IteratorDescriptor.cs source code in C# .NET

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Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / XmlUtils / System / Xml / Xsl / IlGen / IteratorDescriptor.cs / 1305376 / IteratorDescriptor.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
using System; 
using System.Collections; 
using System.Collections.Generic;
using System.Xml; 
using System.Xml.XPath;
using System.Xml.Schema;
using System.Globalization;
using System.Diagnostics; 
using System.Reflection;
using System.Reflection.Emit; 
using System.Xml.Xsl.Runtime; 

namespace System.Xml.Xsl.IlGen { 

    /// 
    /// Type of location in which iterator items are stored.
    ///  
    internal enum ItemLocation {
        None = 0, 
        Stack,                              // Each value is stored as the top value on the IL stack 
        Parameter,                          // Each value is stored as a parameter to the current method
        Local,                              // Each value is stored as a local variable in the current method 
        Current,                            // Each value is stored as an iterator's Current property
        Global,                             // Each value is stored as a global variable
    };
 

    ///  
    /// None--Not in a branching context 
    /// True--Branch if boolean expression evaluates to true
    /// False--Branch if boolean expression evaluates to false 
    /// 
    internal enum BranchingContext {None, OnTrue, OnFalse};

    ///  
    /// Describes the Clr type and location of items returned by an iterator.
    /// This struct is meant to be immutable. 
    ///  
    internal struct StorageDescriptor {
        private ItemLocation location; 
        private object locationObject;
        private Type itemStorageType;
        private bool isCached;
 

        //----------------------------------------------- 
        // Create Methods 
        //-----------------------------------------------
 
        /// 
        /// Create default, empty StorageDescriptor.
        /// 
        public static StorageDescriptor None() { 
            return new StorageDescriptor();
        } 
 
        /// 
        /// Create a StorageDescriptor for an item located on the stack. 
        /// 
        public static StorageDescriptor Stack(Type itemStorageType, bool isCached) {
            StorageDescriptor storage = new StorageDescriptor();
            storage.location = ItemLocation.Stack; 
            storage.itemStorageType = itemStorageType;
            storage.isCached = isCached; 
            return storage; 
        }
 
        /// 
        /// Create a StorageDescriptor for an item which is a parameter to the current method.
        /// 
        public static StorageDescriptor Parameter(int paramIndex, Type itemStorageType, bool isCached) { 
            StorageDescriptor storage = new StorageDescriptor();
            storage.location = ItemLocation.Parameter; 
            storage.locationObject = paramIndex; 
            storage.itemStorageType = itemStorageType;
            storage.isCached = isCached; 
            return storage;
        }

        ///  
        /// Create a StorageDescriptor for an item located in a local variable.
        ///  
        public static StorageDescriptor Local(LocalBuilder loc, Type itemStorageType, bool isCached) { 
            Debug.Assert(loc.LocalType == itemStorageType ||
                         typeof(IList<>).MakeGenericType(itemStorageType).IsAssignableFrom(loc.LocalType), 
                         "Type " + itemStorageType + " does not match the local variable's type");

            StorageDescriptor storage = new StorageDescriptor();
            storage.location = ItemLocation.Local; 
            storage.locationObject = loc;
            storage.itemStorageType = itemStorageType; 
            storage.isCached = isCached; 
            return storage;
        } 

        /// 
        /// Create a StorageDescriptor for an item which is the Current item in an iterator.
        ///  
        public static StorageDescriptor Current(LocalBuilder locIter, Type itemStorageType) {
            Debug.Assert(locIter.LocalType.GetMethod("get_Current").ReturnType == itemStorageType, 
                         "Type " + itemStorageType + " does not match type of Current property."); 

            StorageDescriptor storage = new StorageDescriptor(); 
            storage.location = ItemLocation.Current;
            storage.locationObject = locIter;
            storage.itemStorageType = itemStorageType;
            return storage; 
        }
 
        ///  
        /// Create a StorageDescriptor for an item located in a global variable.
        ///  
        public static StorageDescriptor Global(MethodInfo methGlobal, Type itemStorageType, bool isCached) {
            Debug.Assert(methGlobal.ReturnType == itemStorageType ||
                         typeof(IList<>).MakeGenericType(itemStorageType).IsAssignableFrom(methGlobal.ReturnType),
                         "Type " + itemStorageType + " does not match the global method's return type"); 

