nomsu/lib/file_hash.nom

#!/usr/bin/env nomsu -V4.8.10
#
    This file defines some actions for hashing files and looking up files by hash.

use "lib/os.nom"
use "lib/base64.nom"

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lua> "local \%use_sha1, \%hashlib = pcall(require, 'openssl.digest')"

test:
    assume (hash "hello world") == (hash "hello world")
    assume ((hash "hello world") != (hash "goodbye")) or barf "\
        ..Hash collision:
            (hash "hello world") = \(hash "hello world")
            (hash "goodbye") = \(hash "goodbye")"
    
    assume (..)
        (..)
            hash "\
                ..This is a really long string meant to stress test the hashing function and
                ensure that it's not overflowing with long inputs."
        ..!= "inf"
    
    assume ((hash "\000") != (hash "\000\000\000\000\000")) or barf "\
        ..Incorrect hashing of null strings"
    if %use_sha1:
        assume ((hash "hello world") == "Kq5sNclPz7QV2+lfQIuc6R7oRu0=")
if %use_sha1:
    externally (hash %) means:
        %hash = (=lua "\%hashlib.new('sha1'):final(\%)")
        return (base64 %hash)
..else:
    # TODO: remove warning?
    say "\
        ..\027[31;1mWARNING: OpenSSL module not found. Defaulting to a non-cryptographically secure hash function.\027[0m"
    externally (hash %) means:
        %bytes = (%::bytes)
        %hash = (%bytes.1 << 7)
        for %i in 2 to (size of %bytes):
            %hash = ((1000003 * %hash) ~ %bytes.%i)
        %hash = (%hash ~ (size of %bytes))
        return "\%hash"

externally (file with hash %hash) means:
    for file %filename in ".":
        %contents = (read file %filename)
        %file_hash = (hash %contents)
        if (%file_hash == %hash): return %filename

(hash of file %filename) parses as (hash (read file %filename))