Fix Mono runtime failures.

src/ZstdSharp/Unsafe/Bitstream.cs

@@ -10,7 +10,7 @@ namespace ZstdSharp.Unsafe
 {
     public static unsafe partial class Methods
     {
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_BIT_mask => new uint[32]
         {
             0,

src/ZstdSharp/Unsafe/FseCompress.cs

@@ -446,7 +446,7 @@ private static nuint FSE_normalizeM2(short* norm, uint tableLog, uint* count, nu
             return 0;
         }
 
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_rtbTable => new uint[8]
         {
             0,

src/ZstdSharp/Unsafe/ZstdCompress.cs

@@ -2015,7 +2015,7 @@ public static nuint ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameter
             }
         }
 
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<ulong> Span_srcSizeTiers => new ulong[4]
         {
             16 * (1 << 10),

src/ZstdSharp/Unsafe/ZstdCompressSequences.cs

@@ -7,7 +7,7 @@ namespace ZstdSharp.Unsafe
 {
     public static unsafe partial class Methods
     {
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_kInverseProbabilityLog256 => new uint[256]
         {
             0,

src/ZstdSharp/Unsafe/ZstdDecompressBlock.cs

@@ -735,7 +735,7 @@ private static nuint ZSTD_decodeSeqHeaders(ZSTD_DCtx_s* dctx, int* nbSeqPtr, voi
             return (nuint)(ip - istart);
         }
 
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_dec32table => new uint[8]
         {
             0,
@@ -752,7 +752,7 @@ private static nuint ZSTD_decodeSeqHeaders(ZSTD_DCtx_s* dctx, int* nbSeqPtr, voi
 
         private static readonly uint* dec32table = GetArrayPointer(new uint[8] { 0, 1, 2, 1, 4, 4, 4, 4 });
 #endif
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<int> Span_dec64table => new int[8]
         {
             8,

src/ZstdSharp/Unsafe/ZstdDecompressInternal.cs

@@ -7,7 +7,7 @@ namespace ZstdSharp.Unsafe
 {
     public static unsafe partial class Methods
     {
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_LL_base => new uint[36]
         {
             0,
@@ -52,7 +52,7 @@ public static unsafe partial class Methods
 
         private static readonly uint* LL_base = GetArrayPointer(new uint[36] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22, 24, 28, 32, 40, 48, 64, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000, 0x10000 });
 #endif
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_OF_base => new uint[32]
         {
             0,
@@ -134,7 +134,7 @@ public static unsafe partial class Methods
 
         private static readonly byte* OF_bits = GetArrayPointer(new byte[32] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 });
 #endif
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_ML_base => new uint[53]
         {
             3,

src/ZstdSharp/Unsafe/ZstdInternal.cs

@@ -13,7 +13,7 @@ namespace ZstdSharp.Unsafe
 {
     public static unsafe partial class Methods
     {
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_repStartValue => new uint[3]
         {
             1,
@@ -73,7 +73,7 @@ public static unsafe partial class Methods
 
         private static readonly byte* LL_bits = GetArrayPointer(new byte[36] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 });
 #endif
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<short> Span_LL_defaultNorm => new short[36]
         {
             4,
@@ -244,7 +244,7 @@ public static unsafe partial class Methods
         private static readonly short* ML_defaultNorm = GetArrayPointer(new short[53] { 1, 4, 3, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, (short)(-1), (short)(-1), (short)(-1), (short)(-1), (short)(-1), (short)(-1), (short)(-1) });
 #endif
         private const uint ML_defaultNormLog = 6;
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<short> Span_OF_defaultNorm => new short[29]
         {
             1,

src/ZstdSharp/Unsafe/ZstdLdmGeartab.cs

@@ -6,7 +6,7 @@ namespace ZstdSharp.Unsafe
 {
     public static unsafe partial class Methods
     {
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<ulong> Span_ZSTD_ldm_gearTab => new ulong[256]
         {
             0xf5b8f72c5f77775c,

src/ZstdSharp/Unsafe/ZstdOpt.cs

@@ -87,7 +87,7 @@ private static uint ZSTD_scaleStats(uint* table, uint lastEltIndex, uint logTarg
             return ZSTD_downscaleStats(table, lastEltIndex, ZSTD_highbit32(factor), base_directive_e.base_1guaranteed);
         }
 
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_baseLLfreqs => new uint[36]
         {
             4,
@@ -132,7 +132,7 @@ private static uint ZSTD_scaleStats(uint* table, uint lastEltIndex, uint logTarg
 
         private static readonly uint* baseLLfreqs = GetArrayPointer(new uint[36] { 4, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 });
 #endif
-#if NET8_0_OR_GREATER
+#if NET7_0_OR_GREATER
         private static ReadOnlySpan<uint> Span_baseOFCfreqs => new uint[32]
         {
             6,

src/ZstdSharp/UnsafeHelper.cs

@@ -70,11 +70,13 @@ public static void free(void* ptr)
         public static T* GetArrayPointer<T>(T[] array) where T : unmanaged
         {
             var size = (uint)(sizeof(T) * array.Length);
-#if NET5_0_OR_GREATER
+#if NET9_0_OR_GREATER
             // This function is used to allocate memory for static data blocks.
             // We have to use AllocateTypeAssociatedMemory and link the memory's
             // lifetime to this assembly, in order to prevent memory leaks when
             // loading the assembly in an unloadable AssemblyLoadContext.
+            // While introduced in .NET 5, we call this only in .NET 9+, because
+            // it's not implemented in the Mono runtime until then.
             var destination = (T*)RuntimeHelpers.AllocateTypeAssociatedMemory(typeof(UnsafeHelper), (int)size);
 #else
             var destination = (T*)malloc(size);