ensure that pkgTagFile isn't writing past Buffer length

[apt.git] / apt-pkg / tagfile.cc

diff --git a/apt-pkg/tagfile.cc b/apt-pkg/tagfile.cc
index 42a44453f256b98a103a0fa9164717566c1daeb3..aa0f1eee8a15ad5b5b295026178ea476db1b4804 100644 (file)
--- a/apt-pkg/tagfile.cc
+++ b/apt-pkg/tagfile.cc
@@ -1,56 +1,147 @@
 // -*- mode: cpp; mode: fold -*-
 // Description                                                         /*{{{*/
 // -*- mode: cpp; mode: fold -*-
 // Description                                                         /*{{{*/

-// $Id: tagfile.cc,v 1.7 1998/07/12 23:58:39 jgg Exp $
+// $Id: tagfile.cc,v 1.37.2.2 2003/12/31 16:02:30 mdz Exp $

 /* ######################################################################
 
    Fast scanner for RFC-822 type header information
    
 /* ######################################################################
 
    Fast scanner for RFC-822 type header information
    

-   This uses a rotating 64K buffer to load the package information into.
+   This uses a rotating buffer to load the package information into.

    The scanner runs over it and isolates and indexes a single section.
    
    ##################################################################### */
                                                                        /*}}}*/
 // Include Files                                                       /*{{{*/
    The scanner runs over it and isolates and indexes a single section.
    
    ##################################################################### */
                                                                        /*}}}*/
 // Include Files                                                       /*{{{*/

-#ifdef __GNUG__
-#pragma implementation "apt-pkg/tagfile.h"
-#endif
+#include<config.h>

 
 #include <apt-pkg/tagfile.h>
 #include <apt-pkg/error.h>
 
 #include <apt-pkg/tagfile.h>
 #include <apt-pkg/error.h>

-#include <apt-pkg/init.h>
+#include <apt-pkg/strutl.h>
+#include <apt-pkg/fileutl.h>

 
 #include <string>
 #include <stdio.h>
 
 #include <string>
 #include <stdio.h>

+#include <ctype.h>
+
+#include <apti18n.h>

                                                                        /*}}}*/
 
                                                                        /*}}}*/
 

+using std::string;
+
+class pkgTagFilePrivate
+{
+public:
+   pkgTagFilePrivate(FileFd *pFd, unsigned long long Size) : Fd(*pFd), Buffer(NULL),
+                                                            Start(NULL), End(NULL),
+                                                            Done(false), iOffset(0),
+                                                            Size(Size)
+   {
+   }
+   FileFd &Fd;
+   char *Buffer;
+   char *Start;
+   char *End;
+   bool Done;
+   unsigned long long iOffset;
+   unsigned long long Size;
+};
+

 // TagFile::pkgTagFile - Constructor                                   /*{{{*/
 // ---------------------------------------------------------------------
 /* */
 // TagFile::pkgTagFile - Constructor                                   /*{{{*/
 // ---------------------------------------------------------------------
 /* */

-pkgTagFile::pkgTagFile(File &Fd) : Fd(Fd)
+pkgTagFile::pkgTagFile(FileFd *pFd,unsigned long long Size)

 {
 {

-   Buffer = new char[64*1024];
-   Start = End = Buffer + 64*1024;
-   Left = Fd.Size();
-   iOffset = 0;
+   /* The size is increased by 4 because if we start with the Size of the
+      filename we need to try to read 1 char more to see an EOF faster, 1
+      char the end-pointer can be on and maybe 2 newlines need to be added
+      to the end of the file -> 4 extra chars */
+   Size += 4;
+   d = new pkgTagFilePrivate(pFd, Size);
+
+   if (d->Fd.IsOpen() == false)
+   {
+      d->Start = d->End = d->Buffer = 0;
+      d->Done = true;
+      d->iOffset = 0;
+      return;
+   }
+   
+   d->Buffer = new char[Size];
+   d->Start = d->End = d->Buffer;
+   d->Done = false;
+   d->iOffset = 0;

