README.md completed for rustecal-types-string (#30)

Author: rex-schilasky

rustecal-types-string/README.md

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+# rustecal-types-string
+
+`rustecal-types-string` provides a simple wrapper for UTF-8 string messages (`Arc<str>`) to use with the typed eCAL Pub/Sub API.
+
+## Features
+
+- **StringMessage**: wrap and transport UTF-8 string payloads
+- Implements `PublisherMessage` and `SubscriberMessage` for seamless integration
+- Zero-copy where possible via `Arc<str>`
+- No extra dependencies beyond `rustecal-core` and `rustecal-pubsub`
+
+## Installation
+
+Add to your **workspace** `Cargo.toml`:
+
+```toml
+[dependencies]
+rustecal-types-string = "0.1"
+```
+
+## Usage
+
+### Publisher Example
+
+```rust
+use std::sync::Arc;
+use rustecal::{Ecal, EcalComponents, TypedPublisher};
+use rustecal_types_string::StringMessage;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    Ecal::initialize(Some("string publisher"), EcalComponents::DEFAULT)?;
+
+    let publisher = TypedPublisher::<StringMessage>::new("hello")?;
+
+    while Ecal::ok() {
+        let message = StringMessage { data: Arc::from("Hello from Rust") };
+        publisher.send(&message);
+
+        std::thread::sleep(std::time::Duration::from_millis(500));
+    }
+
+    Ecal::finalize();
+    Ok(())
+}
+```
+
+### Subscriber Example
+
+```rust
+use rustecal::{Ecal, EcalComponents, TypedSubscriber};
+use rustecal_types_string::StringMessage;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    Ecal::initialize(Some("string subscriber"), EcalComponents::DEFAULT)?;
+
+    let mut subscriber = TypedSubscriber::<StringMessage>::new("hello")?;
+    subscriber.set_callback(|message| {
+        println!("Received: {}", message.payload.data)
+    });
+
+    while Ecal::ok() {
+        std::thread::sleep(std::time::Duration::from_millis(500));
+    }
+
+    Ecal::finalize();
+    Ok(())
+}
+```
+
+## Traits Reference
+
+- **`PublisherMessage`**
+
+  - `fn datatype() -> DataTypeInfo`
+  - `fn to_bytes(&self) -> Arc<[u8]>`
+
+- **`SubscriberMessage`**
+
+  - `fn datatype() -> DataTypeInfo`
+  - `fn from_bytes(bytes: Arc<[u8]>, _data_type_info: &DataTypeInfo) -> Option<Self>`
+
+## See Also
+
+- `rustecal-types-bytes` for raw binary data messages
+- `rustecal-types-protobuf` for Protobuf-based messages
+- `rustecal-types-serde` for JSON/CBOR/MessagePack via Serde
+- Examples in the `rustecal-samples/pubsub` directory