apt-pkg/contrib/mmap.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.cc,v 1.7 1998/07/19 04:42:14 jgg Exp $
   4 /* ######################################################################
   5
   6    MMap Class - Provides 'real' mmap or a faked mmap using read().
   7
   8    MMap cover class.
   9
  10    Some broken versions of glibc2 (libc6) have a broken definition
  11    of mmap that accepts a char * -- all other systems (and libc5) use
  12    void *. We can't safely do anything here that would be portable, so
  13    libc6 generates warnings -- which should be errors, g++ isn't properly
  14    strict.
  15
  16    The configure test notes that some OS's have broken private mmap's
  17    so on those OS's we can't use mmap. This means we have to use
  18    configure to test mmap and can't rely on the POSIX
  19    _POSIX_MAPPED_FILES test.
  20
  21    ##################################################################### */
  22                                                                         /*}}}*/
  23 // Include Files                                                        /*{{{*/
  24 #ifdef __GNUG__
  25 #pragma implementation "apt-pkg/mmap.h"
  26 #endif
  27
  28 #define _BSD_SOURCE
  29 #include <apt-pkg/mmap.h>
  30 #include <apt-pkg/error.h>
  31
  32 #include <sys/mman.h>
  33 #include <sys/stat.h>
  34 #include <sys/user.h>
  35 #include <unistd.h>
  36 #include <fcntl.h>
  37                                                                         /*}}}*/
  38
  39 // MMap::MMap - Constructor                                             /*{{{*/
  40 // ---------------------------------------------------------------------
  41 /* */
  42 MMap::MMap(FileFd &F,unsigned long Flags) : Fd(F), Flags(Flags), iSize(0),
  43                      Base(0)
  44 {
  45    if ((Flags & NoImmMap) != NoImmMap)
  46       Map();
  47 }
  48                                                                         /*}}}*/
  49 // MMap::~MMap - Destructor                                             /*{{{*/
  50 // ---------------------------------------------------------------------
  51 /* */
  52 MMap::~MMap()
  53 {
  54    Close(true);
  55 }
  56                                                                         /*}}}*/
  57 // MMap::Map - Perform the mapping                                      /*{{{*/
  58 // ---------------------------------------------------------------------
  59 /* */
  60 bool MMap::Map()
  61 {
  62    iSize = Fd.Size();
  63
  64    // Set the permissions.
  65    int Prot = PROT_READ;
  66    int Map = MAP_SHARED;
  67    if ((Flags & ReadOnly) != ReadOnly)
  68       Prot |= PROT_WRITE;
  69    if ((Flags & Public) != Public)
  70       Map = MAP_PRIVATE;
  71
  72    // Map it.
  73    Base = mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  74    if (Base == (void *)-1)
  75       return _error->Errno("mmap","Couldn't make mmap of %u bytes",iSize);
  76
  77    return true;
  78 }
  79                                                                         /*}}}*/
  80 // MMap::Close - Close the map                                          /*{{{*/
  81 // ---------------------------------------------------------------------
  82 /* */
  83 bool MMap::Close(bool DoClose, bool DoSync)
  84 {
  85    if (Fd.IsOpen() == false)
  86       return true;
  87
  88    if (DoSync == true)
  89       Sync();
  90
  91    if (munmap((char *)Base,iSize) != 0)
  92       _error->Warning("Unable to munmap");
  93
  94    iSize = 0;
  95    if (DoClose == true)
  96       Fd.Close();
  97    return true;
  98 }
  99                                                                         /*}}}*/
 100 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 101 // ---------------------------------------------------------------------
 102 /* This is done in syncronous mode - the docs indicate that this will
 103    not return till all IO is complete */
 104 bool MMap::Sync()
 105 {
 106    if ((Flags & ReadOnly) != ReadOnly)
 107       if (msync((char *)Base,iSize,MS_SYNC) != 0)
 108          return _error->Error("msync","Unable to write mmap");
 109    return true;
 110 }
 111                                                                         /*}}}*/
 112 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 113 // ---------------------------------------------------------------------
