feat(http): add custom processing to responses using response steps

CHANGELOG.md

@@ -7,7 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://git.rustybever.be/Chewing_Bever/lander/src/branch/dev)
 
-* Fully decoupled HTTP loop functionnality
+* HTTP Loop
+    * Fully decoupled functionality from Lander-specific code
+    * Users can now define custom global & request-local contexts
+    * Introduced "response steps", allowing custom code during the response
+      part of a request
 
 ## [0.1.0](https://git.rustybever.be/Chewing_Bever/lander/src/tag/0.1.0)
 

Makefile

@@ -43,7 +43,7 @@ libtrie:
 liblsm:
 	$(MAKE) -C lsm
 
-.PHONY: bin
+.PHONY: $(BIN)
 $(BIN): libtrie liblsm $(OBJS)
 	$(CC) -o $@ $(OBJS) $(_LDFLAGS)
 
@@ -58,11 +58,17 @@ $(BUILD_DIR)/$(THIRDPARTY_DIR)/%.c.o: $(THIRDPARTY_DIR)/%.c
 
 # =====TESTING=====
 .PHONY: run
-run: bin
+run: $(BIN)
 	LANDER_API_KEY=test \
 		LANDER_DATA_DIR=data \
 		'$(BUILD_DIR)/$(BIN_FILENAME)'
 
+.PHONY: valgrind
+valgrind: $(BIN)
+	LANDER_API_KEY=test \
+		LANDER_DATA_DIR=data \
+		valgrind '$(BUILD_DIR)/$(BIN_FILENAME)'
+
 .PHONY: test
 test: $(TARGETS_TEST)
 

include/http_loop.h

@@ -27,9 +27,10 @@ typedef enum http_route_type {
  * Function describing a step in a route's processing.
  *
  * @param conn connection to process
- * @return whether the processing can immediately advance to the next step. A
- * step should return false if it's e.g. waiting for I/O, and can therefore not
- * finish its task in the current cycle of the event loop.
+ * @return whether processing can proceed to the next step without performing
+ * I/O first. For a request step, `false` means more data needs to be read
+ * before the step can finish its processing. For response steps, `false` means
+ * there's new data in the write buffer that needs to be written.
  */
 typedef bool (*step)(event_loop_conn *conn);
 
@@ -44,6 +45,7 @@ typedef struct http_route {
   // starting the http loop
   regex_t *regex;
   step steps[HTTP_LOOP_MAX_STEPS];
+  step steps_res[HTTP_LOOP_MAX_STEPS];
 } http_route;
 
 /**
@@ -116,14 +118,6 @@ typedef struct event_loop http_loop;
  */
 bool http_loop_handle_request(event_loop_conn *conn);
 
-/**
- * Write the HTTP response to the file descriptor. This is the "write_data"
- * function for the event loop.
- *
- * @param conn connection to process
- */
-void http_loop_write_response(event_loop_conn *conn);
-
 /**
  * Try to parse the incoming data as an HTTP request.
  *
@@ -148,6 +142,14 @@ void http_loop_route_request(event_loop_conn *conn);
  */
 void http_loop_process_request(event_loop_conn *conn);
 
+/**
+ * Handles the response processing. This is the `write_data` function for the
+ * event loop.
+ *
+ * @param conn connection to process
+ */
+void http_loop_handle_response(event_loop_conn *conn);
+
 /**
  * Request step that consumes the request body and stores it in a buffer.
  *
@@ -180,6 +182,21 @@ bool http_loop_step_auth(event_loop_conn *conn);
  */
 bool http_loop_step_switch_res(event_loop_conn *conn);
 
