jruby/jruby · error · Zlib::Error

stream is not ready

Error message

stream is not ready

What it means

Error "stream is not ready" thrown in jruby/jruby.

Source

Thrown at core/src/main/java/org/jruby/ext/zlib/ZStream.java:246

    public IRubyObject close() {
        return close(getCurrentContext());
    }

    @JRubyMethod(name = {"close", "end"})
    public IRubyObject close(ThreadContext context) {
        checkClosed(context);
        internalClose();
        closed = true;
        return context.nil;
    }

    @Deprecated(since = "10.0.0.0")
    void checkClosed() {
        checkClosed(getCurrentContext());
    }

    void checkClosed(ThreadContext context) {
        if (closed) throw RubyZlib.newZlibError(context, "stream is not ready");
    }

    // TODO: remove when JZlib checks the given level
    static int checkLevel(ThreadContext context, int level) {
        if ((level < 0 || level > 9) && level != JZlib.Z_DEFAULT_COMPRESSION) {
            throw RubyZlib.newStreamError(context, "stream error: invalid level");
        }
        return level;
    }

    /**
     * We only do windowBits=15(32K buffer, LZ77 algorithm) since java.util.zip
     * only allows it. NOTE: deflateInit2 of zlib.c also accepts MAX_WBITS +
     * 16(gzip compression). inflateInit2 also accepts MAX_WBITS + 16(gzip
     * decompression) and MAX_WBITS + 32(automatic detection of gzip and LZ77).
     */
    // TODO: remove when JZlib checks the given windowBits
    static int checkWindowBits(ThreadContext context, int value, boolean forInflate) {

View on GitHub (pinned to fb650c13e0)

Solutions

1. The zlib stream was used before it was ready (not initialized or already ended). Initialize/reset the stream before use and do not use it after end().

When it happens

Trigger: Thrown at core/src/main/java/org/jruby/ext/zlib/ZStream.java:246 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jruby/jruby@fb650c13e0 (2026-08-23). Data as JSON: /api/errors/b5b0b0f7002fe44b. Report an issue: GitHub.