update changelog

Author: gregnazario

CHANGELOG.md

@@ -1,10 +1,48 @@
 # Changelog
 
+## [Unreleased]
+
+### Security
+
+- **Memory amplification protection**: Deserialization now validates that claimed sequence/string lengths are plausible given the remaining input, preventing DoS attacks where a small malicious payload could trigger large memory allocations.
+- **Duplicate map key detection**: Serialization now returns `Error::NonCanonicalMap` when duplicate keys are encountered instead of silently dropping duplicates, ensuring data integrity.
+
+### Added
+
+- `to_bytes_with_capacity()` function for pre-allocating output buffers when the serialized size is known or estimated, reducing allocations.
+- Comprehensive `# Errors` documentation sections on all public functions.
+- `#[must_use]` attribute on `is_human_readable()`.
+- Explicit `#![forbid(unsafe_code)]` via Cargo.toml lints section.
+- Full pedantic clippy lint compliance with minimal, justified exceptions for binary serialization casts.
+- `rustfmt.toml` configuration for consistent code formatting.
+
+### Changed
+
+- **Optimized ULEB128 encoding/decoding**: Added fast paths for single-byte values (0-127), which are common for sequence lengths and enum variant indices.
+- **Optimized bulk byte reading**: Deserialization now uses slice splitting instead of byte-by-byte copying for integer parsing.
+- **Added `#[inline]` hints** on hot serialization/deserialization paths for better performance.
+- Replaced `sort_by` with `sort_unstable_by` for map key sorting (faster, no stability needed for unique keys).
+
+### CI/CD
+
+- Added separate CI jobs for formatting (`cargo fmt`), linting (`cargo clippy`), testing, coverage, documentation, and MSRV verification.
+- Added code coverage reporting with Codecov integration and 90% line coverage threshold.
+- Added Minimum Supported Rust Version (MSRV) check at Rust 1.78.0.
+- Improved CI caching for faster builds.
+- Documentation builds now use `-D warnings` to catch doc issues.
+
+### Testing
+
+- Expanded test suite with security-focused tests for memory amplification and duplicate key detection.
+- Added tests for `to_bytes_with_capacity`, `from_bytes_seed`, and other previously uncovered code paths.
+- Improved benchmark suite with comprehensive type coverage and deserialization benchmarks.
+
 ## [v0.1.1] - 2020-12-11
 - Renaming crate into "bcs".
 
 ## [v0.1.0] - 2020-11-17
 - Initial release.
 
+[Unreleased]: https://github.com/diem/bcs/compare/v0.1.1...HEAD
 [v0.1.1]: https://github.com/diem/bcs/releases/tag/v0.1.1
 [v0.1.0]: https://github.com/diem/bcs/releases/tag/v0.1.0