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;;; bytes.el --- Working with byte values -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;;; Commentary:
;; Functions to help with human-readable representations of byte values.
;;
;; Usage:
;; See the test cases for example usage. Or better yet, I should use a type of
;; structured documentation that would allow me to expose a view into the test
;; suite here. Is this currently possible in Elisp?
;;
;; API:
;; - serialize :: Integer -> String
;;
;; Wish list:
;; - Rounding: e.g. (bytes (* 1024 1.7)) => "2KB"
;;; Code:
;; TODO: Support -ibabyte variants like Gibibyte (GiB).
;; Ranges:
;; B: [ 0, 1e3)
;; KB: [ 1e3, 1e6)
;; MB: [ 1e6, 1e6)
;; GB: [ 1e9, 1e12)
;; TB: [1e12, 1e15)
;; PB: [1e15, 1e18)
;;
;; Note: I'm currently not support exabytes because that causes the integer to
;; overflow. I imagine a larger integer type may exist, but for now, I'll
;; treat this as a YAGNI.
(require 'prelude)
(require 'tuple)
(require 'math)
(require 'number)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Constants
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defconst bytes/kb (math/exp 2 10)
"Number of bytes in a kilobyte.")
(defconst bytes/mb (math/exp 2 20)
"Number of bytes in a megabytes.")
(defconst bytes/gb (math/exp 2 30)
"Number of bytes in a gigabyte.")
(defconst bytes/tb (math/exp 2 40)
"Number of bytes in a terabyte.")
(defconst bytes/pb (math/exp 2 50)
"Number of bytes in a petabyte.")
(defconst bytes/eb (math/exp 2 60)
"Number of bytes in an exabyte.")
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun bytes/classify (x)
"Return unit that closest fits byte count, X."
(prelude/assert (number/whole? x))
(cond
((and (>= x 0) (< x bytes/kb)) 'byte)
((and (>= x bytes/kb) (< x bytes/mb)) 'kilobyte)
((and (>= x bytes/mb) (< x bytes/gb)) 'megabyte)
((and (>= x bytes/gb) (< x bytes/tb)) 'gigabyte)
((and (>= x bytes/tb) (< x bytes/pb)) 'terabyte)
((and (>= x bytes/pb) (< x bytes/eb)) 'petabyte)))
(defun bytes/to-string (x)
"Convert integer X into a human-readable string."
(let ((base-and-unit
(pcase (bytes/classify x)
('byte (tuple/from 1 "B"))
('kilobyte (tuple/from bytes/kb "KB"))
('megabyte (tuple/from bytes/mb "MB"))
('gigabyte (tuple/from bytes/gb "GB"))
('terabyte (tuple/from bytes/tb "TB"))
('petabyte (tuple/from bytes/pb "PB")))))
(string/format "%d%s"
(round x (tuple/first base-and-unit))
(tuple/second base-and-unit))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Tests
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(progn
(prelude/assert
(equal "1000B" (bytes/to-string 1000)))
(prelude/assert
(equal "2KB" (bytes/to-string (* 2 bytes/kb))))
(prelude/assert
(equal "17MB" (bytes/to-string (* 17 bytes/mb))))
(prelude/assert
(equal "419GB" (bytes/to-string (* 419 bytes/gb))))
(prelude/assert
(equal "999TB" (bytes/to-string (* 999 bytes/tb))))
(prelude/assert
(equal "2PB" (bytes/to-string (* 2 bytes/pb)))))
(provide 'bytes)
;;; bytes.el ends here
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