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Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[2.0.0] - 2026-03-11

Added

  • Stream metadata now includes revision/ack tracking to prevent missed unread-update signaling when writers outpace reader acknowledgements
  • Stream writer serialization lock and reader snapshot consistency checks to avoid torn reads under concurrent writers
  • Queue producer serialization lock to prevent concurrent producer slot/index races
  • Queue consumer serialization lock to prevent concurrent consumer read-index races
  • Regression test coverage for Issue #3 behavior and concurrent writer/producer coherence
  • New lsm_bench contention benchmark executable and top-level make bench command
  • CI benchmark execution on ubuntu-latest matrix leg

Changed

  • Stream wire layout metadata changed from |flags|size|data| to an extended metadata header (flags + revision + ack + size + lock + data)
  • Queue metadata header expanded to include producer and consumer lock state

Fixed

  • hasNewData() no longer drops unread updates when multiple writes occur before markAsRead()
  • Concurrent stream writers no longer produce mixed/torn payload snapshots in stress tests
  • Concurrent queue producers no longer corrupt message prefixes or race write index updates in stress tests
  • Concurrent queue consumers no longer race read-index updates in stress tests

Performance

  • Expected performance impact: slight to moderate throughput drop in write-heavy workloads due to writer/producer/consumer lock serialization under contention
  • Typical impact is low for single-writer/single-producer use, and higher under heavy contention where correctness is now prioritized

Breaking Changes

  • This is a wire-layout breaking change for stream and queue metadata
  • Existing processes built against the old in-memory format must not interoperate with this new build until all participants are updated together

[1.10.0] - 2026-03-11

Added

  • Makefile with build, test, clean, examples and setup targets wrapping CMake
  • Re-verified current macOS aarch64 (Apple Silicon) support on Sequoia 15.7.3
  • New test case on Memory accessors, getWriteFlags logic, std::span write overloads, segment overwrite, queue capacity=1 edge case, maxMessageSize boundary and concurrent writing; also added docs to understand the tests better
  • .vscode/c_cpp_properties.json for C++20 IntelliSense on macOS (arm64/aarch64)
  • No-flake stability test: re-runs the full suite 1000 times as subprocesses to catch timing-dependent failures (cross-platform, skips itself via LSM_NOFLAKE env var)
  • Added macos-latest to GitHub Actions CI matrix with LSM_NOFLAKE=1 to skip the 1000-iteration flake test in CI
  • example/ directory with three runnable examples: stream transfer (C++), message queue (C++), and raw shared memory (C via lsm_c wrapper)
  • make examples target to build and run all examples
  • Pure C wrapper (lsm_c.h / lsm_c.cpp) exposing Memory as opaque-handle C functions
  • Rust FFI bindings (ffi/rust/) with safe SharedMemory wrapper, unit tests, and runnable example
  • ffi/rust/Makefile with setup, build, test, example, and clean targets
  • Zig FFI bindings (ffi/zig/) with idiomatic SharedMemory wrapper, unit tests, and runnable example (Zig 0.15+)
  • ffi/zig/Makefile with setup, build, test, example, and clean targets
  • Go FFI bindings (ffi/go/) via cgo with SharedMemory wrapper, unit tests, and runnable example
  • ffi/go/Makefile with setup, build, test, example, and clean targets

Changed

  • Improved README: added supported platforms table, building instructions, tightened examples and documentation
  • Added more detailed documentation for SharedMemoryQueue and Windows persistency features in README
  • Added Makefile to simplify setup, build and test processes for developers
  • README: added screenshot, pure C example with lsm_c wrapper

[1.9.0] - 2026-02-13

Added

  • Linux: Default permissions set to 0777.

[1.8.0] - 2026-02-06

Added

  • Windows: ACL inheritance for shared file, clean close/reopen when applying settings.

[1.7.0] - 2026-02-06

Added

  • SharedMemoryQueue: New FIFO message queue functionality for inter-process communication
    • Thread-safe enqueue/dequeue operations using atomic counters
    • Configurable capacity and maximum message size
    • peek() method to inspect messages without removing them
    • Status methods: isEmpty(), isFull(), size(), capacity()
    • Supports single producer/single consumer and single producer/multiple consumers patterns
  • Windows persistency support for shared memory segments
    • Persistent file-backed shared memory on Windows using %PROGRAMDATA%/shared_memory/ directory
    • Automatic directory creation and permission management on Windows
    • Configurable persistence with persist parameter in constructor

Changed

  • Updated C++20 requirements with std::atomic support for queue operations
  • Improved memory layout with atomic operations for queue counters
  • Enhanced Windows implementation with better file handle management

Fixed

  • Memory leak prevention in queue implementation
  • Proper cleanup of shared memory on all platforms

Previous Versions

Prior to version 1.7.0, the library supported:

  • Basic shared memory creation and access on Windows, Linux, and macOS
  • Stream-based data transfer with SharedMemoryWriteStream and SharedMemoryReadStream
  • Support for std::string, float*, and double* array types
  • Change detection with flag bit flipping
  • Single value access via .data()[index] API