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 #include <stdio.h>
  24
  25 #include <string>
  26
  27 class FileFd;
  28
  29 class pkgTagSection
  30 {
  31    const char *Section;
  32    // We have a limit of 256 tags per section.
  33    unsigned int Indexes[256];
  34    unsigned int AlphaIndexes[0x100];
  35    unsigned int TagCount;
  36    // dpointer placeholder (for later in case we need it)
  37    void *d;
  38
  39    /* This very simple hash function for the last 8 letters gives
  40       very good performance on the debian package files */
  41    inline static unsigned long AlphaHash(const char *Text, const char *End = 0)
  42    {
  43       unsigned long Res = 0;
  44       for (; Text != End && *Text != ':' && *Text != 0; Text++)
  45          Res = ((unsigned long)(*Text) & 0xDF) ^ (Res << 1);
  46       return Res & 0xFF;
  47    }
  48
  49    protected:
  50    const char *Stop;
  51
  52    public:
  53
  54    inline bool operator ==(const pkgTagSection &rhs) {return Section == rhs.Section;};
  55    inline bool operator !=(const pkgTagSection &rhs) {return Section != rhs.Section;};
  56
  57    bool Find(const char *Tag,const char *&Start, const char *&End) const;
  58    bool Find(const char *Tag,unsigned &Pos) const;
  59    std::string FindS(const char *Tag) const;
  60    signed int FindI(const char *Tag,signed long Default = 0) const ;
  61    unsigned long long FindULL(const char *Tag, unsigned long long const &Default = 0) const;
  62    bool FindFlag(const char *Tag,unsigned long &Flags,
  63                  unsigned long Flag) const;
  64    bool static const FindFlag(unsigned long &Flags, unsigned long Flag,
  65                                 const char* Start, const char* Stop);
  66    bool Scan(const char *Start,unsigned long MaxLength);
  67    inline unsigned long size() const {return Stop - Section;};
  68    void Trim();
  69    virtual void TrimRecord(bool BeforeRecord, const char* &End);
  70
  71    inline unsigned int Count() const {return TagCount;};
  72    inline bool Exists(const char* const Tag) {return AlphaIndexes[AlphaHash(Tag)] != 0;}
  73
  74    inline void Get(const char *&Start,const char *&Stop,unsigned int I) const
  75                    {Start = Section + Indexes[I]; Stop = Section + Indexes[I+1];}
  76
  77    inline void GetSection(const char *&Start,const char *&Stop) const
  78    {
  79       Start = Section;
  80       Stop = this->Stop;
  81    };
  82
  83    pkgTagSection() : Section(0), TagCount(0), Stop(0) {};
  84    virtual ~pkgTagSection() {};
  85 };
  86
  87 class pkgTagFilePrivate;
  88 class pkgTagFile
  89 {
  90    pkgTagFilePrivate *d;
  91
  92    bool Fill();
  93    bool Resize();
  94
  95    public:
  96
  97    bool Step(pkgTagSection &Section);
  98    unsigned long Offset();
  99    bool Jump(pkgTagSection &Tag,unsigned long long Offset);
 100
 101    pkgTagFile(FileFd *F,unsigned long long Size = 32*1024);
 102    virtual ~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