From b706afaf671ae70f6451f1bd9f1e4ed6c9e9d18d Mon Sep 17 00:00:00 2001
From: Christopher Vagnetoft <cvagnetoft@gmail.com>
Date: Sun, 25 Feb 2024 15:49:14 +0100
Subject: [PATCH] Implemented header packing logic

---
 README.md                         |  6 +++---
 src/Header/HeaderBag.php          | 10 ++++++++-
 src/Header/HeaderPacker.php       | 34 +++++++++++++++++++++++++++++--
 tests/Header/HeaderPackerTest.php | 19 ++++++++++++++++-
 4 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 55fe406..7b2730e 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,9 @@ This is a project that is exploring the feasability and practicality of bringing
 
 Currently implemented:
 
-* Huffman encoding (for compressed headers)
-* Header parsing (including dictionary)
-* Frame parsing (not all frame types)
+* Huffman encoding and decoding (for compressed headers)
+* Header parsing and packing (only static dictionary, no dynamic dictionary)
+* Frame parsing core (not all frame types)
 
 ## Notes
 
diff --git a/src/Header/HeaderBag.php b/src/Header/HeaderBag.php
index 7d723dd..6cf9ced 100644
--- a/src/Header/HeaderBag.php
+++ b/src/Header/HeaderBag.php
@@ -2,15 +2,18 @@
 
 namespace NoccyLabs\React\Http2\Header;
 
+use ArrayIterator;
+use IteratorAggregate;
 use NoccyLabs\React\Http2\Huffman\Codec;
 use NoccyLabs\React\Http2\Huffman\Dictionary;
+use Traversable;
 
 /**
  * An ordered list of HTTP/2 headers
  * 
  * 
  */
-class HeaderBag
+class HeaderBag implements IteratorAggregate
 {
 
     private array $headers = [];
@@ -24,4 +27,9 @@ class HeaderBag
     {
         $this->headers[] = [ $name, $value ];
     }
+
+    public function getIterator(): Traversable
+    {
+        return new ArrayIterator($this->headers);
+    }
 }
\ No newline at end of file
diff --git a/src/Header/HeaderPacker.php b/src/Header/HeaderPacker.php
index ef44a8e..792bd22 100644
--- a/src/Header/HeaderPacker.php
+++ b/src/Header/HeaderPacker.php
@@ -79,6 +79,8 @@ class HeaderPacker
     ];
     private const STATIC_TABLE_SIZE = 62; // considering unused index 0
 
+    private array $dynamicTable = [];
+
     public function __construct()
     {
         if (!self::$huffman) self::$huffman = new Codec(Dictionary::createRfc7541Dictionary());
@@ -88,6 +90,20 @@ class HeaderPacker
     {
         $packed = '';
 
+        foreach ($headers as [$header,$value]) {
+            if ($index = $this->lookupIndexForHeader($header,$value)) {
+                // Indexed
+                $packed .= chr(0x80 | ($index & 0x7F));
+            } elseif ($index = $this->lookupIndexForHeader($header,null)) {
+                // Indexed literal
+                $packed .= chr(0x40 | ($index & 0x3F));
+                $value = self::$huffman->encode($value);
+                $packed .= chr(0x80 | strlen($value) & 0x7F);
+                $packed .= $value;
+            } else {
+                // Literal
+            }
+        }
 
         return $packed;
     }
@@ -149,7 +165,21 @@ class HeaderPacker
 
     private function getIndexedHeader(int $index): array
     {
-        return self::$staticTable[$index];
+        if ($index < self::STATIC_TABLE_SIZE)
+            return self::$staticTable[$index];
+        // TODO bounds check
+        return $this->dynamicTable[$index - self::STATIC_TABLE_SIZE];
     }
 
-}
\ No newline at end of file
+    private function lookupIndexForHeader(string $header, ?string $value): ?int
+    {
+        foreach (self::$staticTable as $index=>[$iName, $iValue]) {
+            if ($header === $iName && $value === $iValue) return $index;
+        }
+        foreach ($this->dynamicTable as $index=>[$iName, $iValue]) {
+            if ($header === $iName && $value === $iValue) return $index + self::STATIC_TABLE_SIZE;
+        }
+        return null;
+    }
+
+}
diff --git a/tests/Header/HeaderPackerTest.php b/tests/Header/HeaderPackerTest.php
index dc66449..5b8f8cd 100644
--- a/tests/Header/HeaderPackerTest.php
+++ b/tests/Header/HeaderPackerTest.php
@@ -26,5 +26,22 @@ class HeaderPackerTest extends \PHPUnit\Framework\TestCase
 
     }
 
+    public function testPackingExamplesFromRfc7541()
+    {
+        $packer = new HeaderPacker();
 
-}
\ No newline at end of file
+        $expect = "\x82\x86\x84\x41\x8c\xf1\xe3\xc2\xe5\xf2\x3a\x6b\xa0\xab\x90\xf4\xff";
+        $in = new HeaderBag([
+            ':method' => 'GET',
+            ':scheme' => 'http',
+            ':path' => '/',
+            ':authority' => 'www.example.com'
+        ]);
+        $out = $packer->packHeaders($in);
+
+        $this->assertEquals($expect, $out);
+
+    }
+
+
+}