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+# mruby-encoding
+
+This mrbgem provides a lightweight, "poorman's" encoding functionality for mruby. It is designed to offer basic encoding support, primarily focused on UTF-8 and ASCII-8BIT.
+
+## Summary
+
+- **License:** MIT
+- **Author:** mruby developers
+- **Supported Encodings:**
+  - `Encoding::UTF_8`
+  - `Encoding::ASCII_8BIT` (aliased as `Encoding::BINARY`)
+
+## Functionality
+
+This gem introduces an `Encoding` module and extends the `String` and `Integer` classes with encoding-related methods.
+
+### `Encoding` Module
+
+A module (not a class, unlike standard Ruby) that holds encoding constants.
+
+- `Encoding::UTF_8`: Represents the UTF-8 encoding.
+- `Encoding::ASCII_8BIT`: Represents the ASCII-8BIT encoding.
+- `Encoding::BINARY`: An alias for `Encoding::ASCII_8BIT`.
+
+### `String` Methods
+
+- `string.valid_encoding? -> true or false`
+  - Returns `true` if the string is correctly encoded (particularly useful for UTF-8 strings). For `ASCII-8BIT` strings, it generally returns `true`.
+- `string.encoding -> EncodingConstant`
+  - Returns the encoding of the string. This will be `Encoding::UTF_8` or `Encoding::BINARY`.
+- `string.force_encoding(encoding_name) -> string`
+  - Changes the string's reported encoding to the specified `encoding_name` (e.g., "UTF-8", "ASCII-8BIT", "BINARY").
+  - The actual byte sequence of the string is not changed.
+  - Raises an `ArgumentError` if an unsupported encoding name is provided.
+
+### `Integer` Method
+
+- `integer.chr(encoding_name = Encoding::BINARY) -> String`
+  - Returns a single-character string represented by the integer.
+  - If `encoding_name` is "UTF-8", the integer is treated as a Unicode codepoint.
+  - If `encoding_name` is "ASCII-8BIT" or "BINARY" (the default), the integer is treated as a byte value (0-255).
+  - Raises a `RangeError` if the integer is out of the valid range for the specified encoding.
+  - Raises an `ArgumentError` for unknown encoding names.
+
+## Usage Example
+
+```ruby
+# main.rb
+if __ENCODING__ == "UTF-8"
+  s = "helloあ"
+  puts s.encoding  #=> Encoding::UTF_8
+  puts s.valid_encoding? #=> true
+
+  s2 = "\xff".force_encoding("UTF-8")
+  puts s2.valid_encoding? #=> false
+
+  s3 = "world"
+  s3.force_encoding("BINARY")
+  puts s3.encoding #=> Encoding::BINARY
+  puts s3.valid_encoding? #=> true (ASCII-8BIT strings are generally considered valid)
+
+  puts 65.chr #=> "A" (defaults to ASCII-8BIT)
+  puts 230.chr("UTF-8") #=> "æ" (if U+00E6 is æ)
+  # For mruby, this might be different based on actual UTF-8 char mapping
+  # For example, 12354.chr("UTF-8") might be "あ"
+else
+  s = "hello"
+  puts s.encoding #=> Encoding::BINARY (or ASCII-8BIT)
+
+  # Attempting to force to UTF-8 in a non-UTF-8 mruby build might be limited
+  # or behave as ASCII-8BIT depending on mruby's core string handling.
+end
+
+# Force encoding
+my_string = "\xE3\x81\x82" # UTF-8 bytes for "あ"
+puts my_string.encoding # Might be BINARY by default if not created as UTF-8 literal
+
+my_string.force_encoding("UTF-8")
+puts my_string.encoding #=> Encoding::UTF_8
+puts my_string #=> あ
+
+invalid_utf8 = "\xff\xfe"
+invalid_utf8.force_encoding("UTF-8")
+puts invalid_utf8.valid_encoding? #=> false
+
+# Integer#chr
+puts 65.chr # => "A"
+puts 65.chr("BINARY") # => "A"
+
+# When mruby is compiled with MRB_UTF8_STRING
+if Object.const_defined?(:MRB_UTF8_STRING)
+  puts 12354.chr("UTF-8") # => "あ"
+  # puts 0x110000.chr("UTF-8") #=> RangeError
+end
+
+```