Revert "Remove custom allocator."

src/native/libs/System.IO.Compression.Native/CMakeLists.txt

@@ -36,6 +36,10 @@ set(NATIVECOMPRESSION_SOURCES
     pal_zlib.c
 )
 
+if (HOST_WIN32 OR CLR_CMAKE_TARGET_WIN32)
+    list(APPEND NATIVECOMPRESSION_SOURCES "zlib_allocator_win.c")
+endif()
+
 if (NOT CLR_CMAKE_TARGET_BROWSER AND NOT CLR_CMAKE_TARGET_WASI)
     set (NATIVECOMPRESSION_SOURCES
         ${NATIVECOMPRESSION_SOURCES}

src/native/libs/System.IO.Compression.Native/pal_zlib.c

@@ -8,6 +8,7 @@
 #ifdef _WIN32
     #define c_static_assert(e) static_assert((e),"")
     #include "../Common/pal_utilities.h"
+    #include <zlib_allocator.h>
 #else
     #include "pal_utilities.h"
 #endif
@@ -39,6 +40,11 @@ static int32_t Init(PAL_ZStream* stream)
 {
     z_stream* zStream = (z_stream*)calloc(1, sizeof(z_stream));
 
+#ifdef _WIN32
+    zStream->zalloc = z_custom_calloc;
+    zStream->zfree = z_custom_cfree;
+#endif
+
     stream->internalState = zStream;
 
     if (zStream != NULL)

src/native/libs/System.IO.Compression.Native/zlib_allocator.h

@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#include <zconf.h> // voidpf
+
+voidpf z_custom_calloc(voidpf opaque, unsigned items, unsigned size);
+
+void z_custom_cfree(voidpf opaque, voidpf ptr);

src/native/libs/System.IO.Compression.Native/zlib_allocator_win.c

@@ -0,0 +1,87 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#include <Windows.h>
+#include <heapapi.h>
+#include <intsafe.h>
+#include <crtdbg.h> /* _ASSERTE */
+
+#include <zlib_allocator.h>
+
+/* A custom allocator for zlib that uses a dedicated heap.
+   This provides better performance and avoids fragmentation
+   that can occur on Windows when using the default process heap.
+ */
+
+// Gets the special heap we'll allocate from.
+HANDLE GetZlibHeap()
+{
+#ifdef _WIN64
+    static HANDLE s_hPublishedHeap = NULL;
+
+    // If already initialized, return immediately.
+    // We don't need a volatile read here since the publish is performed with release semantics.
+    if (s_hPublishedHeap != NULL) { return s_hPublishedHeap; }
+
+    // Attempt to create a new heap. The heap will be dynamically sized.
+    HANDLE hNewHeap = HeapCreate(0, 0, 0);
+
+    if (hNewHeap != NULL)
+    {
+        // We created a new heap. Attempt to publish it.
+        if (InterlockedCompareExchangePointer(&s_hPublishedHeap, hNewHeap, NULL) != NULL)
+        {
+            HeapDestroy(hNewHeap); // Somebody published before us. Destroy our heap.
+            hNewHeap = NULL; // Guard against accidental use later in the method.
+        }
+    }
+    else
+    {
+        // If we can't create a new heap, fall back to the process default heap.
+        InterlockedCompareExchangePointer(&s_hPublishedHeap, GetProcessHeap(), NULL);
+    }
+
+    // Some thread - perhaps us, perhaps somebody else - published the heap. Return it.
+    // We don't need a volatile read here since the publish is performed with release semantics.
+    _ASSERTE(s_hPublishedHeap != NULL);
+    return s_hPublishedHeap;
+#else
+    // We don't want to create a new heap in a 32-bit process because it could end up
+    // reserving too much of the address space. Instead, fall back to the normal process heap.
+    return GetProcessHeap();
+#endif
+}
+
+voidpf z_custom_calloc(opaque, items, size)
+    voidpf opaque;
+    unsigned items;
+    unsigned size;
+{
+
+    SIZE_T cbRequested;
+    if (sizeof(items) + sizeof(size) <= sizeof(cbRequested))
+    {
+        // multiplication can't overflow; no need for safeint
+        cbRequested = (SIZE_T)items * (SIZE_T)size;
+    }
+    else
+    {
+        // multiplication can overflow; go through safeint
+        if (FAILED(SIZETMult(items, size, &cbRequested))) { return NULL; }
+    }
+
+    return HeapAlloc(GetZlibHeap(), 0, cbRequested);
+}
+
+void z_custom_cfree(opaque, ptr)
+    voidpf opaque;
+    voidpf ptr;
+{
+    if (ptr == NULL) { return; } // ok to free nullptr
+
+    if (!HeapFree(GetZlibHeap(), 0, ptr)) { goto Fail; }
+    return;
+
+Fail:
+    __fastfail(FAST_FAIL_HEAP_METADATA_CORRUPTION);
+}