apt-pkg/contrib/mmap.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.h,v 1.12 2001/05/14 05:16:43 jgg Exp $
   4 /* ######################################################################
   5
   6    MMap Class - Provides 'real' mmap or a faked mmap using read().
   7
   8    The purpose of this code is to provide a generic way for clients to
   9    access the mmap function. In enviroments that do not support mmap
  10    from file fd's this function will use read and normal allocated
  11    memory.
  12
  13    Writing to a public mmap will always fully comit all changes when the
  14    class is deleted. Ie it will rewrite the file, unless it is readonly
  15
  16    The DynamicMMap class is used to help the on-disk data structure
  17    generators. It provides a large allocated workspace and members
  18    to allocate space from the workspace in an effecient fashion.
  19
  20    This source is placed in the Public Domain, do with it what you will
  21    It was originally written by Jason Gunthorpe.
  22
  23    ##################################################################### */
  24                                                                         /*}}}*/
  25 #ifndef PKGLIB_MMAP_H
  26 #define PKGLIB_MMAP_H
  27
  28
  29 #include <string>
  30 #include <apt-pkg/fileutl.h>
  31
  32 using std::string;
  33
  34 /* This should be a 32 bit type, larger tyes use too much ram and smaller
  35    types are too small. Where ever possible 'unsigned long' should be used
  36    instead of this internal type */
  37 typedef unsigned int map_ptrloc;
  38
  39 class MMap
  40 {
  41    protected:
  42
  43    unsigned long Flags;
  44    unsigned long iSize;
  45    void *Base;
  46
  47    // In case mmap can not be used, we keep a dup of the file
  48    // descriptor that should have been mmaped so that we can write to
  49    // the file in Sync().
  50    FileFd *SyncToFd;
  51
  52    bool Map(FileFd &Fd);
  53    bool Close(bool DoSync = true);
  54
  55    public:
  56
  57    enum OpenFlags {NoImmMap = (1<<0),Public = (1<<1),ReadOnly = (1<<2),
  58                    UnMapped = (1<<3), Moveable = (1<<4), Fallback = (1 << 5)};
  59
  60    // Simple accessors
  61    inline operator void *() {return Base;};
  62    inline void *Data() {return Base;};
  63    inline unsigned long Size() {return iSize;};
  64
  65    // File manipulators
  66    bool Sync();
  67    bool Sync(unsigned long Start,unsigned long Stop);
  68
  69    MMap(FileFd &F,unsigned long Flags);
  70    MMap(unsigned long Flags);
  71    virtual ~MMap();
  72 };
  73
  74 class DynamicMMap : public MMap
  75 {
  76    public:
  77
  78    // This is the allocation pool structure
  79    struct Pool
  80    {
  81       unsigned long ItemSize;
  82       unsigned long Start;
  83       unsigned long Count;
  84    };
  85
  86    protected:
  87
  88    FileFd *Fd;
  89    unsigned long WorkSpace;
  90    unsigned long const GrowFactor;
  91    unsigned long const Limit;
  92    Pool *Pools;
  93    unsigned int PoolCount;
  94
  95    bool Grow();
  96
  97    public:
  98
  99    // Allocation
 100    unsigned long RawAllocate(unsigned long Size,unsigned long Aln = 0);
 101    unsigned long Allocate(unsigned long ItemSize);
 102    unsigned long WriteString(const char *String,unsigned long Len = (unsigned long)-1);
 103    inline unsigned long WriteString(const string &S) {return WriteString(S.c_str(),S.length());};
 104    void UsePools(Pool &P,unsigned int Count) {Pools = &P; PoolCount = Count;};
 105
 106    DynamicMMap(FileFd &F,unsigned long Flags,unsigned long const &WorkSpace = 2*1024*1024,
 107                unsigned long const &Grow = 1024*1024, unsigned long const &Limit = 0);
 108    DynamicMMap(unsigned long Flags,unsigned long const &WorkSpace = 2*1024*1024,
 109                unsigned long const &Grow = 1024*1024, unsigned long const &Limit = 0);
 110    virtual ~DynamicMMap();
 111 };
 112
 113 #endif