[rp-download] Set an "Accept:" header for the expected MIME type.

Expected MIME types:
- .png: image/png
- .jpg: image/jpeg
- .txt: text/plain

Not sure if this will make any real difference, but we might as well
set it anyway.

src/rp-download/CurlDownloader.cpp

@@ -195,6 +195,21 @@ int CurlDownloader::download(void)
 		curl_easy_setopt(curl, CURLOPT_TIMECONDITION, CURL_TIMECOND_IFMODSINCE);
 	}
 
+	// Custom headers
+	struct curl_slist *req_headers = nullptr;
+	if (!m_reqMimeType.empty()) {
+		// Add the "Accept:" header.
+		tstring accept_header = _T("Accept: ");
+		accept_header += m_reqMimeType;
+
+		req_headers = curl_slist_append(req_headers, accept_header.c_str());
+		
+	}
+
+	if (req_headers) {
+		curl_easy_setopt(curl, CURLOPT_HTTPHEADER, req_headers);
+	}
+
 	// Header and data functions.
 	curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, parse_header);
 	curl_easy_setopt(curl, CURLOPT_HEADERDATA, this);
@@ -254,6 +269,7 @@ int CurlDownloader::download(void)
 			break;
 	}
 
+	curl_slist_free_all(req_headers);
 	curl_easy_cleanup(curl);
 	if (ret != 0) {
 		return ret;

src/rp-download/IDownloader.cpp

@@ -138,6 +138,37 @@ void IDownloader::setIfModifiedSince(time_t timestamp)
 	m_if_modified_since = timestamp;
 }
 
+/**
+ * Get the specified MIME type(s) for the "Accept:" header.
+ * @return MIME type(s), or nullptr if not set.
+ */
+const TCHAR *IDownloader::requestedMimeType(void) const
+{
+	return (!m_reqMimeType.empty()) ? m_reqMimeType.c_str() : nullptr;
+}
+
+/**
+ * Set the valid MIME type(s) for the "Accept:" header.
+ * @param mimeType Valid MIME type(s), or nullptr to clear.
+ */
+void IDownloader::setRequestedMimeType(const TCHAR *mimeType)
+{
+	if (mimeType) {
+		m_reqMimeType = mimeType;
+	} else {
+		m_reqMimeType.clear();
+	}
+}
+
+/**
+ * Set the valid MIME type(s) for the "Accept:" header.
+ * @param mimeType Valid MIME type(s), or nullptr to clear.
+ */
+void IDownloader::setRequestedMimeType(const std::tstring &mimeType)
+{
+	m_reqMimeType = mimeType;
+}
+
 /** Data accessors **/
 
 /**

src/rp-download/IDownloader.hpp

@@ -86,6 +86,24 @@ public:
 	 */
 	void setIfModifiedSince(time_t timestamp);
 
+	/**
+	 * Get the specified MIME type(s) for the "Accept:" header.
+	 * @return MIME type(s), or nullptr if not set.
+	 */
+	const TCHAR *requestedMimeType(void) const;
+
+	/**
+	 * Set the valid MIME type(s) for the "Accept:" header.
+	 * @param mimeType Valid MIME type(s), or nullptr to clear.
+	 */
+	void setRequestedMimeType(const TCHAR *mimeType);
+
+	/**
+	 * Set the valid MIME type(s) for the "Accept:" header.
+	 * @param mimeType Valid MIME type(s), or nullptr to clear.
+	 */
+	void setRequestedMimeType(const std::tstring &mimeType);
+
 public:
 	/** Data accessors **/
 
@@ -140,6 +158,7 @@ protected:
 
 	time_t m_mtime;			// Last-Modified response
 	time_t m_if_modified_since;	// If-Modified-Since request
+	std::tstring m_reqMimeType;	// MIME type for "Accept:" header
 
 	size_t m_maxSize;		// Maximum buffer size. (0 == unlimited)
 	std::tstring m_userAgent;	// User-Agent

src/rp-download/WinInetDownloader.cpp

@@ -77,7 +77,8 @@ int WinInetDownloader::download(void)
 		}
 	}
 
-	tstring headers;
+	// Custom headers
+	tstring req_headers;
 	if (m_if_modified_since >= 0) {
 		// Add an "If-Modified-Since" header.
 		// FIXME: +4 is needed to avoid ERROR_INSUFFICIENT_BUFFER.
@@ -87,17 +88,26 @@ int WinInetDownloader::download(void)
 		UnixTimeToSystemTime(m_if_modified_since, &st);
 		BOOL bRet = InternetTimeFromSystemTime(&st, INTERNET_RFC1123_FORMAT, szTime, sizeof(szTime));
 		if (bRet) {
-			headers = _T("If-Modified-Since: ");
-			headers += szTime;
+			req_headers = _T("If-Modified-Since: ");
+			req_headers += szTime;
 		}
 	}
+	if (!m_reqMimeType.empty()) {
+		// Add the "Accept:" header.
+		if (!req_headers.empty()) {
+			req_headers += _T("\r\n");
+		}
+
+		req_headers += _T("Accept: ");
+		req_headers += m_reqMimeType;
+	}
 
 	// Request the URL.
 	HINTERNET hURL = InternetOpenUrl(
 		hConnection,	// hInternet
 		m_url.c_str(),	// lpszUrl (Latin-1 characters only!)
-		!headers.empty() ? headers.data() : nullptr,	// lpszHeaders
-		static_cast<DWORD>(headers.size()),	// dwHeaderLength
+		!req_headers.empty() ? req_headers.data() : nullptr,	// lpszHeaders
+		static_cast<DWORD>(req_headers.size()),			// dwHeaderLength
 		dwFlags,	// dwFlags
 		reinterpret_cast<DWORD_PTR>(this));	// dwContext
 	if (!hURL) {

src/rp-download/rp-download.cpp

@@ -213,6 +213,33 @@ static int get_file_size_and_mtime(const TCHAR *filename, off64_t *pFileSize, ti
 	return 0;
 }
 
+/**
+ * Get the MIME type for the specified cache key (or filename).
+ * @param cache_key Cache key (or filename)
+ * @return MIME type, or nullptr if not supported
+ */
+static const TCHAR *getMimeType(const TCHAR *cache_key)
+{
+	// Find the last dot.
+	const TCHAR *const dotpos = _tcsrchr(cache_key, _T('.'));
+	if (!dotpos) {
+		return nullptr;
+	}
+
+	// Check the file extension.
+	const TCHAR *mimeType = nullptr;
+
+	if (!_tcscmp(dotpos, _T(".png"))) {
+		mimeType = _T("image/png");
+	} else if (!_tcscmp(dotpos, _T(".jpg"))) {
+		mimeType = _T("image/jpg");
+	} else if (!_tcscmp(dotpos, _T(".txt"))) {
+		mimeType = _T("text/plain");
+	}
+
+	return mimeType;
+}
+
 /**
  * rp-download: Download an image from a supported online database.
  * @param cache_key Cache key, e.g. "ds/cover/US/ADAE.png"
@@ -519,6 +546,12 @@ int RP_C_API _tmain(int argc, TCHAR *argv[])
 		downloader.setIfModifiedSince(filemtime);
 	}
 
+	// Set the MIME type, if available.
+	const TCHAR *mimeType = getMimeType(cache_key);
+	if (mimeType) {
+		downloader.setRequestedMimeType(mimeType);
+	}
+
 	downloader.setUrl(full_url);
 	ret = downloader.download();
 	if (ret != 0) {