minivmac4ios/libhfs/node.c

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2016-05-21 13:01:57 +00:00
/*
* libhfs - library for reading and writing Macintosh HFS volumes
* Copyright (C) 1996-1998 Robert Leslie
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: node.c,v 1.9 1998/11/02 22:09:05 rob Exp $
*/
# ifdef HAVE_CONFIG_H
# include "config.h"
# endif
# include <stdlib.h>
# include <string.h>
# include <errno.h>
# include "libhfs.h"
# include "node.h"
# include "data.h"
# include "btree.h"
/* total bytes used by records (NOT including record offsets) */
# define NODEUSED(n) \
((size_t) ((n).roff[(n).nd.ndNRecs] - (n).roff[0]))
/* total bytes available for new records (INCLUDING record offsets) */
# define NODEFREE(n) \
((size_t) (HFS_BLOCKSZ - (n).roff[(n).nd.ndNRecs] - \
2 * ((n).nd.ndNRecs + 1)))
/*
* NAME: node->init()
* DESCRIPTION: construct an empty node
*/
void n_init(node *np, btree *bt, int type, int height)
{
np->bt = bt;
np->nnum = (unsigned long) -1;
np->nd.ndFLink = 0;
np->nd.ndBLink = 0;
np->nd.ndType = type;
np->nd.ndNHeight = height;
np->nd.ndNRecs = 0;
np->nd.ndResv2 = 0;
np->rnum = -1;
np->roff[0] = 0x00e;
memset(&np->data, 0, sizeof(np->data));
}
/*
* NAME: node->new()
* DESCRIPTION: allocate a new b*-tree node
*/
int n_new(node *np)
{
btree *bt = np->bt;
unsigned long num;
if (bt->hdr.bthFree == 0)
ERROR(EIO, "b*-tree full");
num = 0;
while (num < bt->hdr.bthNNodes && BMTST(bt->map, num))
++num;
if (num == bt->hdr.bthNNodes)
ERROR(EIO, "free b*-tree node not found");
np->nnum = num;
BMSET(bt->map, num);
--bt->hdr.bthFree;
bt->flags |= HFS_BT_UPDATE_HDR;
return 0;
fail:
return -1;
}
/*
* NAME: node->free()
* DESCRIPTION: deallocate and remove a b*-tree node
*/
int n_free(node *np)
{
btree *bt = np->bt;
node sib;
if (bt->hdr.bthFNode == np->nnum)
bt->hdr.bthFNode = np->nd.ndFLink;
if (bt->hdr.bthLNode == np->nnum)
bt->hdr.bthLNode = np->nd.ndBLink;
if (np->nd.ndFLink > 0)
{
if (bt_getnode(&sib, bt, np->nd.ndFLink) == -1)
goto fail;
sib.nd.ndBLink = np->nd.ndBLink;
if (bt_putnode(&sib) == -1)
goto fail;
}
if (np->nd.ndBLink > 0)
{
if (bt_getnode(&sib, bt, np->nd.ndBLink) == -1)
goto fail;
sib.nd.ndFLink = np->nd.ndFLink;
if (bt_putnode(&sib) == -1)
goto fail;
}
BMCLR(bt->map, np->nnum);
++bt->hdr.bthFree;
bt->flags |= HFS_BT_UPDATE_HDR;
return 0;
fail:
return -1;
}
/*
* NAME: compact()
* DESCRIPTION: clean up a node, removing deleted records
*/
static
void compact(node *np)
{
byte *ptr;
int offset, nrecs, i;
offset = 0x00e;
ptr = np->data + offset;
nrecs = 0;
for (i = 0; i < np->nd.ndNRecs; ++i)
{
const byte *rec;
int reclen;
rec = HFS_NODEREC(*np, i);
reclen = HFS_RECLEN(*np, i);
if (HFS_RECKEYLEN(rec) > 0)
{
np->roff[nrecs++] = offset;
offset += reclen;
if (ptr == rec)
ptr += reclen;
else
{
while (reclen--)
*ptr++ = *rec++;
}
}
}
np->roff[nrecs] = offset;
np->nd.ndNRecs = nrecs;
}
/*
* NAME: node->search()
* DESCRIPTION: locate a record in a node, or the record it should follow
*/
int n_search(node *np, const byte *pkey)
{
const btree *bt = np->bt;
byte key1[HFS_MAX_KEYLEN], key2[HFS_MAX_KEYLEN];
int i, comp = -1;
bt->keyunpack(pkey, key2);
for (i = np->nd.ndNRecs; i--; )
{
const byte *rec;
rec = HFS_NODEREC(*np, i);
if (HFS_RECKEYLEN(rec) == 0)
continue; /* deleted record */
bt->keyunpack(rec, key1);
comp = bt->keycompare(key1, key2);
if (comp <= 0)
break;
}
np->rnum = i;
return comp == 0;
}
/*
* NAME: node->index()
* DESCRIPTION: create an index record from a key and node pointer
*/
void n_index(const node *np, byte *record, unsigned int *reclen)
{
const byte *key = HFS_NODEREC(*np, 0);
if (np->bt == &np->bt->f.vol->cat)
{
/* force the key length to be 0x25 */
HFS_SETKEYLEN(record, 0x25);
memset(record + 1, 0, 0x25);
memcpy(record + 1, key + 1, HFS_RECKEYLEN(key));
}
else
memcpy(record, key, HFS_RECKEYSKIP(key));
d_putul(HFS_RECDATA(record), np->nnum);
