osobhandClaude Opus 5.5
8196fab72a
An internal node's child pointer is an address, the child's record count and (below the first internal level) the child subtree's total record count. libhdf5 (H5B2__hdr_init) encodes the record count in the width of a leaf's maximum and the subtree total in the width of cum_max_nrec for that depth, computed level by level from the node size. The reader guessed 2 * leaf_max and leaf_max^depth, which agree at depth 2 but not at depth 3: a 24 000-link group's name index has depth 3, its root's pointers were read 3 bytes wide instead of 2, and listing failed with a garbage heap offset. Regression tests: dense_group_with_a_three_level_name_index (h5py writes 24 000 links; listing compared with h5py) and subtree_capacity_matches_libhdf5. Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
701 lines
24 KiB
Rust
701 lines
24 KiB
Rust
//! HDF5 B-tree v2 parsing.
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#[cfg(not(feature = "std"))]
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use alloc::vec::Vec;
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#[cfg(feature = "checksum")]
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use byteorder::{ByteOrder, LittleEndian};
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use crate::error::FormatError;
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/// Parsed B-tree v2 header (signature "BTHD").
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#[derive(Debug, Clone)]
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pub struct BTreeV2Header {
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/// B-tree type: 5=links indexed by name, 6=links indexed by creation order, etc.
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pub tree_type: u8,
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/// Node size in bytes.
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pub node_size: u32,
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/// Record size in bytes.
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pub record_size: u16,
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/// Depth of the tree (0 = root is a leaf).
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pub depth: u16,
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/// Address of root node.
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pub root_node_address: u64,
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/// Number of records in the root node.
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pub num_records_in_root: u16,
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/// Total number of records in all nodes.
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pub total_records: u64,
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}
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/// A single record from a B-tree v2 node.
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#[derive(Debug, Clone)]
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pub struct BTreeV2Record {
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/// Raw record bytes (record_size bytes).
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pub data: Vec<u8>,
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}
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fn read_offset(data: &[u8], pos: usize, size: u8) -> Result<u64, FormatError> {
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let s = size as usize;
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if pos.checked_add(s).is_none_or(|end| end > data.len()) {
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return Err(FormatError::UnexpectedEof {
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expected: pos.saturating_add(s),
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available: data.len(),
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});
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}
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Ok(match size {
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2 => u16::from_le_bytes([data[pos], data[pos + 1]]) as u64,
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4 => u32::from_le_bytes([data[pos], data[pos + 1], data[pos + 2], data[pos + 3]]) as u64,
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8 => u64::from_le_bytes([
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data[pos],
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data[pos + 1],
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data[pos + 2],
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data[pos + 3],
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data[pos + 4],
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data[pos + 5],
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data[pos + 6],
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data[pos + 7],
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]),
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_ => return Err(FormatError::InvalidOffsetSize(size)),
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})
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}
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fn ensure_len(data: &[u8], pos: usize, needed: usize) -> Result<(), FormatError> {
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match pos.checked_add(needed) {
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Some(end) if end <= data.len() => Ok(()),
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_ => Err(FormatError::UnexpectedEof {
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expected: pos.saturating_add(needed),
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available: data.len(),
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}),
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}
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}
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/// Compute the number of bytes needed to represent a count, using variable-width encoding.
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/// B-tree v2 uses this for the number of records fields in internal nodes.
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fn bytes_for_max_records(max_nrec: u64) -> usize {
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if max_nrec == 0 {
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return 1;
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}
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let bits = 64 - max_nrec.leading_zeros() as usize;
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bits.div_ceil(8)
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}
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/// Read a variable-width unsigned integer (1-8 bytes, LE).
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fn read_var_uint(data: &[u8], pos: usize, width: usize) -> Result<u64, FormatError> {
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ensure_len(data, pos, width)?;
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let mut val = 0u64;
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for i in 0..width {
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val |= (data[pos + i] as u64) << (i * 8);
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}
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Ok(val)
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}
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impl BTreeV2Header {
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/// Parse a B-tree v2 header at the given offset.