 114 /* */
 115 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 116 {
 117    if ((Flags & ReadOnly) != ReadOnly)
 118       if (msync((char *)Base+(int)(Start/PAGE_SIZE)*PAGE_SIZE,Stop - Start,MS_SYNC) != 0)
 119          return _error->Error("msync","Unable to write mmap");
 120    return true;
 121 }
 122                                                                         /*}}}*/
 123
 124 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 125 // ---------------------------------------------------------------------
 126 /* */
 127 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long WorkSpace) :
 128              MMap(F,Flags | NoImmMap), WorkSpace(WorkSpace)
 129 {
 130    unsigned long EndOfFile = Fd.Size();
 131    Fd.Seek(WorkSpace);
 132    char C = 0;
 133    Fd.Write(&C,sizeof(C));
 134    Map();
 135    iSize = EndOfFile;
 136 }
 137                                                                         /*}}}*/
 138 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 139 // ---------------------------------------------------------------------
 140 /* We truncate the file to the size of the memory data set */
 141 DynamicMMap::~DynamicMMap()
 142 {
 143    unsigned long EndOfFile = iSize;
 144    Sync();
 145    iSize = WorkSpace;
 146    Close(false,false);
 147    ftruncate(Fd.Fd(),EndOfFile);
 148    Fd.Close();
 149 }
 150                                                                         /*}}}*/
 151 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 152 // ---------------------------------------------------------------------
 153 /* This allocates a block of memory aligned to the given size */
 154 unsigned long DynamicMMap::RawAllocate(unsigned long Size,unsigned long Aln)
 155 {
 156    unsigned long Result = iSize;
 157    if (Aln != 0)
 158       Result += Aln - (iSize%Aln);
 159
 160    iSize = Result + Size;
 161
 162    // Just in case error check
 163    if (Result > WorkSpace)
 164    {
 165       _error->Error("Dynamic MMap ran out of room");
 166       return 0;
 167    }
 168    return Result;
 169 }
 170                                                                         /*}}}*/
 171 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 172 // ---------------------------------------------------------------------
 173 /* This allocates an Item of size ItemSize so that it is aligned to its
 174    size in the file. */
 175 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 176 {
 177    // Look for a matching pool entry
 178    Pool *I;
 179    Pool *Empty = 0;
 180    for (I = Pools; I != Pools + PoolCount; I++)
 181    {
 182       if (I->ItemSize == 0)
 183          Empty = I;
 184       if (I->ItemSize == ItemSize)
 185          break;
 186    }
 187
 188    // No pool is allocated, use an unallocated one
 189    if (I == Pools + PoolCount)
 190    {
 191       // Woops, we ran out, the calling code should allocate more.
 192       if (Empty == 0)
 193       {
 194          _error->Error("Ran out of allocation pools");
 195          return 0;
 196       }
 197
 198       I = Empty;
 199       I->ItemSize = ItemSize;
 200       I->Count = 0;
 201    }
 202
 203    // Out of space, allocate some more
 204    if (I->Count == 0)
 205    {
 206       I->Count = 20*1024/ItemSize;
 207       I->Start = RawAllocate(I->Count*ItemSize,ItemSize);
 208    }
 209
 210    I->Count--;
 211    unsigned long Result = I->Start;
 212    I->Start += ItemSize;
 213    return Result/ItemSize;
 214 }
 215                                                                         /*}}}*/
 216 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 217 // ---------------------------------------------------------------------
 218 /* Strings are not aligned to anything */
 219 unsigned long DynamicMMap::WriteString(const char *String,
 220                                        unsigned long Len)
 221 {
 222    unsigned long Result = iSize;
 223    // Just in case error check
 224    if (Result > WorkSpace)
 225    {
 226       _error->Error("Dynamic MMap ran out of room");
 227       return 0;
 228    }
 229
 230    if (Len == 0)
 231       Len = strlen(String);
 232    iSize += Len + 1;
 233    memcpy((char *)Base + Result,String,Len);
 234    ((char *)Base)[Result + Len] = 0;
 235    return Result;
 236 }
 237                                                                         /*}}}*/