From a6925de9bca8579637fa8a4152ab2b77ef5ca90e Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Mon, 13 Oct 2025 13:32:36 +0200
Subject: refactor builds cmd (#566)

Move builds download code from builds_cmd.cpp to remotestorelib
---
 src/zenutil/bufferedopenfile.cpp | 75 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 src/zenutil/bufferedopenfile.cpp

(limited to 'src/zenutil/bufferedopenfile.cpp')

diff --git a/src/zenutil/bufferedopenfile.cpp b/src/zenutil/bufferedopenfile.cpp
new file mode 100644
index 000000000..360011302
--- /dev/null
+++ b/src/zenutil/bufferedopenfile.cpp
@@ -0,0 +1,75 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenutil/bufferedopenfile.h>
+
+#include <zencore/scopeguard.h>
+#include <zencore/trace.h>
+
+namespace zen {
+
+BufferedOpenFile::BufferedOpenFile(const std::filesystem::path Path,
+								   std::atomic<uint64_t>&	   OpenReadCount,
+								   std::atomic<uint64_t>&	   CurrentOpenFileCount,
+								   std::atomic<uint64_t>&	   ReadCount,
+								   std::atomic<uint64_t>&	   ReadByteCount)
+: m_Source(Path, BasicFile::Mode::kRead)
+, m_SourceSize(m_Source.FileSize())
+, m_OpenReadCount(OpenReadCount)
+, m_CurrentOpenFileCount(CurrentOpenFileCount)
+, m_ReadCount(ReadCount)
+, m_ReadByteCount(ReadByteCount)
+
+{
+	m_OpenReadCount++;
+	m_CurrentOpenFileCount++;
+}
+
+BufferedOpenFile::~BufferedOpenFile()
+{
+	m_CurrentOpenFileCount--;
+}
+
+CompositeBuffer
+BufferedOpenFile::GetRange(uint64_t Offset, uint64_t Size)
+{
+	ZEN_TRACE_CPU("BufferedOpenFile::GetRange");
+
+	ZEN_ASSERT((m_CacheBlockIndex == (uint64_t)-1) || m_Cache);
+	auto _ = MakeGuard([&]() { ZEN_ASSERT((m_CacheBlockIndex == (uint64_t)-1) || m_Cache); });
+
+	ZEN_ASSERT((Offset + Size) <= m_SourceSize);
+	const uint64_t BlockIndexStart = Offset / BlockSize;
+	const uint64_t BlockIndexEnd   = (Offset + Size - 1) / BlockSize;
+
+	std::vector<SharedBuffer> BufferRanges;
+	BufferRanges.reserve(BlockIndexEnd - BlockIndexStart + 1);
+
+	uint64_t ReadOffset = Offset;
+	for (uint64_t BlockIndex = BlockIndexStart; BlockIndex <= BlockIndexEnd; BlockIndex++)
+	{
+		const uint64_t BlockStartOffset = BlockIndex * BlockSize;
+		if (m_CacheBlockIndex != BlockIndex)
+		{
+			uint64_t CacheSize = Min(BlockSize, m_SourceSize - BlockStartOffset);
+			ZEN_ASSERT(CacheSize > 0);
+			m_Cache = IoBuffer(CacheSize);
+			m_Source.Read(m_Cache.GetMutableView().GetData(), CacheSize, BlockStartOffset);
+			m_ReadCount++;
+			m_ReadByteCount += CacheSize;
+			m_CacheBlockIndex = BlockIndex;
+		}
+
+		const uint64_t BytesRead = ReadOffset - Offset;
+		ZEN_ASSERT(BlockStartOffset <= ReadOffset);
+		const uint64_t OffsetIntoBlock = ReadOffset - BlockStartOffset;
+		ZEN_ASSERT(OffsetIntoBlock < m_Cache.GetSize());
+		const uint64_t BlockBytes = Min(m_Cache.GetSize() - OffsetIntoBlock, Size - BytesRead);
+		BufferRanges.emplace_back(SharedBuffer(IoBuffer(m_Cache, OffsetIntoBlock, BlockBytes)));
+		ReadOffset += BlockBytes;
+	}
+	CompositeBuffer Result(std::move(BufferRanges));
+	ZEN_ASSERT(Result.GetSize() == Size);
+	return Result;
+}
+
+}  // namespace zen
-- 
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