lexicographic-integer

create lexicographic string keys for positive integers without zero-padding

At most, a number will take 10 bytes to store (2 more bytes than a regular double) but all numbers less than 251 only take a single byte.

example

pack

var lexi = require('lexicographic-integer');
console.log(lexi.pack(12345));

output:

[ 252, 47, 62 ]

unpack

To convert the arrays back into integers, just do .unpack():

var lexi = require('lexicographic-integer');
console.log(lexi.unpack([ 252, 47, 62 ]));

output:

hex list

var lexi = require('lexicographic-integer');

for (var n = 0; n < 5; n++) {
    console.log(n, lexi.pack(n, 'hex'));
}

console.log('...');

for (var n = 248; n < 257; n++) {
    console.log(n, lexi.pack(n, 'hex'));
}

console.log('...');

for (var n = 5000; n < 5005; n++) {
    console.log(n, lexi.pack(n, 'hex'));
}

console.log('...');

for (var n = 21378213; n < Number.MAX_VALUE; n *= 1513254198219212) {
    console.log(n, lexi.pack(n, 'hex'));
}

output:

0 '00'
1 '01'
2 '02'
3 '03'
4 '04'
...
248 'f8'
249 'f9'
250 'fa'
251 'fb00'
252 'fb01'
253 'fb02'
254 'fb03'
255 'fb04'
256 'fb05'
...
5000 'fc128d'
5001 'fc128e'
5002 'fc128f'
5003 'fc1290'
5004 'fc1291'
...
21378213 'fe014633aa'
3.2350670572674536e+22 'ff2a0db3777bb94c'
4.895478805930646e+37 'ff5d09351659b187'
7.408103855367726e+52 'ff8f0c6004db1f28'
1.121034425997914e+68 'ffc20850f8bf332a'
1.696410051489608e+83 'fff40b2d6c283bb4'
2.5670996323179187e+98 'fffb2b0f05dd909879'
3.884674295852086e+113 'fffb5e0a187f7c58cd'
5.87849968691243e+128 'fffb900d91aaff96fe'
8.895664330450558e+143 'fffbc3091e5fb56b0c'
1.3461401394003201e+159 'fffbf50c417dbf1c6c'
2.03705221733893e+174 'fffc0128083c74d68fa0'
3.08257781987989e+189 'fffc015a0b11d96218aa'
4.6647238272706696e+204 'fffc018c0ee0ce4aceb6'
7.058912915150531e+219 'fffc01bf09ff97d9a0a7'
1.0681929603715358e+235 'fffc01f10d7031e40fc8'
1.6164474817904348e+250 'fffc02240907e1192454'
2.4460959380202488e+265 'fffc02560c2341f2013d'
3.701564947456103e+280 'fffc028908282389ba9c'
5.601408696719025e+295 'fffc02bb0af68aa1140f'

methods

var lexi = require('lexicographic-integer')

lexi.pack(n, encoding='array')

If encoding is undefined or 'array', return an array of byte values between 0 and 255, inclusive for the integer n.

If encoding is 'hex', return a lexicographic hex string for the integer n.

lexi.unpack(bytes)

Convert an array of bytes returned by .pack() back into the original javascript number.

install

With npm do:

npm install lexicographic-integer

license

MIT

aplunk / lexicographic-integer Goto Github PK