1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
'use strict';
var s = [0x0000, 0x0000, 0x0000, 0x0000];
/**
* Multiply two 64-bit values represented as arrays of four 16-bit words.
*
* Arrays use little-endian word order (least-significant 16-bit word first).
* The result is truncated to the lower 64 bits and returned as a 4-element
* array of 16-bit words.
*
* @param {Array<number>} a - Multiplicand (4 × 16-bit words, little-endian)
* @param {Array<number>} b - Multiplier (4 × 16-bit words, little-endian)
* @returns {Array<number>} Product as 4 × 16-bit words (little-endian)
*/
function mul(a, b) {
var r = [0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000];
for (var j = 0; j < 4; j++) {
var k = 0;
for (var i = 0; i < 4; i++) {
var t = a[i] * b[j] + r[i+j] + k;
r[i+j] = t & 0xffff;
k = t >>> 16;
}
r[j+4] = k;
}
r.length = 4;
return r;
}
/**
* Add a small integer to a 64-bit value represented as four 16-bit words.
*
* Treats `a` as a little-endian 64-bit value (4 × 16-bit words). Adds the
* integer `n` to the least-significant word and propagates carry across
* subsequent 16-bit words. The result is truncated to 64 bits and returned
* as a 4-element array of 16-bit words (little-endian).
*
* @param {Array<number>} a - Addend as 4 × 16-bit words (little-endian)
* @param {number} n - Value to add (integer carry)
* @returns {Array<number>} Sum as 4 × 16-bit words (little-endian)
*/
function add(a, n) {
var r = [0x0000, 0x0000, 0x0000, 0x0000],
k = n;
for (var i = 0; i < 4; i++) {
var t = a[i] + k;
r[i] = t & 0xffff;
k = t >>> 16;
}
return r;
}
/**
* Shift a 64-bit value (4 × 16-bit words, little-endian) right by `n` bits.
*
* The input array is treated as little-endian 16-bit words. Bits shifted out
* on the right are discarded; the returned array contains the lower 64-bit
* result after the logical right shift.
*
* @param {Array<number>} a - Source value as 4 × 16-bit words (little-endian)
* @param {number} n - Number of bits to shift right (non-negative integer)
* @returns {Array<number>} Shifted value as 4 × 16-bit words (little-endian)
*/
function shr(a, n) {
var r = [a[0], a[1], a[2], a[3], 0x0000],
i = 4,
k = 0;
for (; n > 16; n -= 16, i--)
for (var j = 0; j < 4; j++)
r[j] = r[j+1];
for (; i > 0; i--) {
var s = r[i-1];
r[i-1] = (s >>> n) | k;
k = ((s & ((1 << n) - 1)) << (16 - n));
}
r.length = 4;
return r;
}
return L.Class.extend({
/**
* Seed the PRNG state.
*
* The seed is treated as a 32-bit integer; the lower 16 bits are stored
* in `s[0]`, the upper 16 bits in `s[1]`. `s[2]` and `s[3]` are zeroed.
*
* @param {number} n - Seed value (32-bit integer)
* @returns {void}
*/
seed: function(n) {
n = (n - 1)|0;
s[0] = n & 0xffff;
s[1] = n >>> 16;
s[2] = 0;
s[3] = 0;
},
/**
* Produce the next PRNG 32-bit integer.
*
* Advances the internal state and returns a 32-bit pseudo-random integer
* derived from the current state.
*
* @returns {number} 32-bit pseudo-random integer (JS number)
*/
int: function() {
s = mul(s, [0x7f2d, 0x4c95, 0xf42d, 0x5851]);
s = add(s, 1);
var r = shr(s, 33);
return (r[1] << 16) | r[0];
},
/**
* Return a pseudo-random value.
*
* Overloads:
* - get() -> number in [0, 1]
* - get(upper) -> integer in [1, upper]
* - get(lower, upper) -> integer in [lower, upper]
*
* @param {number} [lower=0] - Lower bound (when two args supplied)
* @param {number} [upper=0] - Upper bound (when one or two args supplied)
* @returns {number} Random value (float in [0,1] or integer in requested range)
*/
get: function() {
var r = (this.int() % 0x7fffffff) / 0x7fffffff, l, u;
switch (arguments.length) {
case 0:
return r;
case 1:
l = 1;
u = arguments[0]|0;
break;
case 2:
l = arguments[0]|0;
u = arguments[1]|0;
break;
}
return Math.floor(r * (u - l + 1)) + l;
},
/**
* Derive a deterministic hex color from an input string.
*
* The color is produced by seeding the PRNG from a string-derived
* hash and producing RGB components. Returns a `#rrggbb` hex string.
*
* @param {string} string - Input string used to derive the color
* @returns {string} Hex color string in `#rrggbb` format
*/
derive_color: function(string) {
this.seed(parseInt(sfh(string), 16));
var r = this.get(128),
g = this.get(128),
min = 0,
max = 128;
if ((r + g) < 128)
min = 128 - r - g;
else
max = 255 - r - g;
var b = min + Math.floor(this.get() * (max - min));
return '#%02x%02x%02x'.format(0xff - r, 0xff - g, 0xff - b);
}
});
|
