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      1 //===- MSFCommon.h - Common types and functions for MSF files ---*- 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_DEBUGINFO_MSF_MSFCOMMON_H
     11 #define LLVM_DEBUGINFO_MSF_MSFCOMMON_H
     12 
     13 #include "llvm/ADT/ArrayRef.h"
     14 #include "llvm/ADT/BitVector.h"
     15 #include "llvm/Support/Endian.h"
     16 #include "llvm/Support/Error.h"
     17 #include "llvm/Support/MathExtras.h"
     18 #include <cstdint>
     19 #include <vector>
     20 
     21 namespace llvm {
     22 namespace msf {
     23 
     24 static const char Magic[] = {'M',  'i',  'c',    'r', 'o', 's',  'o',  'f',
     25                              't',  ' ',  'C',    '/', 'C', '+',  '+',  ' ',
     26                              'M',  'S',  'F',    ' ', '7', '.',  '0',  '0',
     27                              '\r', '\n', '\x1a', 'D', 'S', '\0', '\0', '\0'};
     28 
     29 // The superblock is overlaid at the beginning of the file (offset 0).
     30 // It starts with a magic header and is followed by information which
     31 // describes the layout of the file system.
     32 struct SuperBlock {
     33   char MagicBytes[sizeof(Magic)];
     34   // The file system is split into a variable number of fixed size elements.
     35   // These elements are referred to as blocks.  The size of a block may vary
     36   // from system to system.
     37   support::ulittle32_t BlockSize;
     38   // The index of the free block map.
     39   support::ulittle32_t FreeBlockMapBlock;
     40   // This contains the number of blocks resident in the file system.  In
     41   // practice, NumBlocks * BlockSize is equivalent to the size of the MSF
     42   // file.
     43   support::ulittle32_t NumBlocks;
     44   // This contains the number of bytes which make up the directory.
     45   support::ulittle32_t NumDirectoryBytes;
     46   // This field's purpose is not yet known.
     47   support::ulittle32_t Unknown1;
     48   // This contains the block # of the block map.
     49   support::ulittle32_t BlockMapAddr;
     50 };
     51 
     52 struct MSFLayout {
     53   MSFLayout() = default;
     54 
     55   uint32_t mainFpmBlock() const {
     56     assert(SB->FreeBlockMapBlock == 1 || SB->FreeBlockMapBlock == 2);
     57     return SB->FreeBlockMapBlock;
     58   }
     59 
     60   uint32_t alternateFpmBlock() const {
     61     // If mainFpmBlock is 1, this is 2.  If mainFpmBlock is 2, this is 1.
     62     return 3U - mainFpmBlock();
     63   }
     64 
     65   const SuperBlock *SB = nullptr;
     66   BitVector FreePageMap;
     67   ArrayRef<support::ulittle32_t> DirectoryBlocks;
     68   ArrayRef<support::ulittle32_t> StreamSizes;
     69   std::vector<ArrayRef<support::ulittle32_t>> StreamMap;
     70 };
     71 
     72 /// Describes the layout of a stream in an MSF layout.  A "stream" here
     73 /// is defined as any logical unit of data which may be arranged inside the MSF
     74 /// file as a sequence of (possibly discontiguous) blocks.  When we want to read
     75 /// from a particular MSF Stream, we fill out a stream layout structure and the
     76 /// reader uses it to determine which blocks in the underlying MSF file contain
     77 /// the data, so that it can be pieced together in the right order.
     78 class MSFStreamLayout {
     79 public:
     80   uint32_t Length;
     81   std::vector<support::ulittle32_t> Blocks;
     82 };
     83 
     84 /// Determine the layout of the FPM stream, given the MSF layout.  An FPM
     85 /// stream spans 1 or more blocks, each at equally spaced intervals throughout
     86 /// the file.
     87 MSFStreamLayout getFpmStreamLayout(const MSFLayout &Msf,
     88                                    bool IncludeUnusedFpmData = false,
     89                                    bool AltFpm = false);
     90 
     91 inline bool isValidBlockSize(uint32_t Size) {
     92   switch (Size) {
     93   case 512:
     94   case 1024:
     95   case 2048:
     96   case 4096:
     97     return true;
     98   }
     99   return false;
    100 }
    101 
    102 // Super Block, Fpm0, Fpm1, and Block Map
    103 inline uint32_t getMinimumBlockCount() { return 4; }
    104 
    105 // Super Block, Fpm0, and Fpm1 are reserved.  The Block Map, although required
    106 // need not be at block 3.
    107 inline uint32_t getFirstUnreservedBlock() { return 3; }
    108 
    109 inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) {
    110   return divideCeil(NumBytes, BlockSize);
    111 }
    112 
    113 inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) {
    114   return BlockNumber * BlockSize;
    115 }
    116 
    117 inline uint32_t getFpmIntervalLength(const MSFLayout &L) {
    118   return L.SB->BlockSize;
    119 }
    120 
    121 /// Given an MSF with the specified block size and number of blocks, determine
    122 /// how many pieces the specified Fpm is split into.
    123 /// \p BlockSize - the block size of the MSF
    124 /// \p NumBlocks - the total number of blocks in the MSF
    125 /// \p IncludeUnusedFpmData - When true, this will count every block that is
    126 ///    both in the file and matches the form of an FPM block, even if some of
    127 ///    those FPM blocks are unused (a single FPM block can describe the
    128 ///    allocation status of up to 32,767 blocks, although one appears only
    129 ///    every 4,096 blocks).  So there are 8x as many blocks that match the
    130 ///    form as there are blocks that are necessary to describe the allocation
    131 ///    status of the file.  When this parameter is false, these extraneous
    132 ///    trailing blocks are not counted.
    133 inline uint32_t getNumFpmIntervals(uint32_t BlockSize, uint32_t NumBlocks,
    134                                    bool IncludeUnusedFpmData, int FpmNumber) {
    135   assert(FpmNumber == 1 || FpmNumber == 2);
    136   if (IncludeUnusedFpmData) {
    137     // This calculation determines how many times a number of the form
    138     // BlockSize * k + N appears in the range [0, NumBlocks).  We only need to
    139     // do this when unused data is included, since the number of blocks dwarfs
    140     // the number of fpm blocks.
    141     return divideCeil(NumBlocks - FpmNumber, BlockSize);
    142   }
    143 
    144   // We want the minimum number of intervals required, where each interval can
    145   // represent BlockSize * 8 blocks.
    146   return divideCeil(NumBlocks, 8 * BlockSize);
    147 }
    148 
    149 inline uint32_t getNumFpmIntervals(const MSFLayout &L,
    150                                    bool IncludeUnusedFpmData = false,
    151                                    bool AltFpm = false) {
    152   return getNumFpmIntervals(L.SB->BlockSize, L.SB->NumBlocks,
    153                             IncludeUnusedFpmData,
    154                             AltFpm ? L.alternateFpmBlock() : L.mainFpmBlock());
    155 }
    156 
    157 Error validateSuperBlock(const SuperBlock &SB);
    158 
    159 } // end namespace msf
    160 } // end namespace llvm
    161 
    162 #endif // LLVM_DEBUGINFO_MSF_MSFCOMMON_H
    163