bfind.c

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/*
 *  linux/fs/hfs/bfind.c
 *
 * Copyright (C) 2001
 * Brad Boyer ([email protected])
 * (C) 2003 Ardis Technologies <[email protected]>
 *
 * Search routines for btrees
 */

#include <linux/slab.h>
#include "btree.h"

int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
{
    void *ptr;

    fd->tree = tree;
    fd->bnode = NULL;
    ptr = kmalloc(tree->max_key_len * 2 + 4, GFP_KERNEL);
    if (!ptr)
        return -ENOMEM;
    fd->search_key = ptr;
    fd->key = ptr + tree->max_key_len + 2;
    dprint(DBG_BNODE_REFS, "find_init: %d (%p)\n", tree->cnid, __builtin_return_address(0));
    mutex_lock(&tree->tree_lock);
    return 0;
}

void hfs_find_exit(struct hfs_find_data *fd)
{
    hfs_bnode_put(fd->bnode);
    kfree(fd->search_key);
    dprint(DBG_BNODE_REFS, "find_exit: %d (%p)\n", fd->tree->cnid, __builtin_return_address(0));
    mutex_unlock(&fd->tree->tree_lock);
    fd->tree = NULL;
}

/* Find the record in bnode that best matches key (not greater than...)*/
int __hfs_brec_find(struct hfs_bnode *bnode, struct hfs_find_data *fd)
{
    int cmpval;
    u16 off, len, keylen;
    int rec;
    int b, e;
    int res;

    b = 0;
    e = bnode->num_recs - 1;
    res = -ENOENT;
    do {
        rec = (e + b) / 2;
        len = hfs_brec_lenoff(bnode, rec, &off);
        keylen = hfs_brec_keylen(bnode, rec);
        if (keylen == 0) {
            res = -EINVAL;
            goto fail;
        }
        hfs_bnode_read(bnode, fd->key, off, keylen);
        cmpval = bnode->tree->keycmp(fd->key, fd->search_key);
        if (!cmpval) {
            e = rec;
            res = 0;
            goto done;
        }
        if (cmpval < 0)
            b = rec + 1;
        else
            e = rec - 1;
    } while (b <= e);
    if (rec != e && e >= 0) {
        len = hfs_brec_lenoff(bnode, e, &off);
        keylen = hfs_brec_keylen(bnode, e);
        if (keylen == 0) {
            res = -EINVAL;
            goto fail;
        }
        hfs_bnode_read(bnode, fd->key, off, keylen);
    }
done:
    fd->record = e;
    fd->keyoffset = off;
    fd->keylength = keylen;
    fd->entryoffset = off + keylen;
    fd->entrylength = len - keylen;
fail:
    return res;
}

/* Traverse a B*Tree from the root to a leaf finding best fit to key */
/* Return allocated copy of node found, set recnum to best record */
int hfs_brec_find(struct hfs_find_data *fd)
{
    struct hfs_btree *tree;
    struct hfs_bnode *bnode;
    u32 nidx, parent;
    __be32 data;
    int height, res;

    tree = fd->tree;
    if (fd->bnode)
        hfs_bnode_put(fd->bnode);
    fd->bnode = NULL;
    nidx = tree->root;
    if (!nidx)
        return -ENOENT;
    height = tree->depth;
    res = 0;
    parent = 0;
    for (;;) {
        bnode = hfs_bnode_find(tree, nidx);
        if (IS_ERR(bnode)) {
            res = PTR_ERR(bnode);
            bnode = NULL;
            break;
        }
        if (bnode->height != height)
            goto invalid;
        if (bnode->type != (--height ? HFS_NODE_INDEX : HFS_NODE_LEAF))
            goto invalid;
        bnode->parent = parent;

        res = __hfs_brec_find(bnode, fd);
        if (!height)
            break;
        if (fd->record < 0)
            goto release;

        parent = nidx;
        hfs_bnode_read(bnode, &data, fd->entryoffset, 4);
        nidx = be32_to_cpu(data);
        hfs_bnode_put(bnode);
    }
    fd->bnode = bnode;
    return res;

invalid:
    printk(KERN_ERR "hfs: inconsistency in B*Tree (%d,%d,%d,%u,%u)\n",
        height, bnode->height, bnode->type, nidx, parent);
    res = -EIO;
release:
    hfs_bnode_put(bnode);
    return res;
}

int hfs_brec_read(struct hfs_find_data *fd, void *rec, int rec_len)
{
    int res;

    res = hfs_brec_find(fd);
    if (res)
        return res;
    if (fd->entrylength > rec_len)
        return -EINVAL;
    hfs_bnode_read(fd->bnode, rec, fd->entryoffset, fd->entrylength);
    return 0;
}

int hfs_brec_goto(struct hfs_find_data *fd, int cnt)
{
    struct hfs_btree *tree;
    struct hfs_bnode *bnode;
    int idx, res = 0;
    u16 off, len, keylen;

    bnode = fd->bnode;
    tree = bnode->tree;

    if (cnt < 0) {
        cnt = -cnt;
        while (cnt > fd->record) {
            cnt -= fd->record + 1;
            fd->record = bnode->num_recs - 1;
            idx = bnode->prev;
            if (!idx) {
                res = -ENOENT;
                goto out;
            }
            hfs_bnode_put(bnode);
            bnode = hfs_bnode_find(tree, idx);
            if (IS_ERR(bnode)) {
                res = PTR_ERR(bnode);
                bnode = NULL;
                goto out;
            }
        }
        fd->record -= cnt;
    } else {
        while (cnt >= bnode->num_recs - fd->record) {
            cnt -= bnode->num_recs - fd->record;
            fd->record = 0;
            idx = bnode->next;
            if (!idx) {
                res = -ENOENT;
                goto out;
            }
            hfs_bnode_put(bnode);
            bnode = hfs_bnode_find(tree, idx);
            if (IS_ERR(bnode)) {
                res = PTR_ERR(bnode);
                bnode = NULL;
                goto out;
            }
        }
        fd->record += cnt;
    }

    len = hfs_brec_lenoff(bnode, fd->record, &off);
    keylen = hfs_brec_keylen(bnode, fd->record);
    if (keylen == 0) {
        res = -EINVAL;
        goto out;
    }
    fd->keyoffset = off;
    fd->keylength = keylen;
    fd->entryoffset = off + keylen;
    fd->entrylength = len - keylen;
    hfs_bnode_read(bnode, fd->key, off, keylen);
out:
    fd->bnode = bnode;
    return res;
}