apt-pkg/contrib/mmap.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.cc,v 1.22 2001/05/27 05:19:30 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 #define _BSD_SOURCE
  25 #include <apt-pkg/mmap.h>
  26 #include <apt-pkg/error.h>
  27
  28 #include <apti18n.h>
  29
  30 #include <sys/mman.h>
  31 #include <sys/stat.h>
  32 #include <unistd.h>
  33 #include <fcntl.h>
  34
  35 #include <cstring>
  36                                                                         /*}}}*/
  37
  38 // MMap::MMap - Constructor                                             /*{{{*/
  39 // ---------------------------------------------------------------------
  40 /* */
  41 MMap::MMap(FileFd &F,unsigned long Flags) : Flags(Flags), iSize(0),
  42                      Base(0)
  43 {
  44    if ((Flags & NoImmMap) != NoImmMap)
  45       Map(F);
  46 }
  47                                                                         /*}}}*/
  48 // MMap::MMap - Constructor                                             /*{{{*/
  49 // ---------------------------------------------------------------------
  50 /* */
  51 MMap::MMap(unsigned long Flags) : Flags(Flags), iSize(0),
  52                      Base(0)
  53 {
  54 }
  55                                                                         /*}}}*/
  56 // MMap::~MMap - Destructor                                             /*{{{*/
  57 // ---------------------------------------------------------------------
  58 /* */
  59 MMap::~MMap()
  60 {
  61    Close();
  62 }
  63                                                                         /*}}}*/
  64 // MMap::Map - Perform the mapping                                      /*{{{*/
  65 // ---------------------------------------------------------------------
  66 /* */
  67 bool MMap::Map(FileFd &Fd)
  68 {
  69    iSize = Fd.Size();
  70
  71    // Set the permissions.
  72    int Prot = PROT_READ;
  73    int Map = MAP_SHARED;
  74    if ((Flags & ReadOnly) != ReadOnly)
  75       Prot |= PROT_WRITE;
  76    if ((Flags & Public) != Public)
  77       Map = MAP_PRIVATE;
  78
  79    if (iSize == 0)
  80       return _error->Error(_("Can't mmap an empty file"));
  81
  82    // Map it.
  83    Base = mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  84    if (Base == (void *)-1)
  85       return _error->Errno("mmap",_("Couldn't make mmap of %lu bytes"),iSize);
  86
  87    return true;
  88 }
  89                                                                         /*}}}*/
  90 // MMap::Close - Close the map                                          /*{{{*/
  91 // ---------------------------------------------------------------------
  92 /* */
  93 bool MMap::Close(bool DoSync)
  94 {
  95    if ((Flags & UnMapped) == UnMapped || Base == 0 || iSize == 0)
  96       return true;
  97
  98    if (DoSync == true)
  99       Sync();
 100
 101    if (munmap((char *)Base,iSize) != 0)
 102       _error->Warning("Unable to munmap");
 103
 104    iSize = 0;
 105    Base = 0;
 106    return true;
 107 }
 108                                                                         /*}}}*/
 109 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 110 // ---------------------------------------------------------------------
 111 /* This is done in syncronous mode - the docs indicate that this will
 112    not return till all IO is complete */
 113 bool MMap::Sync()
 114 {
 115    if ((Flags & UnMapped) == UnMapped)
 116       return true;
 117
 118 #ifdef _POSIX_SYNCHRONIZED_IO
 119    if ((Flags & ReadOnly) != ReadOnly)
 120       if (msync((char *)Base,iSize,MS_SYNC) != 0)
 121          return _error->Errno("msync","Unable to write mmap");
 122 #endif
 123    return true;
 124 }
 125                                                                         /*}}}*/
 126 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 127 // ---------------------------------------------------------------------
 128 /* */
 129 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 130 {
 131    if ((Flags & UnMapped) == UnMapped)
 132       return true;
 133
 134 #ifdef _POSIX_SYNCHRONIZED_IO
 135    unsigned long PSize = sysconf(_SC_PAGESIZE);
 136    if ((Flags & ReadOnly) != ReadOnly)
 137       if (msync((char *)Base+(int)(Start/PSize)*PSize,Stop - Start,MS_SYNC) != 0)
 138          return _error->Errno("msync","Unable to write mmap");
 139 #endif
 140    return true;
 141 }
 142                                                                         /*}}}*/
 143
 144 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 145 // ---------------------------------------------------------------------
 146 /* */
 147 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long WorkSpace) :
