apt-pkg/tagfile.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: tagfile.cc,v 1.14 1998/11/13 04:23:36 jgg Exp $
   4 /* ######################################################################
   5
   6    Fast scanner for RFC-822 type header information
   7
   8    This uses a rotating buffer to load the package information into.
   9    The scanner runs over it and isolates and indexes a single section.
  10
  11    ##################################################################### */
  12                                                                         /*}}}*/
  13 // Include Files                                                        /*{{{*/
  14 #ifdef __GNUG__
  15 #pragma implementation "apt-pkg/tagfile.h"
  16 #endif
  17
  18 #include <apt-pkg/tagfile.h>
  19 #include <apt-pkg/error.h>
  20
  21 #include <string>
  22 #include <stdio.h>
  23                                                                         /*}}}*/
  24
  25 // TagFile::pkgTagFile - Constructor                                    /*{{{*/
  26 // ---------------------------------------------------------------------
  27 /* */
  28 pkgTagFile::pkgTagFile(FileFd &Fd,unsigned long Size) : Fd(Fd), Size(Size)
  29 {
  30    Buffer = new char[Size];
  31    Start = End = Buffer;
  32    Left = Fd.Size();
  33    iOffset = 0;
  34    Fill();
  35 }
  36                                                                         /*}}}*/
  37 // TagFile::Step - Advance to the next section                          /*{{{*/
  38 // ---------------------------------------------------------------------
  39 /* If the Section Scanner fails we refill the buffer and try again. */
  40 bool pkgTagFile::Step(pkgTagSection &Tag)
  41 {
  42    if (Tag.Scan(Start,End - Start) == false)
  43    {
  44       if (Fill() == false)
  45          return false;
  46
  47       if (Tag.Scan(Start,End - Start) == false)
  48          return _error->Error("Unable to parse package file");
  49    }
  50    Start += Tag.size();
  51    iOffset += Tag.size();
  52
  53    return true;
  54 }
  55                                                                         /*}}}*/
  56 // TagFile::Fill - Top up the buffer                                    /*{{{*/
  57 // ---------------------------------------------------------------------
  58 /* This takes the bit at the end of the buffer and puts it at the start
  59    then fills the rest from the file */
  60 bool pkgTagFile::Fill()
  61 {
  62    unsigned long EndSize = End - Start;
  63
  64    if (Left == 0)
  65    {
  66       if (EndSize <= 1)
  67          return false;
  68       return true;
  69    }
  70
  71    memmove(Buffer,Start,EndSize);
  72    Start = Buffer;
  73    End = Buffer + EndSize;
  74
  75    // See if only a bit of the file is left
  76    if (Left < Size - (End - Buffer))
  77    {
  78       if (Fd.Read(End,Left) == false)
  79          return false;
  80
  81       End += Left;
  82       Left = 0;
  83    }
  84    else
  85    {
  86       if (Fd.Read(End,Size - (End - Buffer)) == false)
  87          return false;
  88
  89       Left -= Size - (End - Buffer);
  90       End = Buffer + Size;
  91    }
  92    return true;
  93 }
  94                                                                         /*}}}*/
  95 // TagFile::Jump - Jump to a pre-recorded location in the file          /*{{{*/
  96 // ---------------------------------------------------------------------
  97 /* This jumps to a pre-recorded file location and reads the record
  98    that is there */
  99 bool pkgTagFile::Jump(pkgTagSection &Tag,unsigned long Offset)
 100 {
 101    iOffset = Offset;
 102    Left = Fd.Size() - Offset;
 103    if (Fd.Seek(Offset) == false)
 104       return false;
 105    End = Start = Buffer;
 106
 107    if (Fill() == false)
 108       return false;
 109
 110    if (Tag.Scan(Start,End - Start) == false)
 111       return _error->Error("Unable to parse package file");
 112    return true;
 113 }
 114                                                                         /*}}}*/
 115 // TagSection::Scan - Scan for the end of the header information        /*{{{*/
 116 // ---------------------------------------------------------------------
 117 /* This looks for the first double new line in the data stream. It also
 118    indexes the tags in the section. */
 119 bool pkgTagSection::Scan(const char *Start,unsigned long MaxLength)
 120 {
 121    const char *End = Start + MaxLength;
 122    Stop = Section = Start;
 123
 124    TagCount = 0;
 125    Indexes[TagCount++] = Stop - Section;
 126    Stop++;
 127    for (; Stop < End; Stop++)
 128    {
 129       if (Stop[-1] != '\n')
 130          continue;
 131
 132       // Skip line feeds
 133       for (; Stop[0] == '\r' && Stop < End; Stop++);
 134
 135       if (Stop[0] == '\n')
 136       {
 137          // Extra one at the end to simplify find
 138          Indexes[TagCount] = Stop - Section;
 139          for (; (Stop[0] == '\n' || Stop[0] == '\r') && Stop < End; Stop++);
 140          return true;
 141       }
 142
 143       if (isspace(Stop[0]) == 0)
 144          Indexes[TagCount++] = Stop - Section;
 145
 146       // Just in case.
 147       if (TagCount > sizeof(Indexes)/sizeof(Indexes[0]))
 148          TagCount = sizeof(Indexes)/sizeof(Indexes[0]);
 149    }
 150    return false;
 151 }
 152                                                                         /*}}}*/
 153 // TagSection::Find - Locate a tag                                      /*{{{*/
 154 // ---------------------------------------------------------------------
 155 /* This searches the section for a tag that matches the given string. */
 156 bool pkgTagSection::Find(const char *Tag,const char *&Start,
 157                          const char *&End)
 158 {
 159    unsigned int Length = strlen(Tag);
 160    for (unsigned int I = 0; I != TagCount; I++)
 161    {
 162       if (strncasecmp(Tag,Section + Indexes[I],Length) != 0)
 163          continue;
 164
 165       // Make sure the colon is in the right place
 166       const char *C = Section + Length + Indexes[I];
 167       for (; isspace(*C) != 0; C++);
 168       if (*C != ':')
 169          continue;
 170
 171       // Strip off the gunk from the start end
 172       Start = C;
 173       End = Section + Indexes[I+1];
 174       for (; (isspace(*Start) != 0 || *Start == ':') && Start < End; Start++);
 175       for (; isspace(End[-1]) != 0 && End > Start; End--);
 176
 177       return true;
 178    }
 179    Start = End = 0;
 180    return false;
 181 }
 182                                                                         /*}}}*/