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    ##################################################################### */
  17                                                                         /*}}}*/
  18 // Include Files                                                        /*{{{*/
  19 #define _BSD_SOURCE
  20 #include <config.h>
  21
  22 #include <apt-pkg/mmap.h>
  23 #include <apt-pkg/error.h>
  24 #include <apt-pkg/fileutl.h>
  25
  26 #include <sys/mman.h>
  27 #include <sys/stat.h>
  28 #include <unistd.h>
  29 #include <fcntl.h>
  30 #include <stdlib.h>
  31 #include <errno.h>
  32 #include <cstring>
  33
  34 #include <apti18n.h>
  35                                                                         /*}}}*/
  36
  37 // MMap::MMap - Constructor                                             /*{{{*/
  38 // ---------------------------------------------------------------------
  39 /* */
  40 MMap::MMap(FileFd &F,unsigned long Flags) : Flags(Flags), iSize(0),
  41                      Base(0), SyncToFd(NULL)
  42 {
  43    if ((Flags & NoImmMap) != NoImmMap)
  44       Map(F);
  45 }
  46                                                                         /*}}}*/
  47 // MMap::MMap - Constructor                                             /*{{{*/
  48 // ---------------------------------------------------------------------
  49 /* */
  50 MMap::MMap(unsigned long Flags) : Flags(Flags), iSize(0),
  51                      Base(0), SyncToFd(NULL)
  52 {
  53 }
  54                                                                         /*}}}*/
  55 // MMap::~MMap - Destructor                                             /*{{{*/
  56 // ---------------------------------------------------------------------
  57 /* */
  58 MMap::~MMap()
  59 {
  60    Close();
  61 }
  62                                                                         /*}}}*/
  63 // MMap::Map - Perform the mapping                                      /*{{{*/
  64 // ---------------------------------------------------------------------
  65 /* */
  66 bool MMap::Map(FileFd &Fd)
  67 {
  68    iSize = Fd.Size();
  69
  70    // Set the permissions.
  71    int Prot = PROT_READ;
  72    int Map = MAP_SHARED;
  73    if ((Flags & ReadOnly) != ReadOnly)
  74       Prot |= PROT_WRITE;
  75    if ((Flags & Public) != Public)
  76       Map = MAP_PRIVATE;
  77
  78    if (iSize == 0)
  79       return _error->Error(_("Can't mmap an empty file"));
  80
  81    // Map it.
  82    Base = mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  83    if (Base == (void *)-1)
  84    {
  85       if (errno == ENODEV || errno == EINVAL)
  86       {
  87          // The filesystem doesn't support this particular kind of mmap.
  88          // So we allocate a buffer and read the whole file into it.
  89          int const dupped_fd = dup(Fd.Fd());
  90          if (dupped_fd == -1)
  91             return _error->Errno("mmap", _("Couldn't duplicate file descriptor %i"), Fd.Fd());
  92
  93          Base = new unsigned char[iSize];
  94          SyncToFd = new FileFd (dupped_fd);
  95          if (!SyncToFd->Seek(0L) || !SyncToFd->Read(Base, iSize))
  96             return false;
  97       }
  98       else
  99          return _error->Errno("mmap",_("Couldn't make mmap of %llu bytes"),
 100                               iSize);
 101      }
 102
 103    return true;
 104 }
 105                                                                         /*}}}*/
 106 // MMap::Close - Close the map                                          /*{{{*/
 107 // ---------------------------------------------------------------------
 108 /* */
 109 bool MMap::Close(bool DoSync)
 110 {
 111    if ((Flags & UnMapped) == UnMapped || validData() == false || iSize == 0)
 112       return true;
 113
 114    if (DoSync == true)
 115       Sync();
 116
 117    if (SyncToFd != NULL)
 118    {
 119       delete[] (char *)Base;
 120       delete SyncToFd;
 121       SyncToFd = NULL;
 122    }
 123    else
 124    {
 125       if (munmap((char *)Base, iSize) != 0)
 126          _error->WarningE("mmap", _("Unable to close mmap"));
 127    }
 128
 129    iSize = 0;
 130    Base = 0;
