tools/dsymutil/NonRelocatableStringpool.h

   1 //===- NonRelocatableStringpool.h - A simple stringpool  --------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
  11 #define LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
  12
  13 #include "llvm/ADT/StringMap.h"
  14 #include "llvm/ADT/StringRef.h"
  15 #include "llvm/Support/Allocator.h"
  16 #include <cstdint>
  17 #include <utility>
  18
  19 namespace llvm {
  20 namespace dsymutil {
  21
  22 /// \brief A string table that doesn't need relocations.
  23 ///
  24 /// We are doing a final link, no need for a string table that
  25 /// has relocation entries for every reference to it. This class
  26 /// provides this ablitity by just associating offsets with
  27 /// strings.
  28 class NonRelocatableStringpool {
  29 public:
  30   /// \brief Entries are stored into the StringMap and simply linked
  31   /// together through the second element of this pair in order to
  32   /// keep track of insertion order.
  33   using MapTy =
  34       StringMap<std::pair<uint32_t, StringMapEntryBase *>, BumpPtrAllocator>;
  35
  36   NonRelocatableStringpool() : Sentinel(0), Last(&Sentinel) {
  37     // Legacy dsymutil puts an empty string at the start of the line
  38     // table.
  39     getStringOffset("");
  40   }
  41
  42   /// \brief Get the offset of string \p S in the string table. This
  43   /// can insert a new element or return the offset of a preexisitng
  44   /// one.
  45   uint32_t getStringOffset(StringRef S);
  46
  47   /// \brief Get permanent storage for \p S (but do not necessarily
  48   /// emit \p S in the output section).
  49   /// \returns The StringRef that points to permanent storage to use
  50   /// in place of \p S.
  51   StringRef internString(StringRef S);
  52
  53   // \brief Return the first entry of the string table.
  54   const MapTy::MapEntryTy *getFirstEntry() const {
  55     return getNextEntry(&Sentinel);
  56   }
  57
  58   // \brief Get the entry following \p E in the string table or null
  59   // if \p E was the last entry.
  60   const MapTy::MapEntryTy *getNextEntry(const MapTy::MapEntryTy *E) const {
  61     return static_cast<const MapTy::MapEntryTy *>(E->getValue().second);
  62   }
  63
  64   uint64_t getSize() { return CurrentEndOffset; }
  65
  66 private:
  67   MapTy Strings;
  68   uint32_t CurrentEndOffset = 0;
  69   MapTy::MapEntryTy Sentinel, *Last;
  70 };
  71
  72 } // end namespace dsymutil
  73 } // end namespace llvm
  74
  75 #endif // LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H