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pub fn parse(
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file_data: &[u8],
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offset: usize,
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offset_size: u8,
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length_size: u8,
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) -> Result<BTreeV2Header, FormatError> {
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ensure_len(file_data, offset, 4)?;
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if &file_data[offset..offset + 4] != b"BTHD" {
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return Err(FormatError::InvalidBTreeV2Signature);
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}
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ensure_len(file_data, offset, 4 + 1 + 1 + 4 + 2 + 2 + 1 + 1)?;
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let version = file_data[offset + 4];
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if version != 0 {
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return Err(FormatError::InvalidBTreeV2Version(version));
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}
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let tree_type = file_data[offset + 5];
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let node_size = u32::from_le_bytes([
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file_data[offset + 6],
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file_data[offset + 7],
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file_data[offset + 8],
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file_data[offset + 9],
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]);
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let record_size = u16::from_le_bytes([file_data[offset + 10], file_data[offset + 11]]);
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let depth = u16::from_le_bytes([file_data[offset + 12], file_data[offset + 13]]);
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let _split_percent = file_data[offset + 14];
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let _merge_percent = file_data[offset + 15];
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let mut pos = offset + 16;
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let root_node_address = read_offset(file_data, pos, offset_size)?;
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pos += offset_size as usize;
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ensure_len(file_data, pos, 2)?;
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let num_records_in_root = u16::from_le_bytes([file_data[pos], file_data[pos + 1]]);
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pos += 2;
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let total_records = read_offset(file_data, pos, length_size)?;
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#[allow(unused_assignments)]
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{
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pos += length_size as usize;
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}
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// Validate header checksum
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#[cfg(feature = "checksum")]
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{
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ensure_len(file_data, pos, 4)?;
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let stored = LittleEndian::read_u32(&file_data[pos..pos + 4]);
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let computed = crate::checksum::jenkins_lookup3(&file_data[offset..pos]);
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if computed != stored {
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return Err(FormatError::ChecksumMismatch {
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expected: stored,
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computed,
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});
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}
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}
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Ok(BTreeV2Header {
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tree_type,
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node_size,
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record_size,
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depth,
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root_node_address,
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num_records_in_root,
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total_records,
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})
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}
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}
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/// Compute maximum records per node for a given depth level.
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/// leaf: (node_size - overhead) / record_size
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/// internal: depends on pointers
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fn max_records_leaf(node_size: u32, record_size: u16) -> u64 {
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// Leaf overhead: signature(4) + version(1) + type(1) + checksum(4) = 10
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let overhead = 10u32;
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if node_size <= overhead || record_size == 0 {
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return 0;
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}
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((node_size - overhead) / record_size as u32) as u64
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}
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/// Deepest B-tree v2 accepted. See [`collect_btree_v2_records`].
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const MAX_DEPTH: u16 = 64;
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/// Take `n` records from the traversal's budget, or refuse the tree.
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fn spend(budget: &mut usize, n: usize) -> Result<(), FormatError> {
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*budget = budget
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.checked_sub(n)
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.ok_or(FormatError::NestingDepthExceeded)?;
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Ok(())
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}
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/// Collect all records from a B-tree v2 by traversing from the root.
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pub fn collect_btree_v2_records(
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file_data: &[u8],
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header: &BTreeV2Header,
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offset_size: u8,
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length_size: u8,
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) -> Result<Vec<BTreeV2Record>, FormatError> {
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if header.total_records == 0 || header.num_records_in_root == 0 {
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return Ok(Vec::new());
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}
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// Recursion is one frame per level, and the depth is read from the file:
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// a crafted header claiming 65 535 levels over a node that is its own
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// child overflowed the stack. 64 matches the fractal heap's guard, and no
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// real tree comes close — even at the minimum fan-out of two it would
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// hold more than 2^64 records.
