From 9b3acce828e5d0eeb0f510845b16a39614336301 Mon Sep 17 00:00:00 2001
From: Gregory Oschwald <oschwald@gmail.com>
Date: Thu, 3 Feb 2022 13:16:35 -0800
Subject: [PATCH] Add back netstandard2.0 support

Also remove requirements from README.md as the NuGet page covers this
and is less likely to get out of sync.
---
 MaxMind.Db.Benchmark/MaxMind.Db.Benchmark.csproj | 3 ++-
 MaxMind.Db.Test/MaxMind.Db.Test.csproj           | 3 ++-
 MaxMind.Db/Buffer.cs                             | 6 ++++++
 MaxMind.Db/MaxMind.Db.csproj                     | 2 +-
 README.md                                        | 5 -----
 releasenotes.md                                  | 3 ++-
 6 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/MaxMind.Db.Benchmark/MaxMind.Db.Benchmark.csproj b/MaxMind.Db.Benchmark/MaxMind.Db.Benchmark.csproj
index 35bbafe..2e9e852 100644
--- a/MaxMind.Db.Benchmark/MaxMind.Db.Benchmark.csproj
+++ b/MaxMind.Db.Benchmark/MaxMind.Db.Benchmark.csproj
@@ -3,7 +3,8 @@
   <PropertyGroup>
     <Description>Benchmark project to validate .NET reader for the MaxMind DB file format</Description>
     <VersionPrefix>4.0.0</VersionPrefix>
-    <TargetFrameworks>net6.0;net5.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT' ">net6.0;net5.0;net461;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">net6.0;net5.0;netcoreapp3.1</TargetFrameworks>
     <AssemblyName>MaxMind.Db.Benchmark</AssemblyName>
     <OutputType>Exe</OutputType>
     <PackageId>MaxMind.Db.Benchmark</PackageId>
diff --git a/MaxMind.Db.Test/MaxMind.Db.Test.csproj b/MaxMind.Db.Test/MaxMind.Db.Test.csproj
index 8ed34d6..4ab5b22 100644
--- a/MaxMind.Db.Test/MaxMind.Db.Test.csproj
+++ b/MaxMind.Db.Test/MaxMind.Db.Test.csproj
@@ -3,7 +3,8 @@
   <PropertyGroup>
     <Description>Test project to validate .NET reader for the MaxMind DB file format</Description>
     <VersionPrefix>4.0.0</VersionPrefix>
-    <TargetFrameworks>net6.0;net5.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT' ">net6.0;net5.0;net461;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">net6.0;net5.0;netcoreapp3.1</TargetFrameworks>
     <AssemblyName>MaxMind.Db.Test</AssemblyName>
     <AssemblyOriginatorKeyFile>../MaxMind.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
diff --git a/MaxMind.Db/Buffer.cs b/MaxMind.Db/Buffer.cs
index 231ff28..cf609f9 100644
--- a/MaxMind.Db/Buffer.cs
+++ b/MaxMind.Db/Buffer.cs
@@ -52,7 +52,13 @@ internal double ReadDouble(long offset)
         /// </summary>
         internal float ReadFloat(long offset)
         {
+#if NETSTANDARD2_0
+            var buffer = Read(offset, 4);
+            Array.Reverse(buffer);
+            return BitConverter.ToSingle(buffer, 0);
+#else
             return BitConverter.Int32BitsToSingle(ReadInt(offset));
+#endif
         }
 
         /// <summary>
diff --git a/MaxMind.Db/MaxMind.Db.csproj b/MaxMind.Db/MaxMind.Db.csproj
index b89eaba..acb958b 100644
--- a/MaxMind.Db/MaxMind.Db.csproj
+++ b/MaxMind.Db/MaxMind.Db.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <Description>.NET reader for the MaxMind DB file format</Description>
     <VersionPrefix>4.0.0</VersionPrefix>
-    <TargetFrameworks>net6.0;net5.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net6.0;net5.0;netstandard2.1;netstandard2.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>MaxMind.Db</AssemblyName>
     <AssemblyOriginatorKeyFile>../MaxMind.snk</AssemblyOriginatorKeyFile>
diff --git a/README.md b/README.md
index 26a12e7..13ad31e 100644
--- a/README.md
+++ b/README.md
@@ -5,11 +5,6 @@
 This is the .NET API for reading MaxMind DB files. MaxMind DB is a binary file
 format that stores data indexed by IP address subnets (IPv4 or IPv6).
 
-## Requirements ##
-
-This library works with .NET 5.0 and above and .NET Standard
-3.1 or above.
-
 ## Installation ##
 
 ### NuGet ###
diff --git a/releasenotes.md b/releasenotes.md
index b902c90..acd7c7c 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -2,7 +2,8 @@
 
 ## 4.0.0 (2022-02-03) ##
 
-* This library now requires .NET 5.0 or greater or .NET Standard 3.1.
+* This library no longer targets .NET 4.6.1.
+* .NET 6.0 was added as a target.
 
 ## 3.0.0 (2020-11-16) ##