Add string representations for compression API

Author: thekid

src/main/php/com/mongodb/io/Compression.class.php

@@ -1,12 +1,17 @@
 <?php namespace com\mongodb\io;
 
+use lang\Value;
+use util\{Comparison, Objects};
+
 /** 
  * Compression negotiation and selection.
  * 
  * @see   https://github.com/mongodb/specifications/blob/master/source/compression/OP_COMPRESSED.md
  * @test  com.mongodb.unittest.CompressionTest
  */
-class Compression {
+class Compression implements Value {
+  use Comparison;
+
   private static $negotiable= [];
   private $compressors;
 
@@ -81,4 +86,9 @@ public function for($sections, $length) {
     // Currently always select the first compressor negotiated
     return current($this->compressors);
   }
+
+  /** @return string */
+  public function toString() {
+    return nameof($this).'@'.Objects::stringOf($this->compressors);
+  }
 }

src/main/php/com/mongodb/io/Compressor.class.php

@@ -1,10 +1,15 @@
 <?php namespace com\mongodb\io;
 
-abstract class Compressor {
+use lang\Value;
+
+abstract class Compressor implements Value {
   public $id;
 
   public abstract function compress($data);
 
   public abstract function decompress($compressed);
 
+  public function hashCode() { return 'C'.$this->id; }
+
+  public function compareTo($value) { return $value instanceof self ? $this->id <=> $value->id : 1; }
 }

src/main/php/com/mongodb/io/Zlib.class.php

@@ -16,4 +16,9 @@ public function compress($data) {
   public function decompress($compressed) {
     return gzuncompress($compressed);
   }
+
+  /** @return string */
+  public function toString() {
+    return nameof($this).'(id: '.$this->id.', level: '.$this->level.')';
+  }
 }

src/main/php/com/mongodb/io/Zstd.class.php

@@ -16,4 +16,9 @@ public function compress($data) {
   public function decompress($compressed) {
     return zstd_uncompress($compressed);
   }
+
+  /** @return string */
+  public function toString() {
+    return nameof($this).'(id: '.$this->id.', level: '.$this->level.')';
+  }
 }