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if header.depth > MAX_DEPTH {
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return Err(FormatError::NestingDepthExceeded);
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}
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// A valid tree stores each record once, in its own bytes, so it cannot
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// hold more records than the file has room for. Children are addresses,
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// though, and nothing makes them distinct: levels whose children all
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// point at one shared node below reach it fan-out^depth times, which is
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// millions of records from a few kilobytes. Counting against what the
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// file could physically contain bounds that without trusting the
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// header's own `total_records`.
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let mut budget = file_data.len() / usize::from(header.record_size.max(1));
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let max_leaf_nrec = max_records_leaf(header.node_size, header.record_size);
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if header.depth == 0 {
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// Root is a leaf
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parse_leaf_records(
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file_data,
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header.root_node_address as usize,
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header.num_records_in_root,
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header.record_size,
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)
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} else {
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// Root is internal; traverse recursively
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let mut records = Vec::new();
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collect_internal_records(
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file_data,
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header.root_node_address as usize,
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header.num_records_in_root,
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header.depth,
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header.record_size,
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header.node_size,
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offset_size,
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length_size,
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max_leaf_nrec,
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&mut budget,
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&mut records,
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)?;
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Ok(records)
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}
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}
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/// Parse records from a leaf node (signature "BTLF").
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fn parse_leaf_records(
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file_data: &[u8],
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offset: usize,
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num_records: u16,
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record_size: u16,
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) -> Result<Vec<BTreeV2Record>, FormatError> {
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// signature(4) + version(1) + type(1) = 6 bytes header
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ensure_len(file_data, offset, 6)?;
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if &file_data[offset..offset + 4] != b"BTLF" {
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return Err(FormatError::InvalidBTreeV2Signature);
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}
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let pos = offset + 6;
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let rs = record_size as usize;
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let total = (num_records as usize)
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.checked_mul(rs)
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.ok_or(FormatError::UnexpectedEof {
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expected: usize::MAX,
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available: file_data.len(),
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})?;
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ensure_len(file_data, pos, total)?;
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// Validate checksum: 4 bytes after records + padding
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#[cfg(feature = "checksum")]
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{
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let checksum_pos = pos + total;
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if file_data.len() >= checksum_pos + 4 {
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let stored = LittleEndian::read_u32(&file_data[checksum_pos..checksum_pos + 4]);
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let computed = crate::checksum::jenkins_lookup3(&file_data[offset..checksum_pos]);
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if computed != stored {
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return Err(FormatError::ChecksumMismatch {
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expected: stored,
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computed,
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});
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}
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}
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}
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let mut records = Vec::with_capacity(num_records as usize);
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for i in 0..num_records as usize {
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let start = pos + i * rs;
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records.push(BTreeV2Record {
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data: file_data[start..start + rs].to_vec(),
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});
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}
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Ok(records)
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}
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/// Recursively collect records from an internal node.
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#[allow(clippy::too_many_arguments, clippy::only_used_in_recursion)]
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fn collect_internal_records(
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file_data: &[u8],
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offset: usize,
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num_records: u16,
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depth: u16,
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record_size: u16,
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node_size: u32,
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offset_size: u8,
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length_size: u8,
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max_leaf_nrec: u64,
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budget: &mut usize,
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out: &mut Vec<BTreeV2Record>,
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) -> Result<(), FormatError> {
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// signature(4) + version(1) + type(1) = 6
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ensure_len(file_data, offset, 6)?;
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if &file_data[offset..offset + 4] != b"BTIN" {
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return Err(FormatError::InvalidBTreeV2Signature);
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}
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let nr = num_records as usize;
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let rs = record_size as usize;
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let mut pos = offset + 6;
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// Read all records first
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let records_total = nr.checked_mul(rs).ok_or(FormatError::UnexpectedEof {
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expected: usize::MAX,
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available: file_data.len(),
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})?;
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ensure_len(file_data, pos, records_total)?;
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let records_start = pos;
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pos += records_total;
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// Child pointer layout, as libhdf5 computes it (H5B2__hdr_init): the
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// child's record count is always encoded in the width needed for a
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// *leaf's* maximum, and — below the first internal level — the child
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// subtree's total record count in the width needed for the most records
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// a subtree of that depth can hold.
