1		% (c) 2009-2026 Lehrstuhl fuer Softwaretechnik und Programmiersprachen,
2		% Heinrich Heine Universitaet Duesseldorf
3		% This software is licenced under EPL 1.0 (http://www.eclipse.org/org/documents/epl-v10.html)
4
5		:- module(probhash, [hash_term/2, hash_to_atom/2, raw_sha_hash/2, raw_sha_hash_file/3]).
6
7		:- use_module('../../src/module_information.pl').
8
9		:- module_info(group,infrastructure).
10		:- module_info(description,'This is the interface to C code for generating good hashes (SHA-1, 160 bits).').
11
12		:- use_module(probsrc(error_manager),[add_error/4]).
13		:- use_module(probsrc(tools_strings),[ajoin/2]).
14
15		:- load_files(library(system), [when(compile_time), imports([environ/2])]).
16
17		:- if((predicate_property(load_foreign_resource(_), _),
18		\+ environ(prob_c_probhash,false))).
19		% -Dprob_c_probhash=false
20
21		:- use_module(library(fastrw),[ fast_buf_read/2,
22		fast_buf_write/3 ]).
23
24		foreign_resource(probhash,[sha1,sha1_file]).
25		foreign(sha1,sha1(+address(char),+integer,[-term])).
26		foreign(sha1_file,sha1_file(+atom,[-term])). % returns the list of bytes or error(Reason)
27
28		:- dynamic loaded/1.
29
30		:- use_module(probsrc(pathes_lib),[safe_load_foreign_resource/2]).
31
32		% loads the library once; if loading fails, the error is reported once by safe_load_foreign_resource
33		% and init_probhash fails from then on (without trying to load the library again)
34		init_probhash :-
35		(loaded(Res) -> true
36		; (safe_load_foreign_resource(probhash,probhash) -> Res = success ; Res = failure),
37		assertz(loaded(Res))
38		),
39		Res = success.
40
41
42		% input: term
43		% output: hash value as a biginteger (the byte order is reversed)
44		hash_term(Term,Hash) :- raw_sha_hash(Term,H), hash_to_int(H,Hash).
45
46		:- use_module(library(file_systems),[file_exists/1]).
47
48		raw_sha_hash_file(Atom,_,Span) :-
49		\+ file_exists(Atom),!,
50		add_error(probhash,'File does not exist: ',Atom,Span),fail.
51		raw_sha_hash_file(Atom,Hash,Span) :-
52		init_probhash,
53		sha1_file(Atom,Result),
54		(Result = error(Reason)
55		-> ajoin(['Could not read file (',Reason,'): '],Msg),
56		add_error(probhash,Msg,Atom,Span),
57		fail
58		; Hash = Result
59		).
60
61
62
63		% input: raw hash
64		% output: hash value as a biginteger (the byte order is reversed)
65		hash_to_int(X,Y) :- hash_to_int(X,0,Y).
66		hash_to_int([],A,A).
67		hash_to_int([H|T],A,R) :- A2 is A * 256 + H, hash_to_int(T,A2,R).
68
69		% raw sha hashing, input is a term, output a raw hash, i.e., a list of 20 bytes
70		raw_sha_hash(Term,Digest) :-
71		init_probhash,
72		fast_buf_write(Term,Len,Addr),
73		sha1(Addr,Len,Digest).
74
75		% input: raw hash value
76		% output: hash value as an atom
77		hash_to_atom(H,ResultAtom) :-
78		raw_sha_hash(H,H2), hash_to_int(H2,X),
79		number_codes(X, C),atom_codes(ResultAtom,C).
80
81		% input: raw hash value
82		% output: hash value as 5 32-bit chunks
83		hash_to_32bit([V1,V2,V3,V4,V5,V6,V7,V8,V9,V10,V11,V12,V13,V14,V15,V16,V17,V18,V19,V20],[H1,H2,H3,H4,H5]) :-
84		hash_to_int([V1,V2,V3,V4],H1),
85		hash_to_int([V5,V6,V7,V8],H2),
86		hash_to_int([V9,V10,V11,V12],H3),
87		hash_to_int([V13,V14,V15,V16],H4),
88		hash_to_int([V17,V18,V19,V20],H5).
89
90		%-----------------------
91		:- else.
92		%-----------------------
93
94		:- write('Using Prolog term_hash instead of probhash C SHA1 extension (can cause collisions!!)'),nl.
95
96		:- use_module(probsrc(hashing),[my_term_hash/2]).
97		hash_term(Term,Hash) :- my_term_hash(Term,Hash).
98		hash_to_atom(Term,Hash) :- my_term_hash(Term,Hash).
99		raw_sha_hash(Term,Hash) :- my_term_hash(Term,Hash). % TODO: convert to list
100
101		raw_sha_hash_file(_,_,Span) :-
102		add_error(probhash,'Not implemented: ',raw_sha_hash_file,Span),fail.
103
104		:- endif.