tools/dsymutil/NonRelocatableStringpool.h

   1 //===- NonRelocatableStringpool.h - A simple stringpool  --------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
  10 #define LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
  11
  12 #include "SymbolMap.h"
  13
  14 #include "llvm/ADT/StringMap.h"
  15 #include "llvm/ADT/StringRef.h"
  16 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
  17 #include "llvm/Support/Allocator.h"
  18 #include <cstdint>
  19 #include <vector>
  20
  21 namespace llvm {
  22 namespace dsymutil {
  23
  24 /// A string table that doesn't need relocations.
  25 ///
  26 /// We are doing a final link, no need for a string table that has relocation
  27 /// entries for every reference to it. This class provides this ability by just
  28 /// associating offsets with strings.
  29 class NonRelocatableStringpool {
  30 public:
  31   /// Entries are stored into the StringMap and simply linked together through
  32   /// the second element of this pair in order to keep track of insertion
  33   /// order.
  34   using MapTy = StringMap<DwarfStringPoolEntry, BumpPtrAllocator>;
  35
  36   NonRelocatableStringpool(
  37       SymbolMapTranslator Translator = SymbolMapTranslator())
  38       : Translator(Translator) {
  39     // Legacy dsymutil puts an empty string at the start of the line table.
  40     EmptyString = getEntry("");
  41   }
  42
  43   DwarfStringPoolEntryRef getEntry(StringRef S);
  44
  45   /// Get the offset of string \p S in the string table. This can insert a new
  46   /// element or return the offset of a pre-existing one.
  47   uint32_t getStringOffset(StringRef S) { return getEntry(S).getOffset(); }
  48
  49   /// Get permanent storage for \p S (but do not necessarily emit \p S in the
  50   /// output section). A latter call to getStringOffset() with the same string
  51   /// will chain it though.
  52   ///
  53   /// \returns The StringRef that points to permanent storage to use
  54   /// in place of \p S.
  55   StringRef internString(StringRef S);
  56
  57   uint64_t getSize() { return CurrentEndOffset; }
  58
  59   /// Return the list of strings to be emitted. This does not contain the
  60   /// strings which were added via internString only.
  61   std::vector<DwarfStringPoolEntryRef> getEntriesForEmission() const;
  62
  63 private:
  64   MapTy Strings;
  65   uint32_t CurrentEndOffset = 0;
  66   unsigned NumEntries = 0;
  67   DwarfStringPoolEntryRef EmptyString;
  68   SymbolMapTranslator Translator;
  69 };
  70
  71 /// Helper for making strong types.
  72 template <typename T, typename S> class StrongType : public T {
  73 public:
  74   template <typename... Args>
  75   explicit StrongType(Args... A) : T(std::forward<Args>(A)...) {}
  76 };
  77
  78 /// It's very easy to introduce bugs by passing the wrong string pool in the
  79 /// dwarf linker. By using strong types the interface enforces that the right
  80 /// kind of pool is used.
  81 struct UniqueTag {};
  82 struct OffsetsTag {};
  83 using UniquingStringPool = StrongType<NonRelocatableStringpool, UniqueTag>;
  84 using OffsetsStringPool = StrongType<NonRelocatableStringpool, OffsetsTag>;
  85
  86 } // end namespace dsymutil
  87 } // end namespace llvm
  88
  89 #endif // LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H