apt-pkg/contrib/mmap.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.cc,v 1.21 2001/02/20 07:03:17 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 <apti18n.h>
  33
  34 #include <sys/mman.h>
  35 #include <sys/stat.h>
  36 #include <unistd.h>
  37 #include <fcntl.h>
  38                                                                         /*}}}*/
  39
  40 // MMap::MMap - Constructor                                             /*{{{*/
  41 // ---------------------------------------------------------------------
  42 /* */
  43 MMap::MMap(FileFd &F,unsigned long Flags) : Flags(Flags), iSize(0),
  44                      Base(0)
  45 {
  46    if ((Flags & NoImmMap) != NoImmMap)
  47       Map(F);
  48 }
  49                                                                         /*}}}*/
  50 // MMap::MMap - Constructor                                             /*{{{*/
  51 // ---------------------------------------------------------------------
  52 /* */
  53 MMap::MMap(unsigned long Flags) : Flags(Flags), iSize(0),
  54                      Base(0)
  55 {
  56 }
  57                                                                         /*}}}*/
  58 // MMap::~MMap - Destructor                                             /*{{{*/
  59 // ---------------------------------------------------------------------
  60 /* */
  61 MMap::~MMap()
  62 {
  63    Close();
  64 }
  65                                                                         /*}}}*/
  66 // MMap::Map - Perform the mapping                                      /*{{{*/
  67 // ---------------------------------------------------------------------
  68 /* */
  69 bool MMap::Map(FileFd &Fd)
  70 {
  71    iSize = Fd.Size();
  72
  73    // Set the permissions.
  74    int Prot = PROT_READ;
  75    int Map = MAP_SHARED;
  76    if ((Flags & ReadOnly) != ReadOnly)
  77       Prot |= PROT_WRITE;
  78    if ((Flags & Public) != Public)
  79       Map = MAP_PRIVATE;
  80
  81    if (iSize == 0)
  82       return _error->Error(_("Can't mmap an empty file"));
  83
  84    // Map it.
  85    Base = mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  86    if (Base == (void *)-1)
  87       return _error->Errno("mmap",_("Couldn't make mmap of %lu bytes"),iSize);
  88
  89    return true;
  90 }
  91                                                                         /*}}}*/
  92 // MMap::Close - Close the map                                          /*{{{*/
  93 // ---------------------------------------------------------------------
  94 /* */
  95 bool MMap::Close(bool DoSync)
  96 {
  97    if ((Flags & UnMapped) == UnMapped || Base == 0 || iSize == 0)
  98       return true;
  99
 100    if (DoSync == true)
 101       Sync();
 102
 103    if (munmap((char *)Base,iSize) != 0)
 104       _error->Warning("Unable to munmap");
 105
 106    iSize = 0;
 107    Base = 0;
 108    return true;
 109 }
 110                                                                         /*}}}*/
 111 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 112 // ---------------------------------------------------------------------
 113 /* This is done in syncronous mode - the docs indicate that this will
 114    not return till all IO is complete */
 115 bool MMap::Sync()
 116 {
 117    if ((Flags & UnMapped) == UnMapped)
 118       return true;
 119
 120 #ifdef _POSIX_SYNCHRONIZED_IO
 121    if ((Flags & ReadOnly) != ReadOnly)
 122       if (msync((char *)Base,iSize,MS_SYNC) != 0)
 123          return _error->Errno("msync","Unable to write mmap");
 124 #endif
 125    return true;
 126 }
 127                                                                         /*}}}*/
 128 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 129 // ---------------------------------------------------------------------
 130 /* */
 131 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 132 {
 133    if ((Flags & UnMapped) == UnMapped)
 134       return true;
 135
 136 #ifdef _POSIX_SYNCHRONIZED_IO
 137    unsigned long PSize = sysconf(_SC_PAGESIZE);
 138    if ((Flags & ReadOnly) != ReadOnly)
 139       if (msync((char *)Base+(int)(Start/PSize)*PSize,Stop - Start,MS_SYNC) != 0)
 140          return _error->Errno("msync","Unable to write mmap");
 141 #endif
 142    return true;
 143 }
 144                                                                         /*}}}*/
 145
 146 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 147 // ---------------------------------------------------------------------
 148 /* */
 149 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long WorkSpace) :
