livefiles_cs_plugin/lf_cs_checksum.h

   1 //
   2 // Copyright (c) 2009-2019 Apple Inc. All rights reserved.
   3 //
   4 // lf_cs_checksum.h - Defines for checksum handling for livefiles
   5 //                    Apple_CoreStorage plugin.
   6 //
   7 // This header is copied from CoreStorage project.
   8 //
   9
  10 #ifndef _LF_CS_CHECKSUM_H
  11 #define _LF_CS_CHECKSUM_H
  12
  13 #include <stdint.h>
  14 #include <string.h>
  15 #include <stddef.h>
  16 #include <stdbool.h>
  17
  18 //
  19 // Checksum Algorithm
  20 //
  21 // Every metadata block has a checksum to check the data integrity.  Different
  22 // checksum algorithms can be used by CoreStorage, and [[lvg_checksum_alg]] in
  23 // [[lvg_info_t]] records what checksum algorithm to use.  For the first
  24 // prototype, I am copying the CRC algorithm from the UDF project.
  25 //
  26 // The fletcher 2 algorithm used by ZFS has fundamental flaws.  And a variation
  27 // of the fletcher 8 algorithm could be used, which is 2 times faster than
  28 // CRC32 and 4 times faster than fletcher.
  29 //
  30 // <cksum definitions>=
  31 //
  32 #define MAX_CKSUM_NBYTES 8
  33
  34 enum cksum_alg {
  35         CKSUM_NONE,
  36         CKSUM_ALG_CRC_32, // CRC-32 algorithm copied from CRC32-C polynomial
  37 };
  38 typedef enum cksum_alg cksum_alg_t;
  39
  40
  41 #define BITS_PER_BYTE 8L
  42 #define META_CKSUM_BITS (MAX_CKSUM_NBYTES * BITS_PER_BYTE)
  43
  44 //
  45 // Initialize checksum for a certain algorithm
  46 //
  47 bool cksum_init(cksum_alg_t alg, uint8_t cksum[MAX_CKSUM_NBYTES]);
  48
  49 //
  50 // cksum - Calculate checksum of data for len bytes
  51 //
  52 // Existing value of cksum is also used to calculate the checksum.  In order to
  53 // calculate cksums of different memory chunks, this function can be called
  54 // several times:
  55 //
  56 //     cksum(alg, data1, len1, cksum);
  57 //     cksum(alg, data2, len2, cksum);
  58 //
  59 // and the resultant cksum is calculated on two chunks
  60 //
  61 void cksum(cksum_alg_t alg, const void *data, size_t len,
  62                 uint8_t cksum[MAX_CKSUM_NBYTES]);
  63
  64 #endif /* _LF_CS_CHECKSUM_H */