+/**
+ * Write the HTTP header back to the connection. If `res->head` is not set, a
+ * header will be generated for you.
+ *
+ * @param conn connection to process
+ */
+bool http_loop_step_write_header(event_loop_conn *conn);
+
+/**
+ * Write the HTTP body back to the connection.
+ *
+ * @param conn connection to process
+ */
+bool http_loop_step_write_body(event_loop_conn *conn);
+
 /**
  * Initialize a new http loop.
  *

src/http_loop/http_loop.c

@@ -54,7 +54,7 @@ event_loop *http_loop_init(http_route *routes, size_t route_count,
   el->ctx_init = (void *(*)(void *))http_loop_ctx_init;
   el->ctx_free = (void (*)(void *))http_loop_ctx_free;
   el->handle_data = http_loop_handle_request;
-  el->write_data = http_loop_write_response;
+  el->write_data = http_loop_handle_response;
 
   http_loop_gctx *gctx = http_loop_gctx_init();
   gctx->c = custom_gctx;

src/http_loop/http_loop_req.c

@@ -138,13 +138,11 @@ void http_loop_process_request(event_loop_conn *conn) {
     ctx->current_step++;
   }
 
-  if (conn->state != event_loop_conn_state_req) {
-    return;
-  }
-
-  // If we've reached the end of the list of step functions, we report the
-  // request as finished by clearing its route
-  if (ctx->route->steps[ctx->current_step] == NULL) {
-    http_loop_ctx_reset(ctx);
+  // Request processing can stop early by switching the connection state
+  // Either way, we reset the step counter as it will be used by the response
+  // steps
+  if ((conn->state != event_loop_conn_state_req) ||
+      (ctx->route->steps[ctx->current_step] == NULL)) {
+    ctx->current_step = 0;
   }
 }

src/http_loop/http_loop_res.c

@@ -48,7 +48,7 @@ void http_loop_init_header(http_response *res) {
   res->head_len = buf_size + 1;
 }
 
-void http_loop_write_response(event_loop_conn *conn) {
+bool http_loop_step_write_header(event_loop_conn *conn) {
   http_response *res = &((http_loop_ctx *)conn->ctx)->res;
 
   // Create head response
@@ -56,43 +56,68 @@ void http_loop_write_response(event_loop_conn *conn) {
     http_loop_init_header(res);
   }
 
-  // The final iteration marks the end of the response, after which we reset the
-  // context so a next request can be processed
-  if (res->head_written == res->head_len &&
-      res->body.expected_len == res->body.len) {
-    http_loop_ctx_reset(conn->ctx);
-    conn->state = event_loop_conn_state_req;
-    return;
+  // Step has finished its work
+  if (res->head_written == res->head_len) {
+    return true;
   }
 
-  if (res->head_written < res->head_len) {
-    size_t bytes_to_write = MIN(res->head_len - res->head_written,
-                                EVENT_LOOP_BUFFER_SIZE - conn->wbuf_size);
-    memcpy(&conn->wbuf[conn->wbuf_size], &res->head[res->head_written],
+  size_t bytes_to_write = MIN(res->head_len - res->head_written,
+                              EVENT_LOOP_BUFFER_SIZE - conn->wbuf_size);
+  memcpy(&conn->wbuf[conn->wbuf_size], &res->head[res->head_written],
+         bytes_to_write);
+
+  conn->wbuf_size += bytes_to_write;
+  res->head_written += bytes_to_write;
+
+  return false;
+}
+
+bool http_loop_step_write_body(event_loop_conn *conn) {
+  http_response *res = &((http_loop_ctx *)conn->ctx)->res;
+
+  if (res->body.expected_len == res->body.len) {
+    return true;
+  }
+
+  size_t bytes_to_write = MIN(res->body.expected_len - res->body.len,
+                              EVENT_LOOP_BUFFER_SIZE - conn->wbuf_size);
+
+  size_t bytes_written;
+
+  switch (res->body.type) {
+  case http_body_buf:
+    memcpy(&conn->wbuf[conn->wbuf_size], &(res->body.buf)[res->body.len],
            bytes_to_write);
-
     conn->wbuf_size += bytes_to_write;
-    res->head_written += bytes_to_write;
+    res->body.len += bytes_to_write;
+    break;
+  case http_body_file:
+    bytes_written = fread(&conn->wbuf[conn->wbuf_size], sizeof(uint8_t),
+                          bytes_to_write, res->body.file);
+    conn->wbuf_size += bytes_written;
+    res->body.len += bytes_written;
+    break;
   }
 
