static void test_uleb(void) { uint32_t i, val; uint8_t buf[2]; int encode_ret, decode_ret; for (i = 0; i <= 0x3fff; i++) { encode_ret = uleb128_encode_small(&buf[0], i); decode_ret = uleb128_decode_small(&buf[0], &val); g_assert(encode_ret == decode_ret); g_assert(i == val); } /* decode invalid value */ buf[0] = 0x80; buf[1] = 0x80; decode_ret = uleb128_decode_small(&buf[0], &val); g_assert(decode_ret == -1); g_assert(val == 0); }
static void test_encode_decode_1_byte(void) { uint8_t *buffer = g_malloc0(PAGE_SIZE); uint8_t *test = g_malloc0(PAGE_SIZE); uint8_t *compressed = g_malloc(PAGE_SIZE); int dlen = 0, rc = 0; uint8_t buf[2]; test[PAGE_SIZE - 1] = 1; dlen = xbzrle_encode_buffer(buffer, test, PAGE_SIZE, compressed, PAGE_SIZE); g_assert(dlen == (uleb128_encode_small(&buf[0], 4095) + 2)); rc = xbzrle_decode_buffer(compressed, dlen, buffer, PAGE_SIZE); g_assert(rc == PAGE_SIZE); g_assert(memcmp(test, buffer, PAGE_SIZE) == 0); g_free(buffer); g_free(compressed); g_free(test); }
/* page = zrun nzrun | zrun nzrun page zrun = length nzrun = length byte... length = uleb128 encoded integer */ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen, uint8_t *dst, int dlen) { uint32_t zrun_len = 0, nzrun_len = 0; int d = 0, i = 0; long res; uint8_t *nzrun_start = NULL; g_assert(!(((uintptr_t)old_buf | (uintptr_t)new_buf | slen) % sizeof(long))); while (i < slen) { /* overflow */ if (d + 2 > dlen) { return -1; } /* not aligned to sizeof(long) */ res = (slen - i) % sizeof(long); while (res && old_buf[i] == new_buf[i]) { zrun_len++; i++; res--; } /* word at a time for speed */ if (!res) { while (i < slen && (*(long *)(old_buf + i)) == (*(long *)(new_buf + i))) { i += sizeof(long); zrun_len += sizeof(long); } /* go over the rest */ while (i < slen && old_buf[i] == new_buf[i]) { zrun_len++; i++; } } /* buffer unchanged */ if (zrun_len == slen) { return 0; } /* skip last zero run */ if (i == slen) { return d; } d += uleb128_encode_small(dst + d, zrun_len); zrun_len = 0; nzrun_start = new_buf + i; /* overflow */ if (d + 2 > dlen) { return -1; } /* not aligned to sizeof(long) */ res = (slen - i) % sizeof(long); while (res && old_buf[i] != new_buf[i]) { i++; nzrun_len++; res--; } /* word at a time for speed, use of 32-bit long okay */ if (!res) { /* truncation to 32-bit long okay */ unsigned long mask = (unsigned long)0x0101010101010101ULL; while (i < slen) { unsigned long xor; xor = *(unsigned long *)(old_buf + i) ^ *(unsigned long *)(new_buf + i); if ((xor - mask) & ~xor & (mask << 7)) { /* found the end of an nzrun within the current long */ while (old_buf[i] != new_buf[i]) { nzrun_len++; i++; } break; } else { i += sizeof(long); nzrun_len += sizeof(long); } } } d += uleb128_encode_small(dst + d, nzrun_len); /* overflow */ if (d + nzrun_len > dlen) { return -1; } memcpy(dst + d, nzrun_start, nzrun_len); d += nzrun_len; nzrun_len = 0; } return d; }