Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Xor Based Zero Run Length Encoding |
| 3 | * |
| 4 | * Copyright 2013 Red Hat, Inc. and/or its affiliates |
| 5 | * |
| 6 | * Authors: |
| 7 | * Orit Wasserman <owasserm@redhat.com> |
| 8 | * |
| 9 | * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| 10 | * See the COPYING file in the top-level directory. |
| 11 | * |
| 12 | */ |
| 13 | #include "qemu-common.h" |
| 14 | #include "include/migration/migration.h" |
| 15 | |
| 16 | /* |
| 17 | page = zrun nzrun |
| 18 | | zrun nzrun page |
| 19 | |
| 20 | zrun = length |
| 21 | |
| 22 | nzrun = length byte... |
| 23 | |
| 24 | length = uleb128 encoded integer |
| 25 | */ |
| 26 | int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen, |
| 27 | uint8_t *dst, int dlen) |
| 28 | { |
| 29 | uint32_t zrun_len = 0, nzrun_len = 0; |
| 30 | int d = 0, i = 0; |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 31 | long res; |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 32 | uint8_t *nzrun_start = NULL; |
| 33 | |
| 34 | g_assert(!(((uintptr_t)old_buf | (uintptr_t)new_buf | slen) % |
| 35 | sizeof(long))); |
| 36 | |
| 37 | while (i < slen) { |
| 38 | /* overflow */ |
| 39 | if (d + 2 > dlen) { |
| 40 | return -1; |
| 41 | } |
| 42 | |
| 43 | /* not aligned to sizeof(long) */ |
| 44 | res = (slen - i) % sizeof(long); |
| 45 | while (res && old_buf[i] == new_buf[i]) { |
| 46 | zrun_len++; |
| 47 | i++; |
| 48 | res--; |
| 49 | } |
| 50 | |
| 51 | /* word at a time for speed */ |
| 52 | if (!res) { |
| 53 | while (i < slen && |
| 54 | (*(long *)(old_buf + i)) == (*(long *)(new_buf + i))) { |
| 55 | i += sizeof(long); |
| 56 | zrun_len += sizeof(long); |
| 57 | } |
| 58 | |
| 59 | /* go over the rest */ |
| 60 | while (i < slen && old_buf[i] == new_buf[i]) { |
| 61 | zrun_len++; |
| 62 | i++; |
| 63 | } |
| 64 | } |
| 65 | |
| 66 | /* buffer unchanged */ |
| 67 | if (zrun_len == slen) { |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | /* skip last zero run */ |
| 72 | if (i == slen) { |
| 73 | return d; |
| 74 | } |
| 75 | |
| 76 | d += uleb128_encode_small(dst + d, zrun_len); |
| 77 | |
| 78 | zrun_len = 0; |
| 79 | nzrun_start = new_buf + i; |
| 80 | |
| 81 | /* overflow */ |
| 82 | if (d + 2 > dlen) { |
| 83 | return -1; |
| 84 | } |
| 85 | /* not aligned to sizeof(long) */ |
| 86 | res = (slen - i) % sizeof(long); |
| 87 | while (res && old_buf[i] != new_buf[i]) { |
| 88 | i++; |
| 89 | nzrun_len++; |
| 90 | res--; |
| 91 | } |
| 92 | |
| 93 | /* word at a time for speed, use of 32-bit long okay */ |
| 94 | if (!res) { |
| 95 | /* truncation to 32-bit long okay */ |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 96 | unsigned long mask = (unsigned long)0x0101010101010101ULL; |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 97 | while (i < slen) { |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 98 | unsigned long xor; |
| 99 | xor = *(unsigned long *)(old_buf + i) |
| 100 | ^ *(unsigned long *)(new_buf + i); |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 101 | if ((xor - mask) & ~xor & (mask << 7)) { |
| 102 | /* found the end of an nzrun within the current long */ |
| 103 | while (old_buf[i] != new_buf[i]) { |
| 104 | nzrun_len++; |
| 105 | i++; |
| 106 | } |
| 107 | break; |
| 108 | } else { |
| 109 | i += sizeof(long); |
| 110 | nzrun_len += sizeof(long); |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | d += uleb128_encode_small(dst + d, nzrun_len); |
| 116 | /* overflow */ |
| 117 | if (d + nzrun_len > dlen) { |
| 118 | return -1; |
| 119 | } |
| 120 | memcpy(dst + d, nzrun_start, nzrun_len); |
| 121 | d += nzrun_len; |
| 122 | nzrun_len = 0; |
| 123 | } |
| 124 | |
| 125 | return d; |
| 126 | } |
| 127 | |
| 128 | int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen) |
| 129 | { |
| 130 | int i = 0, d = 0; |
| 131 | int ret; |
| 132 | uint32_t count = 0; |
| 133 | |
| 134 | while (i < slen) { |
| 135 | |
| 136 | /* zrun */ |
| 137 | if ((slen - i) < 2) { |
| 138 | return -1; |
| 139 | } |
| 140 | |
| 141 | ret = uleb128_decode_small(src + i, &count); |
| 142 | if (ret < 0 || (i && !count)) { |
| 143 | return -1; |
| 144 | } |
| 145 | i += ret; |
| 146 | d += count; |
| 147 | |
| 148 | /* overflow */ |
| 149 | if (d > dlen) { |
| 150 | return -1; |
| 151 | } |
| 152 | |
| 153 | /* nzrun */ |
| 154 | if ((slen - i) < 2) { |
| 155 | return -1; |
| 156 | } |
| 157 | |
| 158 | ret = uleb128_decode_small(src + i, &count); |
| 159 | if (ret < 0 || !count) { |
| 160 | return -1; |
| 161 | } |
| 162 | i += ret; |
| 163 | |
| 164 | /* overflow */ |
| 165 | if (d + count > dlen || i + count > slen) { |
| 166 | return -1; |
| 167 | } |
| 168 | |
| 169 | memcpy(dst + d, src + i, count); |
| 170 | d += count; |
| 171 | i += count; |
| 172 | } |
| 173 | |
| 174 | return d; |
| 175 | } |