path: root/src/dblspace_dec.c

/*
dblspace_dec.c

DMSDOS CVF-FAT module: [dbl|drv]space cluster read and decompression routines.

******************************************************************************
DMSDOS (compressed MSDOS filesystem support) for Linux
written 1995-1998 by Frank Gockel and Pavel Pisa

    (C) Copyright 1995-1998 by Frank Gockel
    (C) Copyright 1996-1998 by Pavel Pisa

Some code of dmsdos has been copied from the msdos filesystem
so there are the following additional copyrights:

    (C) Copyright 1992,1993 by Werner Almesberger (msdos filesystem)
    (C) Copyright 1994,1995 by Jacques Gelinas (mmap code)
    (C) Copyright 1992-1995 by Linus Torvalds

DMSDOS was inspired by the THS filesystem (a simple doublespace
DS-0-2 compressed read-only filesystem) written 1994 by Thomas Scheuermann.

The DMSDOS code is distributed under the Gnu General Public Licence.
See file COPYING for details.
******************************************************************************

*/

#ifdef __KERNEL__
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/locks.h>
#include <linux/fs.h>
#include <linux/malloc.h>
#include <linux/msdos_fs.h>
#include <asm/system.h>
#include <asm/segment.h>
#include <asm/bitops.h>
#include <asm/byteorder.h>
#endif

#include "dmsdos.h"

#ifdef __DMSDOS_LIB__
/* some interface hacks */
#include"lib_interface.h"
#include<malloc.h>
#include<string.h>
#include<errno.h>
#endif

#ifdef __GNUC__
#define INLINE static inline
#else
/* non-gnu compilers may not like inline */
#define INLINE static
#endif

/* we always need DS decompression */

#if defined(__GNUC__) && defined(__i386__) && defined(USE_ASM)
#define USE_GNU_ASM_i386

/* copy block, overlaping part is replaced by repeat of previous part */
/* pointers and counter are modified to point after block */
#define M_MOVSB(D,S,C) \
__asm__ /*__volatile__*/(\
	"cld\n\t" \
	"rep\n\t" \
	"movsb\n" \
	:"=D" (D),"=S" (S),"=c" (C) \
	:"0" (D),"1" (S),"2" (C) \
	:"memory")


#else

#ifdef __GNUC__
/* non-gnu compilers may not like warning directive */
#warning USE_GNU_ASM_I386 not defined, using "C" equivalent
#endif

#define M_MOVSB(D,S,C) for(;(C);(C)--) *((__u8*)(D)++)=*((__u8*)(S)++)

#endif

#if !defined(le16_to_cpu)
    /* for old kernel versions - works only on i386 */
    #define le16_to_cpu(v) (v)
#endif

/* for reading and writting from/to bitstream */
typedef
 struct {
   __u32 buf;	/* bit buffer */
     int pb;	/* already readed bits from buf */
   __u16 *pd;	/* first not readed input data */
   __u16 *pe;	/* after end of data */
 } bits_t;

const unsigned dblb_bmsk[]=
   {0x0,0x1,0x3,0x7,0xF,0x1F,0x3F,0x7F,0xFF,
    0x1FF,0x3FF,0x7FF,0xFFF,0x1FFF,0x3FFF,0x7FFF,0xFFFF};

/* read next 16 bits from input */
#define RDN_G16(bits) \
   { \
    (bits).buf>>=16; \
    (bits).pb-=16; \
    if((bits).pd<(bits).pe) \
    { \
     (bits).buf|=((__u32)(le16_to_cpu(*((bits).pd++))))<<16; \
    }; \
   }

/* prepares at least 16 bits for reading */
#define RDN_PR(bits,u) \
   { \
    if((bits).pb>=16) RDN_G16(bits); \
    u=(bits).buf>>(bits).pb; \
   }

/* initializes reading from bitstream */
INLINE void dblb_rdi(bits_t *pbits,void *pin,unsigned lin)
{
  pbits->pb=32;
  pbits->pd=(__u16*)pin;
  pbits->pe=pbits->pd+((lin+1)>>1);
}

/* reads n<=16 bits from bitstream *pbits */
INLINE unsigned dblb_rdn(bits_t *pbits,int n)
{
  unsigned u;
  RDN_PR(*pbits,u);
  pbits->pb+=n;
  u&=dblb_bmsk[n];
  return u;
}

