From: "ioquatix (Samuel Williams) via ruby-core" <ruby-core@ml.ruby-lang.org>
To: ruby-core@ml.ruby-lang.org
Cc: "ioquatix (Samuel Williams)" <noreply@ruby-lang.org>
Subject: [ruby-core:116456] [Ruby master Feature#20215] Introduce `IO#readable?`
Date: Fri, 26 Jan 2024 05:19:17 +0000 (UTC) [thread overview]
Message-ID: <redmine.issue-20215.20240126051916.3344@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-20215.20240126051916.3344@ruby-lang.org
Issue #20215 has been reported by ioquatix (Samuel Williams).
----------------------------------------
Feature #20215: Introduce `IO#readable?`
https://bugs.ruby-lang.org/issues/20215
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
There are some cases where, as an optimisation, it's useful to know whether more data is potentially available.
We already have `IO#eof?` but the problem with using `IO#eof?` is that it can block indefinitely for sockets.
Therefore, code which uses `IO#eof?` to determine if there is potentially more data, may hang.
```ruby
def make_request(path = "/")
client = connect_remote_host
# HTTP/1.0 request:
client.write("GET #{path} HTTP/1.0\r\n\r\n")
# Read response
client.gets("\r\n") # => "HTTP/1.0 200 OK\r\n"
# Assuming connection close, there are two things the server can do:
# 1. peer.close
# 2. peer.write(...); peer.close
if client.eof? # <--- Can hang here!
puts "Connection closed"
# Avoid yielding as we know there definitely won't be any data.
else
puts "Connection open, data may be available..."
# There might be data available, so yield.
yield(client)
end
ensure
client&.close
end
make_request do |client|
puts client.read # <--- Prefer to wait here.
end
```
The proposed `IO#readable?` is similar to `IO#eof?` but rather than blocking, would simply return false. The expectation is the user will subsequently call `read` which may then wait.
The proposed implementation would look something like this:
```ruby
class IO
def readable?
!!self.closed?
end
end
class BasicSocket
# Is it likely that the socket is still connected?
# May return false positive, but won't return false negative.
def readable?
return false unless super
# If we can wait for the socket to become readable, we know that the socket may still be open.
result = self.recv_nonblock(1, MSG_PEEK, exception: false)
# No data was available - newer Ruby can return nil instead of empty string:
return false if result.nil?
# Either there was some data available, or we can wait to see if there is data avaialble.
return !result.empty? || result == :wait_readable
rescue Errno::ECONNRESET
# This might be thrown by recv_nonblock.
return false
end
end
```
For `IO` itself, when there is buffered data, `readable?` would also return true immediately, similar to `eof?`. This is not shown in the above implementation as I'm not sure if there is any Ruby method which exposes "there is buffered data".
--
https://bugs.ruby-lang.org/
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next parent reply other threads:[~2024-01-26 5:19 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-26 5:19 ioquatix (Samuel Williams) via ruby-core [this message]
2024-02-01 6:19 ` [ruby-core:116546] [Ruby master Feature#20215] Introduce `IO#readable?` shyouhei (Shyouhei Urabe) via ruby-core
2024-02-01 14:59 ` [ruby-core:116547] " Dan0042 (Daniel DeLorme) via ruby-core
2024-02-02 21:06 ` [ruby-core:116561] " Eregon (Benoit Daloze) via ruby-core
2024-02-03 17:13 ` [ruby-core:116566] " Dan0042 (Daniel DeLorme) via ruby-core
2024-02-03 19:53 ` [ruby-core:116567] " Dan0042 (Daniel DeLorme) via ruby-core
2024-02-19 18:44 ` [ruby-core:116851] " forthoney (Seong-Heon Jung) via ruby-core
2024-04-16 1:13 ` [ruby-core:117521] " ioquatix (Samuel Williams) via ruby-core
2024-04-16 9:54 ` [ruby-core:117528] " ioquatix (Samuel Williams) via ruby-core
2024-04-16 17:36 ` [ruby-core:117537] " mame (Yusuke Endoh) via ruby-core
2024-04-17 0:07 ` [ruby-core:117541] " ioquatix (Samuel Williams) via ruby-core
2024-04-17 1:13 ` [ruby-core:117542] " akr (Akira Tanaka) via ruby-core
2024-04-17 4:25 ` [ruby-core:117544] " ioquatix (Samuel Williams) via ruby-core
2024-04-17 23:16 ` [ruby-core:117580] " akr (Akira Tanaka) via ruby-core
2024-04-19 1:20 ` [ruby-core:117603] " Dan0042 (Daniel DeLorme) via ruby-core
2024-04-22 4:06 ` [ruby-core:117636] " ioquatix (Samuel Williams) via ruby-core
2024-04-22 4:08 ` [ruby-core:117637] " ioquatix (Samuel Williams) via ruby-core
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