Decode #13

.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["mix.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

README.md

@@ -1,45 +1,102 @@
-# elixir-base58-encode
-[![Hex pm](http://img.shields.io/hexpm/v/b58.svg?style=flat)](https://hex.pm/packages/b58)
-[![Build Status](https://travis-ci.org/dwyl/base58encode.svg?branch=master)](https://travis-ci.org/dwyl/base58encode)
-[![codecov](https://codecov.io/gh/dwyl/base58encode/branch/master/graph/badge.svg)](https://codecov.io/gh/dwyl/base58encode)
+<div align="center">
 
-This module provides the `Base58Encode.encode/1` function which takes an **Elixir binary** and returns its base58 String representation.
+# `b58` - _Minimalist_ Elixir Base58 Encoding/Decoding Library
+
+[![Build Status](https://img.shields.io/travis/dwyl/base58/master.svg?style=flat-square)](https://travis-ci.org/dwyl/base58)
+[![codecov.io](https://img.shields.io/codecov/c/github/dwyl/base58/master.svg?style=flat-square)](http://codecov.io/github/dwyl/base58?branch=master)
+[![Hex.pm](https://img.shields.io/hexpm/v/base58?color=brightgreen&style=flat-square)](https://hex.pm/packages/base58)
+[![Libraries.io dependency status](https://img.shields.io/librariesio/release/hex/base58?logoColor=brightgreen&style=flat-square)](https://libraries.io/hex/base58)
+[![contributions welcome](https://img.shields.io/badge/contributions-welcome-brightgreen.svg?style=flat-square)](https://github.com/dwyl/base58/issues)
+[![HitCount](http://hits.dwyl.io/dwyl/base58.svg)](http://hits.dwyl.io/dwyl/base58)
+<!-- uncomment when service is working ...
+[![Inline docs](http://inch-ci.org/github/dwyl/base58.svg?branch=master&style=flat-square)](http://inch-ci.org/github/dwyl/base58)
+-->
+
+![base58-encode-hero-image](https://user-images.githubusercontent.com/194400/80292242-1d2de500-874d-11ea-8514-91a8fdfabfde.jpg)
+
+
+</div>
+
+`Base58` provides two functions to
+work with Base58 encoded strings: `Base58.encode/1` and `Base58.decode/1`  <br />
+`encode/1` takes an **Elixir binary** (_String, Number, etc._)
+and returns a Base58 encoded String. <br />
+`decode/1` receives a Base58 encoded String and returns a binary.
 
 See the section [What is an Elixir binary?](#what-is-an-elixir-binary) for more information about the binary type in Elixir.
 
-## How to use the module
+## How to use the module?
+
+### 1. Add the package to you dependencies
+
+Open your `mix.exs` file and add the following line to your `deps`:
+
+```elixir
+defp deps do
+  [
+    {:b58, "~> 1.0"},
+  ]
+end
+```
+
+and run `mix deps.get`
+
+### 2. Invoke the `encode/1` function with a binary as parameter:
+
+```elixir
+Base58.encode("foo")
+"bQbp"
+```
+
+### 3. Invoke the `decode/1` function with a `base58` encoded string:
+
+```elixir
+Base58.encode("hello") |> Base58.decode()
+"hello"
+```
+
+<br />
+
+
+See `example/example.exs` file
+for a simple example of how to use the module. <br />
+You can also run this example with `mix run example/example.exs`
+
 
-1. Add the package to you dependencies
+### Note: `Integer` Values are Converted to `String`
+
+When encoding an `Integer`
+the value is converted to a `String` before encoding
+so when it is decoded it will be a string e.g:
+
+```elixir
+Base58.encode(42) |> Base58.decode()
+"42"
+```
+
+This isn't ideal if you _expected_ an `Integer`
+but there is no way to encode the **`type`** of the data.
+So if you _know_ that you need it to be an `int`,
+convert it back to a numeric value with `Base58.decode_to_int/1`:
+
+```elixir
+iex(1)> Base58.encode(42) |> Base58.decode_to_int()
+42
+```
 
-  ```
-  defp deps do
-    [b58: "~> 0.1.0"]
-  end
-  ```
 
-  and run `mix deps.get`
 
-2. Call the `encode` function with a binary as parameter:
+<br /> <br />
 
- ```
- Base58Encode.encode("foo")
- "bQbp"
- ```
+## Why?
 
- if the parameter is not an Elixir binary the function will return `:error`. In
- this example 42 is an Integer and not a binary (`is_binary(42)` will return `false`)
 
- ```
- Base58Encode.encode(42)
- :error
- ```
 
- See `example/example.exs` file for a simple example on how to use the module.
- You can also run this example with `mix run example/example.exs`
 
-## What is base58?
+## What is Base58?
 
