Adding Claude.md

Author: lookbusy1344

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+HashRust is a CLI file hashing utility written in Rust that supports multiple hash algorithms (MD5, SHA1, SHA2, SHA3, Blake2, Whirlpool, CRC32) with multi-threading capabilities via Rayon. The project uses a modular architecture with separate modules for hashing logic, algorithm types, and CLI processing.
+
+## Common Commands
+
+### Building
+- `cargo build` - Development build
+- `cargo build -r` or `cargo build --release` - Release build (recommended for performance)
+
+### Testing
+- `cargo test` - Run unit tests (located in src/unit_tests.rs)
+- `cargo test --test integration_tests` - Run integration tests
+
+### Code Quality
+- `cargo check` - Fast compilation check without producing binary
+- `cargo clippy` - Run linter with standard warnings
+- `cargo clippy -- -D clippy::all -D clippy::pedantic` - Run pedantic clippy checks (matches .vscode/tasks.json)
+- `cargo fmt` - Format code
+
+### Running
+- `cargo run -- *.txt -a sha3` - Run with file glob and algorithm
+- `cargo run -- --help` - Show help
+
+## Code Architecture
+
+### Module Structure
+- `main.rs` - CLI argument parsing, main worker function, and threading coordination
+- `classes.rs` - Core types: `HashAlgorithm` enum, `OutputEncoding` enum, `ConfigSettings` struct, `BasicHash` wrapper
+- `hasher.rs` - Generic hashing implementation using Digest trait, file I/O optimization for small/large files
+- `crc32.rs` - Custom CRC32 implementation (separate from other hash algorithms)
+- `unit_tests.rs` - Unit test module
+
+### Key Design Patterns
+- Uses Rust's `Digest` trait for generic hash algorithm implementation
+- Multi-threading via Rayon's parallel iterators (`par_iter`)
+- Single-threaded fallback for single files or when explicitly requested
+- Enum-driven algorithm selection with `strum` for string parsing
+- Buffer size optimization: small files (≤32KB) read entirely, larger files use 32KB chunks
+
+### Algorithm Support
+- CRC32 outputs as U32 format only (10-digit zero-padded)
+- All other algorithms support Hex (default), Base64, Base32 encoding
+- Default algorithm is SHA3-256
+
+### Configuration
+- `ConfigSettings` struct centralizes all CLI options
+- Supports glob patterns with case-sensitive option
+- File input via CLI args or stdin pipe
+- Optional file count limiting
+
+### Error Handling
+- Uses `anyhow` for error propagation
+- Graceful handling of file access errors
+- Validates algorithm/encoding combinations
+
+## Development Notes
+
+### Copilot Instructions Integration
+- Target senior engineers (15+ years experience)
+- Use modern Rust idioms and functional style
+- Keep code concise, avoid unchanged code in suggestions
+- Brief commit messages preferred
+
+### Performance Considerations
+- Multi-threading is default behavior
+- Buffer size optimized for typical file sizes
+- Uses BufReader for efficient file I/O
+- Release builds use LTO and panic=abort for size/speed
+
+## Development Workflow
+
+**IMPORTANT: Always run `cargo fmt` after making any code changes to ensure consistent formatting.**