Add per-request compression control to HttpResponse (#2451)

Author: levi42x

lib/inc/drogon/HttpResponse.h

@@ -161,6 +161,12 @@ class DROGON_EXPORT HttpResponse
         setCustomStatusCode(code, message.data(), message.length());
     }
 
+    /// Set whether the response should be compress.
+    virtual void setAllowCompression(bool allow) = 0;
+
+    /// Get whether the response allow compression.
+    virtual bool allowCompression() const = 0;
+
     /// Get the creation timestamp of the response.
     virtual const trantor::Date &creationDate() const = 0;
 
@@ -560,9 +566,9 @@ class DROGON_EXPORT HttpResponse
     virtual const std::string &sendfileName() const = 0;
 
     /**
-     * @brief Returns the range of the file response as a pair ot size_t
+     * @brief Returns the range of the file response as a pair of size_t
      * (offset, length). Length of 0 means the entire file is sent. Behavior of
-     * this function is undefined if the response if not a file response
+     * this function is undefined if the response is not a file response
      */
     using SendfileRange = std::pair<size_t, size_t>;  // { offset, length }
     virtual const SendfileRange &sendfileRange() const = 0;

lib/src/HttpResponseImpl.cc

@@ -54,6 +54,16 @@ static inline HttpResponsePtr genHttpResponse(const std::string &viewName,
 }
 }  // namespace drogon
 
+void HttpResponseImpl::setAllowCompression(bool allow)
+{
+    allowCompression_ = allow;
+}
+
+bool HttpResponseImpl::allowCompression() const
+{
+    return allowCompression_;
+}
+
 HttpResponsePtr HttpResponse::newHttpResponse()
 {
     auto res = std::make_shared<HttpResponseImpl>(k200OK, CT_TEXT_HTML);
@@ -960,6 +970,12 @@ void HttpResponseImpl::parseJson() const
 
 bool HttpResponseImpl::shouldBeCompressed() const
 {
+    // If the developer said "No" stop immediately.
+    if (!allowCompression_)
+    {
+        return false;
+    }
+
     if (streamCallback_ || asyncStreamCallback_ || !sendfileName_.empty() ||
         contentType() >= CT_APPLICATION_OCTET_STREAM ||
         getBody().length() < 1024 ||

lib/src/HttpResponseImpl.h

@@ -463,6 +463,12 @@ class DROGON_EXPORT HttpResponseImpl : public HttpResponse
     }
 
   private:
+    bool allowCompression_{true};
+
+    void setAllowCompression(bool allow) override;
+
+    bool allowCompression() const override;
+
     void setBody(const char *body, size_t len) override
     {
         bodyPtr_ = std::make_shared<HttpMessageStringViewBody>(body, len);