javascript - What is the accepted way to send 64-bit values over JSON?

Question

Some of my data are 64-bit integers. I would like to send these to a JavaScript program running on a page.

However, as far as I can tell, integers in most JavaScript implementations are 32-bit signed quantities.

My two options seem to be:

1. Send the values as strings
2. Send the values as 64-bit floating point numbers

Option (1) isn't perfect, but option (2) seems far less perfect (loss of data).

How have you handled this situation?

Answer 1

This seems to be less a problem with JSON and more a problem with Javascript itself. What are you planning to do with these numbers? If it's just a magic token that you need to pass back to the website later on, by all means simply use a string containing the value. If you actually have to do arithmetic on the value, you could possibly write your own Javascript routines for 64-bit arithmetic.

One way that you could represent values in Javascript (and hence JSON) would be by splitting the numbers into two 32-bit values, eg.

  [ 12345678, 12345678 ]

To split a 64-bit value into two 32-bit values, do something like this:

  output_values[0] = (input_value >> 32) & 0xffffffff;
  output_values[1] = input_value & 0xffffffff;

Then to recombine two 32-bit values to a 64-bit value:

  input_value = ((int64_t) output_values[0]) << 32) | output_values[1];