INLINE int dblb_rdoffs(bits_t *pbits)
{ unsigned u;
  RDN_PR(*pbits,u);
  switch (u&3)
  {
    case 0: case 2:
      pbits->pb+=1+6;  return 63&(u>>1);
    case 1:
      pbits->pb+=2+8;  return (255&(u>>2))+64;
  }
  pbits->pb+=2+12; return (4095&(u>>2))+320;
}

INLINE int dblb_rdlen(bits_t *pbits)
{ unsigned u;
  RDN_PR(*pbits,u);
  switch (u&15)
  { case  1: case  3: case  5: case  7:
    case  9: case 11: case 13: case 15:
      pbits->pb++;     return 3;
    case  2: case  6:
    case 10: case 14:
      pbits->pb+=2+1;  return (1&(u>>2))+4;
    case  4: case 12:
      pbits->pb+=3+2;  return (3&(u>>3))+6;
    case  8:
      pbits->pb+=4+3;  return (7&(u>>4))+10;
    case  0: ;
  }
  switch ((u>>4)&15)
  { case  1: case  3: case  5: case  7:
    case  9: case 11: case 13: case 15:
      pbits->pb+=5+4;  return (15&(u>>5))+18;
    case  2: case  6:
    case 10: case 14:
      pbits->pb+=6+5;  return (31&(u>>6))+34;
    case  4: case 12:
      pbits->pb+=7+6;  return (63&(u>>7))+66;
    case  8:
      pbits->pb+=8+7;  return (127&(u>>8))+130;
    case  0: ;
  }
  pbits->pb+=9;
  if(u&256) return dblb_rdn(pbits,8)+258;
  return -1;
}

INLINE int dblb_decrep(bits_t *pbits, __u8 **p, void *pout, __u8 *pend,
		 int repoffs, int k, int flg)
{ int replen;
  __u8 *r;

  if(repoffs==0){LOG_DECOMP("DMSDOS: decrb: zero offset ?\n");return -2;}
  if(repoffs==0x113f)
  { 
    int pos=*p-(__u8*)pout;
    LOG_DECOMP("DMSDOS: decrb: 0x113f sync found.\n");
    if((pos%512) && !(flg&0x4000))
    { LOG_DECOMP("DMSDOS: decrb: sync at decompressed pos %d ?\n",pos);
      return -2;
    }
    return 0;
  }
  replen=dblb_rdlen(pbits)+k;

  if(replen<=0)
    {LOG_DECOMP("DMSDOS: decrb: illegal count ?\n");return -2;}
  if((__u8*)pout+repoffs>*p)
    {LOG_DECOMP("DMSDOS: decrb: of>pos ?\n");return -2;}
  if(*p+replen>pend)
    {LOG_DECOMP("DMSDOS: decrb: output overfill ?\n");return -2;}
  r=*p-repoffs;
  M_MOVSB(*p,r,replen);
  return 0;
}

/* DS decompression */
/* flg=0x4000 is used, when called from stacker_dec.c, because of
   stacker does not store original cluster size and it can mean,
   that last cluster in file can be ended by garbage */
int ds_dec(void* pin,int lin, void* pout, int lout, int flg)
{ 
  __u8 *p, *pend;
  unsigned u, repoffs;
  int r;
  bits_t bits;

  dblb_rdi(&bits,pin,lin);
  p=(__u8*)pout;pend=p+lout;
  if((dblb_rdn(&bits,16))!=0x5344) return -1;
    
  u=dblb_rdn(&bits,16);
  LOG_DECOMP("DMSDOS: DS decompression version %d\n",u);
  
  do
  { r=0;
    RDN_PR(bits,u);
    switch(u&3)
    {
      case 0:
	bits.pb+=2+6;
	repoffs=(u>>2)&63;
	r=dblb_decrep(&bits,&p,pout,pend,repoffs,-1,flg);
	break;
      case 1:
	bits.pb+=2+7;
	*(p++)=(u>>2)|128;
	break;
      case 2:
	bits.pb+=2+7;
	*(p++)=(u>>2)&127;
	break;
      case 3:
	if(u&4) {  bits.pb+=3+12; repoffs=((u>>3)&4095)+320; }
	else  {  bits.pb+=3+8;  repoffs=((u>>3)&255)+64; };
	r=dblb_decrep(&bits,&p,pout,pend,repoffs,-1,flg);
	break;
    }
  }while((r==0)&&(p<pend));
  
