apache/flink · error · IndexOutOfBoundsException

Length cannot be negative.

Error message

Length cannot be negative.

What it means

Thrown by DataInputDeserializer.read(byte[], int off, int len) when len is negative. The method rejects negative read lengths up front with a clear message.

Source

Thrown at flink-core/src/main/java/org/apache/flink/core/memory/DataInputDeserializer.java:389

    @Override
    public void skipBytesToRead(int numBytes) throws IOException {
        int skippedBytes = skipBytes(numBytes);

        if (skippedBytes < numBytes) {
            throw new EOFException("Could not skip " + numBytes + " bytes.");
        }
    }

    @Override
    public int read(@Nonnull byte[] b, int off, int len) throws IOException {

        if (off < 0) {
            throw new IndexOutOfBoundsException("Offset cannot be negative.");
        }

        if (len < 0) {
            throw new IndexOutOfBoundsException("Length cannot be negative.");
        }

        if (b.length - off < len) {
            throw new IndexOutOfBoundsException(
                    "Byte array does not provide enough space to store requested data" + ".");
        }

        if (this.position >= this.end) {
            return len == 0 ? 0 : -1;
        } else {
            int toRead = Math.min(this.end - this.position, len);
            System.arraycopy(this.buffer, this.position, b, off, toRead);
            this.position += toRead;

            return toRead;
        }
    }

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Ensure len >= 0 before calling read(b, off, len).
2. Treat len == 0 explicitly (read returns 0) rather than passing a computed negative.
3. Clamp len from external/sourced values: len = Math.max(0, requested).

Example fix

// before
input.read(dst, off, remaining); // remaining may be < 0

// after
if (remaining <= 0) {
    return; // nothing to read
}
input.read(dst, off, remaining);

if (len < 0) {
    throw new IndexOutOfBoundsException("len must be >= 0, got " + len);
}
input.read(dst, off, len);

When it happens

Trigger: Calling read(b, off, len) with len < 0.

Common situations: len derived from a size that underflowed to negative; a remaining-bytes computation that goes below zero; passing a -1 default sentinel.

Related errors

• Invalid bounds.
• Length may not be negative.
• Offset cannot be negative.
• Byte array does not provide enough space to store requested
• Could not skip {numBytes} bytes.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/f474109c73cecd21. Report an issue: GitHub.