Create a from a byte array, and and an offset and length in bits
(buffer: &'a [u8], offset: usize, len: usize)
| 40 | impl<'a> UnalignedBitChunk<'a> { |
| 41 | /// Create a from a byte array, and and an offset and length in bits |
| 42 | pub fn new(buffer: &'a [u8], offset: usize, len: usize) -> Self { |
| 43 | if len == 0 { |
| 44 | return Self { |
| 45 | lead_padding: 0, |
| 46 | trailing_padding: 0, |
| 47 | prefix: None, |
| 48 | chunks: &[], |
| 49 | suffix: None, |
| 50 | }; |
| 51 | } |
| 52 | |
| 53 | let byte_offset = offset / 8; |
| 54 | let offset_padding = offset % 8; |
| 55 | |
| 56 | let bytes_len = (len + offset_padding).div_ceil(8); |
| 57 | let buffer = &buffer[byte_offset..byte_offset + bytes_len]; |
| 58 | |
| 59 | let prefix_mask = compute_prefix_mask(offset_padding); |
| 60 | |
| 61 | // If less than 8 bytes, read into prefix |
| 62 | if buffer.len() <= 8 { |
| 63 | let (suffix_mask, trailing_padding) = compute_suffix_mask(len, offset_padding); |
| 64 | let prefix = read_u64(buffer) & suffix_mask & prefix_mask; |
| 65 | |
| 66 | return Self { |
| 67 | lead_padding: offset_padding, |
| 68 | trailing_padding, |
| 69 | prefix: Some(prefix), |
| 70 | chunks: &[], |
| 71 | suffix: None, |
| 72 | }; |
| 73 | } |
| 74 | |
| 75 | // If less than 16 bytes, read into prefix and suffix |
| 76 | if buffer.len() <= 16 { |
| 77 | let (suffix_mask, trailing_padding) = compute_suffix_mask(len, offset_padding); |
| 78 | let prefix = read_u64(&buffer[..8]) & prefix_mask; |
| 79 | let suffix = read_u64(&buffer[8..]) & suffix_mask; |
| 80 | |
| 81 | return Self { |
| 82 | lead_padding: offset_padding, |
| 83 | trailing_padding, |
| 84 | prefix: Some(prefix), |
| 85 | chunks: &[], |
| 86 | suffix: Some(suffix), |
| 87 | }; |
| 88 | } |
| 89 | |
| 90 | // Read into prefix and suffix as needed |
| 91 | let (prefix, mut chunks, suffix) = unsafe { buffer.align_to::<u64>() }; |
| 92 | assert!( |
| 93 | prefix.len() < 8 && suffix.len() < 8, |
| 94 | "align_to did not return largest possible aligned slice" |
| 95 | ); |
| 96 | |
| 97 | let (alignment_padding, prefix) = match (offset_padding, prefix.is_empty()) { |
| 98 | (0, true) => (0, None), |
| 99 | (_, true) => { |
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