[JCS-88] Block cache fails to validate a cache file on startup when it contains elements with more than 2 blocks.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: jcs-1.3
• Fix Version/s: jcs-2.0-beta-1
• Assignee: Thomas Vandahl
• Reporter: Diego Rivera
• Created: 23/Jan/12 20:51
• Updated: 01/Apr/15 14:51
• Resolved: 02/Apr/12 11:36

Description

The arithmetic for calculating block sizes is wrong. The code adds a term that shouldn't be considered at that point. For each block that needs to be written, the size of the block is currently calculated as:

int chunkSize = Math.min( totalUsed + maxChunkSize, totalBytes - totalUsed )

The term "totalUsed" should not be added to maxChunkSize, since the intent is to construct a chunk that's either as big as is allowed (maxChunkSize) or as big as the remaining bytes (totalBytes - totalUsed). Thus, the correct calculation should be:

int chunkSize = Math.min( maxChunkSize, totalBytes - totalUsed )

The problem occurs in src/java/org/apache/jcs/auxiliary/disk/block/BlockDisk.java, line 196, inside byte[][] getBlockChunks(byte[] complete, int numBlocksNeeded).

A patch has been devised and will be submitted as a comment (since attachments aren't possible at this point). I still need to take the time to devise a unit test for this since the existing unit test passed without issue.