From: duerst@...
Date: 2015-12-14T08:50:48+00:00
Subject: [ruby-core:72110] [Ruby trunk - Feature #11814] String#valid_encoding? without force_encoding

Issue #11814 has been updated by Martin D��rst.


Akinori MUSHA wrote:


> Suppose you have a list of byte arrays which you don't know which encoding they are encoded in, like when you want to guess the encoding of the file names stored in a zip file.
> 
> So, if you had String#valid_encoding?(enc) you could achieve it like this without modifying, copying or concatenating strings:
> 
> ~~~
> POSSIBLE_ENCODINGS = [Encoding::UTF_8, Encoding::Windows_31J, Encoding::ISO_8859_1, Encoding::ASCII_8BIT]
> 
> encoding = byte_arrays.inject(POSSIBLE_ENCODINGS) { |encs, b|
>   encs.select { |enc| b.valid_encoding?(enc) }
> }.first
> ~~~

A few comments on this program:

- Encoding::ASCII_8BIT will pick up garbage. Encoding::US_ASCII is much better.

- Encoding::ISO_8859_1 is always valid, for all bytes, so ASCII8BIT (or US-ASCII) never get used.

- There are many more encodings, but distinguishing them is difficult/impossible with this method.

----------------------------------------
Feature #11814: String#valid_encoding? without force_encoding
https://bugs.ruby-lang.org/issues/11814#change-55525

* Author: Usaku NAKAMURA
* Status: Rejected
* Priority: Normal
* Assignee: 
----------------------------------------
Now we have to set a encoding to a string to validate it, just like:

```ruby
str.force_encoding('euc-jp').valid_encoding?  # => true or false
```

But to modify the string is not so smart.
knu-san requires the way to validate a string without modifiing it [*1].

Then, I propose to add an optional encoding parameter to `String#valid_encoding?`.

```ruby
str.valid_encoding?('euc-jp')  # => true or false
```

A patch is attached.

[*1] https://twitter.com/knu/status/676009662655934465 (in Japanese)

---Files--------------------------------
valid_encoding.patch (4.4 KB)


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