    Fill();
 }
                                                                        /*}}}*/
    Fill();
 }
                                                                        /*}}}*/

+// TagFile::~pkgTagFile - Destructor                                   /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+pkgTagFile::~pkgTagFile()
+{
+   delete [] d->Buffer;
+   delete d;
+}
+                                                                       /*}}}*/
+// TagFile::Offset - Return the current offset in the buffer           /*{{{*/
+unsigned long pkgTagFile::Offset()
+{
+   return d->iOffset;
+}
+                                                                       /*}}}*/
+// TagFile::Resize - Resize the internal buffer                                /*{{{*/
+// ---------------------------------------------------------------------
+/* Resize the internal buffer (double it in size). Fail if a maximum size
+ * size is reached.
+ */
+bool pkgTagFile::Resize()
+{
+   // fail is the buffer grows too big
+   if(d->Size > 1024*1024+1)
+      return false;
+
+   return Resize(d->Size * 2);
+}
+bool pkgTagFile::Resize(unsigned long long const newSize)
+{
+   unsigned long long const EndSize = d->End - d->Start;
+   char *tmp;
+
+   // get new buffer and use it
+   tmp = new char[newSize];
+   memcpy(tmp, d->Buffer, d->Size);
+   d->Size = newSize;
+   delete [] d->Buffer;
+   d->Buffer = tmp;
+
+   // update the start/end pointers to the new buffer
+   d->Start = d->Buffer;
+   d->End = d->Start + EndSize;
+   return true;
+}
+                                                                       /*}}}*/

 // TagFile::Step - Advance to the next section                         /*{{{*/
 // ---------------------------------------------------------------------
 // TagFile::Step - Advance to the next section                         /*{{{*/
 // ---------------------------------------------------------------------

-/* If the Section Scanner fails we refill the buffer and try again. */
+/* If the Section Scanner fails we refill the buffer and try again. 
+ * If that fails too, double the buffer size and try again until a
+ * maximum buffer is reached.
+ */

 bool pkgTagFile::Step(pkgTagSection &Tag)
 {
 bool pkgTagFile::Step(pkgTagSection &Tag)
 {

-   if (Tag.Scan(Start,End - Start) == false)
+   while (Tag.Scan(d->Start,d->End - d->Start) == false)

    {
       if (Fill() == false)
         return false;
       
    {
       if (Fill() == false)
         return false;
       

-      if (Tag.Scan(Start,End - Start) == false)
-        return _error->Error("Unable to parse package file");
-   }   
-   Start += Tag.size();
-   iOffset += Tag.size();
-   
+      if(Tag.Scan(d->Start,d->End - d->Start))
+        break;
+
+      if (Resize() == false)
+        return _error->Error(_("Unable to parse package file %s (1)"),
+                              d->Fd.Name().c_str());
+   }
+   d->Start += Tag.size();
+   d->iOffset += Tag.size();
+
+   Tag.Trim();

    return true;
 }
                                                                        /*}}}*/
    return true;
 }
                                                                        /*}}}*/


@@ -60,84 +151,213 @@ bool pkgTagFile::Step(pkgTagSection &Tag)
    then fills the rest from the file */
 bool pkgTagFile::Fill()
 {
    then fills the rest from the file */
 bool pkgTagFile::Fill()
 {

-   unsigned long Size = End - Start;
+   unsigned long long EndSize = d->End - d->Start;
+   unsigned long long Actual = 0;
+   
+   memmove(d->Buffer,d->Start,EndSize);
+   d->Start = d->Buffer;
+   d->End = d->Buffer + EndSize;

    
    

-   if (Left == 0)
+   if (d->Done == false)

    {
    {

-      if (Size <= 1)
+      // See if only a bit of the file is left
+      unsigned long long const dataSize = d->Size - ((d->End - d->Buffer) + 1);
+      if (d->Fd.Read(d->End, dataSize, &Actual) == false)

         return false;
         return false;

