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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Collections.Generic;
namespace System
{
internal static partial class AppContextDefaultValues
{
public static void PopulateDefaultValues()
{
string platformIdentifier, profile;
int version;
ParseTargetFrameworkName(out platformIdentifier, out profile, out version);
// Call into each library to populate their default switches
PopulateDefaultValuesPartial(platformIdentifier, profile, version);
}
/// <summary>
/// We have this separate method for getting the parsed elements out of the TargetFrameworkName so we can
/// more easily support this on other platforms.
/// </summary>
private static void ParseTargetFrameworkName(out string identifier, out string profile, out int version)
{
string targetFrameworkMoniker = AppDomain.CurrentDomain.SetupInformation.TargetFrameworkName;
if (!TryParseFrameworkName(targetFrameworkMoniker, out identifier, out version, out profile))
{
// If we can't parse the TFM or we don't have a TFM, default to latest behavior for all
// switches (ie. all of them false).
// If we want to use the latest behavior it is enough to set the value of the switch to string.Empty.
// When the get to the caller of this method (PopulateDefaultValuesPartial) we are going to use the
// identifier we just set to decide which switches to turn on. By having an empty string as the
// identifier we are simply saying -- don't turn on any switches, and we are going to get the latest
// behavior for all the switches
identifier = string.Empty;
}
}
// This code was a constructor copied from the FrameworkName class, which is located in System.dll.
// Parses strings in the following format: "<identifier>, Version=[v|V]<version>, Profile=<profile>"
// - The identifier and version is required, profile is optional
// - Only three components are allowed.
// - The version string must be in the System.Version format; an optional "v" or "V" prefix is allowed
private static bool TryParseFrameworkName(String frameworkName, out String identifier, out int version, out String profile)
{
// For parsing a target Framework moniker, from the FrameworkName class
const char c_componentSeparator = ',';
const char c_keyValueSeparator = '=';
const char c_versionValuePrefix = 'v';
const String c_versionKey = "Version";
const String c_profileKey = "Profile";
identifier = profile = string.Empty;
version = 0;
if (frameworkName == null || frameworkName.Length == 0)
{
return false;
}
String[] components = frameworkName.Split(c_componentSeparator);
version = 0;
// Identifer and Version are required, Profile is optional.
if (components.Length < 2 || components.Length > 3)
{
return false;
}
//
// 1) Parse the "Identifier", which must come first. Trim any whitespace
//
identifier = components[0].Trim();
if (identifier.Length == 0)
{
return false;
}
bool versionFound = false;
profile = null;
//
// The required "Version" and optional "Profile" component can be in any order
//
for (int i = 1; i < components.Length; i++)
{
// Get the key/value pair separated by '='
string[] keyValuePair = components[i].Split(c_keyValueSeparator);
if (keyValuePair.Length != 2)
{
return false;
}
// Get the key and value, trimming any whitespace
string key = keyValuePair[0].Trim();
string value = keyValuePair[1].Trim();
//
// 2) Parse the required "Version" key value
//
if (key.Equals(c_versionKey, StringComparison.OrdinalIgnoreCase))
{
versionFound = true;
// Allow the version to include a 'v' or 'V' prefix...
if (value.Length > 0 && (value[0] == c_versionValuePrefix || value[0] == 'V'))
{
value = value.Substring(1);
}
Version realVersion = new Version(value);
// The version class will represent some unset values as -1 internally (instead of 0).
version = realVersion.Major * 10000;
if (realVersion.Minor > 0)
version += realVersion.Minor * 100;
if (realVersion.Build > 0)
version += realVersion.Build;
}
//
// 3) Parse the optional "Profile" key value
//
else if (key.Equals(c_profileKey, StringComparison.OrdinalIgnoreCase))
{
if (!String.IsNullOrEmpty(value))
{
profile = value;
}
}
else
{
return false;
}
}
if (!versionFound)
{
return false;
}
return true;
}
// This is a partial method. Platforms (such as Desktop) can provide an implementation of it that will read override value
// from whatever mechanism is available on that platform. If no implementation is provided, the compiler is going to remove the calls
// to it from the code
static partial void TryGetSwitchOverridePartial(string switchName, ref bool overrideFound, ref bool overrideValue);
/// This is a partial method. This method is responsible for populating the default values based on a TFM.
/// It is partial because each library should define this method in their code to contain their defaults.
static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int version);
}
}
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