Add license and readme

Signed-off-by: Gaëtan Lehmann <[email protected]>

Author: glehmann

LICENSE

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+MIT License
+
+Copyright (c) 2024 Gaëtan Lehmann
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# randstream: Reproducible Stream Generator and Validator
+
+**`randstream`** is a high-performance command-line utility for creating and
+validating reproducible, pseudo-random data streams. It is designed for use
+cases such as verifying storage integrity, benchmarking I/O performance, or
+generating large, arbitrary datasets for testing.
+
+The utility uses a **seed** to ensure that the generated data is reproducible.
+In order to be validatable without regeneration on the data, the stream includes
+a **checksum** of 4 bytes at the end of each chunk.
+It also uses **parallel processing** to ensure maximum throughput on modern
+hardware, while keeping the output identical independently of the number of
+parallel tasks.
+
+## Installation
+
+```bash
+cargo install randstream
+````
+
+## Usage
+
+`randstream` has two main commands: **`generate`** and **`validate`**.
+
+### Generating a Random Stream (`generate`)
+
+Use the generate command to create a reproducible stream of pseudo-random data.
+
+## Validating a Random Stream (`validate`)
+
+Use the `validate` command to verify that an existing stream has not been
+corrupted or altered. The validation process will **re-generate** the data
+internally using the same seed and compare it byte-for-byte with the input
+stream.
+
+### Examples
+
+**Fill a whole block device:**
+
+```bash
+randstream generate /dev/xvdb
+```
+
+**Generate a 100 GB file using a specific seed and 2 parallel tasks:**
+
+```bash
+randstream generate --size 10G --seed 1a234e5678 --jobs 2 output.bin
+```
+
+**Validate a previously generated stream:**
+
+```bash
+randstream generate output.bin
+```