# Requirements Document

## Introduction

This feature adds a simple benchmark option to the existing `bin/checksum.rs` tool via a command-line flag. The benchmark will allow users to test performance across different platforms using a single binary, reporting throughput in GiB/s and the acceleration target used. This enables cross-platform performance comparison without requiring a full development environment checkout.

## Glossary

- **Checksum_Tool**: The existing `bin/checksum.rs` binary application

- **Benchmark_Mode**: A new operational mode that measures and reports performance metrics

- **Acceleration_Target**: The hardware-specific optimization path returned by `get_calculator_target()`

- **Throughput_Metric**: Performance measurement expressed in GiB/s (gibibytes per second)

- **Test_Data**: Randomly generated byte array used for benchmark measurements

- **Black_Box**: Rust's `std::hint::black_box()` function that prevents compiler optimizations during benchmarking

## Requirements

### Requirement 1

**User Story:** As a developer, I want to run performance benchmarks from the checksum tool, so that I can compare CRC performance across different hardware platforms without setting up a full development environment.

#### Acceptance Criteria

1. WHEN the user provides a `-b` flag, THE Checksum_Tool SHALL enter Benchmark_Mode

2. WHILE in Benchmark_Mode, THE Checksum_Tool SHALL generate Test_Data of the specified size once and reuse it for all iterations

3. THE Checksum_Tool SHALL report Throughput_Metric in GiB/s format

4. THE Checksum_Tool SHALL display the Acceleration_Target used for the benchmark

5. THE Checksum_Tool SHALL use Black_Box to prevent compiler optimizations during measurement

### Requirement 2

**User Story:** As a developer, I want to specify benchmark parameters, so that I can control the test conditions for consistent cross-platform comparisons.

#### Acceptance Criteria

1. WHEN the user provides `-a` parameter with `-b` flag, THE Checksum_Tool SHALL use the specified CRC algorithm for benchmarking

2. WHEN the user provides `--size` parameter, THE Checksum_Tool SHALL generate Test_Data of the specified byte size

3. WHEN the user provides `--duration` parameter, THE Checksum_Tool SHALL run the benchmark for the specified number of seconds

4. WHERE no benchmark parameters are provided, THE Checksum_Tool SHALL use default values of 1 MiB for size and 10 seconds for duration

5. THE Checksum_Tool SHALL validate all benchmark parameter values before starting the benchmark

### Requirement 3

**User Story:** As a developer, I want the benchmark to support both file/string input and generated data, so that I can benchmark with specific data or use random data for consistent testing.

#### Acceptance Criteria

1. WHEN the user provides `-b` with `-f` or `-s` flags, THE Checksum_Tool SHALL use the file or string content as Test_Data for benchmarking

2. WHEN the user provides `-b` with `--size` parameter but no `-f` or `-s` flags, THE Checksum_Tool SHALL generate random Test_Data of the specified size

3. IF the user provides `-b` without any data source or size specification, THEN THE Checksum_Tool SHALL generate random Test_Data using the default size

4. THE Checksum_Tool SHALL display appropriate usage information when benchmark parameters are invalid

5. THE Checksum_Tool SHALL maintain backward compatibility with existing checksum functionality