            StorageDescriptor storage = new StorageDescriptor(); 
            storage.location = ItemLocation.Global; 
            storage.locationObject = methGlobal;
            storage.itemStorageType = itemStorageType; 
            storage.isCached = isCached;
            return storage;
        }
 

        //----------------------------------------------- 
        // Accessor Methods 
        //-----------------------------------------------
 
        /// 
        /// Return copy of current descriptor, but change item's location to the stack.
        /// 
        public StorageDescriptor ToStack() { 
            return Stack(this.itemStorageType, this.isCached);
        } 
 
        /// 
        /// Create a StorageDescriptor for an item located in a local variable. 
        /// 
        public StorageDescriptor ToLocal(LocalBuilder loc) {
            return Local(loc, this.itemStorageType, this.isCached);
        } 

        ///  
        /// Create a StorageDescriptor which is the same as this one, except for the item storage type. 
        /// 
        public StorageDescriptor ToStorageType(Type itemStorageType) { 
            StorageDescriptor storage = this;
            storage.itemStorageType = itemStorageType;
            return storage;
        } 

        ///  
        /// Return an enumeration specifying where the value is located. 
        /// 
        public ItemLocation Location { 
            get { return this.location; }
        }

        ///  
        /// Return the index of the parameter that stores this iterator's values.
        ///  
        public int ParameterLocation { 
            get { return (int) this.locationObject; }
        } 

        /// 
        /// Return the LocalBuilder that stores this iterator's values.
        ///  
        public LocalBuilder LocalLocation {
            get { return this.locationObject as LocalBuilder; } 
        } 

        ///  
        /// Return the LocalBuilder that will store this iterator's helper class.  The Current property
        /// on this iterator can be accessed to get the current iteration value.
        /// 
        public LocalBuilder CurrentLocation { 
            get { return this.locationObject as LocalBuilder; }
        } 
 
        /// 
        /// Return the MethodInfo for the method that computes this global value. 
        /// 
        public MethodInfo GlobalLocation {
            get { return this.locationObject as MethodInfo; }
        } 

        ///  
        /// Return true if this iterator's values are cached. 
        /// 
        public bool IsCached { 
            get { return this.isCached; }
        }

        ///  
        /// Return the Clr type of an individual item in the storage location (never an IList<> type).
        ///  
        public Type ItemStorageType { 
            get { return this.itemStorageType; }
        } 
    }

    /// 
    /// Iterators are joined together, are nested within each other, and reference each other.  This internal class 
    /// contains detailed information about iteration next labels, caching, iterator item location, etc.
    ///  
    internal class IteratorDescriptor { 
        private GenerateHelper helper;
 
        // Related iterators
        private IteratorDescriptor iterParent;

        // Iteration 
        private Label lblNext;
        private bool hasNext; 
        private LocalBuilder locPos; 

        // Branching 
        private BranchingContext brctxt;
        private Label lblBranch;

        // Storage 
        private StorageDescriptor storage;
 
 
        //-----------------------------------------------
        // Initialize 
        //-----------------------------------------------

        /// 
        /// Create a "root" IteratorDescriptor which has no parent iterator. 
        /// 
        public IteratorDescriptor(GenerateHelper helper) { 
            Init(null, helper); 
        }
 
        /// 
        /// Create an IteratorDescriptor that is nested in a parent iterator.
        /// 
        public IteratorDescriptor(IteratorDescriptor iterParent) { 
            Init(iterParent, iterParent.helper);
        } 
 
        /// 
        /// Internal helper initializor. 
        /// 
        private void Init(IteratorDescriptor iterParent, GenerateHelper helper) {
            this.helper = helper;
            this.iterParent = iterParent; 
        }
 
 
        //-----------------------------------------------
        // Related Iterators 
        //-----------------------------------------------

        /// 
        /// Return the iterator in which this iterator is nested. 
        /// 
        public IteratorDescriptor ParentIterator { 
            get { return this.iterParent; } 
        }
 