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let child_depth = depth - 1;
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let nrec_width = bytes_for_max_records(max_leaf_nrec);
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let total_nrec_width = if depth > 1 {
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bytes_for_max_records(cum_max_records(
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node_size,
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record_size,
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offset_size,
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max_leaf_nrec,
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child_depth,
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))
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} else {
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0
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};
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let num_children = nr + 1;
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let child_ptr_size = offset_size as usize + nrec_width + total_nrec_width;
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ensure_len(file_data, pos, num_children * child_ptr_size)?;
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// Read child pointers
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let mut children = Vec::with_capacity(num_children);
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for _ in 0..num_children {
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let addr = read_offset(file_data, pos, offset_size)?;
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pos += offset_size as usize;
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let child_nrec = read_var_uint(file_data, pos, nrec_width)? as u16;
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pos += nrec_width;
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pos += total_nrec_width; // skip total records in subtree
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children.push((addr, child_nrec));
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}
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// Interleave: child[0], record[0], child[1], record[1], ..., child[nr]
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// We collect child[0] records, then record[0], then child[1], etc.
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for (i, &(child_addr, child_nrec)) in children.iter().enumerate() {
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if child_depth == 0 {
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// Before parsing, so a refused tree is not also a large allocation.
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spend(budget, usize::from(child_nrec))?;
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let leaf_recs =
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parse_leaf_records(file_data, child_addr as usize, child_nrec, record_size)?;
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out.extend(leaf_recs);
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} else {
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collect_internal_records(
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file_data,
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child_addr as usize,
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child_nrec,
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child_depth,
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record_size,
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node_size,
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offset_size,
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length_size,
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max_leaf_nrec,
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budget,
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out,
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)?;
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}
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// Add record[i] (except after the last child)
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if i < nr {
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let rec_offset = i.checked_mul(rs).ok_or(FormatError::UnexpectedEof {
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expected: usize::MAX,
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available: file_data.len(),
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})?;
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let rec_start =
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records_start
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.checked_add(rec_offset)
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.ok_or(FormatError::UnexpectedEof {
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expected: usize::MAX,
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available: file_data.len(),
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})?;
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let rec_end = rec_start
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.checked_add(rs)
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.ok_or(FormatError::UnexpectedEof {
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expected: usize::MAX,
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available: file_data.len(),
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})?;
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if rec_end > file_data.len() {
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return Err(FormatError::UnexpectedEof {
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expected: rec_end,
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available: file_data.len(),
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});
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}
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spend(budget, 1)?;
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out.push(BTreeV2Record {
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data: file_data[rec_start..rec_end].to_vec(),
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});
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}
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}
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Ok(())
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}
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/// Most records a subtree whose root is at `depth` can hold (libhdf5's
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/// `cum_max_nrec`): a leaf holds `max_leaf_nrec`; an internal node at depth
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/// `d` holds `max_nrec(d)` records and `max_nrec(d) + 1` subtrees of depth
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/// `d - 1`, where `max_nrec(d)` is what fits in a node once each record is
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/// paired with a child pointer of the width depth `d` needs.
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fn cum_max_records(
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node_size: u32,
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record_size: u16,
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offset_size: u8,
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max_leaf_nrec: u64,
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depth: u16,
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) -> u64 {
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// Internal node overhead: signature(4) + version(1) + type(1) + checksum(4).