 148              MMap(F,Flags | NoImmMap), Fd(&F), WorkSpace(WorkSpace)
 149 {
 150    if (_error->PendingError() == true)
 151       return;
 152
 153    unsigned long EndOfFile = Fd->Size();
 154    if (EndOfFile > WorkSpace)
 155       WorkSpace = EndOfFile;
 156    else if(WorkSpace > 0)
 157    {
 158       Fd->Seek(WorkSpace - 1);
 159       char C = 0;
 160       Fd->Write(&C,sizeof(C));
 161    }
 162
 163    Map(F);
 164    iSize = EndOfFile;
 165 }
 166                                                                         /*}}}*/
 167 // DynamicMMap::DynamicMMap - Constructor for a non-file backed map     /*{{{*/
 168 // ---------------------------------------------------------------------
 169 /* This is just a fancy malloc really.. */
 170 DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long WorkSpace) :
 171              MMap(Flags | NoImmMap | UnMapped), Fd(0), WorkSpace(WorkSpace)
 172 {
 173    if (_error->PendingError() == true)
 174       return;
 175
 176    Base = new unsigned char[WorkSpace];
 177    memset(Base,0,WorkSpace);
 178    iSize = 0;
 179 }
 180                                                                         /*}}}*/
 181 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 182 // ---------------------------------------------------------------------
 183 /* We truncate the file to the size of the memory data set */
 184 DynamicMMap::~DynamicMMap()
 185 {
 186    if (Fd == 0)
 187    {
 188       delete [] (unsigned char *)Base;
 189       return;
 190    }
 191
 192    unsigned long EndOfFile = iSize;
 193    iSize = WorkSpace;
 194    Close(false);
 195    ftruncate(Fd->Fd(),EndOfFile);
 196 }
 197                                                                         /*}}}*/
 198 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 199 // ---------------------------------------------------------------------
 200 /* This allocates a block of memory aligned to the given size */
 201 unsigned long DynamicMMap::RawAllocate(unsigned long Size,unsigned long Aln)
 202 {
 203    unsigned long Result = iSize;
 204    if (Aln != 0)
 205       Result += Aln - (iSize%Aln);
 206
 207    iSize = Result + Size;
 208
 209    // Just in case error check
 210    if (Result + Size > WorkSpace)
 211    {
 212       _error->Error("Dynamic MMap ran out of room");
 213       return 0;
 214    }
 215
 216    return Result;
 217 }
 218                                                                         /*}}}*/
 219 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 220 // ---------------------------------------------------------------------
 221 /* This allocates an Item of size ItemSize so that it is aligned to its
 222    size in the file. */
 223 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 224 {
 225    // Look for a matching pool entry
 226    Pool *I;
 227    Pool *Empty = 0;
 228    for (I = Pools; I != Pools + PoolCount; I++)
 229    {
 230       if (I->ItemSize == 0)
 231          Empty = I;
 232       if (I->ItemSize == ItemSize)
 233          break;
 234    }
 235
 236    // No pool is allocated, use an unallocated one
 237    if (I == Pools + PoolCount)
 238    {
 239       // Woops, we ran out, the calling code should allocate more.
 240       if (Empty == 0)
 241       {
 242          _error->Error("Ran out of allocation pools");
 243          return 0;
 244       }
 245
 246       I = Empty;
 247       I->ItemSize = ItemSize;
 248       I->Count = 0;
 249    }
 250
 251    // Out of space, allocate some more
 252    if (I->Count == 0)
 253    {
 254       I->Count = 20*1024/ItemSize;
 255       I->Start = RawAllocate(I->Count*ItemSize,ItemSize);
 256    }
 257
 258    I->Count--;
 259    unsigned long Result = I->Start;
 260    I->Start += ItemSize;
 261    return Result/ItemSize;
 262 }
 263                                                                         /*}}}*/
 264 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 265 // ---------------------------------------------------------------------
 266 /* Strings are not aligned to anything */
 267 unsigned long DynamicMMap::WriteString(const char *String,
 268                                        unsigned long Len)
 269 {
 270    unsigned long Result = iSize;
 271    // Just in case error check
 272    if (Result + Len > WorkSpace)
 273    {
 274       _error->Error("Dynamic MMap ran out of room");
 275       return 0;
 276    }
 277
 278    if (Len == (unsigned long)-1)
 279       Len = strlen(String);
 280    iSize += Len + 1;
 281    memcpy((char *)Base + Result,String,Len);
 282    ((char *)Base)[Result + Len] = 0;
 283    return Result;
 284 }
 285                                                                         /*}}}*/