-      return true;
+      if (Actual != dataSize || d->Fd.Eof() == true)
+        d->Done = true;
+      d->End += Actual;

    }
    
    }
    

-   memmove(Buffer,Start,Size);
-   Start = Buffer;
-   
-   // See if only a bit of the file is left or if 
-   if (Left < End - Buffer - Size)
+   if (d->Done == true)

    {
    {

-      if (Fd.Read(Buffer + Size,Left) == false)
+      if (EndSize <= 3 && Actual == 0)

         return false;
         return false;

-      End = Buffer + Size + Left;
-      Left = 0;
+      if (d->Size - (d->End - d->Buffer) < 4)
+        return true;
+      
+      // Append a double new line if one does not exist
+      unsigned int LineCount = 0;
+      for (const char *E = d->End - 1; E - d->End < 6 && (*E == '\n' || *E == '\r'); E--)
+        if (*E == '\n')
+           LineCount++;
+      if (LineCount < 2)
+      {
+        if ((unsigned)(d->End - d->Buffer) >= d->Size)
+           Resize(d->Size + 3);
+        for (; LineCount < 2; LineCount++)
+           *d->End++ = '\n';
+      }
+      
+      return true;

    }
    }

-   else
+   
+   return true;
+}
+                                                                       /*}}}*/
+// TagFile::Jump - Jump to a pre-recorded location in the file         /*{{{*/
+// ---------------------------------------------------------------------
+/* This jumps to a pre-recorded file location and reads the record
+   that is there */
+bool pkgTagFile::Jump(pkgTagSection &Tag,unsigned long long Offset)
+{
+   // We are within a buffer space of the next hit..
+   if (Offset >= d->iOffset && d->iOffset + (d->End - d->Start) > Offset)

    {
    {

-      if (Fd.Read(Buffer + Size, End - Buffer - Size) == false)
-        return false;
-      Left -= End - Buffer - Size;
-   }   
+      unsigned long long Dist = Offset - d->iOffset;
+      d->Start += Dist;
+      d->iOffset += Dist;
+      return Step(Tag);
+   }
+
+   // Reposition and reload..
+   d->iOffset = Offset;
+   d->Done = false;
+   if (d->Fd.Seek(Offset) == false)
+      return false;
+   d->End = d->Start = d->Buffer;
+   
+   if (Fill() == false)
+      return false;
+
+   if (Tag.Scan(d->Start, d->End - d->Start) == true)
+      return true;
+   
+   // This appends a double new line (for the real eof handling)
+   if (Fill() == false)
+      return false;
+   
+   if (Tag.Scan(d->Start, d->End - d->Start) == false)
+      return _error->Error(_("Unable to parse package file %s (2)"),d->Fd.Name().c_str());
+   

    return true;
 }
                                                                        /*}}}*/
 // TagSection::Scan - Scan for the end of the header information       /*{{{*/
 // ---------------------------------------------------------------------
    return true;
 }
                                                                        /*}}}*/
 // TagSection::Scan - Scan for the end of the header information       /*{{{*/
 // ---------------------------------------------------------------------

-/* This looks for the first double new line in the data stream. It also
-   indexes the tags in the section. */
+/* This looks for the first double new line in the data stream.
+   It also indexes the tags in the section. */

 bool pkgTagSection::Scan(const char *Start,unsigned long MaxLength)
 {
    const char *End = Start + MaxLength;
    Stop = Section = Start;
 bool pkgTagSection::Scan(const char *Start,unsigned long MaxLength)
 {
    const char *End = Start + MaxLength;
    Stop = Section = Start;

-   
+   memset(AlphaIndexes,0,sizeof(AlphaIndexes));
+
+   if (Stop == 0)
+      return false;
+

    TagCount = 0;
    TagCount = 0;

