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  • License MIT

Support for representing 64-bit integers in JavaScript

Package Exports

  • node-int64

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (node-int64) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

JavaScript Numbers are represented as IEEE 754 double-precision floats. Unfortunately, this means they lose integer precision for values beyond +/- 2^^53. For projects that need to accurately handle 64-bit ints, such as node-thrift, a performant, Number-like class is needed. Int64 is that class.

Int64 instances look and feel much like JS-native Numbers. By way of example ...

// First, let's illustrate the problem ...
> (0x123456789).toString(16)
'123456789' // <- what we expect.
> (0x123456789abcdef0).toString(16)
'123456789abcdf00' // <- Ugh!  JS doesn't do big ints. :(

// So let's create a couple Int64s using the above values ...

// Require, of course
> Int64 = require('node-int64')

// x's value is what we expect (the decimal value of 0x123456789)
> x = new Int64(0x123456789)
[Int64 value:4886718345 octets:00 00 00 01 23 45 67 89]

// y's value is Infinity because it's outside the range of integer
// precision.  But that's okay - it's still useful because it's internal
// representation (octets) is what we passed in
> y = new Int64('123456789abcdef0')
[Int64 value:Infinity octets:12 34 56 78 9a bc de f0]

// Let's do some math.  Int64's behave like Numbers.  (Sorry, Int64 isn't
// for doing 64-bit integer arithmetic (yet) - it's just for carrying
// around int64 values
> x + 1
4886718346
> y + 1
Infinity

// Int64 string operations ...
> 'value: ' + x
'value: 4886718345'
> 'value: ' + y
'value: Infinity'
> x.toString(2)
'100100011010001010110011110001001'
> y.toString(2)
'Infinity'

// Use JS's isFinite() method to see if the Int64 value is in the
// integer-precise range of JS values
> isFinite(x)
true
> isFinite(y)
false

// Get an octet string representation.  (Yay, y is what we put in!)
> x.toOctetString()
'0000000123456789'
> y.toOctetString()
'123456789abcdef0'

// Finally, some other ways to create Int64s ...

// Pass hi/lo words
> new Int64(0x12345678, 0x9abcdef0)
[Int64 value:Infinity octets:12 34 56 78 9a bc de f0]

// Pass a Buffer
> new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0]))
[Int64 value:Infinity octets:12 34 56 78 9a bc de f0]

// Pass a Buffer and offset
> new Int64(new Buffer([0,0,0,0,0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0]), 4)
[Int64 value:Infinity octets:12 34 56 78 9a bc de f0]

// Pull out into a buffer
> new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0])).toBuffer()
<Buffer 12 34 56 78 9a bc de f0>

// Or copy into an existing one (at an offset)
> var buf = new Buffer(1024);
> new Int64(new Buffer([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc, 0xde, 0xf0])).copy(buf, 512);