mergerfs/.opencode/plans/threadlocalcache-refactor.md

ThreadLocalCache Method Refactor Plan

Goal

Encapsulate local cache operations into methods of the ThreadLocalCache struct for better code organization and maintainability.

Changes Required

1. Modify ThreadLocalCache struct (lines 70-74)

Add member methods:

• empty() - returns true if cache has no nodes
• remove() - pops and returns head node
• add(Node* node_) - pushes node to head

2. Update call sites

Line 228

Change: if(_local_cache.head == nullptr) → if(_local_cache.empty())

Lines 233-236 (_alloc_impl success path)

Replace:

Node *node = _local_cache.head;
_local_cache.head = node->next;
_local_cache.count--;
mem = static_cast<void*>(node);

With:

mem = static_cast<void*>(_local_cache.remove());

Lines 253-255 (exception handler)

Replace:

node->next = _local_cache.head;
_local_cache.head = node;
_local_cache.count++;

With:

_local_cache.add(node);

Lines 145-147 (_transfer_from_global_to_local)

Replace direct manipulation with _local_cache.add(node)

Lines 169-171 (_transfer_from_local_to_global)

Replace direct manipulation with _local_cache.remove()

Lines 283-285 (free_size)

Replace direct manipulation with _local_cache.add(node)

Benefits

• Eliminates code duplication (add pattern used 3 times)
• Single source of truth for cache operations
• Self-documenting code
• Easier to add bounds checking or assertions later