Implement H2 decoder (#151)

* Implement H2 decoder

* Implement new H2 decoder vtable
* Implement the H2 decoder state machine
* NOTE: Header blocks are not implemented yet, and as such the HEADERS, CONTINUATION, and PUSH_PROMISE frames are incomplete

* Make global states const

* f_ -> frame_

* Appease the MSVC type conversion gods

* Henso PR feedback

* CI Fixes

* Split goaway into 2 states

* Improve error handling and end of state detection

* Handle leftover scratch into streaming state case

* Handle custom frames

* Misc. PR feedback

* uint32_t pass

* Add error handling strategy (don't) to the decoder

* More PR feedback

* Decrement payload_len in unknown frame state

Author: dislogical

include/aws/http/http.h

@@ -48,6 +48,7 @@ enum aws_http_errors {
     AWS_ERROR_HTTP_CONNECTION_MANAGER_SHUTTING_DOWN,
     AWS_ERROR_HTTP_PROTOCOL_ERROR,
     AWS_ERROR_HTTP_STREAM_CLOSED,
+    AWS_ERROR_HTTP_INVALID_FRAME_SIZE,
 
     AWS_ERROR_HTTP_END_RANGE = 0x0C00,
 };

include/aws/http/private/h2_decoder.h

@@ -18,13 +18,30 @@
 
 #include <aws/http/private/http_impl.h>
 
+struct aws_h2_decoder_vtable {
+
+    int (*on_headers)(uint32_t stream_id, void *userdata);
+    int (*on_end_headers)(uint32_t stream_id, void *userdata);
+
+    int (*on_data)(uint32_t stream_id, const struct aws_byte_cursor *data, void *userdata);
+
+    int (*on_rst_stream)(uint32_t stream_id, uint32_t error_code, void *userdata);
+
+    int (*on_ping)(bool ack, uint8_t opaque_data[8], void *userdata);
+    int (*on_setting)(uint16_t setting, uint32_t value, void *userdata);
+    int (*on_settings_ack)(void *userdata);
+    int (*on_goaway)(uint32_t last_stream, uint32_t error_code, uint32_t debug_data_length, void *userdata);
+    int (*on_goaway_debug_data)(const struct aws_byte_cursor *data, void *userdata);
+};
+
 /**
  * Structure used to initialize an `aws_h2_decoder`.
  */
 struct aws_h2_decoder_params {
     struct aws_allocator *alloc;
     void *user_data;
-    struct aws_http_decoder_vtable vtable;
+    struct aws_h2_decoder_vtable vtable;
+    void *userdata;
 };
 
 struct aws_h2_decoder;

source/h2_connection.c

@@ -49,12 +49,8 @@ static struct aws_http_connection_vtable s_h2_connection_vtable = {
     .update_window = NULL,
 };
 
-static const struct aws_http_decoder_vtable s_h2_decoder_vtable = {
-    .on_request = NULL,
-    .on_response = NULL,
-    .on_header = NULL,
-    .on_body = NULL,
-    .on_done = NULL,
+static const struct aws_h2_decoder_vtable s_h2_decoder_vtable = {
+    .on_data = NULL,
 };
 
 /* Common new() logic for server & client */