-   Indexes[TagCount++] = Stop - Section;
-   Stop++;
-   for (; Stop < End; Stop++)
+   while (TagCount+1 < sizeof(Indexes)/sizeof(Indexes[0]) && Stop < End)

    {
    {

-      if (Stop[-1] != '\n')
-        continue;
-      if (Stop[0] == '\n')
+       TrimRecord(true,End);
+
+      // Start a new index and add it to the hash
+      if (isspace(Stop[0]) == 0)
+      {
+        Indexes[TagCount++] = Stop - Section;
+        AlphaIndexes[AlphaHash(Stop,End)] = TagCount;
+      }
+
+      Stop = (const char *)memchr(Stop,'\n',End - Stop);
+      
+      if (Stop == 0)
+        return false;
+
+      for (; Stop+1 < End && Stop[1] == '\r'; Stop++);
+
+      // Double newline marks the end of the record
+      if (Stop+1 < End && Stop[1] == '\n')

       {
       {

-        // Extra one at the end to simplify find

         Indexes[TagCount] = Stop - Section;
         Indexes[TagCount] = Stop - Section;

-        for (; Stop[0] == '\n' && Stop < End; Stop++);
+        TrimRecord(false,End);

         return true;
         return true;

-        break;

       }
       
       }
       

-      if (isspace(Stop[0]) == 0)
-        Indexes[TagCount++] = Stop - Section;
-      
-      // Just in case.
-      if (TagCount > sizeof(Indexes)/sizeof(Indexes[0]))
-        TagCount = sizeof(Indexes)/sizeof(Indexes[0]);
-   }   
+      Stop++;
+   }
+

    return false;
 }
                                                                        /*}}}*/
    return false;
 }
                                                                        /*}}}*/

+// TagSection::TrimRecord - Trim off any garbage before/after a record /*{{{*/
+// ---------------------------------------------------------------------
+/* There should be exactly 2 newline at the end of the record, no more. */
+void pkgTagSection::TrimRecord(bool BeforeRecord, const char*& End)
+{
+   if (BeforeRecord == true)
+      return;
+   for (; Stop < End && (Stop[0] == '\n' || Stop[0] == '\r'); Stop++);
+}
+                                                                       /*}}}*/
+// TagSection::Trim - Trim off any trailing garbage                    /*{{{*/
+// ---------------------------------------------------------------------
+/* There should be exactly 1 newline at the end of the buffer, no more. */
+void pkgTagSection::Trim()
+{
+   for (; Stop > Section + 2 && (Stop[-2] == '\n' || Stop[-2] == '\r'); Stop--);
+}
+                                                                       /*}}}*/
+// TagSection::Exists - return True if a tag exists                    /*{{{*/
+bool pkgTagSection::Exists(const char* const Tag)
+{
+   unsigned int tmp;
+   return Find(Tag, tmp);
+}
+                                                                       /*}}}*/

 // TagSection::Find - Locate a tag                                     /*{{{*/
 // ---------------------------------------------------------------------
 /* This searches the section for a tag that matches the given string. */
 // TagSection::Find - Locate a tag                                     /*{{{*/
 // ---------------------------------------------------------------------
 /* This searches the section for a tag that matches the given string. */

-bool pkgTagSection::Find(const char *Tag,const char *&Start,
-                        const char *&End)
+bool pkgTagSection::Find(const char *Tag,unsigned int &Pos) const

 {
    unsigned int Length = strlen(Tag);
 {
    unsigned int Length = strlen(Tag);

-   for (unsigned int I = 0; I != TagCount; I++)
+   unsigned int I = AlphaIndexes[AlphaHash(Tag)];
+   if (I == 0)
+      return false;
+   I--;
+   
+   for (unsigned int Counter = 0; Counter != TagCount; Counter++, 
+       I = (I+1)%TagCount)

    {
    {

-      if (strncasecmp(Tag,Section + Indexes[I],Length) != 0)
+      const char *St;
+      St = Section + Indexes[I];
+      if (strncasecmp(Tag,St,Length) != 0)

         continue;
 
