Implemented SigV4A (#40)

* Implemented should_sign_header callback

* Added SigV4A to SigningAlgorithm

* Added SigV4A test

* Added debugging info to README

* Fixed memory leak from argument vectors

* Fixed memory leak of stream read buffers

* Added support for callables as option values

* Added should_sign_header support and test

* Fixed ELG type bug exposed by aws-crt-ffi change

* Updated to aws-crt-ffi v0.2.0

src/AWS/CRT/Auth/SigningAlgorithm.php

@@ -7,4 +7,5 @@ namespace AWS\CRT\Auth;
 
 class SigningAlgorithm {
     const SIGv4 = 0;
-}
+    const SIGv4_ASYMMETRIC = 1;
+}

src/AWS/CRT/Auth/SigningConfigAWS.php

@@ -23,7 +23,8 @@ class SigningConfigAWS extends NativeResource {
             'signed_body_value' => null,
             'signed_body_header_type' => SignedBodyHeaderType::NONE,
             'expiration_in_seconds' => 0,
-            'date' => time()
+            'date' => time(),
+            'should_sign_header' => null,
         ];
     }
 
@@ -57,6 +58,9 @@ class SigningConfigAWS extends NativeResource {
         self::$crt->signing_config_aws_set_expiration_in_seconds(
             $sc, $options->expiration_in_seconds->asInt());
         self::$crt->signing_config_aws_set_date($sc, $options->date->asInt());
+        if ($should_sign_header = $options->should_sign_header->asCallable()) {
+            self::$crt->signing_config_aws_set_should_sign_header_fn($sc, $should_sign_header);
+        }
     }
 
     function __destruct()

src/AWS/CRT/CRT.php

@@ -317,6 +317,10 @@ final class CRT {
         self::$impl->aws_crt_signing_config_aws_set_date($signing_config, $timestamp);
     }
 
+    function signing_config_aws_set_should_sign_header_fn($signing_config, $should_sign_header_fn) {
+        self::$impl->aws_crt_signing_config_aws_set_should_sign_header_fn($signing_config, $should_sign_header_fn);
+    }
+
     function signable_new_from_http_request($http_message) {
         return self::$impl->aws_crt_signable_new_from_http_request($http_message);
     }

src/AWS/CRT/Options.php

@@ -34,6 +34,10 @@ final class OptionValue {
     public function asArray() {
         return is_array($this->value) ? $this->value : (!empty($this->value) ? [$this->value] : []);
     }
+
+    public function asCallable() {
+        return is_callable($this->value) ? $this->value : null;
+    }
 }
 
 final class Options {