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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   const SuperBlock *SB = nullptr;
     56   BitVector FreePageMap;
     57   ArrayRef<support::ulittle32_t> DirectoryBlocks;
     58   ArrayRef<support::ulittle32_t> StreamSizes;
     59   std::vector<ArrayRef<support::ulittle32_t>> StreamMap;
     60 };
     61 
     62 /// \brief Describes the layout of a stream in an MSF layout.  A "stream" here
     63 /// is defined as any logical unit of data which may be arranged inside the MSF
     64 /// file as a sequence of (possibly discontiguous) blocks.  When we want to read
     65 /// from a particular MSF Stream, we fill out a stream layout structure and the
     66 /// reader uses it to determine which blocks in the underlying MSF file contain
     67 /// the data, so that it can be pieced together in the right order.
     68 class MSFStreamLayout {
     69 public:
     70   uint32_t Length;
     71   std::vector<support::ulittle32_t> Blocks;
     72 };
     73 
     74 /// \brief Determine the layout of the FPM stream, given the MSF layout.  An FPM
     75 /// stream spans 1 or more blocks, each at equally spaced intervals throughout
     76 /// the file.
     77 MSFStreamLayout getFpmStreamLayout(const MSFLayout &Msf,
     78                                    bool IncludeUnusedFpmData = false,
     79                                    bool AltFpm = false);
     80 
     81 inline bool isValidBlockSize(uint32_t Size) {
     82   switch (Size) {
     83   case 512:
     84   case 1024:
     85   case 2048:
     86   case 4096:
     87     return true;
     88   }
     89   return false;
     90 }
     91 
     92 // Super Block, Fpm0, Fpm1, and Block Map
     93 inline uint32_t getMinimumBlockCount() { return 4; }
     94 
     95 // Super Block, Fpm0, and Fpm1 are reserved.  The Block Map, although required
     96 // need not be at block 3.
     97 inline uint32_t getFirstUnreservedBlock() { return 3; }
     98 
     99 inline uint64_t bytesToBlocks(uint64_t NumBytes, uint64_t BlockSize) {
    100   return divideCeil(NumBytes, BlockSize);
    101 }
    102 
    103 inline uint64_t blockToOffset(uint64_t BlockNumber, uint64_t BlockSize) {
    104   return BlockNumber * BlockSize;
    105 }
    106 
    107 inline uint32_t getFpmIntervalLength(const MSFLayout &L) {
    108   return L.SB->BlockSize;
    109 }
    110 
    111 inline uint32_t getNumFpmIntervals(const MSFLayout &L,
    112                                    bool IncludeUnusedFpmData = false) {
    113   if (IncludeUnusedFpmData)
    114     return divideCeil(L.SB->NumBlocks, L.SB->BlockSize);
    115 
    116   // We want the minimum number of intervals required, where each interval can
    117   // represent BlockSize * 8 blocks.
    118   return divideCeil(L.SB->NumBlocks, 8 * L.SB->BlockSize);
    119 }
    120 
    121 Error validateSuperBlock(const SuperBlock &SB);
    122 
    123 } // end namespace msf
    124 } // end namespace llvm
    125 
    126 #endif // LLVM_DEBUGINFO_MSF_MSFCOMMON_H
    127