m2m/codec/
brotli.rs

1//! Brotli compression codec (Algorithm::Brotli).
2//!
3//! Uses Brotli compression for high compression ratios on larger payloads.
4//! Output is base64-encoded for wire transmission.
5
6use base64::{engine::general_purpose::STANDARD as BASE64, Engine};
7use brotli::{CompressorWriter, Decompressor};
8use std::io::{Read, Write};
9
10use super::{Algorithm, CompressionResult};
11use crate::error::{M2MError, Result};
12
13/// Brotli compression quality (0-11, higher = better compression, slower)
14const DEFAULT_QUALITY: u32 = 11;
15
16/// Window size for Brotli (larger = better compression for large files)
17const DEFAULT_WINDOW_SIZE: u32 = 22;
18
19/// Brotli codec
20#[derive(Clone)]
21pub struct BrotliCodec {
22    /// Compression quality (0-11)
23    pub quality: u32,
24    /// Window size (10-24)
25    pub window_size: u32,
26}
27
28impl Default for BrotliCodec {
29    fn default() -> Self {
30        Self {
31            quality: DEFAULT_QUALITY,
32            window_size: DEFAULT_WINDOW_SIZE,
33        }
34    }
35}
36
37impl BrotliCodec {
38    /// Create new Brotli codec with default settings
39    pub fn new() -> Self {
40        Self::default()
41    }
42
43    /// Create codec with custom quality
44    pub fn with_quality(quality: u32) -> Self {
45        Self {
46            quality: quality.min(11),
47            ..Default::default()
48        }
49    }
50
51    /// Compress bytes to Brotli format
52    pub fn compress_bytes(&self, data: &[u8]) -> Result<Vec<u8>> {
53        let mut compressed = Vec::new();
54        {
55            let mut writer =
56                CompressorWriter::new(&mut compressed, 4096, self.quality, self.window_size);
57            writer
58                .write_all(data)
59                .map_err(|e| M2MError::Compression(e.to_string()))?;
60        }
61        Ok(compressed)
62    }
63
64    /// Decompress Brotli bytes
65    pub fn decompress_bytes(&self, data: &[u8]) -> Result<Vec<u8>> {
66        let mut decompressor = Decompressor::new(data, 4096);
67        let mut decompressed = Vec::new();
68        decompressor
69            .read_to_end(&mut decompressed)
70            .map_err(|e| M2MError::Decompression(e.to_string()))?;
71        Ok(decompressed)
72    }
73
74    /// Compress string to wire format: `#M2M[v3.0]|DATA:<base64>`
75    pub fn compress(&self, content: &str) -> Result<CompressionResult> {
76        let compressed = self.compress_bytes(content.as_bytes())?;
77        let encoded = BASE64.encode(&compressed);
78        let wire = format!("#M2M[v3.0]|DATA:{encoded}");
79        let wire_len = wire.len();
80
81        Ok(CompressionResult::new(
82            wire,
83            Algorithm::Brotli,
84            content.len(),
85            wire_len,
86        ))
87    }
88
89    /// Decompress from wire format
90    pub fn decompress(&self, wire: &str) -> Result<String> {
91        let data = wire
92            .strip_prefix("#M2M[v3.0]|DATA:")
93            .ok_or_else(|| M2MError::InvalidMessage("Invalid Brotli wire format".to_string()))?;
94
95        let compressed = BASE64.decode(data)?;
96        let decompressed = self.decompress_bytes(&compressed)?;
97
98        String::from_utf8(decompressed)
99            .map_err(|e| M2MError::Decompression(format!("Invalid UTF-8: {e}")))
100    }
101}
102
103#[cfg(test)]
104mod tests {
105    use super::*;
106
107    #[test]
108    fn test_compress_decompress() {
109        let codec = BrotliCodec::new();
110        let original =
111            r#"{"model":"gpt-4o","messages":[{"role":"user","content":"Hello, world!"}]}"#;
112
113        let result = codec.compress(original).unwrap();
114        assert!(result.data.starts_with("#M2M[v3.0]|DATA:"));
115
116        let decompressed = codec.decompress(&result.data).unwrap();
117        assert_eq!(decompressed, original);
118    }
119
120    #[test]
121    fn test_compression_ratio() {
122        let codec = BrotliCodec::new();
123
124        // Repetitive content compresses well
125        let original = r#"{"messages":[{"role":"user","content":"Hello"},{"role":"assistant","content":"Hi there!"},{"role":"user","content":"How are you?"},{"role":"assistant","content":"I'm doing great, thank you for asking!"}]}"#;
126
127        let result = codec.compress(original).unwrap();
128
129        // Brotli should achieve some compression
130        println!(
131            "Original: {} bytes, Compressed: {} bytes, Ratio: {:.2}",
132            result.original_bytes,
133            result.compressed_bytes,
134            result.byte_ratio()
135        );
136    }
137
138    #[test]
139    fn test_bytes_roundtrip() {
140        let codec = BrotliCodec::new();
141        let original = b"Hello, Brotli! This is a test of byte compression.";
142
143        let compressed = codec.compress_bytes(original).unwrap();
144        let decompressed = codec.decompress_bytes(&compressed).unwrap();
145
146        assert_eq!(decompressed, original);
147    }
148}
m2m/codec/brotli.rs

m2m/codec/
brotli.rs