-  if (res->body.len < res->body.expected_len) {
-    size_t bytes_to_write = MIN(res->body.expected_len - res->body.len,
-                                EVENT_LOOP_BUFFER_SIZE - conn->wbuf_size);
-    size_t bytes_written;
+  return false;
+}
 
-    switch (res->body.type) {
-    case http_body_buf:
-      memcpy(&conn->wbuf[conn->wbuf_size], &(res->body.buf)[res->body.len],
-             bytes_to_write);
-      conn->wbuf_size += bytes_to_write;
-      res->body.len += bytes_to_write;
-      break;
-    case http_body_file:
-      bytes_written = fread(&conn->wbuf[conn->wbuf_size], sizeof(uint8_t),
-                            bytes_to_write, res->body.file);
-      conn->wbuf_size += bytes_written;
-      res->body.len += bytes_written;
-      break;
-    }
+void http_loop_handle_response(event_loop_conn *conn) {
+  http_loop_ctx *ctx = conn->ctx;
+
+  while ((conn->state == event_loop_conn_state_res) &&
+         (ctx->route->steps_res[ctx->current_step] != NULL) &&
+         ctx->route->steps_res[ctx->current_step](conn)) {
+    ctx->current_step++;
+  }
+
+  // Response processing can stop early be switching the connection state
+  // After response processing has finished its work, we reset the context to
+  // prepare for a new request
+  if ((conn->state != event_loop_conn_state_res) ||
+      (ctx->route->steps_res[ctx->current_step] == NULL)) {
+    http_loop_ctx_reset(ctx);
+
+    conn->state = event_loop_conn_state_req;
   }
 }

src/lander/lander.c

@@ -6,21 +6,33 @@ http_route lander_routes[] = {
     {.type = http_route_literal,
      .method = http_get,
      .path = "/",
-     .steps = {lander_get_index, NULL}},
-    {.type = http_route_regex,
-     .method = http_get,
-     .path = "^/([^/]+)$",
-     .steps = {lander_get_entry, NULL}},
-    {.type = http_route_regex,
-     .method = http_post,
-     .path = "^/s(l?)/([^/]*)$",
-     .steps = {http_loop_step_auth, http_loop_step_body_to_buf,
-               lander_post_redirect, NULL}},
+     .steps = {lander_get_index, NULL},
+     .steps_res = {http_loop_step_write_header, http_loop_step_write_body,
+                   NULL}},
+    {
+        .type = http_route_regex,
+        .method = http_get,
+        .path = "^/([^/]+)$",
+        .steps = {lander_get_entry, NULL},
+        .steps_res = {http_loop_step_write_header, http_loop_step_write_body,
+                      NULL},
+    },
+    {
+        .type = http_route_regex,
+        .method = http_post,
+        .path = "^/s(l?)/([^/]*)$",
+        .steps = {http_loop_step_auth, http_loop_step_body_to_buf,
+                  lander_post_redirect, NULL},
+        .steps_res = {http_loop_step_write_header, http_loop_step_write_body,
+                      NULL},
+    },
     {.type = http_route_regex,
      .method = http_post,
      .path = "^/p(l?)/([^/]*)$",
      .steps = {http_loop_step_auth, lander_post_paste,
-               http_loop_step_body_to_file, http_loop_step_switch_res, NULL}},
+               http_loop_step_body_to_file, http_loop_step_switch_res, NULL},
+     .steps_res = {http_loop_step_write_header, http_loop_step_write_body,
+                   NULL}},
 };
 
 void *lander_gctx_init() { return calloc(1, sizeof(lander_gctx)); }