feat: Add size method to CompressionEngine trait

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/compression_engine.rs

@@ -184,4 +184,57 @@ pub trait CompressionEngine {
     /// # Examples
     ///
     /// ```
-    /// let engine
+    /// let engine = /* some engine */;
+    /// let size = engine.size("file.gz".into()).unwrap();
+    /// println!("Decompressed size: {} bytes", size);
+    /// ```
+    fn size(&self, file_path: PathBuf) -> Result<usize> {
+        let mut reader = self.open(file_path)?;
+        let mut buffer = [0; libc::BUFSIZ as usize];
+        let mut size: usize = 0;
+
+        loop {
+            let n = reader.read(&mut buffer[..libc::BUFSIZ as usize])?;
+            if n == 0 {
+                debug!("COMPRESSION: EOF");
+                break;
+            }
+
+            size += n;
+        }
+
+        Ok(size)
+    }
+}
+
+lazy_static! {
+    /// Mapping of compression types to their external program implementations
+    pub static ref COMPRESSION_PROGRAMS: EnumMap<CompressionType, Option<CompressionEngineProgram>> = enum_map! {
+        CompressionType::LZ4 => {
+            let program = CompressionEngineProgram::new("lz4", vec!["-c"], vec!["-d", "-c"]);
+            if program.supported { Some(program) } else { None }
+        },
+        CompressionType::GZip => {
+            let program = CompressionEngineProgram::new("gzip", vec!["-c"], vec!["-d", "-c"]);
+            if program.supported { Some(program) } else { None }
+        },
+        CompressionType::BZip2 => {
+            let program = CompressionEngineProgram::new("bzip2", vec!["-qcf"], vec!["-dcf"]);
+            if program.supported { Some(program) } else { None }
+        },
+        CompressionType::XZ => {
+            let program = CompressionEngineProgram::new("xz", vec!["-qcf"], vec!["-dcf"]);
+            if program.supported { Some(program) } else { None }
+        },
+        CompressionType::ZStd => {
+            let program = CompressionEngineProgram::new("zstd", vec!["-qcf"], vec!["-dcf"]);
+            if program.supported { Some(program) } else { None }
+        },
+        CompressionType::None => None
+    };
+}
+
+/// Gets a compression engine for the specified compression type.
+///
+/// Dynamically selects and instantiates the appropriate compression engine
+/// based on feature flags