feat(http): add step for parsing content-length header

include/http_loop.h

@@ -166,6 +166,13 @@ bool http_loop_step_body_to_buf(event_loop_conn *conn);
  */
 bool http_loop_step_body_to_file(event_loop_conn *conn);
 
+/**
+ * Try to parse the Content-Length header.
+ *
+ * @param conn connection to process
+ */
+bool http_loop_step_parse_content_length(event_loop_conn *conn);
+
 /**
  * Authenticate the request using the X-Api-Key header.
  *
@@ -201,7 +208,7 @@ bool http_loop_step_write_body(event_loop_conn *conn);
  * Initialize a new http loop.
  *
  * @param routes array of routes that should be served
- * @parma route_count how many elements are in `routes`
+ * @param route_count how many elements are in `routes`
  * @param custom_gctx the application's custom global context; can be NULL
  * @param custom_ctx_init function to initialize a new custom context
  * @param custom_ctx_reset function to reset a custom context

src/http_loop/http_loop_req.c

@@ -144,5 +144,6 @@ void http_loop_process_request(event_loop_conn *conn) {
   if ((conn->state != event_loop_conn_state_req) ||
       (ctx->route->steps[ctx->current_step] == NULL)) {
     ctx->current_step = 0;
+    conn->state = event_loop_conn_state_res;
   }
 }

src/http_loop/http_loop_steps.c

@@ -1,5 +1,6 @@
 #include <math.h>
 
+#include "http_loop.h"
 #include "lander.h"
 
 /*
@@ -22,12 +23,44 @@ static bool string_to_num(size_t *res, const char *s, size_t len) {
   return true;
 }
 
+bool http_loop_step_parse_content_length(event_loop_conn *conn) {
+  http_loop_ctx *ctx = conn->ctx;
+
+  for (size_t i = 0; i < ctx->req.num_headers; i++) {
+    struct phr_header *header = &ctx->req.headers[i];
+
+    if (strncmp(header->name, "Content-Length", header->name_len) == 0) {
+      // If the content length header is present but contains an invalid
+      // number, we return a bad request error
+      if (!string_to_num(&ctx->req.body.expected_len, header->value,
+                         header->value_len)) {
+        ctx->res.status = http_bad_request;
+        conn->state = event_loop_conn_state_res;
+
+        return true;
+      }
+      // The content length was actually 0, so we can instantly return here
+      else if (ctx->req.body.expected_len == 0) {
+        return true;
+      }
+    }
+  }
+
+  // A zero here means there's no content length header
+  if (ctx->req.body.expected_len == 0) {
+    ctx->res.status = http_length_required;
+    conn->state = event_loop_conn_state_res;
+  }
+
+  return true;
+}
+
 /*
  * Try to find and parse the Content-Length header. This function returns true
  * if it was successful. If false is returned, the underlying step should
  * immediately exit.
  */
-static bool try_parse_content_length(event_loop_conn *conn) {
+bool try_parse_content_length(event_loop_conn *conn) {
   http_loop_ctx *ctx = conn->ctx;
 
   for (size_t i = 0; i < ctx->req.num_headers; i++) {