From 7ca6fbc8caf30d0f8b0dca9a294022d3e37c4082 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 22 Apr 2022 10:01:02 +0200
Subject: [PATCH] Move ChunkedVector to its own header

---
 src/libexpr/nixexpr.hh        |  1 +
 src/libexpr/symbol-table.hh   |  1 +
 src/libutil/chunked-vector.hh | 68 +++++++++++++++++++++++++++++++++++
 src/libutil/types.hh          | 59 ------------------------------
 4 files changed, 70 insertions(+), 59 deletions(-)
 create mode 100644 src/libutil/chunked-vector.hh

diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 1a387d4fd..217c7e74d 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -6,6 +6,7 @@
 #include "value.hh"
 #include "symbol-table.hh"
 #include "error.hh"
+#include "chunked-vector.hh"
 
 
 namespace nix {
diff --git a/src/libexpr/symbol-table.hh b/src/libexpr/symbol-table.hh
index d0cd841a0..b6ad60f68 100644
--- a/src/libexpr/symbol-table.hh
+++ b/src/libexpr/symbol-table.hh
@@ -5,6 +5,7 @@
 #include <unordered_map>
 
 #include "types.hh"
+#include "chunked-vector.hh"
 
 namespace nix {
 
diff --git a/src/libutil/chunked-vector.hh b/src/libutil/chunked-vector.hh
new file mode 100644
index 000000000..f15af9cd7
--- /dev/null
+++ b/src/libutil/chunked-vector.hh
@@ -0,0 +1,68 @@
+#pragma once
+
+#include <bits/stdint-uintn.h>
+#include <cstdlib>
+#include <vector>
+#include <limits>
+
+namespace nix {
+
+/* Provides an indexable container like vector<> with memory overhead
+   guarantees like list<> by allocating storage in chunks of ChunkSize
+   elements instead of using a contiguous memory allocation like vector<>
+   does. Not using a single vector that is resized reduces memory overhead
+   on large data sets by on average (growth factor)/2, mostly
+   eliminates copies within the vector during resizing, and provides stable
+   references to its elements. */
+template<typename T, size_t ChunkSize>
+class ChunkedVector {
+private:
+    uint32_t size_ = 0;
+    std::vector<std::vector<T>> chunks;
+
+    /* keep this out of the ::add hot path */
+    [[gnu::noinline]]
+    auto & addChunk()
+    {
+        if (size_ >= std::numeric_limits<uint32_t>::max() - ChunkSize)
+            abort();
+        chunks.emplace_back();
+        chunks.back().reserve(ChunkSize);
+        return chunks.back();
+    }
+
+public:
+    ChunkedVector(uint32_t reserve)
+    {
+        chunks.reserve(reserve);
+        addChunk();
+    }
+
+    uint32_t size() const { return size_; }
+
+    std::pair<T &, uint32_t> add(T value)
+    {
+        const auto idx = size_++;
+        auto & chunk = [&] () -> auto & {
+            if (auto & back = chunks.back(); back.size() < ChunkSize)
+                return back;
+            return addChunk();
+        }();
+        auto & result = chunk.emplace_back(std::move(value));
+        return {result, idx};
+    }
+
+    const T & operator[](uint32_t idx) const
+    {
+        return chunks[idx / ChunkSize][idx % ChunkSize];
+    }
+
+    template<typename Fn>
+    void forEach(Fn fn) const
+    {
+        for (const auto & c : chunks)
+            for (const auto & e : c)
+                fn(e);
+    }
+};
+}
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index bd1dd8bee..6bcbd7e1d 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -103,63 +103,4 @@ public:
     Ptr operator->() const { return Ptr(**this); }
 };
 
-/* Provides an indexable container like vector<> with memory overhead
-   guarantees like list<> by allocating storage in chunks of ChunkSize
-   elements instead of using a contiguous memory allocation like vector<>
-   does. Not using a single vector that is resized reduces memory overhead
-   on large data sets by on average (growth factor)/2, mostly
-   eliminates copies within the vector during resizing, and provides stable
-   references to its elements. */
-template<typename T, size_t ChunkSize>
-class ChunkedVector {
-private:
-    uint32_t size_ = 0;
-    std::vector<std::vector<T>> chunks;
-
-    /* keep this out of the ::add hot path */
-    [[gnu::noinline]]
-    auto & addChunk()
-    {
-        if (size_ >= std::numeric_limits<uint32_t>::max() - ChunkSize)
-            abort();
-        chunks.emplace_back();
-        chunks.back().reserve(ChunkSize);
-        return chunks.back();
-    }
-
-public:
-    ChunkedVector(uint32_t reserve)
-    {
-        chunks.reserve(reserve);
-        addChunk();
-    }
-
-    uint32_t size() const { return size_; }
-
-    std::pair<T &, uint32_t> add(T value)
-    {
-        const auto idx = size_++;
-        auto & chunk = [&] () -> auto & {
-            if (auto & back = chunks.back(); back.size() < ChunkSize)
-                return back;
-            return addChunk();
-        }();
-        auto & result = chunk.emplace_back(std::move(value));
-        return {result, idx};
-    }
-
-    const T & operator[](uint32_t idx) const
-    {
-        return chunks[idx / ChunkSize][idx % ChunkSize];
-    }
-
-    template<typename Fn>
-    void forEach(Fn fn) const
-    {
-        for (const auto & c : chunks)
-            for (const auto & e : c)
-                fn(e);
-    }
-};
-
 }