PARQUET-3261: Fix integer overflow in CapacityByteArrayOutputStream

[yadavay-amzn]

What changes were made?

Fix integer overflow in CapacityByteArrayOutputStream.addSlab() that causes ArithmeticException when writing large ARRAY<STRING> columns (issue #3261).

Root cause (identified by @Kimahriman)

The overflow check in addSlab() used bytesUsed to detect overflow, but bytesUsed is not updated until after addSlab() returns in write(). Additionally, nextSlabSize can be larger than minimumSize (due to the doubling strategy), so checking only bytesUsed + minimumSize was insufficient.

This meant bytesAllocated = Math.addExact(this.bytesAllocated, nextSlabSize) could overflow without being caught by the guard, throwing an uncaught ArithmeticException instead of the intended OutOfMemoryError.

Fix

1. Use bytesAllocated instead of bytesUsed for the overflow check — bytesAllocated is always up to date when addSlab() is called.
2. Cap nextSlabSize when it would cause bytesAllocated to overflow Integer.MAX_VALUE, preventing the uncaught ArithmeticException on the Math.addExact call.

Tests

Added TestCapacityByteArrayOutputStreamOverflow with two tests:

• Verifies that slab allocation near Integer.MAX_VALUE succeeds (previously threw ArithmeticException)
• Verifies that a true overflow still throws OutOfMemoryError as intended

[steveloughran]

LGTM

[yadavay-amzn]

Friendly ping to @wgtmac @Fokko, this is a small doc/parser change that's been LGTM'd by @steveloughran. Could one of you please take a look when you have a moment? Thanks!

[Copilot]

Pull request overview

This pull request fixes an integer-overflow edge case in CapacityByteArrayOutputStream.addSlab(int) that could previously surface as an uncaught ArithmeticException when writing very large values (e.g., large ARRAY<STRING> columns), and adds regression tests to validate the corrected behavior.

Changes:

• Adjust overflow guarding in addSlab() to use bytesAllocated (which is current at slab-allocation time) rather than bytesUsed.
• Cap the computed nextSlabSize so bytesAllocated + nextSlabSize cannot overflow Integer.MAX_VALUE, preventing Math.addExact from throwing unexpectedly.
• Add JUnit regression tests covering both the “near max” capping case and the “true overflow” OutOfMemoryError case.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
parquet-common/src/main/java/org/apache/parquet/bytes/CapacityByteArrayOutputStream.java	Fixes the overflow detection and prevents bytesAllocated growth from triggering an uncaught ArithmeticException.
parquet-common/src/test/java/org/apache/parquet/bytes/TestCapacityByteArrayOutputStreamOverflow.java	Adds regression tests validating slab-size capping near Integer.MAX_VALUE and correct OutOfMemoryError behavior on genuine overflow.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[wgtmac]

Thanks @yadavay-amzn for fixing it and @steveloughran for the review! This makes sense to me.