 131    return true;
 132 }
 133                                                                         /*}}}*/
 134 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 135 // ---------------------------------------------------------------------
 136 /* This is done in syncronous mode - the docs indicate that this will
 137    not return till all IO is complete */
 138 bool MMap::Sync()
 139 {
 140    if ((Flags & UnMapped) == UnMapped)
 141       return true;
 142
 143 #ifdef _POSIX_SYNCHRONIZED_IO
 144    if ((Flags & ReadOnly) != ReadOnly)
 145    {
 146       if (SyncToFd != NULL)
 147       {
 148          if (!SyncToFd->Seek(0) || !SyncToFd->Write(Base, iSize))
 149             return false;
 150       }
 151       else
 152       {
 153          if (msync((char *)Base, iSize, MS_SYNC) < 0)
 154             return _error->Errno("msync", _("Unable to synchronize mmap"));
 155       }
 156    }
 157 #endif
 158    return true;
 159 }
 160                                                                         /*}}}*/
 161 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 162 // ---------------------------------------------------------------------
 163 /* */
 164 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 165 {
 166    if ((Flags & UnMapped) == UnMapped)
 167       return true;
 168
 169 #ifdef _POSIX_SYNCHRONIZED_IO
 170    unsigned long long PSize = sysconf(_SC_PAGESIZE);
 171    if ((Flags & ReadOnly) != ReadOnly)
 172    {
 173       if (SyncToFd != 0)
 174       {
 175          if (!SyncToFd->Seek(0) ||
 176              !SyncToFd->Write (((char *)Base)+Start, Stop-Start))
 177             return false;
 178       }
 179       else
 180       {
 181          if (msync((char *)Base+(unsigned long long)(Start/PSize)*PSize,Stop - Start,MS_SYNC) < 0)
 182             return _error->Errno("msync", _("Unable to synchronize mmap"));
 183       }
 184    }
 185 #endif
 186    return true;
 187 }
 188                                                                         /*}}}*/
 189
 190 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 191 // ---------------------------------------------------------------------
 192 /* */
 193 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long const &Workspace,
 194                          unsigned long const &Grow, unsigned long const &Limit) :
 195                 MMap(F,Flags | NoImmMap), Fd(&F), WorkSpace(Workspace),
 196                 GrowFactor(Grow), Limit(Limit)
 197 {
 198    if (_error->PendingError() == true)
 199       return;
 200
 201    unsigned long long EndOfFile = Fd->Size();
 202    if (EndOfFile > WorkSpace)
 203       WorkSpace = EndOfFile;
 204    else if(WorkSpace > 0)
 205    {
 206       Fd->Seek(WorkSpace - 1);
 207       char C = 0;
 208       Fd->Write(&C,sizeof(C));
 209    }
 210
 211    Map(F);
 212    iSize = EndOfFile;
 213 }
 214                                                                         /*}}}*/
 215 // DynamicMMap::DynamicMMap - Constructor for a non-file backed map     /*{{{*/
 216 // ---------------------------------------------------------------------
 217 /* We try here to use mmap to reserve some space - this is much more
 218    cooler than the fallback solution to simply allocate a char array
 219    and could come in handy later than we are able to grow such an mmap */
 220 DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long const &WorkSpace,
 221                          unsigned long const &Grow, unsigned long const &Limit) :
 222                 MMap(Flags | NoImmMap | UnMapped), Fd(0), WorkSpace(WorkSpace),
 223                 GrowFactor(Grow), Limit(Limit)
 224 {
 225         if (_error->PendingError() == true)
 226                 return;
 227
 228         // disable Moveable if we don't grow
 229         if (Grow == 0)
 230                 this->Flags &= ~Moveable;
 231
 232 #ifndef __linux__
 233         // kfreebsd doesn't have mremap, so we use the fallback
 234         if ((this->Flags & Moveable) == Moveable)
 235                 this->Flags |= Fallback;
 236 #endif
 237
 238 #ifdef _POSIX_MAPPED_FILES
 239         if ((this->Flags & Fallback) != Fallback) {
 240                 // Set the permissions.
