| 30 | namespace kudu { |
| 31 | |
| 32 | void BitmapChangeBits(uint8_t *bitmap, size_t offset, size_t num_bits, bool value) { |
| 33 | DCHECK_GT(num_bits, 0); |
| 34 | |
| 35 | size_t start_byte = (offset >> 3); |
| 36 | size_t end_byte = (offset + num_bits - 1) >> 3; |
| 37 | int single_byte = (start_byte == end_byte); |
| 38 | |
| 39 | // Change the last bits of the first byte |
| 40 | size_t left = offset & 0x7; |
| 41 | size_t right = (single_byte) ? (left + num_bits) : 8; |
| 42 | uint8_t mask = ((0xff << left) & (0xff >> (8 - right))); |
| 43 | if (value) { |
| 44 | bitmap[start_byte++] |= mask; |
| 45 | } else { |
| 46 | bitmap[start_byte++] &= ~mask; |
| 47 | } |
| 48 | |
| 49 | // Nothing left... I'm done |
| 50 | if (single_byte) { |
| 51 | return; |
| 52 | } |
| 53 | |
| 54 | // change the middle bits |
| 55 | if (end_byte > start_byte) { |
| 56 | const uint8_t pattern8[2] = { 0x00, 0xff }; |
| 57 | memset(bitmap + start_byte, pattern8[value], end_byte - start_byte); |
| 58 | } |
| 59 | |
| 60 | // change the first bits of the last byte |
| 61 | right = offset + num_bits - (end_byte << 3); |
| 62 | mask = (0xff >> (8 - right)); |
| 63 | if (value) { |
| 64 | bitmap[end_byte] |= mask; |
| 65 | } else { |
| 66 | bitmap[end_byte] &= ~mask; |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | bool BitmapFindFirst(const uint8_t *bitmap, size_t offset, size_t bitmap_size, |
| 71 | bool value, size_t *idx) { |