busybox/libbb/inode_hash.c

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) many different people.
 * If you wrote this, please acknowledge your work.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
#include "libbb.h"

typedef struct ino_dev_hash_bucket_struct {
	ino_t ino;
	dev_t dev;
	/*
	 * Above fields can be 64-bit, while pointer may be 32-bit.
	 * Putting "next" field here may reduce size of this struct:
	 */
	struct ino_dev_hash_bucket_struct *next;
	/*
	 * Reportedly, on cramfs a file and a dir can have same ino.
	 * Need to also remember "file/dir" bit:
	 */
	char isdir; /* bool */
	char name[1];
} ino_dev_hashtable_bucket_t;

#define HASH_SIZE      311u   /* Should be prime */
#define hash_inode(i)  ((unsigned)(i) % HASH_SIZE)

/* array of [HASH_SIZE] elements */
static ino_dev_hashtable_bucket_t **ino_dev_hashtable;

/*
 * Return name if statbuf->st_ino && statbuf->st_dev are recorded in
 * ino_dev_hashtable, else return NULL
 */
char* FAST_FUNC is_in_ino_dev_hashtable(const struct stat *statbuf)
{
	ino_dev_hashtable_bucket_t *bucket;

	if (!ino_dev_hashtable)
		return NULL;

	bucket = ino_dev_hashtable[hash_inode(statbuf->st_ino)];
	while (bucket != NULL) {
		if ((bucket->ino == statbuf->st_ino)
		 && (bucket->dev == statbuf->st_dev)
		 && (bucket->isdir == !!S_ISDIR(statbuf->st_mode))
		) {
			return bucket->name;
		}
		bucket = bucket->next;
	}
	return NULL;
}

/* Add statbuf to statbuf hash table */
void FAST_FUNC add_to_ino_dev_hashtable(const struct stat *statbuf, const char *name)
{
	int i;
	ino_dev_hashtable_bucket_t *bucket;

	if (!name)
		name = "";
	bucket = xmalloc(sizeof(ino_dev_hashtable_bucket_t) + strlen(name));
	bucket->ino = statbuf->st_ino;
	bucket->dev = statbuf->st_dev;
	bucket->isdir = !!S_ISDIR(statbuf->st_mode);
	strcpy(bucket->name, name);

	if (!ino_dev_hashtable)
		ino_dev_hashtable = xzalloc(HASH_SIZE * sizeof(*ino_dev_hashtable));

	i = hash_inode(statbuf->st_ino);
	bucket->next = ino_dev_hashtable[i];
	ino_dev_hashtable[i] = bucket;
}

#if ENABLE_FEATURE_CLEAN_UP
/* Clear statbuf hash table */
void FAST_FUNC reset_ino_dev_hashtable(void)
{
	int i;
	ino_dev_hashtable_bucket_t *bucket, *next;

	if (!ino_dev_hashtable)
		return;

	for (i = 0; i < HASH_SIZE; i++) {
		bucket = ino_dev_hashtable[i];

		while (bucket != NULL) {
			next = bucket->next;
			free(bucket);
			bucket = next;
		}
	}
	free(ino_dev_hashtable);
	ino_dev_hashtable = NULL;
}
#endif