Build an index for the msgpack map at `offset` in `buf`. Scans all map keys once and records value byte ranges. Returns `None` if `buf` is not a valid map at `offset`.
(buf: &[u8], offset: usize)
| 32 | /// Scans all map keys once and records value byte ranges. |
| 33 | /// Returns `None` if `buf` is not a valid map at `offset`. |
| 34 | pub fn build(buf: &[u8], offset: usize) -> Option<Self> { |
| 35 | let (count, mut pos) = map_header(buf, offset)?; |
| 36 | |
| 37 | if count <= HASH_THRESHOLD { |
| 38 | let mut entries = Vec::with_capacity(count); |
| 39 | for _ in 0..count { |
| 40 | let key_str = if let Some((start, len)) = str_bounds(buf, pos) { |
| 41 | std::str::from_utf8(buf.get(start..start + len)?).ok() |
| 42 | } else { |
| 43 | None |
| 44 | }; |
| 45 | pos = skip_value(buf, pos)?; |
| 46 | let value_start = pos; |
| 47 | let value_end = skip_value(buf, pos)?; |
| 48 | if let Some(key) = key_str { |
| 49 | entries.push((key.into(), value_start, value_end)); |
| 50 | } |
| 51 | pos = value_end; |
| 52 | } |
| 53 | Some(Self { |
| 54 | inner: IndexInner::Flat(entries), |
| 55 | }) |
| 56 | } else { |
| 57 | // Cap pre-allocation: adversarial buffers may claim enormous counts. |
| 58 | // Actual insertions are bounded by the buffer size, so over-allocating |
| 59 | // wastes memory and under-allocating just triggers rehashing. |
| 60 | let cap = count.min(buf.len() / 2 + 1); |
| 61 | let mut offsets = std::collections::HashMap::with_capacity(cap); |
| 62 | for _ in 0..count { |
| 63 | let key_str = if let Some((start, len)) = str_bounds(buf, pos) { |
| 64 | std::str::from_utf8(buf.get(start..start + len)?).ok() |
| 65 | } else { |
| 66 | None |
| 67 | }; |
| 68 | pos = skip_value(buf, pos)?; |
| 69 | let value_start = pos; |
| 70 | let value_end = skip_value(buf, pos)?; |
| 71 | if let Some(key) = key_str { |
| 72 | offsets.insert(key.into(), (value_start, value_end)); |
| 73 | } |
| 74 | pos = value_end; |
| 75 | } |
| 76 | Some(Self { |
| 77 | inner: IndexInner::Map(offsets), |
| 78 | }) |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | /// Create an empty index (no fields). |
| 83 | pub fn empty() -> Self { |
nothing calls this directly
no test coverage detected