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 zero-copy mmap for regular files, streaming for pipes/special files.

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”.

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 zero-copy mmap for regular files: the hash function reads directly from the page cache without any kernel→user memcpy or read() syscalls. MAP_POPULATE prefaults all pages before hashing starts. MADV_HUGEPAGE uses 2MB pages to reduce TLB misses by ~500x.

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. Always parallelizes with 2+ files — rayon’s thread pool is already initialized and work-stealing overhead is minimal (~1µs per file dispatch). With mmap, each thread independently maps and hashes its own file with no shared state, giving near-linear speedup with available cores.