Module hash 

Structs

CheckOptions

Options for check mode.

CheckResult

Result of check mode verification.

Enums

HashAlgorithm

Supported hash algorithms.

Functions

blake2b_hash_data

Hash raw data with BLAKE2b variable output length. output_bytes is the output size in bytes (e.g., 32 for 256-bit).

blake2b_hash_file

Hash a file with BLAKE2b variable output length. Single open + fstat. Uses read() for small files, streaming read+hash for large.

blake2b_hash_reader

Hash a reader with BLAKE2b variable output length. Uses thread-local 1MB buffer for cache-friendly streaming.

blake2b_hash_stdin

Hash stdin with BLAKE2b variable output length. Tries fadvise if stdin is a regular file (shell redirect), then streams.

check_file

Verify checksums from a check file. Each line should be “hash filename” or “hash *filename” or “ALGO (filename) = hash”.

estimate_total_size

Estimate total file size for parallel/sequential decision. Uses a quick heuristic: samples first file and extrapolates. Returns 0 if estimation fails.

hash_bytes

Compute hash of a byte slice directly (zero-copy fast path).

hash_file

Hash a file by path. Single open + fstat to minimize syscalls. Uses read() for small files, streaming read+hash for large files. Replaced mmap with read()+fadvise for better cache behavior: read() keeps data hot in L2/L3 cache, while mmap suffers page table and TLB overhead for sequential single-pass workloads.

hash_reader

Compute hash of data from a reader, returning hex string.

hash_stdin

Hash stdin. Uses fadvise for file redirects, streaming for pipes.

parse_check_line

Parse a checksum line in any supported format.

parse_check_line_tag

Parse a BSD-style tag line: “ALGO (filename) = hash” Returns (expected_hash, filename, optional_bits). bits is the hash length parsed from the algo name (e.g., BLAKE2b-256 -> Some(256)).

print_hash

Print hash result in GNU format: “hash filename\n”

print_hash_tag

Print hash result in BSD tag format: “ALGO (filename) = hash\n”

print_hash_tag_b2sum

Print hash in BSD tag format with BLAKE2b length info: “BLAKE2b (filename) = hash” for 512-bit, or “BLAKE2b-256 (filename) = hash” for other lengths.

print_hash_tag_b2sum_zero

Print hash in BSD tag format with BLAKE2b length info and NUL terminator.

print_hash_tag_zero

Print hash in BSD tag format with NUL terminator.

print_hash_zero

Print hash in GNU format with NUL terminator instead of newline.

readahead_files

Issue readahead hints for a list of file paths to warm the page cache. Uses POSIX_FADV_WILLNEED which is non-blocking and batches efficiently.

should_use_parallel

Check if parallel hashing is worthwhile for the given file paths. Only uses rayon when files are individually large enough for the hash computation to dominate over rayon overhead (thread pool init + work stealing). For many small files (e.g., 100 × 100KB), sequential is much faster.