        //-----------------------------------------------
        // Iteration
        //----------------------------------------------- 

        ///  
        /// Returns true if LabelNext is currently defined.  If not, then this iterator will return 
        /// exactly one result (iterator is cardinality one).
        ///  
        public bool HasLabelNext {
            get { return this.hasNext; }
        }
 
        /// 
        /// Return the label that is anchored to this code iterator's MoveNext code. 
        ///  
        public Label GetLabelNext() {
            Debug.Assert(this.hasNext); 
            return this.lblNext;
        }

        ///  
        /// Set this iterator's next label and storage.  This iterator will range over a set of values located in
        /// "storage".  To get the next value, jump to "lblNext". 
        ///  
        public void SetIterator(Label lblNext, StorageDescriptor storage) {
            this.lblNext = lblNext; 
            this.hasNext = true;
            this.storage = storage;
        }
 
        /// 
        /// Set this iterator to be the same as the specified iterator. 
        ///  
        public void SetIterator(IteratorDescriptor iterInfo) {
            if (iterInfo.HasLabelNext) { 
                this.lblNext = iterInfo.GetLabelNext();
                this.hasNext = true;
            }
 
            this.storage = iterInfo.Storage;
        } 
 
        /// 
        /// Continue iteration until it is complete.  Branch to "lblOnEnd" when iteration is complete. 
        /// 
        /// 
        /// goto LabelNextCtxt;
        /// LabelOnEnd: 
        /// 
        public void LoopToEnd(Label lblOnEnd) { 
            if (this.hasNext) { 
                this.helper.BranchAndMark(this.lblNext, lblOnEnd);
                this.hasNext = false; 
            }

            // After looping is finished, storage is N/A
            this.storage = StorageDescriptor.None(); 
        }
 
        ///  
        /// Storage location containing the position of the current item as an integer.
        /// This location is only defined on iterators, and then only if they might be 
        /// referenced by a PositionOf operator.
        /// 
        public LocalBuilder LocalPosition {
            get { return this.locPos; } 
            set { this.locPos = value; }
        } 
 

        //----------------------------------------------- 
        // Caching
        //-----------------------------------------------

        ///  
        /// Push the count of items in the cache onto the stack.
        ///  
        public void CacheCount() { 
            Debug.Assert(this.storage.IsCached);
            PushValue(); 
            this.helper.CallCacheCount(this.storage.ItemStorageType);
        }

        ///  
        /// If the iterator has been fully cached, then iterate the values one-by-one.
        ///  
        public void EnsureNoCache() { 
            if (this.storage.IsCached) {
                if (!HasLabelNext) { 
                    // If no Next label, this must be a singleton cache
                    EnsureStack();
                    this.helper.LoadInteger(0);
                    this.helper.CallCacheItem(this.storage.ItemStorageType); 

                    this.storage = StorageDescriptor.Stack(this.storage.ItemStorageType, false); 
                } 
                else {
                    // int idx; 
                    LocalBuilder locIdx = this.helper.DeclareLocal("$$$idx", typeof(int));
                    Label lblNext;

                    // Make sure cache is not on the stack 
                    EnsureNoStack("$$$cache");
 
                    // idx = -1; 
                    this.helper.LoadInteger(-1);
                    this.helper.Emit(OpCodes.Stloc, locIdx); 

                    // LabelNext:
                    lblNext = this.helper.DefineLabel();
                    this.helper.MarkLabel(lblNext); 

                    // idx++; 
                    this.helper.Emit(OpCodes.Ldloc, locIdx); 
                    this.helper.LoadInteger(1);
                    this.helper.Emit(OpCodes.Add); 
                    this.helper.Emit(OpCodes.Stloc, locIdx);

                    // if (idx >= cache.Count) goto LabelNextCtxt;
                    this.helper.Emit(OpCodes.Ldloc, locIdx); 
                    CacheCount();
                    this.helper.Emit(OpCodes.Bge, GetLabelNext()); 
 
                    // item = cache[idx];
                    PushValue(); 
                    this.helper.Emit(OpCodes.Ldloc, locIdx);
                    this.helper.CallCacheItem(this.storage.ItemStorageType);

