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sparse.h
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sparse.h
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/* nbdkit
* Copyright (C) 2017-2018 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of Red Hat nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef NBDKIT_SPARSE_H
#define NBDKIT_SPARSE_H
#include <config.h>
#include <stdbool.h>
/* This library implements a sparse array of any size up to 2⁶³-1
* bytes.
*
* The array reads as zeroes until something is written.
*
* The implementation aims to be reasonably efficient for ordinary
* sized disks, while permitting huge (but sparse) disks for testing.
* Everything allocated has to be stored in memory. There is no
* temporary file backing.
*
* The implementation is not protected by locks and issuing parallel
* calls will cause corruption. If your plugin uses this library you
* will probably need to use a suitable thread model such as
* SERIALIZE_ALL_REQUESTS.
*/
struct sparse_array;
/* Allocate the empty sparse array. */
struct sparse_array *alloc_sparse_array (bool debug);
/* Free sparse array. */
extern void free_sparse_array (struct sparse_array *sa);
/* Read bytes from the sparse array.
* Note this can never return an error and never allocates.
*/
extern void sparse_array_read (struct sparse_array *sa, void *buf, uint32_t count, uint64_t offset);
/* Write bytes to the sparse array.
* This can allocate and can return an error.
*/
extern int sparse_array_write (struct sparse_array *sa, const void *buf, uint32_t count, uint64_t offset);
/* Zero byte range in the sparse array.
*
* Zeroing and trimming are the same operation (this implementation
* does not preallocate, since it's not worthwhile for an in-memory
* data structure).
*
* This may free memory, but never returns an error.
*/
extern void sparse_array_zero (struct sparse_array *sa, uint32_t count, uint64_t offset);
#endif /* NBDKIT_SPARSE_H */