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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Text;
using System.Data.SqlClient;
using System.Data.Metadata.Edm;
using System.Data.Common.CommandTrees;
namespace SampleEntityFrameworkProvider
{
/// <summary>
/// The symbol table is quite primitive - it is a stack with a new entry for
/// each scope. Lookups search from the top of the stack to the bottom, until
/// an entry is found.
///
/// The symbols are of the following kinds
/// <list type="bullet">
/// <item><see cref="Symbol"/> represents tables (extents/nested selects/unnests)</item>
/// <item><see cref="JoinSymbol"/> represents Join nodes</item>
/// <item><see cref="Symbol"/> columns.</item>
/// </list>
///
/// Symbols represent names <see cref="SqlGenerator.Visit(DbVariableReferenceExpression)"/> to be resolved,
/// or things to be renamed.
/// </summary>
internal sealed class SymbolTable
{
private List<Dictionary<string, Symbol>> symbols = new List<Dictionary<string, Symbol>>();
internal void EnterScope()
{
symbols.Add(new Dictionary<string, Symbol>(StringComparer.OrdinalIgnoreCase));
}
internal void ExitScope()
{
symbols.RemoveAt(symbols.Count - 1);
}
internal void Add(string name, Symbol value)
{
symbols[symbols.Count - 1][name] = value;
}
internal Symbol Lookup(string name)
{
for (int i = symbols.Count - 1; i >= 0; --i)
{
if (symbols[i].ContainsKey(name))
{
return symbols[i][name];
}
}
return null;
}
}
}
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