apt-pkg/tagfile.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: tagfile.h,v 1.20 2003/05/19 17:13:57 doogie Exp $
   4 /* ######################################################################
   5
   6    Fast scanner for RFC-822 type header information
   7
   8    This parser handles Debian package files (and others). Their form is
   9    RFC-822 type header fields in groups separated by a blank line.
  10
  11    The parser reads the file and provides methods to step linearly
  12    over it or to jump to a pre-recorded start point and read that record.
  13
  14    A second class is used to perform pre-parsing of the record. It works
  15    by indexing the start of each header field and providing lookup
  16    functions for header fields.
  17
  18    ##################################################################### */
  19                                                                         /*}}}*/
  20 #ifndef PKGLIB_TAGFILE_H
  21 #define PKGLIB_TAGFILE_H
  22
  23
  24 #include <apt-pkg/fileutl.h>
  25 #include <stdio.h>
  26
  27 class pkgTagSection
  28 {
  29    const char *Section;
  30
  31    // We have a limit of 256 tags per section.
  32    unsigned int Indexes[256];
  33    unsigned int AlphaIndexes[0x100];
  34
  35    unsigned int TagCount;
  36
  37    /* This very simple hash function for the last 8 letters gives
  38       very good performance on the debian package files */
  39    inline static unsigned long AlphaHash(const char *Text, const char *End = 0)
  40    {
  41       unsigned long Res = 0;
  42       for (; Text != End && *Text != ':' && *Text != 0; Text++)
  43          Res = ((unsigned long)(*Text) & 0xDF) ^ (Res << 1);
  44       return Res & 0xFF;
  45    }
  46
  47
  48    protected:
  49    const char *Stop;
  50
  51    public:
  52
  53    inline bool operator ==(const pkgTagSection &rhs) {return Section == rhs.Section;};
  54    inline bool operator !=(const pkgTagSection &rhs) {return Section != rhs.Section;};
  55
  56    bool Find(const char *Tag,const char *&Start, const char *&End) const;
  57    bool Find(const char *Tag,unsigned &Pos) const;
  58    string FindS(const char *Tag) const;
  59    signed int FindI(const char *Tag,signed long Default = 0) const ;
  60    unsigned long long FindULL(const char *Tag, unsigned long long const &Default = 0) const;
  61    bool FindFlag(const char *Tag,unsigned long &Flags,
  62                  unsigned long Flag) const;
  63    bool static const FindFlag(unsigned long &Flags, unsigned long Flag,
  64                                 const char* Start, const char* Stop);
  65    bool Scan(const char *Start,unsigned long MaxLength);
  66    inline unsigned long size() const {return Stop - Section;};
  67    void Trim();
  68    virtual void TrimRecord(bool BeforeRecord, const char* &End);
  69
  70    inline unsigned int Count() const {return TagCount;};
  71    inline bool Exists(const char* const Tag) {return AlphaIndexes[AlphaHash(Tag)] != 0;}
  72
  73    inline void Get(const char *&Start,const char *&Stop,unsigned int I) const
  74                    {Start = Section + Indexes[I]; Stop = Section + Indexes[I+1];}
  75
  76    inline void GetSection(const char *&Start,const char *&Stop) const
  77    {
  78       Start = Section;
  79       Stop = this->Stop;
  80    };
  81
  82    pkgTagSection() : Section(0), Stop(0) {};
  83 };
  84
  85 class pkgTagFile
  86 {
  87    FileFd &Fd;
  88    char *Buffer;
  89    char *Start;
  90    char *End;
  91    bool Done;
  92    unsigned long iOffset;
  93    unsigned long Size;
  94
  95    bool Fill();
  96    bool Resize();
  97
  98    public:
  99
 100    bool Step(pkgTagSection &Section);
 101    inline unsigned long Offset() {return iOffset;};
 102    bool Jump(pkgTagSection &Tag,unsigned long Offset);
 103
 104    pkgTagFile(FileFd *F,unsigned long Size = 32*1024);
 105    ~pkgTagFile();
 106 };
 107
 108 /* This is the list of things to rewrite. The rewriter
 109    goes through and changes or adds each of these headers
 110    to suit. A zero forces the header to be erased, an empty string
 111    causes the old value to be used. (rewrite rule ignored) */
 112 struct TFRewriteData
 113 {
 114    const char *Tag;
 115    const char *Rewrite;
 116    const char *NewTag;
 117 };
 118 extern const char **TFRewritePackageOrder;
 119 extern const char **TFRewriteSourceOrder;
 120
 121 bool TFRewrite(FILE *Output,pkgTagSection const &Tags,const char *Order[],
 122                TFRewriteData *Rewrite);
 123
 124 #endif