 241                 int Prot = PROT_READ;
 242 #ifdef MAP_ANONYMOUS
 243                 int Map = MAP_PRIVATE | MAP_ANONYMOUS;
 244 #else
 245                 int Map = MAP_PRIVATE | MAP_ANON;
 246 #endif
 247                 if ((this->Flags & ReadOnly) != ReadOnly)
 248                         Prot |= PROT_WRITE;
 249                 if ((this->Flags & Public) == Public)
 250 #ifdef MAP_ANONYMOUS
 251                         Map = MAP_SHARED | MAP_ANONYMOUS;
 252 #else
 253                         Map = MAP_SHARED | MAP_ANON;
 254 #endif
 255
 256                 // use anonymous mmap() to get the memory
 257                 Base = (unsigned char*) mmap(0, WorkSpace, Prot, Map, -1, 0);
 258
 259                 if(Base == MAP_FAILED)
 260                         _error->Errno("DynamicMMap",_("Couldn't make mmap of %lu bytes"),WorkSpace);
 261
 262                 iSize = 0;
 263                 return;
 264         }
 265 #endif
 266         // fallback to a static allocated space
 267         Base = new unsigned char[WorkSpace];
 268         memset(Base,0,WorkSpace);
 269         iSize = 0;
 270 }
 271                                                                         /*}}}*/
 272 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 273 // ---------------------------------------------------------------------
 274 /* We truncate the file to the size of the memory data set */
 275 DynamicMMap::~DynamicMMap()
 276 {
 277    if (Fd == 0)
 278    {
 279       if (validData() == false)
 280          return;
 281 #ifdef _POSIX_MAPPED_FILES
 282       munmap(Base, WorkSpace);
 283 #else
 284       delete [] (unsigned char *)Base;
 285 #endif
 286       return;
 287    }
 288
 289    unsigned long long EndOfFile = iSize;
 290    iSize = WorkSpace;
 291    Close(false);
 292    if(ftruncate(Fd->Fd(),EndOfFile) < 0)
 293       _error->Errno("ftruncate", _("Failed to truncate file"));
 294 }
 295                                                                         /*}}}*/
 296 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 297 // ---------------------------------------------------------------------
 298 /* This allocates a block of memory aligned to the given size */
 299 unsigned long DynamicMMap::RawAllocate(unsigned long long Size,unsigned long Aln)
 300 {
 301    unsigned long long Result = iSize;
 302    if (Aln != 0)
 303       Result += Aln - (iSize%Aln);
 304
 305    iSize = Result + Size;
 306
 307    // try to grow the buffer
 308    while(Result + Size > WorkSpace)
 309    {
 310       if(!Grow())
 311       {
 312          _error->Fatal(_("Dynamic MMap ran out of room. Please increase the size "
 313                          "of APT::Cache-Limit. Current value: %lu. (man 5 apt.conf)"), WorkSpace);
 314          return 0;
 315       }
 316    }
 317    return Result;
 318 }
 319                                                                         /*}}}*/
 320 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 321 // ---------------------------------------------------------------------
 322 /* This allocates an Item of size ItemSize so that it is aligned to its
 323    size in the file. */
 324 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 325 {
 326    // Look for a matching pool entry
 327    Pool *I;
 328    Pool *Empty = 0;
 329    for (I = Pools; I != Pools + PoolCount; ++I)
 330    {
 331       if (I->ItemSize == 0)
 332          Empty = I;
 333       if (I->ItemSize == ItemSize)
 334          break;
 335    }
 336    // No pool is allocated, use an unallocated one
 337    if (I == Pools + PoolCount)
 338    {
 339       // Woops, we ran out, the calling code should allocate more.