 A *base* is a set of characters used for representing numbers.
+https://en.wikipedia.org/wiki/Base58
 
 For example
 - The base 2 (binary system) represents numbers with the digits ` 0 1`

lib/base58.ex

@@ -0,0 +1,114 @@
+defmodule Base58 do
+  @moduledoc """
+  `Base58` provides two functions: `encode/1` and `decode/1`.
+  `encode/1` takes an **Elixir binary** (_String, Number, etc._)
+  and returns a Base58 encoded String.
+  `decode/1` receives a Base58 encoded String and returns a binary.
+  """
+
+  @doc """
+  ## Examples
+
+    iex> Base58.encode("hello")
+    "Cn8eVZg"
+
+    iex> Base58.encode(42)
+    "4yP"
+  """
+  def encode(""), do: ""
+  def encode(binary) when is_binary(binary) do
+    # see https://github.com/dwyl/base58/pull/3#discussion_r252291127
+    decimal = :binary.decode_unsigned(binary)
+
+    if decimal == 0 do
+      # see https://github.com/dwyl/base58/issues/5#issuecomment-459088540
+      leading_zeros(binary, "")
+    else
+      codes = get_codes(decimal, [])
+      leading_zeros(binary, "") <> codes_to_string(codes)
+    end
+  end
+
+  # If the parameter is not a binary convert it to binary before encode.
+  def encode(int) when is_integer(int) do
+    int
+    |> Integer.to_string()
+    |> encode()
+  end
+
+  def encode(val) when is_float(val) do
+    val
+    |> Float.to_string()
+    |> encode()
+  end
+
+  def encode(atom) when is_atom(atom) do
+    atom
+    |> Atom.to_string()
+    |> encode()
+  end
+
+  # return a list of codes (codepoint of base58)
+  defp get_codes(int, codes) do
+    rest = div(int, 58)
+    code = rem(int, 58)
+
+    if rest == 0 do
+      [code | codes]
+    else
+      get_codes(rest, [code | codes])
+    end
+  end
+
+  defp alphanum do
+    [ '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
+    'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
+    'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm',
+    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' ]
+  end
+
+  # match codepoints to the alphabet of base58
+  defp codes_to_string(codes) do
+    codes
+    |> Enum.map(&Enum.at(alphanum(), &1))
+    |> Enum.join()
+  end
+
+  # convert leading zeros to "1"
+  defp leading_zeros(<<0, rest::binary>>, acc) do
+    leading_zeros(rest, acc <> "1")
+  end
+
+  defp leading_zeros(_bin, acc) do
+    acc
+  end
+
+  @doc """
+  `decode/1` decodes the given Base58 string back to binary.
+  ## Examples
+
+    iex> Base58.encode("hello") |> Base58.decode()
+    "hello"
+  """
+  @alnum ~c(123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz)
+
+  def decode(""), do: "" # return empty string unmodified
+  def decode("\0"), do: "" # treat null values as empty
+  def decode(encoded), do: recurse(encoded |> to_char_list, 0)
+  defp recurse([], acc), do: acc |> :binary.encode_unsigned()
+  defp recurse([head | tail], acc) do
+    recurse(tail, (acc * 58) + Enum.find_index(@alnum, &(&1 == head)))
+  end
+
+  @doc """
+  `decode_to_int/1` decodes the given Base58 string back to an Integer.
+  ## Examples
+
+    iex> Base58.encode(42) |> Base58.decode_to_int()
+    42
+  """
+  def decode_to_int(encoded) do
+    decode(encoded)
+    |> String.to_integer()
+  end
+end

mix.exs

@@ -1,13 +1,13 @@
-defmodule Base58Encode.MixProject do
+defmodule Base58.MixProject do
   use Mix.Project
 
   def project do
     [
-      app: :b58,
+      app: :B58,
       name: "b58",
       description: description(),
       package: package(),
-      version: "0.1.1",
+      version: "1.0.0",
       elixir: "~> 1.7",
       start_permanent: Mix.env() == :prod,
       deps: deps(),
@@ -16,7 +16,7 @@ defmodule Base58Encode.MixProject do
         coveralls: :test,
         "coveralls.json": :test
       ],
-      source_url: "https://github.com/dwyl/base58encode"
+      source_url: "https://github.com/dwyl/base58"
     ]
   end
 
@@ -29,23 +29,24 @@ defmodule Base58Encode.MixProject do
 
   # Run "mix help deps" to learn about dependencies.
   defp deps do
-    [ {:excoveralls, "~> 0.10", only: :test},
+    [
+      {:excoveralls, "~> 0.12.3", only: :test},
       {:basefiftyeight, "~> 0.1.0", only: :test},
-      {:stream_data, "~> 0.1", only: :test},
-      {:ex_doc, "~> 0.19.3", only: :dev}
+      {:stream_data, "~> 0.4.3", only: :test},
+      {:ex_doc, "~> 0.21.3", only: :dev}
     ]
   end
 
   defp description() do
-    "Encode an Elixir binary to its base58 representation"
+    "B58 lets you encode an Elixir binary to base58 and decode a base58 string."
   end
 
   defp package() do
     [
       name: "b58",
       licenses: ["GNU GPL v2.0"],
       maintainers: ["dwyl"],
-      links: %{"GitHub" => "https://github.com/dwyl/base58encode"}
+      links: %{"GitHub" => "https://github.com/dwyl/base58"}
     ]
   end
 end