                    SetIterator(lblNext, StorageDescriptor.Stack(this.storage.ItemStorageType, false)); 
                }
            } 
        } 

 
        //-----------------------------------------------
        // If-then-else branching
        //-----------------------------------------------
 
        /// 
        /// Setup a branching context.  All nested iterators compiled in this context must evaluate 
        /// to a single boolean value.  However, these expressions must not push the result as a boolean 
        /// onto the stack.  Instead, if brctxt is BranchType.True, then the expression should
        /// jump to lblBranch if it evaluates to true.  If brctxt is BranchType.False, then the 
        /// branch should happen if the evaluation result is false.
        /// 
        public void SetBranching(BranchingContext brctxt, Label lblBranch) {
            Debug.Assert(brctxt != BranchingContext.None); 
            this.brctxt = brctxt;
            this.lblBranch = lblBranch; 
        } 

        ///  
        /// True if within a branching context.
        /// 
        public bool IsBranching {
            get { return this.brctxt != BranchingContext.None; } 
        }
 
        ///  
        /// Returns the label to which conditionals should branch.
        ///  
        public Label LabelBranch {
            get { return this.lblBranch; }
        }
 
        /// 
        /// If BranchingContext.OnTrue, branch on true.  Otherwise, branch on false. 
        ///  
        public BranchingContext CurrentBranchingContext {
            get { return this.brctxt; } 
        }


        //----------------------------------------------- 
        // Storage
        //----------------------------------------------- 
 
        /// 
        /// Returns information about how and where iterator values are stored. 
        /// 
        public StorageDescriptor Storage {
            get { return this.storage; }
            set { this.storage = value; } 
        }
 
        ///  
        /// Push current item onto the stack without affecting Location.
        ///  
        public void PushValue() {
            switch (this.storage.Location) {
                case ItemLocation.Stack:
                    this.helper.Emit(OpCodes.Dup); 
                    break;
 
                case ItemLocation.Parameter: 
                    this.helper.LoadParameter(this.storage.ParameterLocation);
                    break; 

                case ItemLocation.Local:
                    this.helper.Emit(OpCodes.Ldloc, this.storage.LocalLocation);
                    break; 

                case ItemLocation.Current: 
                    this.helper.Emit(OpCodes.Ldloca, this.storage.CurrentLocation); 
                    this.helper.Call(this.storage.CurrentLocation.LocalType.GetMethod("get_Current"));
                    break; 

                default:
                    Debug.Assert(false, "Invalid location: " + this.storage.Location);
                    break; 
            }
        } 
 
        /// 
        /// Ensure that the current item is pushed onto the stack. 
        /// 
        public void EnsureStack() {
            switch (this.storage.Location) {
                case ItemLocation.Stack: 
                    // Already on the stack
                    return; 
 
                case ItemLocation.Parameter:
                case ItemLocation.Local: 
                case ItemLocation.Current:
                    PushValue();
                    break;
 
                case ItemLocation.Global:
                    // Call method that computes the value of this global value 
                    this.helper.LoadQueryRuntime(); 
                    this.helper.Call(this.storage.GlobalLocation);
                    break; 

                default:
                    Debug.Assert(false, "Invalid location: " + this.storage.Location);
                    break; 
            }
 
            this.storage = this.storage.ToStack(); 
        }
 
        /// 
        /// If the current item is on the stack, move it to a local variable.
        /// 
        public void EnsureNoStack(string locName) { 
            if (this.storage.Location == ItemLocation.Stack)
                EnsureLocal(locName); 
        } 

        ///  
        /// If current item is not already in a local variable, then move it to a local variable of the specified name.
        /// 
        public void EnsureLocal(string locName) {
            if (this.storage.Location != ItemLocation.Local) { 
                if (this.storage.IsCached)
                    EnsureLocal(this.helper.DeclareLocal(locName, typeof(IList<>).MakeGenericType(this.storage.ItemStorageType))); 
                else 
                    EnsureLocal(this.helper.DeclareLocal(locName, this.storage.ItemStorageType));
            } 
        }