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const PREFIX: u64 = 10;
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let nrec_width = bytes_for_max_records(max_leaf_nrec) as u64;
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let mut cum = max_leaf_nrec;
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let mut cum_width = 0u64;
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for d in 1..=depth {
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let ptr = u64::from(offset_size) + nrec_width + if d > 1 { cum_width } else { 0 };
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let max_nrec = u64::from(node_size)
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.saturating_sub(PREFIX)
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.saturating_sub(ptr)
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/ (u64::from(record_size) + ptr).max(1);
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cum = max_nrec
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.saturating_add(1)
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.saturating_mul(cum)
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.saturating_add(max_nrec);
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cum_width = bytes_for_max_records(cum) as u64;
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}
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cum
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[allow(clippy::too_many_arguments)]
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fn build_btree_v2_header(
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tree_type: u8,
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node_size: u32,
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record_size: u16,
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depth: u16,
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root_addr: u64,
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num_records_root: u16,
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total_records: u64,
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offset_size: u8,
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length_size: u8,
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) -> Vec<u8> {
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let mut buf = Vec::new();
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buf.extend_from_slice(b"BTHD");
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buf.push(0); // version
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buf.push(tree_type);
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buf.extend_from_slice(&node_size.to_le_bytes());
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buf.extend_from_slice(&record_size.to_le_bytes());
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buf.extend_from_slice(&depth.to_le_bytes());
|
|
buf.push(85); // split_percent
|
|
buf.push(40); // merge_percent
|
|
match offset_size {
|
|
4 => buf.extend_from_slice(&(root_addr as u32).to_le_bytes()),
|
|
8 => buf.extend_from_slice(&root_addr.to_le_bytes()),
|
|
_ => {}
|
|
}
|
|
buf.extend_from_slice(&num_records_root.to_le_bytes());
|
|
match length_size {
|
|
4 => buf.extend_from_slice(&(total_records as u32).to_le_bytes()),
|
|
8 => buf.extend_from_slice(&total_records.to_le_bytes()),
|
|
_ => {}
|
|
}
|
|
let checksum = crate::checksum::jenkins_lookup3(&buf);
|
|
buf.extend_from_slice(&checksum.to_le_bytes());
|
|
buf
|
|
}
|
|
|
|
fn build_leaf_node(tree_type: u8, records: &[&[u8]]) -> Vec<u8> {
|
|
let mut buf = Vec::new();
|
|
buf.extend_from_slice(b"BTLF");
|
|
buf.push(0); // version
|
|
buf.push(tree_type);
|
|
for rec in records {
|
|
buf.extend_from_slice(rec);
|
|
}
|
|
let checksum = crate::checksum::jenkins_lookup3(&buf);
|
|
buf.extend_from_slice(&checksum.to_le_bytes());
|
|
buf
|
|
}
|
|
|
|
/// An internal node laid out exactly as `collect_internal_records` will
|
|
/// read it at `depth`: `records` zeroed records, then `children` pointers,
|
|
/// all to `child_addr` claiming `child_nrec` records.
|
|
fn internal_node(
|
|
depth: u16,
|
|
node_size: u32,
|
|
record_size: u16,
|
|
records: usize,
|
|
children: usize,
|
|
child_addr: u64,
|
|
child_nrec: u64,
|
|
) -> Vec<u8> {
|
|
let max_leaf = max_records_leaf(node_size, record_size);
|
|
let nrec_width = bytes_for_max_records(max_leaf);
|
|
let total_width = if depth > 1 {
|
|
bytes_for_max_records(cum_max_records(
|
|
node_size,
|
|
record_size,
|
|
8,
|
|
max_leaf,
|
|
depth - 1,
|
|
))
|
|
} else {
|
|
0
|
|
};
|
|
let mut buf = b"BTIN".to_vec();
|
|
buf.extend_from_slice(&[0, 5]);
|
|
buf.resize(buf.len() + records * record_size as usize, 0);
|
|
for _ in 0..children {
|
|
buf.extend_from_slice(&child_addr.to_le_bytes());
|
|
buf.extend_from_slice(&child_nrec.to_le_bytes()[..nrec_width]);
|
|
buf.resize(buf.len() + total_width, 0);
|
|
}
|
|
buf
|
|
}
|
|
|
|
fn header(depth: u16, root: u64, root_nrec: u16, total: u64) -> BTreeV2Header {
|
|
BTreeV2Header {
|
|
tree_type: 5,
|
|
node_size: 512,
|
|
record_size: 8,
|
|
depth,
|
|
root_node_address: root,
|
|
num_records_in_root: root_nrec,
|
|
total_records: total,
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn a_node_that_is_its_own_child_is_rejected_not_recursed() {
|
|
// One internal node whose two children are itself, under a header
|
|
// claiming the deepest tree a u16 allows. The layout stops depending
|
|
// on depth once the subtree-total width saturates, so every level
|
|
// parses cleanly and recursion runs ~65 000 frames deep: before the
|
|
// cap this overflowed the stack and aborted the process, from a file
|
|
// of under 100 bytes.