  if(r<0) return r;

  if(!(flg&0x4000))
  { 
    u=dblb_rdn(&bits,3);if(u==7) u=dblb_rdn(&bits,12)+320;
    if(u!=0x113f)
    { LOG_DECOMP("DMSDOS: decrb: final sync not found?\n");
      return -2;
    }
  }

  return p-(__u8*)pout;
}

/* JM decompression */
int jm_dec(void* pin,int lin, void* pout, int lout, int flg)
{ 
  __u8 *p, *pend;
  unsigned u, repoffs;
  int r;
  bits_t bits;

  dblb_rdi(&bits,pin,lin);
  p=(__u8*)pout;pend=p+lout;
  if((dblb_rdn(&bits,16))!=0x4D4A) return -1;

  u=dblb_rdn(&bits,16);
  LOG_DECOMP("DMSDOS: JM decompression version %d\n",u);

  do
  { r=0;
    RDN_PR(bits,u);
    switch(u&3)
    {
      case 0:
      case 2:
	bits.pb+=8;
	*(p++)=(u>>1)&127;
	break;
      case 1:
	bits.pb+=2;
	repoffs=dblb_rdoffs(&bits);
	r=dblb_decrep(&bits,&p,pout,pend,repoffs,0,flg);
	break;
      case 3:
	bits.pb+=9;
	*(p++)=((u>>2)&127)|128;
	break;
    }
  }
  while((r==0)&&(p<pend));

  if(r<0) return r;

  if(!(flg&0x4000))
  { 
    u=dblb_rdn(&bits,2);if(u==1) u=dblb_rdoffs(&bits);
    if(u!=0x113f)
    { LOG_DECOMP("DMSDOS: decrb: final sync not found?\n");
      return -2;
    }
  }

  return p-(__u8*)pout;
}


/* decompress a compressed doublespace/drivespace cluster clusterk to clusterd
*/
int dbl_decompress(unsigned char*clusterd, unsigned char*clusterk,
               Mdfat_entry*mde)
{
	int sekcount;
	int r, lin, lout;

	sekcount=mde->size_hi_minus_1+1;
	lin=(mde->size_lo_minus_1+1)*SECTOR_SIZE;
	lout=(mde->size_hi_minus_1+1)*SECTOR_SIZE;

  switch(clusterk[0]+((int)clusterk[1]<<8)+
         ((int)clusterk[2]<<16)+((int)clusterk[3]<<24))
  {
    case DS_0_0:
    case DS_0_1:
    case DS_0_2:
        LOG_DECOMP("DMSDOS: decompressing DS-0-x\n");
        r=ds_dec(clusterk,lin,clusterd,lout,0);
        if(r<=0)
        { printk(KERN_ERR "DMSDOS: error in DS-0-x compressed data.\n");
          return -2;
        }	
        LOG_DECOMP("DMSDOS: decompress finished.\n");
	return 0;
	
    case JM_0_0:
    case JM_0_1:
        LOG_DECOMP("DMSDOS: decompressing JM-0-x\n");
        r=jm_dec(clusterk,lin,clusterd,lout,0);
	if(r<=0)
	{ printk(KERN_ERR "DMSDOS: error in JM-0-x compressed data.\n");
	  return -2;
	}
	LOG_DECOMP("DMSDOS: decompress finished.\n");
	return 0;

#ifdef DMSDOS_CONFIG_DRVSP3
    case SQ_0_0:
        LOG_DECOMP("DMSDOS: decompressing SQ-0-0\n"); 
        r=sq_dec(clusterk,lin,clusterd,lout,0);
        if(r<=0)
        { printk(KERN_ERR "DMSDOS: SQ-0-0 decompression failed.\n");   
          return -1;
        }
	LOG_DECOMP("DMSDOS: decompress finished.\n");
	return 0;
#endif
        
    default:	
	printk(KERN_ERR "DMSDOS: compression method not recognized.\n");
	return -1;
	
