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Avoid fast-path IO writes when IO has ext enc #759

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Merged
merged 1 commit into from
Mar 10, 2025
Merged

Avoid fast-path IO writes when IO has ext enc #759

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34 changes: 33 additions & 1 deletion java/src/json/ext/Generator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
*/
package json.ext;

import org.jcodings.Encoding;
import org.jcodings.specific.UTF8Encoding;
import org.jruby.Ruby;
import org.jruby.RubyArray;
Expand All @@ -15,6 +16,7 @@
import org.jruby.RubyFixnum;
import org.jruby.RubyFloat;
import org.jruby.RubyHash;
import org.jruby.RubyIO;
import org.jruby.RubyString;
import org.jruby.RubySymbol;
import org.jruby.runtime.Helpers;
Expand Down Expand Up @@ -81,11 +83,41 @@ static <T extends IRubyObject> RubyString generateJson(ThreadContext context, T
return handler.generateNew(context, session, object);
}

BufferedOutputStream buffer = new BufferedOutputStream(new IOOutputStream(io), IO_BUFFER_SIZE);
BufferedOutputStream buffer =
new BufferedOutputStream(
new PatchedIOOutputStream(io, UTF8Encoding.INSTANCE),
IO_BUFFER_SIZE);
handler.generateToBuffer(context, session, object, buffer);
return io;
}

/**
* A version of IOOutputStream hacked to avoid fast-path RubyIO calls when the target IO has an external encoding.
*
* All calls to the underlying IO will be done dynamically and all incoming bytes wrapped in RubyString instances.
* This avoids bugs in the fast-path logic in JRuby 9.4.12.0 and earlier that fails to properly handle writing bytes
* when the source and target destination are the same.
*
* See https://github.com/jruby/jruby/issues/8682
*/
private static class PatchedIOOutputStream extends IOOutputStream {
public PatchedIOOutputStream(IRubyObject io, Encoding encoding) {
super(io, encoding);
}

@Override
public RubyIO getRealIO(IRubyObject io) {
RubyIO realIO = super.getRealIO(io);

// if the real IO has an external encoding, don't use fast path
if (realIO == null || realIO.getEnc() != null) {
return null;
}

return realIO;
}
}

/**
* Returns the best serialization handler for the given object.
*/
Expand Down