|
|
let mut data = internal_node(u16::MAX, 512, 8, 1, 2, 0, 1);
|
|
data.resize(4096, 0);
|
|
let result = collect_btree_v2_records(&data, &header(u16::MAX, 0, 1, 1), 8, 8);
|
|
assert!(result.is_err(), "{result:?}");
|
|
}
|
|
|
|
#[test]
|
|
fn a_shared_subtree_cannot_multiply_the_work() {
|
|
// A chain of distinct levels, each node's children all pointing at the
|
|
// single node below, ending in a real leaf. Every node parses and
|
|
// nothing is cyclic, yet the leaf is reached fan-out^depth times: 62
|
|
// children over 4 levels is ~15 million leaf visits from a few
|
|
// kilobytes. A valid tree cannot hold more records than the file has
|
|
// room for, so that bounds the traversal instead.
|
|
let (node_size, record_size) = (512u32, 8u16);
|
|
let fanout = 62usize;
|
|
let depth = 4u16;
|
|
let leaf = build_leaf_node(5, &[&[0u8; 8][..]]);
|
|
|
|
// Lay out root first, then each lower level, then the leaf.
|
|
let mut nodes: Vec<Vec<u8>> = Vec::new();
|
|
let mut addrs = Vec::new();
|
|
let mut at = 0u64;
|
|
let mut sizes = Vec::new();
|
|
for d in (1..=depth).rev() {
|
|
let n = internal_node(d, node_size, record_size, fanout - 1, fanout, 0, 0);
|
|
sizes.push(n.len());
|
|
}
|
|
for size in &sizes {
|
|
addrs.push(at);
|
|
at += *size as u64;
|
|
}
|
|
let leaf_addr = at;
|
|
for (i, d) in (1..=depth).rev().enumerate() {
|
|
let (child, child_nrec) = if d == 1 {
|
|
(leaf_addr, 1)
|
|
} else {
|
|
(addrs[i + 1], fanout as u64 - 1)
|
|
};
|
|
nodes.push(internal_node(
|
|
d,
|
|
node_size,
|
|
record_size,
|
|
fanout - 1,
|
|
fanout,
|
|
child,
|
|
child_nrec,
|
|
));
|
|
}
|
|
let mut data: Vec<u8> = nodes.concat();
|
|
data.extend_from_slice(&leaf);
|
|
data.resize(data.len() + 64, 0);
|
|
|
|
let started = std::time::Instant::now();
|
|
let result =
|
|
collect_btree_v2_records(&data, &header(depth, 0, fanout as u16 - 1, u64::MAX), 8, 8);
|
|
assert!(
|
|
result.is_err(),
|
|
"expected a refusal, got {} records",
|
|
result.map_or(0, |r| r.len())
|
|
);
|
|
assert!(
|
|
started.elapsed() < std::time::Duration::from_secs(2),
|
|
"took {:?}",
|
|
started.elapsed()
|
|
);
|
|
}
|
|
|
|
#[test]
|
|
fn parse_header() {
|
|
let data = build_btree_v2_header(5, 512, 11, 0, 0x1000, 3, 3, 8, 8);
|
|
let hdr = BTreeV2Header::parse(&data, 0, 8, 8).unwrap();
|
|
assert_eq!(hdr.tree_type, 5);
|
|
assert_eq!(hdr.node_size, 512);
|
|
assert_eq!(hdr.record_size, 11);
|
|
assert_eq!(hdr.depth, 0);
|
|
