// 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.

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
// RuntimeHelpers
//    This class defines a set of static methods that provide support for compilers.
//
//
namespace System.Runtime.CompilerServices {

    using System;
    using System.Security;
    using System.Runtime;
    using System.Runtime.CompilerServices;
    using System.Runtime.InteropServices;
    using System.Runtime.ConstrainedExecution;
    using System.Runtime.Serialization;
    using System.Security.Permissions;
    using System.Threading;
    using System.Runtime.Versioning;
    using System.Diagnostics.Contracts;

    public static class RuntimeHelpers
    {
        // Exposed here as a more appropriate place than on FormatterServices itself,
        // which is a high level reflection heavy type.
        public static Object GetUninitializedObject(Type type)
        {
            return FormatterServices.GetUninitializedObject(type);
        }

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern void InitializeArray(Array array,RuntimeFieldHandle fldHandle);

        // GetObjectValue is intended to allow value classes to be manipulated as 'Object'
        // but have aliasing behavior of a value class.  The intent is that you would use
        // this function just before an assignment to a variable of type 'Object'.  If the
        // value being assigned is a mutable value class, then a shallow copy is returned 
        // (because value classes have copy semantics), but otherwise the object itself
        // is returned.  
        //
        // Note: VB calls this method when they're about to assign to an Object
        // or pass it as a parameter.  The goal is to make sure that boxed 
        // value types work identical to unboxed value types - ie, they get 
        // cloned when you pass them around, and are always passed by value.  
        // Of course, reference types are not cloned.
        //
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern Object GetObjectValue(Object obj);

        // RunClassConstructor causes the class constructor for the given type to be triggered
        // in the current domain.  After this call returns, the class constructor is guaranteed to
        // have at least been started by some thread.  In the absence of class constructor
        // deadlock conditions, the call is further guaranteed to have completed.
        //
        // This call will generate an exception if the specified class constructor threw an 
        // exception when it ran. 

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern void _RunClassConstructor(RuntimeType type);

        public static void RunClassConstructor(RuntimeTypeHandle type) 
        {
            _RunClassConstructor(type.GetRuntimeType());
        }

        // RunModuleConstructor causes the module constructor for the given type to be triggered
        // in the current domain.  After this call returns, the module constructor is guaranteed to
        // have at least been started by some thread.  In the absence of module constructor
        // deadlock conditions, the call is further guaranteed to have completed.
        //
        // This call will generate an exception if the specified module constructor threw an 
        // exception when it ran. 

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern void _RunModuleConstructor(System.Reflection.RuntimeModule module);

        public static void RunModuleConstructor(ModuleHandle module) 
        {
           _RunModuleConstructor(module.GetRuntimeModule());
        }


        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode), SuppressUnmanagedCodeSecurity]
        internal static extern void _CompileMethod(IRuntimeMethodInfo method);

        public static void PrepareMethod(RuntimeMethodHandle method){}
        public static void PrepareMethod(RuntimeMethodHandle method, RuntimeTypeHandle[] instantiation){}
        public static void PrepareContractedDelegate(Delegate d){}
        
        public static void PrepareDelegate(Delegate d)
        {
            if (d == null)
            {
                throw new ArgumentNullException ("d");
            }
        }

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern int GetHashCode(Object o);

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public new static extern bool Equals(Object o1, Object o2);

        public static int OffsetToStringData
        {
            // This offset is baked in by string indexer intrinsic, so there is no harm
            // in getting it baked in here as well.
            [System.Runtime.Versioning.NonVersionable] 
            get {
                // Number of bytes from the address pointed to by a reference to
                // a String to the first 16-bit character in the String.  Skip 
                // over the MethodTable pointer, & String 
                // length.  Of course, the String reference points to the memory 
                // after the sync block, so don't count that.  
                // This property allows C#'s fixed statement to work on Strings.
                // On 64 bit platforms, this should be 12 (8+4) and on 32 bit 8 (4+4).
#if BIT64
                return 12;
#else // 32
                return 8;
#endif // BIT64
            }
        }

        // This method ensures that there is sufficient stack to execute the average Framework function.
        // If there is not enough stack, then it throws System.InsufficientExecutionStackException.
        // Note: this method is not part of the CER support, and is not to be confused with ProbeForSufficientStack
        // below.
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        public static extern void EnsureSufficientExecutionStack();

        // This method ensures that there is sufficient stack to execute the average Framework function.
        // If there is not enough stack, then it return false.
        // Note: this method is not part of the CER support, and is not to be confused with ProbeForSufficientStack
        // below.
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        public static extern bool TryEnsureSufficientExecutionStack();

        public static void ProbeForSufficientStack()
        {
        }

        // This method is a marker placed immediately before a try clause to mark the corresponding catch and finally blocks as
        // constrained. There's no code here other than the probe because most of the work is done at JIT time when we spot a call to this routine.
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
        public static void PrepareConstrainedRegions()
        {
            ProbeForSufficientStack();
        }

        // When we detect a CER with no calls, we can point the JIT to this non-probing version instead
        // as we don't need to probe.
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
        public static void PrepareConstrainedRegionsNoOP()
        {
        }

        public delegate void TryCode(Object userData);

        public delegate void CleanupCode(Object userData, bool exceptionThrown);

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern void ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData);

        [PrePrepareMethod]
        internal static void ExecuteBackoutCodeHelper(Object backoutCode, Object userData, bool exceptionThrown)
        {
            ((CleanupCode)backoutCode)(userData, exceptionThrown);
        }
    }
}