# Streamget

## Analysis of the Streamget Project

This is **streamget**, a robust C program for recording streaming audio (MP3) from internet radio stations. Here's a complete analysis:

### Main Functionality

**streamget** is designed to record MP3 streams from Icecast servers with automatic reconnection on connection loss. The program:

- Receives streaming MP3 data from a URL
- Writes the stream to a file
- Automatically reconnects when the connection drops
- Stops after a specified time duration
- Typically started via cron to make recordings at specific times

### Core Functionality (src/main.c)

**Key features:**

1. **Robust streaming**: Keeps trying to reconnect on connection loss
2. **Timing control**:
   - Time limit for total recording duration (default 4 hours)
   - Timer can start at program launch or on first successful connection
3. **Reconnect logic**:
   - `connect_timeout`: Time between initial connection attempts (default 20 sec)
   - `connect_period`: How long to keep trying initial connection
   - `reconnect_timeout`: Time between reconnection attempts (default 1 sec)
   - `reconnect_period`: How long to keep trying to reconnect
4. **Daemon mode**: Can run in the background
5. **File locking**: Prevents multiple instances writing to the same file
6. **Progress/verbose modes**: For monitoring and debugging
7. **Signal handling**: SIGALRM for time limit, SIGCONT to parent when recording starts

### URL Handling (src/url_fopen.c)

Smart abstraction layer on top of libcurl:

- **Transparent file I/O interface**: Uses familiar functions like `fopen()`, `fread()`, `fgets()`
- **Dual mode**:
  - Local files → standard C file I/O
  - URLs → libcurl with buffering
- **Non-blocking I/O**: Uses `curl_multi` interface with `select()` for asynchronous transfers
- **Automatic buffering**: Dynamically growing buffer for streaming data
- **HTTP features**: Follows redirects automatically, custom user-agent support

### Helper Functions

**daemonize.c**: Standard Unix daemon creation via double-fork pattern
**lock.c**: File locking with `fcntl()` to prevent race conditions

### Build System

- **Autotools setup**: configure.in, Makefile.am
- **Dependencies**: libcurl 7.9.7 or later
- **Compiler flags**: `-Wall -ggdb` for warnings and debug info

### Typical Use Case

```bash
streamget \
  --url http://radio.station.com:8000/stream.mp3 \
  --output /path/to/recording.mp3 \
  --time-limit 3600 \
  --log /var/log/streamget.log \
  --daemonize \
  --verbose
```

This records 1 hour from the stream, logs to file, and runs in the background.

### Technical Quality

**Strengths:**

- Robust error handling with errno checking
- Proper signal handling
- EINTR retry loops on syscalls
- Clean separation of concerns
- Good logging infrastructure

**Design Patterns:**

- State machine in main loop (IDLE, CONNECTING, CONNECTED, RECONNECTING, etc.)
- Callback pattern for libcurl data
- Resource cleanup via goto-based error handling

This is professional C code for a reliable recording system for internet radio streaming.

## Copyright

Copyright (c) 2025 Kerkdienst Gemist B.V.
Author: K.J. Wierenga <k.j.wierenga@kerkdienstgemist.nl>