/*
   "kernel_string_pool.c"

   created by: grayspace aka J. Leveille
   for: UbixOS Project
   date: May 11, 2002

   purpose: to provide a mechanism for maintaining a pool of strings
            for use by the kernel without unnecessary waste of memory

   NOTEs:
      - for now only ASCII is supported
      - done quickly, pretty hacky

   TODO:
      - expand to support unicode
      - use huffman encoding instead

   $Id$
*/

#include "../../grayspace-misc/gsdefines.h"
#include "../../sys/include/misc/kernel_string_pool.h"

// returns pointer to character *after* substring read
static char * ReadSubString( char * p_dst, const BYTEg * p_substr )
{
   char * p_retval;
   char * p_curdst;
   const char * p_cursubstr;

   p_retval = p_dst + (*p_substr) + 1;
   p_cursubstr = (const char *) (p_substr + 1);

   do
   {
      *p_curdst = *p_cursubstr;
      p_cursubstr++;
      p_curdst++;
   }
   while( p_curdst < p_retval );

   return p_retval;
}

// returns pointer to character *after* space appended after substring read
static char * ReadSubStringAppendSpace( char * p_dst, const BYTEg * p_substr )
{
   char * p_retval;
      
   p_retval = ReadSubString( p_dst, p_substr );
   *p_retval = ' ';
   p_retval++;

   return p_retval;
}

// gets the substring indicated by 'id' from the pool 'p_ksp' into 'p_dst'
// - returns pointer to 'p_dst'
char * KSTR_POOL_GetString( KSTR_POOL * p_ksp, char * p_dst, DWORDg id )
{
   DWORDg numsubstrs;
   DWORDg offset;
   char * p_curdst;
   const BYTEg * p_substr;
   const BYTEg * p_krnstr;

   numsubstrs = (id & 0xFF);
   offset = (id >> 8);
   p_krnstr = p_ksp->p_krnstrs + offset;

   while( numsubstrs )
   {
      // find substring
      offset = (DWORDg) *p_krnstr;
      p_krnstr++;
      if( offset == 255 )
      {
         offset += (((DWORDg) *p_krnstr)<<8);
         p_krnstr++;
         offset += (DWORDg) *p_krnstr;
         p_krnstr++;
      }
      p_substr =  p_ksp->p_substrs + p_ksp->p_substr_off[offset];

      // append to destination and also append a space
      p_curdst = ReadSubStringAppendSpace( p_curdst, p_substr );

      // one less sub string
      numsubstrs--;
   }

   // find final substring
   offset = (DWORDg) *p_krnstr;
   p_krnstr++;
   if( offset == 255 )
   {
      offset += (((DWORDg) *p_krnstr)<<8);
      p_krnstr++;
      offset += (DWORDg) *p_krnstr;
      p_krnstr++;
   }
   p_substr =  p_ksp->p_substrs + p_ksp->p_substr_off[offset];

   // append to destination
   p_curdst = ReadSubString( p_curdst, p_substr );

   return p_dst;
}