if (reclen)
*reclen = HFS_RECKEYSKIP(record) + 4;
}
/*
* NAME: split()
* DESCRIPTION: divide a node into two and insert a record
*/
static
int split(node *left, byte *record, unsigned int *reclen)
{
btree *bt = left->bt;
node n, *right = &n, *side = 0;
int mark, i;
/* create a second node by cloning the first */
*right = *left;
if (n_new(right) == -1)
goto fail;
left->nd.ndFLink = right->nnum;
right->nd.ndBLink = left->nnum;
/* divide all records evenly between the two nodes */
mark = (NODEUSED(*left) + 2 * left->nd.ndNRecs + *reclen + 2) >> 1;
if (left->rnum == -1)
{
side = left;
mark -= *reclen + 2;
}
for (i = 0; i < left->nd.ndNRecs; ++i)
{
node *np;
byte *rec;
np = (mark > 0) ? right : left;
rec = HFS_NODEREC(*np, i);
mark -= HFS_RECLEN(*np, i) + 2;
HFS_SETKEYLEN(rec, 0);
if (left->rnum == i)
{
side = (mark > 0) ? left : right;
mark -= *reclen + 2;
}
}
compact(left);
compact(right);
/* insert the new record and store the modified nodes */
ASSERT(side);
n_search(side, record);
n_insertx(side, record, *reclen);
if (bt_putnode(left) == -1 ||
bt_putnode(right) == -1)
goto fail;
/* create an index record in the parent for the new node */
n_index(right, record, reclen);
/* update link pointers */
if (bt->hdr.bthLNode == left->nnum)
{
bt->hdr.bthLNode = right->nnum;
bt->flags |= HFS_BT_UPDATE_HDR;
}
if (right->nd.ndFLink > 0)
{
node sib;
if (bt_getnode(&sib, right->bt, right->nd.ndFLink) == -1)
goto fail;
sib.nd.ndBLink = right->nnum;
if (bt_putnode(&sib) == -1)
goto fail;
}
return 0;
fail:
return -1;
}
/*
* NAME: node->insertx()
* DESCRIPTION: insert a record into a node (which must already have room)
*/
void n_insertx(node *np, const byte *record, unsigned int reclen)
{
int rnum, i;
byte *ptr;
rnum = np->rnum + 1;
/* push other records down to make room */
for (ptr = HFS_NODEREC(*np, np->nd.ndNRecs) + reclen;
ptr > HFS_NODEREC(*np, rnum) + reclen; --ptr)
*(ptr - 1) = *(ptr - 1 - reclen);
++np->nd.ndNRecs;
for (i = np->nd.ndNRecs; i > rnum; --i)
np->roff[i] = np->roff[i - 1] + reclen;
/* write the new record */
memcpy(HFS_NODEREC(*np, rnum), record, reclen);
}
/*
* NAME: node->insert()
* DESCRIPTION: insert a new record into a node; return a record for parent
*/
int n_insert(node *np, byte *record, unsigned int *reclen)
{
/* check for free space */
if (np->nd.ndNRecs >= HFS_MAX_NRECS ||
*reclen + 2 > NODEFREE(*np))
return split(np, record, reclen);
n_insertx(np, record, *reclen);
*reclen = 0;
return bt_putnode(np);
}
/*
* NAME: join()
* DESCRIPTION: combine two nodes into a single node
*/
static
int join(node *left, node *right, byte *record, int *flag)
{
int i, offset;
/* copy records and offsets */
memcpy(HFS_NODEREC(*left, left->nd.ndNRecs),
HFS_NODEREC(*right, 0), NODEUSED(*right));
offset = left->roff[left->nd.ndNRecs] - right->roff[0];
for (i = 1; i <= right->nd.ndNRecs; ++i)
left->roff[++left->nd.ndNRecs] = offset + right->roff[i];
if (bt_putnode(left) == -1)
goto fail;
/* eliminate node and update link pointers */
if (n_free(right) == -1)
goto fail;
HFS_SETKEYLEN(record, 0);
*flag = 1;
return 0;
fail:
return -1;
}
/*
* NAME: node->delete()
* DESCRIPTION: remove a record from a node
*/
int n_delete(node *np, byte *record, int *flag)
{
byte *rec;
rec = HFS_NODEREC(*np, np->rnum);
HFS_SETKEYLEN(rec, 0);
compact(np);
if (np->nd.ndNRecs == 0)
{
if (n_free(np) == -1)
goto fail;
HFS_SETKEYLEN(record, 0);
*flag = 1;
return 0;
}
/* see if we can join with our left sibling */
if (np->nd.ndBLink > 0)
{
node left;
if (bt_getnode(&left, np->bt, np->nd.ndBLink) == -1)
goto fail;
if (np->nd.ndNRecs + left.nd.ndNRecs <= HFS_MAX_NRECS &&
NODEUSED(*np) + 2 * np->nd.ndNRecs <= NODEFREE(left))
return join(&left, np, record, flag);
}
if (np->rnum == 0)
{
/* special case: first record changed; update parent record key */
n_index(np, record, 0);
*flag = 1;
}
return bt_putnode(np);
fail:
return -1;
}