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 | */ |
Peter Maydell | 1393a48 | 2016-01-26 18:16:54 +0000 | [diff] [blame] | 13 | #include "qemu/osdep.h" |
Veronia Bahaa | f348b6d | 2016-03-20 19:16:19 +0200 | [diff] [blame] | 14 | #include "qemu/cutils.h" |
Juan Quintela | 709e3fe | 2017-04-05 21:47:50 +0200 | [diff] [blame] | 15 | #include "xbzrle.h" |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 16 | |
| 17 | /* |
| 18 | page = zrun nzrun |
| 19 | | zrun nzrun page |
| 20 | |
| 21 | zrun = length |
| 22 | |
| 23 | nzrun = length byte... |
| 24 | |
| 25 | length = uleb128 encoded integer |
| 26 | */ |
| 27 | int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen, |
| 28 | uint8_t *dst, int dlen) |
| 29 | { |
| 30 | uint32_t zrun_len = 0, nzrun_len = 0; |
| 31 | int d = 0, i = 0; |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 32 | long res; |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 33 | uint8_t *nzrun_start = NULL; |
| 34 | |
| 35 | g_assert(!(((uintptr_t)old_buf | (uintptr_t)new_buf | slen) % |
| 36 | sizeof(long))); |
| 37 | |
| 38 | while (i < slen) { |
| 39 | /* overflow */ |
| 40 | if (d + 2 > dlen) { |
| 41 | return -1; |
| 42 | } |
| 43 | |
| 44 | /* not aligned to sizeof(long) */ |
| 45 | res = (slen - i) % sizeof(long); |
| 46 | while (res && old_buf[i] == new_buf[i]) { |
| 47 | zrun_len++; |
| 48 | i++; |
| 49 | res--; |
| 50 | } |
| 51 | |
| 52 | /* word at a time for speed */ |
| 53 | if (!res) { |
| 54 | while (i < slen && |
| 55 | (*(long *)(old_buf + i)) == (*(long *)(new_buf + i))) { |
| 56 | i += sizeof(long); |
| 57 | zrun_len += sizeof(long); |
| 58 | } |
| 59 | |
| 60 | /* go over the rest */ |
| 61 | while (i < slen && old_buf[i] == new_buf[i]) { |
| 62 | zrun_len++; |
| 63 | i++; |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | /* buffer unchanged */ |
| 68 | if (zrun_len == slen) { |
| 69 | return 0; |
| 70 | } |
| 71 | |
| 72 | /* skip last zero run */ |
| 73 | if (i == slen) { |
| 74 | return d; |
| 75 | } |
| 76 | |
| 77 | d += uleb128_encode_small(dst + d, zrun_len); |
| 78 | |
| 79 | zrun_len = 0; |
| 80 | nzrun_start = new_buf + i; |
| 81 | |
| 82 | /* overflow */ |
| 83 | if (d + 2 > dlen) { |
| 84 | return -1; |
| 85 | } |
| 86 | /* not aligned to sizeof(long) */ |
| 87 | res = (slen - i) % sizeof(long); |
| 88 | while (res && old_buf[i] != new_buf[i]) { |
| 89 | i++; |
| 90 | nzrun_len++; |
| 91 | res--; |
| 92 | } |
| 93 | |
| 94 | /* word at a time for speed, use of 32-bit long okay */ |
| 95 | if (!res) { |
| 96 | /* truncation to 32-bit long okay */ |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 97 | unsigned long mask = (unsigned long)0x0101010101010101ULL; |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 98 | while (i < slen) { |
Peter Maydell | 968fc24 | 2014-03-28 15:12:57 +0000 | [diff] [blame] | 99 | unsigned long xor; |
| 100 | xor = *(unsigned long *)(old_buf + i) |
| 101 | ^ *(unsigned long *)(new_buf + i); |
Orit Wasserman | ba2e28e | 2013-01-31 09:12:15 +0200 | [diff] [blame] | 102 | if ((xor - mask) & ~xor & (mask << 7)) { |
| 103 | /* found the end of an nzrun within the current long */ |
| 104 | while (old_buf[i] != new_buf[i]) { |
| 105 | nzrun_len++; |
| 106 | i++; |
| 107 | } |
| 108 | break; |
| 109 | } else { |
| 110 | i += sizeof(long); |
| 111 | nzrun_len += sizeof(long); |
| 112 | } |
| 113 | } |
| 114 | } |
| 115 | |
| 116 | d += uleb128_encode_small(dst + d, nzrun_len); |
| 117 | /* overflow */ |
| 118 | if (d + nzrun_len > dlen) { |
| 119 | return -1; |
| 120 | } |
| 121 | memcpy(dst + d, nzrun_start, nzrun_len); |
| 122 | d += nzrun_len; |
| 123 | nzrun_len = 0; |
| 124 | } |
| 125 | |
| 126 | return d; |
| 127 | } |
| 128 | |
| 129 | int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen) |
| 130 | { |
| 131 | int i = 0, d = 0; |
| 132 | int ret; |
| 133 | uint32_t count = 0; |
| 134 | |
| 135 | while (i < slen) { |
| 136 | |
| 137 | /* zrun */ |
| 138 | if ((slen - i) < 2) { |
| 139 | return -1; |
| 140 | } |
| 141 | |
| 142 | ret = uleb128_decode_small(src + i, &count); |
| 143 | if (ret < 0 || (i && !count)) { |
| 144 | return -1; |
| 145 | } |
| 146 | i += ret; |
| 147 | d += count; |
| 148 | |
| 149 | /* overflow */ |
| 150 | if (d > dlen) { |
| 151 | return -1; |
| 152 | } |
| 153 | |
| 154 | /* nzrun */ |
| 155 | if ((slen - i) < 2) { |
| 156 | return -1; |
| 157 | } |
| 158 | |
| 159 | ret = uleb128_decode_small(src + i, &count); |
| 160 | if (ret < 0 || !count) { |
| 161 | return -1; |
| 162 | } |
| 163 | i += ret; |
| 164 | |
| 165 | /* overflow */ |
| 166 | if (d + count > dlen || i + count > slen) { |
| 167 | return -1; |
| 168 | } |
| 169 | |
| 170 | memcpy(dst + d, src + i, count); |
| 171 | d += count; |
| 172 | i += count; |
| 173 | } |
| 174 | |
| 175 | return d; |
| 176 | } |