       // Make sure the colon is in the right place
         continue;
 
       // Make sure the colon is in the right place

-      const char *C = Section + Length + Indexes[I];
+      const char *C = St + Length;
+      for (; isspace(*C) != 0; C++);
+      if (*C != ':')
+        continue;
+      Pos = I;
+      return true;
+   }
+
+   Pos = 0;
+   return false;
+}
+                                                                       /*}}}*/
+// TagSection::Find - Locate a tag                                     /*{{{*/
+// ---------------------------------------------------------------------
+/* This searches the section for a tag that matches the given string. */
+bool pkgTagSection::Find(const char *Tag,const char *&Start,
+                        const char *&End) const
+{
+   unsigned int Length = strlen(Tag);
+   unsigned int I = AlphaIndexes[AlphaHash(Tag)];
+   if (I == 0)
+      return false;
+   I--;
+   
+   for (unsigned int Counter = 0; Counter != TagCount; Counter++, 
+       I = (I+1)%TagCount)
+   {
+      const char *St;
+      St = Section + Indexes[I];
+      if (strncasecmp(Tag,St,Length) != 0)
+        continue;
+      
+      // Make sure the colon is in the right place
+      const char *C = St + Length;

       for (; isspace(*C) != 0; C++);
       if (*C != ':')
         continue;
       for (; isspace(*C) != 0; C++);
       if (*C != ':')
         continue;


@@ -145,11 +365,295 @@ bool pkgTagSection::Find(const char *Tag,const char *&Start,
       // Strip off the gunk from the start end
       Start = C;
       End = Section + Indexes[I+1];
       // Strip off the gunk from the start end
       Start = C;
       End = Section + Indexes[I+1];

+      if (Start >= End)
+        return _error->Error("Internal parsing error");
+      

       for (; (isspace(*Start) != 0 || *Start == ':') && Start < End; Start++);
       for (; isspace(End[-1]) != 0 && End > Start; End--);
       for (; (isspace(*Start) != 0 || *Start == ':') && Start < End; Start++);
       for (; isspace(End[-1]) != 0 && End > Start; End--);

+      

       return true;
    }
       return true;
    }

+   

    Start = End = 0;
    return false;
 }
                                                                        /*}}}*/
    Start = End = 0;
    return false;
 }
                                                                        /*}}}*/

