1/************************************************
2
3  bubblebabble.c - BubbleBabble encoding support
4
5  $Author: nobu $
6  created at: Fri Oct 13 18:31:42 JST 2006
7
8  Copyright (C) 2006 Akinori MUSHA
9
10  $Id: bubblebabble.c 27437 2010-04-22 08:04:13Z nobu $
11
12************************************************/
13
14#include "ruby.h"
15#include "digest.h"
16
17static ID id_digest;
18
19static VALUE
20bubblebabble_str_new(VALUE str_digest)
21{
22    char *digest;
23    size_t digest_len;
24    VALUE str;
25    char *p;
26    size_t i, j, seed = 1;
27    static const char vowels[] = {
28        'a', 'e', 'i', 'o', 'u', 'y'
29    };
30    static const char consonants[] = {
31        'b', 'c', 'd', 'f', 'g', 'h', 'k', 'l', 'm', 'n',
32        'p', 'r', 's', 't', 'v', 'z', 'x'
33    };
34
35    StringValue(str_digest);
36    digest = RSTRING_PTR(str_digest);
37    digest_len = RSTRING_LEN(str_digest);
38
39    if ((LONG_MAX - 2) / 3 < (digest_len | 1)) {
40	rb_raise(rb_eRuntimeError, "digest string too long");
41    }
42
43    str = rb_str_new(0, (digest_len | 1) * 3 + 2);
44    p = RSTRING_PTR(str);
45
46    i = j = 0;
47    p[j++] = 'x';
48
49    for (;;) {
50        unsigned char byte1, byte2;
51
52        if (i >= digest_len) {
53            p[j++] = vowels[seed % 6];
54            p[j++] = consonants[16];
55            p[j++] = vowels[seed / 6];
56            break;
57        }
58
59        byte1 = digest[i++];
60        p[j++] = vowels[(((byte1 >> 6) & 3) + seed) % 6];
61        p[j++] = consonants[(byte1 >> 2) & 15];
62        p[j++] = vowels[((byte1 & 3) + (seed / 6)) % 6];
63
64        if (i >= digest_len) {
65            break;
66        }
67
68        byte2 = digest[i++];
69        p[j++] = consonants[(byte2 >> 4) & 15];
70        p[j++] = '-';
71        p[j++] = consonants[byte2 & 15];
72
73        seed = (seed * 5 + byte1 * 7 + byte2) % 36;
74    }
75
76    p[j] = 'x';
77
78    return str;
79}
80
81/*
82 * call-seq:
83 *     Digest.bubblebabble(string) -> bubblebabble_string
84 *
85 * Returns a BubbleBabble encoded version of a given _string_.
86 */
87static VALUE
88rb_digest_s_bubblebabble(VALUE klass, VALUE str)
89{
90    return bubblebabble_str_new(str);
91}
92
93/*
94 * call-seq:
95 *     Digest::Class.bubblebabble(string, ...) -> hash_string
96 *
97 * Returns the BubbleBabble encoded hash value of a given _string_.
98 */
99static VALUE
100rb_digest_class_s_bubblebabble(int argc, VALUE *argv, VALUE klass)
101{
102    return bubblebabble_str_new(rb_funcall2(klass, id_digest, argc, argv));
103}
104
105/*
106 * call-seq:
107 *     digest_obj.bubblebabble -> hash_string
108 *
109 * Returns the resulting hash value in a Bubblebabble encoded form.
110 */
111static VALUE
112rb_digest_instance_bubblebabble(VALUE self)
113{
114    return bubblebabble_str_new(rb_funcall(self, id_digest, 0));
115}
116
117/*
118 * This module adds some methods to Digest classes to perform
119 * BubbleBabble encoding.
120 */
121void
122Init_bubblebabble(void)
123{
124    VALUE mDigest, mDigest_Instance, cDigest_Class;
125
126    rb_require("digest");
127
128    mDigest = rb_path2class("Digest");
129    mDigest_Instance = rb_path2class("Digest::Instance");
130    cDigest_Class = rb_path2class("Digest::Class");
131
132    /* Digest::bubblebabble() */
133    rb_define_module_function(mDigest, "bubblebabble", rb_digest_s_bubblebabble, 1);
134
135    /* Digest::Class::bubblebabble() */
136    rb_define_singleton_method(cDigest_Class, "bubblebabble", rb_digest_class_s_bubblebabble, -1);
137
138    /* Digest::Instance#bubblebabble() */
139    rb_define_method(mDigest_Instance, "bubblebabble", rb_digest_instance_bubblebabble, 0);
140
141    id_digest = rb_intern("digest");
142}
143