lapo.it
1// Big integer base-10 printing library
2// Copyright (c) 2008-2024 Lapo Luchini <lapo@lapo.it>
3
4// Permission to use, copy, modify, and/or distribute this software for any
5// purpose with or without fee is hereby granted, provided that the above
6// copyright notice and this permission notice appear in all copies.
7//
8// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15
16let max = 10000000000000; // biggest 10^n integer that can still fit 2^53 when multiplied by 256
17
18export class Int10 {
19 /**
20 * Arbitrary length base-10 value.
21 * @param {number} value - Optional initial value (will be 0 otherwise).
22 */
23 constructor(value) {
24 this.buf = [+value || 0];
25 }
26
27 /**
28 * Multiply value by m and add c.
29 * @param {number} m - multiplier, must be < =256
30 * @param {number} c - value to add
31 */
32 mulAdd(m, c) {
33 // assert(m <= 256)
34 let b = this.buf,
35 l = b.length,
36 i, t;
37 for (i = 0; i < l; ++i) {
38 t = b[i] * m + c;
39 if (t < max)
40 c = 0;
41 else {
42 c = 0|(t / max);
43 t -= c * max;
44 }
45 b[i] = t;
46 }
47 if (c > 0)
48 b[i] = c;
49 }
50
51 /**
52 * Subtract value.
53 * @param {number} c - value to subtract
54 */
55 sub(c) {
56 let b = this.buf,
57 l = b.length,
58 i, t;
59 for (i = 0; i < l; ++i) {
60 t = b[i] - c;
61 if (t < 0) {
62 t += max;
63 c = 1;
64 } else
65 c = 0;
66 b[i] = t;
67 }
68 while (b[b.length - 1] === 0)
69 b.pop();
70 }
71
72 /**
73 * Convert to decimal string representation.
74 * @param {*} base - optional value, only value accepted is 10
75 */
76 toString(base) {
77 if ((base || 10) != 10)
78 throw 'only base 10 is supported';
79 let b = this.buf,
80 s = b[b.length - 1].toString();
81 for (let i = b.length - 2; i >= 0; --i)
82 s += (max + b[i]).toString().substring(1);
83 return s;
84 }
85
86 /**
87 * Convert to Number value representation.
88 * Will probably overflow 2^53 and thus become approximate.
89 */
90 valueOf() {
91 let b = this.buf,
92 v = 0;
93 for (let i = b.length - 1; i >= 0; --i)
94 v = v * max + b[i];
95 return v;
96 }
97
98 /**
99 * Return value as a simple Number (if it is <= 10000000000000), or return this.
100 */
101 simplify() {
102 let b = this.buf;
103 return (b.length == 1) ? b[0] : this;
104 }
105
106}