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    bool FindFlag(const char *Tag,unsigned long &Flags,
  61                  unsigned long Flag) const;
  62    bool Scan(const char *Start,unsigned long MaxLength);
  63    inline unsigned long size() const {return Stop - Section;};
  64    void Trim();
  65    virtual void TrimRecord(bool BeforeRecord, const char* &End);
  66
  67    inline unsigned int Count() const {return TagCount;};
  68    inline bool Exists(const char* const Tag) {return AlphaIndexes[AlphaHash(Tag)] != 0;}
  69
  70    inline void Get(const char *&Start,const char *&Stop,unsigned int I) const
  71                    {Start = Section + Indexes[I]; Stop = Section + Indexes[I+1];}
  72
  73    inline void GetSection(const char *&Start,const char *&Stop) const
  74    {
  75       Start = Section;
  76       Stop = this->Stop;
  77    };
  78
  79    pkgTagSection() : Section(0), Stop(0) {};
  80 };
  81
  82 class pkgTagFile
  83 {
  84    FileFd &Fd;
  85    char *Buffer;
  86    char *Start;
  87    char *End;
  88    bool Done;
  89    unsigned long iOffset;
  90    unsigned long Size;
  91
  92    bool Fill();
  93    bool Resize();
  94
  95    public:
  96
  97    bool Step(pkgTagSection &Section);
  98    inline unsigned long Offset() {return iOffset;};
  99    bool Jump(pkgTagSection &Tag,unsigned long Offset);
 100
 101    pkgTagFile(FileFd *F,unsigned long Size = 32*1024);
 102    ~pkgTagFile();
 103 };
 104
 105 /* This is the list of things to rewrite. The rewriter
 106    goes through and changes or adds each of these headers
 107    to suit. A zero forces the header to be erased, an empty string
 108    causes the old value to be used. (rewrite rule ignored) */
 109 struct TFRewriteData
 110 {
 111    const char *Tag;
 112    const char *Rewrite;
 113    const char *NewTag;
 114 };
 115 extern const char **TFRewritePackageOrder;
 116 extern const char **TFRewriteSourceOrder;
 117
 118 bool TFRewrite(FILE *Output,pkgTagSection const &Tags,const char *Order[],
 119                TFRewriteData *Rewrite);
 120
 121 #endif