        /// 
        /// Ensure that current item is saved to the specified local variable. 
        /// 
        public void EnsureLocal(LocalBuilder bldr) { 
            if (this.storage.LocalLocation != bldr) { 
                // Push value onto stack and then save to bldr
                EnsureStack(); 
                this.helper.Emit(OpCodes.Stloc, bldr);
                this.storage = this.storage.ToLocal(bldr);
            }
        } 

        ///  
        /// Discard the current item if it is pushed onto the stack. 
        /// 
        public void DiscardStack() { 
            if (this.storage.Location == ItemLocation.Stack) {
                this.helper.Emit(OpCodes.Pop);
                this.storage = StorageDescriptor.None();
            } 
        }
 
        ///  
        /// Ensure that the iterator's items are not cached, and that the current item is pushed onto the stack.
        ///  
        public void EnsureStackNoCache() {
            EnsureNoCache();
            EnsureStack();
        } 

        ///  
        /// Ensure that the iterator's items are not cached, and that if the current item is pushed onto the stack, 
        /// that it is moved to a local variable.
        ///  
        public void EnsureNoStackNoCache(string locName) {
            EnsureNoCache();
            EnsureNoStack(locName);
        } 

        ///  
        /// Ensure that the iterator's items are not cached, and that if the current item is not already in a local, 
        /// variable, that it is moved to a local variable of the specified name.
        ///  
        public void EnsureLocalNoCache(string locName) {
            EnsureNoCache();
            EnsureLocal(locName);
        } 

        ///  
        /// Ensure that the iterator's items are not cached and that the current item is saved to the specified local variable. 
        /// 
        public void EnsureLocalNoCache(LocalBuilder bldr) { 
            EnsureNoCache();
            EnsureLocal(bldr);
        }
 
        /// 
        /// Each XmlQueryType has multiple legal CLR representations.  Ensure that all items returned by this iterator are in 
        /// the Clr representation specified by "storageTypeDest". 
        /// 
        public void EnsureItemStorageType(XmlQueryType xmlType, Type storageTypeDest) { 
            // If source type = destination type, then done
            if (this.storage.ItemStorageType == storageTypeDest)
                goto SetStorageType;
 
            Debug.Assert(this.storage.ItemStorageType == typeof(XPathItem) || storageTypeDest == typeof(XPathItem),
                         "EnsureItemStorageType must convert to or from Item"); 
 
            // If items are cached,
            if (this.storage.IsCached) { 
                // Check for special case of IList -> IList
                if (this.storage.ItemStorageType == typeof(XPathNavigator)) {
                    EnsureStack();
                    this.helper.Call(XmlILMethods.NavsToItems); 
                    goto SetStorageType;
                } 
 
                // Check for special case of IList -> IList
                if (storageTypeDest == typeof(XPathNavigator)) { 
                    EnsureStack();
                    this.helper.Call(XmlILMethods.ItemsToNavs);
                    goto SetStorageType;
                } 
            }
 
            // Iterate over each item, and convert each to the destination type 
            EnsureStackNoCache();
 
            // If source type is Item,
            if (this.storage.ItemStorageType == typeof(XPathItem)) {
                // Then downcast to Navigator
                if (storageTypeDest == typeof(XPathNavigator)) { 
                    this.helper.Emit(OpCodes.Castclass, typeof(XPathNavigator));
                } 
                else { 
                    // Call ValueAs methods for atomic types
                    this.helper.CallValueAs(storageTypeDest); 
                }
                goto SetStorageType;
            }
            else if (this.storage.ItemStorageType == typeof(XPathNavigator)) { 
                // No-op if converting from XPathNavigator to XPathItem
                Debug.Assert(storageTypeDest == typeof(XPathItem), "Must be converting from XPathNavigator to XPathItem"); 
                goto SetStorageType; 
            }
 
            // Destination type must be item, so generate code to create an XmlAtomicValue
            this.helper.LoadInteger(this.helper.StaticData.DeclareXmlType(xmlType));
            this.helper.LoadQueryRuntime();
            this.helper.Call(XmlILMethods.StorageMethods[this.storage.ItemStorageType].ToAtomicValue); 

        SetStorageType: 
            this.storage = this.storage.ToStorageType(storageTypeDest); 
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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