add support in http client to accept multi-range responses (#788)

* add support in http client to accept multi-range responses

1 files changed, 41 insertions, 0 deletions

diff --git a/src/zenhttp/httpclient.cpp b/src/zenhttp/httpclient.cpp
index 078e27b34..998eb27ea 100644
--- a/src/zenhttp/httpclient.cpp
+++ b/src/zenhttp/httpclient.cpp
@@ -104,6 +104,47 @@ HttpClientBase::GetAccessToken()
 
 //////////////////////////////////////////////////////////////////////////
 
+std::vector<std::pair<uint64_t, uint64_t>>
+HttpClient::Response::GetRanges(std::span<const std::pair<uint64_t, uint64_t>> OffsetAndLengthPairs) const
+{
+	std::vector<std::pair<uint64_t, uint64_t>> Result;
+	Result.reserve(OffsetAndLengthPairs.size());
+	if (Ranges.empty())
+	{
+		for (const std::pair<uint64_t, uint64_t>& Range : OffsetAndLengthPairs)
+		{
+			Result.emplace_back(std::make_pair(Range.first, Range.second));
+		}
+		return Result;
+	}
+
+	auto BoundaryIt			   = Ranges.begin();
+	auto OffsetAndLengthPairIt = OffsetAndLengthPairs.begin();
+	while (OffsetAndLengthPairIt != OffsetAndLengthPairs.end())
+	{
+		uint64_t Offset = OffsetAndLengthPairIt->first;
+		uint64_t Length = OffsetAndLengthPairIt->second;
+		while (Offset >= BoundaryIt->RangeOffset + BoundaryIt->RangeLength)
+		{
+			BoundaryIt++;
+			if (BoundaryIt == Ranges.end())
+			{
+				throw std::runtime_error("HttpClient::Response can not fulfill requested range");
+			}
+		}
+		if (Offset + Length > BoundaryIt->RangeOffset + BoundaryIt->RangeLength || Offset < BoundaryIt->RangeOffset)
+		{
+			throw std::runtime_error("HttpClient::Response can not fulfill requested range");
+		}
+		uint64_t OffsetIntoRange	= Offset - BoundaryIt->RangeOffset;
+		uint64_t RangePayloadOffset = BoundaryIt->OffsetInPayload + OffsetIntoRange;
+		Result.emplace_back(std::make_pair(RangePayloadOffset, Length));
+
+		OffsetAndLengthPairIt++;
+	}
+	return Result;
+}
+
 CbObject
 HttpClient::Response::AsObject() const
 {