apt-pkg/contrib/mmap.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.cc,v 1.9 1998/11/12 03:14:39 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    if (iSize == 0)
  73       return _error->Error("Can't mmap an empty file");
  74
  75    // Map it.
  76    Base = mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  77    if (Base == (void *)-1)
  78       return _error->Errno("mmap","Couldn't make mmap of %u bytes",iSize);
  79
  80    return true;
  81 }
  82                                                                         /*}}}*/
  83 // MMap::Close - Close the map                                          /*{{{*/
  84 // ---------------------------------------------------------------------
  85 /* */
  86 bool MMap::Close(bool DoClose, bool DoSync)
  87 {
  88    if (Fd.IsOpen() == false)
  89       return true;
  90
  91    if (DoSync == true)
  92       Sync();
  93
  94    if (munmap((char *)Base,iSize) != 0)
  95       _error->Warning("Unable to munmap");
  96
  97    iSize = 0;
  98    if (DoClose == true)
  99       Fd.Close();
 100    return true;
 101 }
 102                                                                         /*}}}*/
 103 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 104 // ---------------------------------------------------------------------
 105 /* This is done in syncronous mode - the docs indicate that this will
 106    not return till all IO is complete */
 107 bool MMap::Sync()
 108 {
 109    if ((Flags & ReadOnly) != ReadOnly)
 110       if (msync((char *)Base,iSize,MS_SYNC) != 0)
 111          return _error->Error("msync","Unable to write mmap");
 112    return true;
 113 }
 114                                                                         /*}}}*/
 115 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 116 // ---------------------------------------------------------------------
 117 /* */
 118 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 119 {
 120    if ((Flags & ReadOnly) != ReadOnly)
 121       if (msync((char *)Base+(int)(Start/PAGE_SIZE)*PAGE_SIZE,Stop - Start,MS_SYNC) != 0)
 122          return _error->Error("msync","Unable to write mmap");
 123    return true;
 124 }
 125                                                                         /*}}}*/
 126
 127 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 128 // ---------------------------------------------------------------------
 129 /* */
 130 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long WorkSpace) :
 131              MMap(F,Flags | NoImmMap), WorkSpace(WorkSpace)
 132 {
 133    unsigned long EndOfFile = Fd.Size();
 134    Fd.Seek(WorkSpace);
 135    char C = 0;
 136    Fd.Write(&C,sizeof(C));
 137    Map();
 138    iSize = EndOfFile;
 139 }
 140                                                                         /*}}}*/
 141 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 142 // ---------------------------------------------------------------------
 143 /* We truncate the file to the size of the memory data set */
 144 DynamicMMap::~DynamicMMap()
 145 {
 146    unsigned long EndOfFile = iSize;
 147    Sync();
 148    iSize = WorkSpace;
 149    Close(false,false);
 150    ftruncate(Fd.Fd(),EndOfFile);
 151    Fd.Close();
 152 }
 153                                                                         /*}}}*/
 154 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 155 // ---------------------------------------------------------------------
 156 /* This allocates a block of memory aligned to the given size */
 157 unsigned long DynamicMMap::RawAllocate(unsigned long Size,unsigned long Aln)
 158 {
 159    unsigned long Result = iSize;
 160    if (Aln != 0)
 161       Result += Aln - (iSize%Aln);
 162
 163    iSize = Result + Size;
 164
 165    // Just in case error check
 166    if (Result + Size > WorkSpace)
 167    {
 168       _error->Error("Dynamic MMap ran out of room");
 169       return 0;
 170    }
 171    return Result;
 172 }
 173                                                                         /*}}}*/
 174 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 175 // ---------------------------------------------------------------------
 176 /* This allocates an Item of size ItemSize so that it is aligned to its
 177    size in the file. */
 178 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 179 {
 180    // Look for a matching pool entry
 181    Pool *I;
 182    Pool *Empty = 0;
 183    for (I = Pools; I != Pools + PoolCount; I++)
 184    {
 185       if (I->ItemSize == 0)
 186          Empty = I;
 187       if (I->ItemSize == ItemSize)
 188          break;
 189    }
 190
 191    // No pool is allocated, use an unallocated one
 192    if (I == Pools + PoolCount)
 193    {
 194       // Woops, we ran out, the calling code should allocate more.
 195       if (Empty == 0)
 196       {
 197          _error->Error("Ran out of allocation pools");
 198          return 0;
 199       }
 200
 201       I = Empty;
 202       I->ItemSize = ItemSize;
 203       I->Count = 0;
 204    }
 205
 206    // Out of space, allocate some more
 207    if (I->Count == 0)
 208    {
 209       I->Count = 20*1024/ItemSize;
 210       I->Start = RawAllocate(I->Count*ItemSize,ItemSize);
 211    }
 212
 213    I->Count--;
 214    unsigned long Result = I->Start;
 215    I->Start += ItemSize;
 216    return Result/ItemSize;
 217 }
 218                                                                         /*}}}*/
 219 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 220 // ---------------------------------------------------------------------
 221 /* Strings are not aligned to anything */
 222 unsigned long DynamicMMap::WriteString(const char *String,
 223                                        unsigned long Len)
 224 {
 225    unsigned long Result = iSize;
 226    // Just in case error check
 227    if (Result > WorkSpace)
 228    {
 229       _error->Error("Dynamic MMap ran out of room");
 230       return 0;
 231    }
 232
 233    if (Len == 0)
 234       Len = strlen(String);
 235    iSize += Len + 1;
 236    memcpy((char *)Base + Result,String,Len);
 237    ((char *)Base)[Result + Len] = 0;
 238    return Result;
 239 }
 240                                                                         /*}}}*/