1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2007-2013, University of Amsterdam
    7                              VU University Amsterdam
    8    All rights reserved.
    9
   10    Redistribution and use in source and binary forms, with or without
   11    modification, are permitted provided that the following conditions
   12    are met:
   13
   14    1. Redistributions of source code must retain the above copyright
   15       notice, this list of conditions and the following disclaimer.
   16
   17    2. Redistributions in binary form must reproduce the above copyright
   18       notice, this list of conditions and the following disclaimer in
   19       the documentation and/or other materials provided with the
   20       distribution.
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   22    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   26    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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   34*/
   35
   36:- module(crypto_hash,
   37          [ sha_hash/3,                 % +Data, -Hash, +Options
   38            sha_new_ctx/2,              % -NewContext, +Options
   39            sha_hash_ctx/4,             % +OldCtx, +Data, -NewCtx, -Hash
   40            hmac_sha/4,                 % +Key, +Data, -Hash, +Options
   41            file_sha1/2,                % +File, -SHA1
   42            hash_atom/2                 % +Hash, -HexAtom
   43          ]).   44:- use_module(library(shlib)).   45
   46:- use_foreign_library(foreign(sha4pl)).

 sha_hash(+Data, -Hash, +Options) is det

Hash is the SHA hash of Data, The conversion is controlled by Options:

algorithm(+Algorithm)

One of sha1 (default), sha224, sha256, sha384 or sha512

encoding(+Encoding)

If Data is a sequence of character codes, this must be translated into a sequence of bytes, because that is what the hashing requires. The default encoding is utf8. The other meaningful value is octet, claiming that Data contains raw bytes.

Arguments:

Data	- is either an atom, string or code-list
Hash	- is a packed string

 sha_new_ctx(-NewContext, +Options) is det

NewContext is unified with the empty SHA computation context (which includes the Options.) It could later be passed to sha_hash_ctx/4. For Options, see sha_hash/3.

Arguments:

NewContext

- is an opaque pure Prolog term that is subject to garbage collection.

 sha_hash_ctx(+OldContext, +Data, -NewContext, -Hash) is det

Hash is the SHA hash of Data. NewContext is the new SHA computation context, while OldContext is the old. OldContext may be produced by a prior invocation of either sha_new_ctx/3 or sha_hash_ctx/4 itself.

This predicate allows a SHA function to be computed in chunks, which may be important while working with Metalink (RFC 5854), BitTorrent or similar technologies, or simply with big files.

 hmac_sha(+Key, +Data, -Hash, +Options) is det

For Options, see sha_hash/3.

 file_sha1(+File, -SHA1:atom) is det

True when SHA1 is the SHA1 hash for the content of File. Options is passed to open/4 and typically used to control whether binary or text encoding must be used. The output is compatible to the sha1sum program found in many systems.

  106file_sha1(File, Hash) :-
  107    setup_call_cleanup(
  108        open(File, read, In, [type(binary)]),
  109        stream_sha1(In, Hash),
  110        close(In)).
  111
  112stream_sha1(Stream, Hash) :-
  113    sha_new_ctx(Ctx0, [encoding(octet)]),
  114    update_hash(Stream, Ctx0, _Ctx, 0, HashCodes),
  115    hash_atom(HashCodes, Hash).
  116
  117update_hash(In, Ctx0, Ctx, Hash0, Hash) :-
  118    at_end_of_stream(In),
  119    !,
  120    Ctx = Ctx0,
  121    Hash = Hash0.
  122update_hash(In, Ctx0, Ctx, _Hash0, Hash) :-
  123    read_pending_codes(In, Data, []),
  124    sha_hash_ctx(Ctx0, Data, Ctx1, Hash1),
  125    update_hash(In, Ctx1, Ctx, Hash1, Hash).

 hash_atom(+HashCodes, -HexAtom) is det

Convert a list of bytes (integers 0..255) into the usual hexadecimal notation. E.g.

?- sha_hash('SWI-Prolog', Hash, []),
   hash_atom(Hash, Hex).
Hash = [61, 128, 252, 38, 121, 69, 229, 85, 199|...],
Hex = '3d80fc267945e555c730403bd0ab0716e2a68c68'.

  141hash_atom(Codes, Hash) :-
  142    phrase(bytes_hex(Codes), HexCodes),
  143    atom_codes(Hash, HexCodes).
  144
  145bytes_hex([]) --> [].
  146bytes_hex([H|T]) -->
  147    { High is H>>4,
  148      Low is H /\ 0xf,
  149      code_type(C0, xdigit(High)),
  150      code_type(C1, xdigit(Low))
  151    },
  152    [C0,C1],
  153    bytes_hex(T)