assert_eq!(hdr.root_node_address, 0x1000);
|
|
assert_eq!(hdr.num_records_in_root, 3);
|
|
assert_eq!(hdr.total_records, 3);
|
|
}
|
|
|
|
#[test]
|
|
fn parse_leaf_with_2_records() {
|
|
let rec1 = [1u8, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
|
|
let rec2 = [11u8, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21];
|
|
let leaf = build_leaf_node(5, &[&rec1, &rec2]);
|
|
|
|
let leaf_offset = 256usize;
|
|
let header = build_btree_v2_header(5, 512, 11, 0, leaf_offset as u64, 2, 2, 8, 8);
|
|
|
|
let mut file_data = vec![0u8; 512];
|
|
file_data[..header.len()].copy_from_slice(&header);
|
|
file_data[leaf_offset..leaf_offset + leaf.len()].copy_from_slice(&leaf);
|
|
|
|
let hdr = BTreeV2Header::parse(&file_data, 0, 8, 8).unwrap();
|
|
let records = collect_btree_v2_records(&file_data, &hdr, 8, 8).unwrap();
|
|
assert_eq!(records.len(), 2);
|
|
assert_eq!(records[0].data, rec1.to_vec());
|
|
assert_eq!(records[1].data, rec2.to_vec());
|
|
}
|
|
|
|
#[test]
|
|
fn invalid_signature() {
|
|
let mut data = build_btree_v2_header(5, 512, 11, 0, 0, 0, 0, 8, 8);
|
|
data[0] = b'X';
|
|
let err = BTreeV2Header::parse(&data, 0, 8, 8).unwrap_err();
|
|
assert_eq!(err, FormatError::InvalidBTreeV2Signature);
|
|
}
|
|
|
|
#[test]
|
|
fn invalid_version() {
|
|
let mut data = build_btree_v2_header(5, 512, 11, 0, 0, 0, 0, 8, 8);
|
|
data[4] = 1; // bad version
|
|
let err = BTreeV2Header::parse(&data, 0, 8, 8).unwrap_err();
|
|
assert_eq!(err, FormatError::InvalidBTreeV2Version(1));
|
|
}
|
|
|
|
#[test]
|
|
fn empty_tree() {
|
|
let header = build_btree_v2_header(5, 512, 11, 0, 0, 0, 0, 8, 8);
|
|
let hdr = BTreeV2Header::parse(&header, 0, 8, 8).unwrap();
|
|
let records = collect_btree_v2_records(&header, &hdr, 8, 8).unwrap();
|
|
assert!(records.is_empty());
|
|
}
|
|
|
|
#[test]
|
|
fn subtree_capacity_matches_libhdf5() {
|
|
// A link-name index (11-byte records, 512-byte nodes, 8-byte
|
|
// addresses): libhdf5's H5B2__hdr_init gives 45 records per leaf,
|
|
// then cum_max_nrec 1 149 at depth 1 and 26 449 at depth 2 — two
|
|
// bytes of subtree count in a depth-3 root's child pointers, where
|
|
// leaf_max^3 = 91 125 would need three.
|
|
let leaf = max_records_leaf(512, 11);
|
|
assert_eq!(leaf, 45);
|
|
assert_eq!(cum_max_records(512, 11, 8, leaf, 0), 45);
|
|
assert_eq!(cum_max_records(512, 11, 8, leaf, 1), 1_149);
|
|
assert_eq!(cum_max_records(512, 11, 8, leaf, 2), 26_449);
|
|
}
|
|
}
|