+// TagSection::FindS - Find a string                                   /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+string pkgTagSection::FindS(const char *Tag) const
+{
+   const char *Start;
+   const char *End;
+   if (Find(Tag,Start,End) == false)
+      return string();
+   return string(Start,End);      
+}
+                                                                       /*}}}*/
+// TagSection::FindI - Find an integer                                 /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+signed int pkgTagSection::FindI(const char *Tag,signed long Default) const
+{
+   const char *Start;
+   const char *Stop;
+   if (Find(Tag,Start,Stop) == false)
+      return Default;
+
+   // Copy it into a temp buffer so we can use strtol
+   char S[300];
+   if ((unsigned)(Stop - Start) >= sizeof(S))
+      return Default;
+   strncpy(S,Start,Stop-Start);
+   S[Stop - Start] = 0;
+   
+   char *End;
+   signed long Result = strtol(S,&End,10);
+   if (S == End)
+      return Default;
+   return Result;
+}
+                                                                       /*}}}*/
+// TagSection::FindULL - Find an unsigned long long integer            /*{{{*/
+// ---------------------------------------------------------------------
+/* */
+unsigned long long pkgTagSection::FindULL(const char *Tag, unsigned long long const &Default) const
+{
+   const char *Start;
+   const char *Stop;
+   if (Find(Tag,Start,Stop) == false)
+      return Default;
+
+   // Copy it into a temp buffer so we can use strtoull
+   char S[100];
+   if ((unsigned)(Stop - Start) >= sizeof(S))
+      return Default;
+   strncpy(S,Start,Stop-Start);
+   S[Stop - Start] = 0;
+   
+   char *End;
+   unsigned long long Result = strtoull(S,&End,10);
+   if (S == End)
+      return Default;
+   return Result;
+}
+                                                                       /*}}}*/
+// TagSection::FindFlag - Locate a yes/no type flag                    /*{{{*/
+// ---------------------------------------------------------------------
+/* The bits marked in Flag are masked on/off in Flags */
+bool pkgTagSection::FindFlag(const char *Tag,unsigned long &Flags,
+                            unsigned long Flag) const
+{
+   const char *Start;
+   const char *Stop;
+   if (Find(Tag,Start,Stop) == false)
+      return true;
+   return FindFlag(Flags, Flag, Start, Stop);
+}
+bool const pkgTagSection::FindFlag(unsigned long &Flags, unsigned long Flag,
+                                       char const* Start, char const* Stop)
+{
+   switch (StringToBool(string(Start, Stop)))
+   {
+      case 0:
+      Flags &= ~Flag;
+      return true;
+
+      case 1:
+      Flags |= Flag;
+      return true;
+
+      default:
+      _error->Warning("Unknown flag value: %s",string(Start,Stop).c_str());
+      return true;
+   }
+   return true;
+}
+                                                                       /*}}}*/
+// TFRewrite - Rewrite a control record                                        /*{{{*/
+// ---------------------------------------------------------------------
+/* This writes the control record to stdout rewriting it as necessary. The
+   override map item specificies the rewriting rules to follow. This also
+   takes the time to sort the feild list. */
+
+/* The order of this list is taken from dpkg source lib/parse.c the fieldinfos
+   array. */
+static const char *iTFRewritePackageOrder[] = {
+                          "Package",
+                          "Essential",
+                          "Status",
+                          "Priority",
+                          "Section",
+                          "Installed-Size",
+                          "Maintainer",
+                          "Original-Maintainer",
+                          "Architecture",
+                          "Source",
+                          "Version",
+                           "Revision",         // Obsolete
+                           "Config-Version",   // Obsolete
+                          "Replaces",
+                          "Provides",
+                          "Depends",
+                          "Pre-Depends",
+                          "Recommends",
+                          "Suggests",
+                          "Conflicts",
+                          "Breaks",
+                          "Conffiles",
+                          "Filename",
+                          "Size",
+                          "MD5Sum",
+                          "SHA1",
+                          "SHA256",
+                          "SHA512",
+                           "MSDOS-Filename",   // Obsolete
+                          "Description",
+                          0};
+static const char *iTFRewriteSourceOrder[] = {"Package",
+                                      "Source",
+                                      "Binary",
+                                      "Version",
+                                      "Priority",
