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NativeSymbolsProvider.cs
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NativeSymbolsProvider.cs
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using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using AsmResolver.Collections;
using AsmResolver.PE.Exports;
using AsmResolver.PE.Imports;
using AsmResolver.PE.Relocations;
using AsmResolver.Shims;
namespace AsmResolver.DotNet.Code.Native
{
/// <summary>
/// Provides a default implementation for <see cref="INativeSymbolsProvider"/> interface, which collects
/// instances of <see cref="ImportedSymbol"/>, and removes any duplicated symbols.
/// </summary>
public class NativeSymbolsProvider : INativeSymbolsProvider
{
private readonly Dictionary<string, ImportedModule> _modules = new();
private readonly Dictionary<ISegmentReference, BaseRelocation> _relocations = new();
private readonly Dictionary<uint, ExportedSymbol> _fixedExportedSymbols = new();
private uint _minExportedOrdinal = uint.MaxValue;
private uint _maxExportedOrdinal = 0;
private readonly List<ExportedSymbol> _floatingExportedSymbols = new();
/// <inheritdoc />
public ISymbol ImportSymbol(ISymbol symbol) => symbol is ImportedSymbol importedSymbol
? GetImportedSymbol(importedSymbol)
: symbol;
private ImportedSymbol GetImportedSymbol(ImportedSymbol symbol)
{
if (symbol.DeclaringModule is null)
throw new ArgumentException($"Symbol {symbol} is not added to a module.");
// Find declaring module.
string? moduleName = symbol.DeclaringModule.Name;
if (moduleName is null)
throw new ArgumentException($"Parent module for symbol {symbol} has no name.");
var module = GetModuleByName(moduleName);
// See if we have already imported this symbol before.
if (TryGetSimilarSymbol(symbol, module, out var existing))
return existing;
// If not, create a copy of the symbol and register it.
var newSymbol = symbol.IsImportByName
? new ImportedSymbol(symbol.Hint, symbol.Name)
: new ImportedSymbol(symbol.Ordinal);
module.Symbols.Add(newSymbol);
return newSymbol;
}
private ImportedModule GetModuleByName(string name)
{
if (!_modules.TryGetValue(name, out var module))
{
module = new ImportedModule(name);
_modules.Add(module.Name!, module);
}
return module;
}
private static bool TryGetSimilarSymbol(
ImportedSymbol symbol,
ImportedModule module,
[NotNullWhen(true)] out ImportedSymbol? existingSymbol)
{
for (int i = 0; i < module.Symbols.Count; i++)
{
var s = module.Symbols[i];
if (symbol.IsImportByName != s.IsImportByName)
continue;
if (symbol.IsImportByName)
{
if (symbol.Name == s.Name)
{
existingSymbol = s;
return true;
}
}
else // if (symbol.IsImportByOrdinal)
{
if (symbol.Ordinal == s.Ordinal)
{
existingSymbol = s;
return true;
}
}
}
existingSymbol = null;
return false;
}
/// <inheritdoc />
public void RegisterBaseRelocation(BaseRelocation relocation)
{
if (_relocations.TryGetValue(relocation.Location, out var existing))
{
if (existing.Type != relocation.Type)
throw new ArgumentException($"Conflicting base relocations for reference {relocation.Location}.");
}
else
{
_relocations.Add(relocation.Location, relocation);
}
}
/// <inheritdoc />
public void RegisterExportedSymbol(ExportedSymbol symbol) => RegisterExportedSymbol(symbol, null);
/// <inheritdoc />
public void RegisterExportedSymbol(ExportedSymbol symbol, uint? newOrdinal)
{
if (!newOrdinal.HasValue)
{
_floatingExportedSymbols.Add(symbol);
return;
}
uint ordinal = newOrdinal.Value;
if (_fixedExportedSymbols.ContainsKey(ordinal))
throw new ArgumentException($"Ordinal {ordinal.ToString()} was already claimed by another exported symbol.");
_fixedExportedSymbols.Add(ordinal, symbol);
_minExportedOrdinal = Math.Min(ordinal, _minExportedOrdinal);
_maxExportedOrdinal = Math.Max(ordinal, _maxExportedOrdinal);
}
/// <summary>
/// Gets a collection of all imported external modules.
/// </summary>
/// <returns>The modules.</returns>
public IEnumerable<ImportedModule> GetImportedModules() => _modules.Values;
/// <summary>
/// Gets a collection of all base relocations that need to be applied in the final PE image.
/// </summary>
/// <returns>The base relocations.</returns>
public IEnumerable<BaseRelocation> GetBaseRelocations() => _relocations.Values;
/// <summary>
/// Gets a collection of all symbols that need to be exported in the final PE image.
/// </summary>
/// <returns>The exported symbols.</returns>
public IEnumerable<ExportedSymbol> GetExportedSymbols(out uint baseOrdinal)
{
baseOrdinal = 1;
if (_fixedExportedSymbols.Count == 0 && _floatingExportedSymbols.Count == 0)
return ArrayShim.Empty<ExportedSymbol>();
// Check if no fixed symbols at all, then just return the floating exports.
if (_fixedExportedSymbols.Count == 0)
return _floatingExportedSymbols;
// Pre-allocate a buffer of symbols.
baseOrdinal = _minExportedOrdinal;
var result = new ExportedSymbol?[_maxExportedOrdinal - _minExportedOrdinal + 1].ToList();
// Put in all the symbols with fixed ordinals.
foreach (var fixedEntry in _fixedExportedSymbols)
result[(int) (fixedEntry.Key - _minExportedOrdinal)] = fixedEntry.Value;
int slotIndex = (int) _minExportedOrdinal;
// Prefer filling in gaps for the floating exported symbols.
int floatingIndex = 0;
for (; floatingIndex < _floatingExportedSymbols.Count && slotIndex < result.Count; floatingIndex++)
{
var floatingEntry = _floatingExportedSymbols[floatingIndex];
while (slotIndex < result.Count && result[slotIndex] is not null)
slotIndex++;
if (slotIndex < result.Count)
result[slotIndex] = floatingEntry;
}
// Are there still floating symbols left?
if (floatingIndex != _floatingExportedSymbols.Count)
{
// Prefer inserting the remainder before first ordinal, and just decrease base ordinal.
int insertBeforeCount = Math.Min((int) _minExportedOrdinal - 1,
_floatingExportedSymbols.Count - floatingIndex);
if (insertBeforeCount > 0)
{
baseOrdinal -= (uint) insertBeforeCount;
result.InsertRange(0, new ExportedSymbol?[insertBeforeCount]);
slotIndex = 0;
for (; floatingIndex < insertBeforeCount; floatingIndex++)
result[slotIndex++] = _floatingExportedSymbols[floatingIndex];
}
// If we still have anything left, add them to the end.
for (; floatingIndex < _floatingExportedSymbols.Count; floatingIndex++)
result.Add(_floatingExportedSymbols[floatingIndex]);
}
// We might still have gaps in the table, fill those up with dummy symbols.
for (slotIndex = 0; slotIndex < result.Count; slotIndex++)
result[slotIndex] ??= new ExportedSymbol(SegmentReference.Null);
return result!;
}
}
}