find the first leafnode in the btree
   * @sb: Filesystem superblock
   * @ds: Datastream containing btree
   * @bt_super: Pointer to the superblock of the btree
   * @this_node: Buffer to return the leafnode in
   * @node_off: Pointer to offset of current node within datastream. Modified
   * 		by the function.
   *
   *
   * Helper function for btree traverse. Moves the current position to the 
   * start of the first leaf node.
   *
   * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
   */
  static int
  befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
  		    befs_btree_super * bt_super, befs_btree_node * this_node,
  		    befs_off_t * node_off)
  {
  
  	befs_debug(sb, "---> befs_btree_seekleaf()");
  
  	if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
  		befs_error(sb, "befs_btree_seekleaf() failed to read "
  			   "node at %Lu", *node_off);
  		goto error;
  	}
  	befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
  
  	if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
  		befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
  		return BEFS_BT_EMPTY;
  	}
  
  	while (!befs_leafnode(this_node)) {
  
  		if (this_node->head.all_key_count == 0) {
  			befs_debug(sb, "befs_btree_seekleaf() encountered "
  				   "an empty interior node: %Lu. Using Overflow "
  				   "node: %Lu", *node_off,
  				   this_node->head.overflow);
  			*node_off = this_node->head.overflow;
  		} else {
  			fs64 *valarray = befs_bt_valarray(this_node);
  			*node_off = fs64_to_cpu(sb, valarray[0]);
  		}
  		if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
  			befs_error(sb, "befs_btree_seekleaf() failed to read "
  				   "node at %Lu", *node_off);
  			goto error;
  		}
  
  		befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
  	}
  	befs_debug(sb, "Node %Lu is a leaf node", *node_off);
  
  	return BEFS_OK;
  
        error:
  	befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
  	return BEFS_ERR;
  }
  
  /**
   * befs_leafnode - Determine if the btree node is a leaf node or an 
   * interior node
   * @node: Pointer to node structure to test
   * 
   * Return 1 if leaf, 0 if interior
   */
  static int
  befs_leafnode(befs_btree_node * node)
  {
  	/* all interior nodes (and only interior nodes) have an overflow node */
  	if (node->head.overflow == befs_bt_inval)
  		return 1;
  	else
  		return 0;
  }
  
  /**
   * befs_bt_keylen_index - Finds start of keylen index in a node
   * @node: Pointer to the node structure to find the keylen index within
   *
   * Returns a pointer to the start of the key length index array
   * of the B+tree node *@node
   *
   * "The length of all the keys in the node is added to the size of the
   * header and then rounded up to a multiple of four to get the beginning
   * of the key length index" (p.88, practical filesystem design).
   *
   * Except that rounding up to 8 works, and rounding up to 4 doesn't.
   */
  static fs16 *
  befs_bt_keylen_index(befs_btree_node * node)
  {
  	const int keylen_align = 8;
  	unsigned long int off =
  	    (sizeof (befs_btree_nodehead) + node->head.all_key_length);
  	ulong tmp = off % keylen_align;
  
  	if (tmp)
  		off += keylen_align - tmp;
  
  	return (fs16 *) ((void *) node->od_node + off);
  }
  
  /**
   * befs_bt_valarray - Finds the start of value array in a node
   * @node: Pointer to the node structure to find the value array within
   *
   * Returns a pointer to the start of the value array
   * of the node pointed to by the node header
   */
  static fs64 *
  befs_bt_valarray(befs_btree_node * node)
  {
  	void *keylen_index_start = (void *) befs_bt_keylen_index(node);
  	size_t keylen_index_size = node->head.all_key_count * sizeof (fs16);
  
  	return (fs64 *) (keylen_index_start + keylen_index_size);
  }
  
  /**
   * befs_bt_keydata - Finds start of keydata array in a node
   * @node: Pointer to the node structure to find the keydata array within
   *
   * Returns a pointer to the start of the keydata array
   * of the node pointed to by the node header 
   */
  static char *
  befs_bt_keydata(befs_btree_node * node)
  {
  	return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
  }
  
  /**
   * befs_bt_get_key - returns a pointer to the start of a key
   * @sb: filesystem superblock
   * @node: node in which to look for the key
   * @index: the index of the key to get
   * @keylen: modified to be the length of the key at @index
   *
   * Returns a valid pointer into @node on success.
   * Returns NULL on failure (bad input) and sets *@keylen = 0
   */
  static char *
  befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
  		int index, u16 * keylen)
  {
  	int prev_key_end;
  	char *keystart;
  	fs16 *keylen_index;
  
  	if (index < 0 || index > node->head.all_key_count) {
  		*keylen = 0;
  		return NULL;
  	}
  
  	keystart = befs_bt_keydata(node);
  	keylen_index = befs_bt_keylen_index(node);
  
  	if (index == 0)
  		prev_key_end = 0;
  	else
  		prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
  
  	*keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
  
  	return keystart + prev_key_end;
  }
  
  /**
   * befs_compare_strings - compare two strings
   * @key1: pointer to the first key to be compared 
   * @keylen1: length in bytes of key1
   * @key2: pointer to the second key to be compared
   * @kelen2: length in bytes of key2
   *
   * Returns 0 if @key1 and @key2 are equal.
   * Returns >0 if @key1 is greater.
   * Returns <0 if @key2 is greater..
   */
  static int
  befs_compare_strings(const void *key1, int keylen1,
  		     const void *key2, int keylen2)
  {
  	int len = min_t(int, keylen1, keylen2);
  	int result = strncmp(key1, key2, len);
  	if (result == 0)
  		result = keylen1 - keylen2;
  	return result;
  }
  
  /* These will be used for non-string keyed btrees */
  #if 0
  static int
  btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
  {
  	return *(int32_t *) key1 - *(int32_t *) key2;
  }
  
  static int
  btree_compare_uint32(cont void *key1, int keylen1,
  		     const void *key2, int keylen2)
  {
  	if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
  		return 0;
  	else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
  		return 1;
  
  	return -1;
  }
  static int
  btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
  {
  	if (*(int64_t *) key1 == *(int64_t *) key2)
  		return 0;
  	else if (*(int64_t *) key1 > *(int64_t *) key2)
  		return 1;
  
  	return -1;
  }
  
  static int
  btree_compare_uint64(cont void *key1, int keylen1,
  		     const void *key2, int keylen2)
  {
  	if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
  		return 0;
  	else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
  		return 1;
  
  	return -1;
  }
  
  static int
  btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
  {
  	float result = *(float *) key1 - *(float *) key2;
  	if (result == 0.0f)
  		return 0;
  
  	return (result < 0.0f) ? -1 : 1;
  }
  
  static int
  btree_compare_double(cont void *key1, int keylen1,
  		     const void *key2, int keylen2)
  {
  	double result = *(double *) key1 - *(double *) key2;
  	if (result == 0.0)
  		return 0;
  
  	return (result < 0.0) ? -1 : 1;
  }
  #endif				//0