Feature #5678

StringIO#to_str

Added by Martin Bosslet over 3 years ago. Updated over 3 years ago.

[ruby-core:41340]
Status:Closed
Priority:Normal
Assignee:Nobuyoshi Nakada

Description

The following raises an error currently:

require 'stringio'
require 'openssl'

io = StringIO.new(OpenSSL::ASN1::Integer.new(1).to_der)
asn = OpenSSL::ASN1.decode io

The reason is that ossl_obj2bio[1] looks for a
T_FILE first, and then it tries to coerce the
input to a String using StringValue. StringValue
itself again expects the presence of to_str,
which is currently missing for StringIO, but
could be easily provided by aliasing
StringIO#string.

I could imagine that the heuristic of ossl_obj2bio
is quite common when working on binary data in a
C extension. Would it therefore be OK to add
StringIO#to_str? Patch attached.

[1] https://github.com/ruby/ruby/blob/trunk/ext/openssl/ossl_bio.c#L17

stringio.patch Magnifier (582 Bytes) Martin Bosslet, 11/28/2011 09:52 AM

History

#1 Updated by Nobuyoshi Nakada over 3 years ago

  • Status changed from Open to Feedback

Martin Bosslet wrote:

The following raises an error currently:

require 'stringio'
require 'openssl'

io = StringIO.new(OpenSSL::ASN1::Integer.new(1).to_der)
asn = OpenSSL::ASN1.decode io

Why do you need to pass `io', not io.string or the result of to_der?

#2 Updated by Martin Bosslet over 3 years ago

Nobuyoshi Nakada wrote:

Martin Bosslet wrote:

The following raises an error currently:

require 'stringio'
require 'openssl'

io = StringIO.new(OpenSSL::ASN1::Integer.new(1).to_der)
asn = OpenSSL::ASN1.decode io

Why do you need to pass `io', not io.string or the result of to_der?

I don't really need to, it's just that I am working on making
ASN1.decode streaming-aware. So I wanted it to work with any
IO or IO-like object and additionally with Strings. That's why
I thought if someone passes a StringIO, they would be surprised
if an error was raised - they passed an IO-like object after all
and there is no apparent reason why this shouldn't work.

I could, however, call StringIO#string as you suggested, but
I would prefer to use StringValue, as a more generic way
of coercing things into Strings. And it would potentially work
for a wider variety of objects, not only limited to StringIO.

Do you see any negative aspects when adding StringIO#to_str?

#3 Updated by Yukihiro Matsumoto over 3 years ago

Hi,

In message "Re: [ruby-trunk - Feature #5678] StringIO#to_str"
on Mon, 28 Nov 2011 11:16:33 +0900, Martin Bosslet Martin.Bosslet@googlemail.com writes:

|Do you see any negative aspects when adding StringIO#to_str?

Yes, to_str should be implemented for objects that have (almost) same
method signature as strings, which is not true for StringIO.

                        matz.

#4 Updated by Martin Bosslet over 3 years ago

  • Status changed from Feedback to Closed

Yukihiro Matsumoto wrote:

Hi,

In message "Re: [ruby-trunk - Feature #5678] StringIO#to_str"
on Mon, 28 Nov 2011 11:16:33 +0900, Martin Bosslet Martin.Bosslet@googlemail.com writes:

|Do you see any negative aspects when adding StringIO#to_str?

Yes, to_str should be implemented for objects that have (almost) same
method signature as strings, which is not true for StringIO.

                      matz.

OK, thank you for clarifying this! I will use StringIO#string then.

#5 Updated by Nikolai Weibull over 3 years ago

On Mon, Nov 28, 2011 at 07:16, Yukihiro Matsumoto matz@ruby-lang.org wrote:

In message "Re: [ruby-trunk - Feature #5678] StringIO#to_str"
   on Mon, 28 Nov 2011 11:16:33 +0900, Martin Bosslet Martin.Bosslet@googlemail.com writes:

|Do you see any negative aspects when adding StringIO#to_str?

Yes, to_str should be implemented for objects that have (almost) same
method signature as strings, which is not true for StringIO.

How about implementing #to_s instead?

#6 Updated by Yukihiro Matsumoto over 3 years ago

Hi,
In message "Re: [ruby-trunk - Feature #5678][Closed] StringIO#to_str"
on Mon, 28 Nov 2011 18:50:12 +0900, Martin Bosslet Martin.Bosslet@googlemail.com writes:

|OK, thank you for clarifying this! I will use StringIO#string then.

At the same time, having ASN1.decode to treat T_FILE but not StringIO
is against duck typing. I think it is better if we can do something.
But I don't have a good idea yet. #to_io does not work here. #to_str
is not appropriate.

                        matz.

#7 Updated by Martin Bosslet over 3 years ago

Yukihiro Matsumoto wrote:

Hi,
In message "Re: [ruby-trunk - Feature #5678][Closed] StringIO#to_str"
on Mon, 28 Nov 2011 18:50:12 +0900, Martin Bosslet Martin.Bosslet@googlemail.com writes:

At the same time, having ASN1.decode to treat T_FILE but not StringIO
is against duck typing. I think it is better if we can do something.
But I don't have a good idea yet. #to_io does not work here. #to_str
is not appropriate.

                      matz.

We could handle StringIO exceptionally by trying to call #string on the
object passed. But that's not too elegant and will probably only work in
the very specific case of StringIO. Implementing #to_s like Nikolai
suggested could be another solution? Then we could apply the following
heuristic that should cover almost any (valid) case:

  1. check for T_FILE
  2. try #to_str
  3. try #to_s ?

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