+                                      "Section",
+                                      "Maintainer",
+                                     "Original-Maintainer",
+                                      "Build-Depends",
+                                      "Build-Depends-Indep",
+                                      "Build-Conflicts",
+                                      "Build-Conflicts-Indep",
+                                      "Architecture",
+                                      "Standards-Version",
+                                      "Format",
+                                      "Directory",
+                                      "Files",
+                                      0};   
+
+/* Two levels of initialization are used because gcc will set the symbol
+   size of an array to the length of the array, causing dynamic relinking 
+   errors. Doing this makes the symbol size constant */
+const char **TFRewritePackageOrder = iTFRewritePackageOrder;
+const char **TFRewriteSourceOrder = iTFRewriteSourceOrder;
+   
+bool TFRewrite(FILE *Output,pkgTagSection const &Tags,const char *Order[],
+              TFRewriteData *Rewrite)
+{
+   unsigned char Visited[256];   // Bit 1 is Order, Bit 2 is Rewrite
+   for (unsigned I = 0; I != 256; I++)
+      Visited[I] = 0;
+
+   // Set new tag up as necessary.
+   for (unsigned int J = 0; Rewrite != 0 && Rewrite[J].Tag != 0; J++)
+   {
+      if (Rewrite[J].NewTag == 0)
+        Rewrite[J].NewTag = Rewrite[J].Tag;
+   }
+   
+   // Write all all of the tags, in order.
+   for (unsigned int I = 0; Order[I] != 0; I++)
+   {
+      bool Rewritten = false;
+      
+      // See if this is a field that needs to be rewritten
+      for (unsigned int J = 0; Rewrite != 0 && Rewrite[J].Tag != 0; J++)
+      {
+        if (strcasecmp(Rewrite[J].Tag,Order[I]) == 0)
+        {
+           Visited[J] |= 2;
+           if (Rewrite[J].Rewrite != 0 && Rewrite[J].Rewrite[0] != 0)
+           {
+              if (isspace(Rewrite[J].Rewrite[0]))
+                 fprintf(Output,"%s:%s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+              else
+                 fprintf(Output,"%s: %s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+           }
+           
+           Rewritten = true;
+           break;
+        }
+      }      
+           
+      // See if it is in the fragment
+      unsigned Pos;
+      if (Tags.Find(Order[I],Pos) == false)
+        continue;
+      Visited[Pos] |= 1;
+
+      if (Rewritten == true)
+        continue;
+      
+      /* Write out this element, taking a moment to rewrite the tag
+         in case of changes of case. */
+      const char *Start;
+      const char *Stop;
+      Tags.Get(Start,Stop,Pos);
+      
+      if (fputs(Order[I],Output) < 0)
+        return _error->Errno("fputs","IO Error to output");
+      Start += strlen(Order[I]);
+      if (fwrite(Start,Stop - Start,1,Output) != 1)
+        return _error->Errno("fwrite","IO Error to output");
+      if (Stop[-1] != '\n')
+        fprintf(Output,"\n");
+   }   
+
+   // Now write all the old tags that were missed.
+   for (unsigned int I = 0; I != Tags.Count(); I++)
+   {
+      if ((Visited[I] & 1) == 1)
+        continue;
+
+      const char *Start;
+      const char *Stop;
+      Tags.Get(Start,Stop,I);
+      const char *End = Start;
+      for (; End < Stop && *End != ':'; End++);
+
+      // See if this is a field that needs to be rewritten
+      bool Rewritten = false;
+      for (unsigned int J = 0; Rewrite != 0 && Rewrite[J].Tag != 0; J++)
+      {
+        if (stringcasecmp(Start,End,Rewrite[J].Tag) == 0)
+        {
+           Visited[J] |= 2;
+           if (Rewrite[J].Rewrite != 0 && Rewrite[J].Rewrite[0] != 0)
+           {
+              if (isspace(Rewrite[J].Rewrite[0]))
+                 fprintf(Output,"%s:%s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+              else
+                 fprintf(Output,"%s: %s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+           }
+           
+           Rewritten = true;
+           break;
+        }
+      }      
+      
+      if (Rewritten == true)
+        continue;
+      
+      // Write out this element
+      if (fwrite(Start,Stop - Start,1,Output) != 1)
+        return _error->Errno("fwrite","IO Error to output");
+      if (Stop[-1] != '\n')
+        fprintf(Output,"\n");
+   }
+   
+   // Now write all the rewrites that were missed
+   for (unsigned int J = 0; Rewrite != 0 && Rewrite[J].Tag != 0; J++)
+   {
+      if ((Visited[J] & 2) == 2)
+        continue;
+      
+      if (Rewrite[J].Rewrite != 0 && Rewrite[J].Rewrite[0] != 0)
+      {
+        if (isspace(Rewrite[J].Rewrite[0]))
+           fprintf(Output,"%s:%s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+        else
+           fprintf(Output,"%s: %s\n",Rewrite[J].NewTag,Rewrite[J].Rewrite);
+      }      
+   }
+      
+   return true;
+}
+                                                                       /*}}}*/