 340       if (Empty == 0)
 341       {
 342          _error->Error("Ran out of allocation pools");
 343          return 0;
 344       }
 345
 346       I = Empty;
 347       I->ItemSize = ItemSize;
 348       I->Count = 0;
 349    }
 350
 351    unsigned long Result = 0;
 352    // Out of space, allocate some more
 353    if (I->Count == 0)
 354    {
 355       const unsigned long size = 20*1024;
 356       I->Count = size/ItemSize;
 357       Pool* oldPools = Pools;
 358       Result = RawAllocate(size,ItemSize);
 359       if (Pools != oldPools)
 360          I += Pools - oldPools;
 361
 362       // Does the allocation failed ?
 363       if (Result == 0 && _error->PendingError())
 364          return 0;
 365       I->Start = Result;
 366    }
 367    else
 368       Result = I->Start;
 369
 370    I->Count--;
 371    I->Start += ItemSize;
 372    return Result/ItemSize;
 373 }
 374                                                                         /*}}}*/
 375 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 376 // ---------------------------------------------------------------------
 377 /* Strings are not aligned to anything */
 378 unsigned long DynamicMMap::WriteString(const char *String,
 379                                        unsigned long Len)
 380 {
 381    if (Len == (unsigned long)-1)
 382       Len = strlen(String);
 383
 384    unsigned long const Result = RawAllocate(Len+1,0);
 385
 386    if (Result == 0 && _error->PendingError())
 387       return 0;
 388
 389    memcpy((char *)Base + Result,String,Len);
 390    ((char *)Base)[Result + Len] = 0;
 391    return Result;
 392 }
 393                                                                         /*}}}*/
 394 // DynamicMMap::Grow - Grow the mmap                                    /*{{{*/
 395 // ---------------------------------------------------------------------
 396 /* This method is a wrapper around different methods to (try to) grow
 397    a mmap (or our char[]-fallback). Encounterable environments:
 398    1. Moveable + !Fallback + linux -> mremap with MREMAP_MAYMOVE
 399    2. Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 400    3. Moveable + Fallback -> realloc
 401    4. !Moveable + !Fallback + linux -> mremap alone - which will fail in 99,9%
 402    5. !Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 403    6. !Moveable + Fallback -> not possible
 404    [ While Moveable and Fallback stands for the equally named flags and
 405      "linux" indicates a linux kernel instead of a freebsd kernel. ]
 406    So what you can see here is, that a MMAP which want to be growable need
 407    to be moveable to have a real chance but that this method will at least try
 408    the nearly impossible 4 to grow it before it finally give up: Never say never. */
 409 bool DynamicMMap::Grow() {
 410         if (Limit != 0 && WorkSpace >= Limit)
 411                 return _error->Error(_("Unable to increase the size of the MMap as the "
 412                                        "limit of %lu bytes is already reached."), Limit);
 413         if (GrowFactor <= 0)
 414                 return _error->Error(_("Unable to increase size of the MMap as automatic growing is disabled by user."));
 415
 416         unsigned long long const newSize = WorkSpace + GrowFactor;
 417
 418         if(Fd != 0) {
 419                 Fd->Seek(newSize - 1);
 420                 char C = 0;
 421                 Fd->Write(&C,sizeof(C));
 422         }
 423
 424         unsigned long const poolOffset = Pools - ((Pool*) Base);
 425
 426         if ((Flags & Fallback) != Fallback) {
 427 #if defined(_POSIX_MAPPED_FILES) && defined(__linux__)
 428    #ifdef MREMAP_MAYMOVE
 429
 430                 if ((Flags & Moveable) == Moveable)
 431                         Base = mremap(Base, WorkSpace, newSize, MREMAP_MAYMOVE);
 432                 else
 433    #endif
 434                         Base = mremap(Base, WorkSpace, newSize, 0);
 435
 436                 if(Base == MAP_FAILED)
 437                         return false;
 438 #else
 439                 return false;
 440 #endif
 441         } else {
 442                 if ((Flags & Moveable) != Moveable)
 443                         return false;
 444
 445                 Base = realloc(Base, newSize);
 446                 if (Base == NULL)
 447                         return false;
 448         }
 449
 450         Pools =(Pool*) Base + poolOffset;
 451         WorkSpace = newSize;
 452         return true;
 453 }
 454                                                                         /*}}}*/