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