hash-utils.h

 1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * Copyright 2023 Red Hat
 4 */
 5
 6#ifndef UDS_HASH_UTILS_H
 7#define UDS_HASH_UTILS_H
 8
 9#include "numeric.h"
10
11#include "geometry.h"
12#include "indexer.h"
13
14/* Utilities for extracting portions of a request name for various uses. */
15
16/* How various portions of a record name are apportioned. */
17enum {
18	VOLUME_INDEX_BYTES_OFFSET = 0,
19	VOLUME_INDEX_BYTES_COUNT = 8,
20	CHAPTER_INDEX_BYTES_OFFSET = 8,
21	CHAPTER_INDEX_BYTES_COUNT = 6,
22	SAMPLE_BYTES_OFFSET = 14,
23	SAMPLE_BYTES_COUNT = 2,
24};
25
26static inline u64 uds_extract_chapter_index_bytes(const struct uds_record_name *name)
27{
28	const u8 *chapter_bits = &name->name[CHAPTER_INDEX_BYTES_OFFSET];
29	u64 bytes = (u64) get_unaligned_be16(chapter_bits) << 32;
30
31	bytes |= get_unaligned_be32(chapter_bits + 2);
32	return bytes;
33}
34
35static inline u64 uds_extract_volume_index_bytes(const struct uds_record_name *name)
36{
37	return get_unaligned_be64(&name->name[VOLUME_INDEX_BYTES_OFFSET]);
38}
39
40static inline u32 uds_extract_sampling_bytes(const struct uds_record_name *name)
41{
42	return get_unaligned_be16(&name->name[SAMPLE_BYTES_OFFSET]);
43}
44
45/* Compute the chapter delta list for a given name. */
46static inline u32 uds_hash_to_chapter_delta_list(const struct uds_record_name *name,
47						 const struct index_geometry *geometry)
48{
49	return ((uds_extract_chapter_index_bytes(name) >> geometry->chapter_address_bits) &
50		((1 << geometry->chapter_delta_list_bits) - 1));
51}
52
53/* Compute the chapter delta address for a given name. */
54static inline u32 uds_hash_to_chapter_delta_address(const struct uds_record_name *name,
55						    const struct index_geometry *geometry)
56{
57	return uds_extract_chapter_index_bytes(name) & ((1 << geometry->chapter_address_bits) - 1);
58}
59
60static inline unsigned int uds_name_to_hash_slot(const struct uds_record_name *name,
61						 unsigned int slot_count)
62{
63	return (unsigned int) (uds_extract_chapter_index_bytes(name) % slot_count);
64}
65
66#endif /* UDS_HASH_UTILS_H */