 150              MMap(F,Flags | NoImmMap), Fd(&F), WorkSpace(WorkSpace)
 151 {
 152    if (_error->PendingError() == true)
 153       return;
 154
 155    unsigned long EndOfFile = Fd->Size();
 156    if (EndOfFile > WorkSpace)
 157       WorkSpace = EndOfFile;
 158    else
 159    {
 160       Fd->Seek(WorkSpace);
 161       char C = 0;
 162       Fd->Write(&C,sizeof(C));
 163    }
 164
 165    Map(F);
 166    iSize = EndOfFile;
 167 }
 168                                                                         /*}}}*/
 169 // DynamicMMap::DynamicMMap - Constructor for a non-file backed map     /*{{{*/
 170 // ---------------------------------------------------------------------
 171 /* This is just a fancy malloc really.. */
 172 DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long WorkSpace) :
 173              MMap(Flags | NoImmMap | UnMapped), Fd(0), WorkSpace(WorkSpace)
 174 {
 175    if (_error->PendingError() == true)
 176       return;
 177
 178    Base = new unsigned char[WorkSpace];
 179    iSize = 0;
 180 }
 181                                                                         /*}}}*/
 182 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 183 // ---------------------------------------------------------------------
 184 /* We truncate the file to the size of the memory data set */
 185 DynamicMMap::~DynamicMMap()
 186 {
 187    if (Fd == 0)
 188    {
 189       delete [] (unsigned char *)Base;
 190       return;
 191    }
 192
 193    unsigned long EndOfFile = iSize;
 194    iSize = WorkSpace;
 195    Close(false);
 196    ftruncate(Fd->Fd(),EndOfFile);
 197 }
 198                                                                         /*}}}*/
 199 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 200 // ---------------------------------------------------------------------
 201 /* This allocates a block of memory aligned to the given size */
 202 unsigned long DynamicMMap::RawAllocate(unsigned long Size,unsigned long Aln)
 203 {
 204    unsigned long Result = iSize;
 205    if (Aln != 0)
 206       Result += Aln - (iSize%Aln);
 207
 208    iSize = Result + Size;
 209
 210    // Just in case error check
 211    if (Result + Size > WorkSpace)
 212    {
 213       _error->Error("Dynamic MMap ran out of room");
 214       return 0;
 215    }
 216
 217    return Result;
 218 }
 219                                                                         /*}}}*/
 220 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 221 // ---------------------------------------------------------------------
 222 /* This allocates an Item of size ItemSize so that it is aligned to its
 223    size in the file. */
 224 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 225 {
 226    // Look for a matching pool entry
 227    Pool *I;
 228    Pool *Empty = 0;
 229    for (I = Pools; I != Pools + PoolCount; I++)
 230    {
 231       if (I->ItemSize == 0)
 232          Empty = I;
 233       if (I->ItemSize == ItemSize)
 234          break;
 235    }
 236
 237    // No pool is allocated, use an unallocated one
 238    if (I == Pools + PoolCount)
 239    {
 240       // Woops, we ran out, the calling code should allocate more.
 241       if (Empty == 0)
 242       {
 243          _error->Error("Ran out of allocation pools");
 244          return 0;
 245       }
 246
 247       I = Empty;
 248       I->ItemSize = ItemSize;
 249       I->Count = 0;
 250    }
 251
 252    // Out of space, allocate some more
 253    if (I->Count == 0)
 254    {
 255       I->Count = 20*1024/ItemSize;
 256       I->Start = RawAllocate(I->Count*ItemSize,ItemSize);
 257    }
 258
 259    I->Count--;
 260    unsigned long Result = I->Start;
 261    I->Start += ItemSize;
 262    return Result/ItemSize;
 263 }
 264                                                                         /*}}}*/
 265 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 266 // ---------------------------------------------------------------------
 267 /* Strings are not aligned to anything */
 268 unsigned long DynamicMMap::WriteString(const char *String,
 269                                        unsigned long Len)
 270 {
 271    unsigned long Result = iSize;
 272    // Just in case error check
 273    if (Result + Len > WorkSpace)
 274    {
 275       _error->Error("Dynamic MMap ran out of room");
 276       return 0;
 277    }
 278
 279    if (Len == (unsigned long)-1)
 280       Len = strlen(String);
 281    iSize += Len + 1;
 282    memcpy((char *)Base + Result,String,Len);
 283    ((char *)Base)[Result + Len] = 0;
 284    return Result;
 285 }
 286                                                                         /*}}}*/