HTTP range responses (RFC 7233) - httpobjectstore (#928)

- Improvement: HTTP range responses (RFC 7233) are now fully compliant across the object store and build store
  - 206 Partial Content responses now include a `Content-Range` header; previously absent for single-range requests, which broke `HttpClient::GetRanges()`
  - 416 Range Not Satisfiable responses now include `Content-Range: bytes */N` as required by RFC 7233
  - Out-of-bounds range requests return 416 Range Not Satisfiable (was 400 Bad Request)
  - Single-byte ranges (`bytes=N-N`) are now correctly accepted (were previously rejected)
  - Range byte positions widened from 32-bit to 64-bit; RFC 7233 imposes no size limit on byte range values
  - Build store binary GET requests with a Range header now return 206 Partial Content with `Content-Range` (previously returned 200 OK without it)

2 files changed, 16 insertions, 2 deletions

diff --git a/src/zenhttp/include/zenhttp/httpcommon.h b/src/zenhttp/include/zenhttp/httpcommon.h
index f9a99f3cc..1d921600d 100644
--- a/src/zenhttp/include/zenhttp/httpcommon.h
+++ b/src/zenhttp/include/zenhttp/httpcommon.h
@@ -19,8 +19,8 @@ class StringBuilderBase;
 
 struct HttpRange
 {
-	uint32_t Start = ~uint32_t(0);
-	uint32_t End   = ~uint32_t(0);
+	uint64_t Start = ~uint64_t(0);
+	uint64_t End   = ~uint64_t(0);
 };
 
 using HttpRanges = std::vector<HttpRange>;
@@ -30,6 +30,16 @@ extern HttpContentType (*ParseContentType)(const std::string_view& ContentTypeSt
 std::string_view ReasonStringForHttpResultCode(int HttpCode);
 bool			 TryParseHttpRangeHeader(std::string_view RangeHeader, HttpRanges& Ranges);
 
+struct MultipartByteRangesResult
+{
+	std::vector<IoBuffer> Parts;
+	std::string			  ContentType;
+};
+
+// Build a multipart/byteranges response body from the given data and ranges.
+// Generates a unique boundary per call. Returns empty Parts if any range is out of bounds.
+MultipartByteRangesResult BuildMultipartByteRanges(const IoBuffer& Data, const HttpRanges& Ranges);
+
 enum class HttpVerb : uint8_t
 {
 	kGet	 = 1 << 0,
diff --git a/src/zenhttp/include/zenhttp/httpserver.h b/src/zenhttp/include/zenhttp/httpserver.h
index e8bfcfd4d..136304426 100644
--- a/src/zenhttp/include/zenhttp/httpserver.h
+++ b/src/zenhttp/include/zenhttp/httpserver.h
@@ -122,11 +122,13 @@ public:
 	virtual void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, std::u8string_view ResponseString) = 0;
 	virtual void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, CompositeBuffer& Payload);
 
+	void WriteResponse(HttpResponseCode ResponseCode, const std::string& CustomContentType, std::span<IoBuffer> Blobs);
 	void WriteResponse(HttpResponseCode ResponseCode, CbObject Data);
 	void WriteResponse(HttpResponseCode ResponseCode, CbArray Array);
 	void WriteResponse(HttpResponseCode ResponseCode, CbPackage Package);
 	void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, std::string_view ResponseString);
 	void WriteResponse(HttpResponseCode ResponseCode, HttpContentType ContentType, IoBuffer Blob);
+	void WriteResponse(HttpContentType ContentType, const IoBuffer& Data, const HttpRanges& Ranges);
 
 	virtual void WriteResponseAsync(std::function<void(HttpServerRequest&)>&& ContinuationHandler) = 0;
 
@@ -152,6 +154,8 @@ protected:
 	std::string_view m_QueryString;
 	mutable uint32_t m_RequestId = ~uint32_t(0);
 	mutable Oid		 m_SessionId = Oid::Zero;
+	std::string		 m_ContentTypeOverride;
+	std::string		 m_ContentRangeHeader;
 
 	inline void SetIsHandled() { m_Flags |= kIsHandled; }