  } /* end switch */
  
  return 0;
}

#ifdef DMSDOS_CONFIG_DRVSP3
/* read the fragments of a fragmented cluster and assemble them */
/* warning: this is guessed from low level viewing drivespace 3 disks
   and may be awfully wrong... we'll see... */
int read_fragments(struct super_block*sb,Mdfat_entry*mde, unsigned char*data)
{ struct buffer_head*bh;
  struct buffer_head*bh2;
  int fragcount;
  int fragpnt;
  int offset;
  int sector;
  int seccount;
  int membytes;
  int safety_counter;
  Dblsb*dblsb=MSDOS_SB(sb)->private_data;
    
  /* read first sector */
  sector=mde->sector_minus_1+1;
  bh=raw_bread(sb,sector);
  if(bh==NULL)return -EIO;
  fragcount=bh->b_data[0];
  if(bh->b_data[1]!=0||bh->b_data[2]!=0||bh->b_data[3]!=0||fragcount<=0||
     fragcount>dblsb->s_sectperclust)
  { printk(KERN_ERR "DMSDOS: read_fragments: cluster does not look fragmented!\n");
    raw_brelse(sb,bh);
    return -EIO;
  }
  membytes=dblsb->s_sectperclust*SECTOR_SIZE;
  if(mde->flags&1)
  { offset=0;
    safety_counter=0;
  }
  else
  { offset=(fragcount+1)*4;  
    /* copy the rest of the sector */
    memcpy(data,&(bh->b_data[offset]),SECTOR_SIZE-offset);
    data+=(SECTOR_SIZE-offset);
    safety_counter=SECTOR_SIZE-offset;
  }
  ++sector;
  seccount=mde->size_lo_minus_1;
  fragpnt=1;
  while(fragpnt<=fragcount)
  { if(fragpnt>1)
    { /* read next fragment pointers */
      seccount=bh->b_data[fragpnt*4+3];
      seccount&=0xff;
      seccount/=4;
      seccount+=1;
      sector=bh->b_data[fragpnt*4];
      sector&=0xff;
      sector+=bh->b_data[fragpnt*4+1]<<8;
      sector&=0xffff;
      sector+=bh->b_data[fragpnt*4+2]<<16;
      sector&=0xffffff;
      sector+=1;
    }
    while(seccount)
    { bh2=raw_bread(sb,sector);
      if(bh2==NULL){raw_brelse(sb,bh);return -EIO;}
      /*printk(KERN_DEBUG "DMSDOS: read_fragments: data=0x%p safety_counter=0x%x sector=%d\n",
             data,safety_counter,sector);*/
      if(safety_counter+SECTOR_SIZE>membytes)
      { int maxbytes=membytes-safety_counter;
        if(maxbytes<=0)
        { printk(KERN_WARNING "DMSDOS: read_fragments: safety_counter exceeds membytes!\n");
          raw_brelse(sb,bh2);
          raw_brelse(sb,bh);
          return -EIO;
        }
        printk(KERN_DEBUG "DMSDOS: read_fragments: size limit reached.\n");
        memcpy(data,bh2->b_data,maxbytes);
        raw_brelse(sb,bh2);
        raw_brelse(sb,bh);
        return membytes;
      }
      else memcpy(data,bh2->b_data,SECTOR_SIZE);
      raw_brelse(sb,bh2);
      data+=SECTOR_SIZE;
      safety_counter+=SECTOR_SIZE;
      ++sector;
      --seccount;
    }
    ++fragpnt;
  }
  raw_brelse(sb,bh);
  
  return safety_counter;
}
#endif

#ifdef DMSDOS_CONFIG_DBL
/* read a complete file cluster and decompress it if necessary; 
   this function is unable to read cluster 0 (CVF root directory) */
/* returns cluster length in bytes or error (<0) */
/* this function is specific to doublespace/drivespace */
int dbl_read_cluster(struct super_block*sb,
                        unsigned char*clusterd, int clusternr)
{	Mdfat_entry mde;
	unsigned char*clusterk;
	int nr_of_sectors;
	int i;
	struct buffer_head*bh;
	int membytes;
	int sector;
	Dblsb*dblsb=MSDOS_SB(sb)->private_data;

	LOG_CLUST("DMSDOS: dbl_read_cluster %d\n",clusternr);

	dbl_mdfat_value(sb,clusternr,NULL,&mde);
	
	if((mde.flags&2)==0)
	{ /* hmm, cluster is unused (it's a lost or ghost cluster)
	     and contains undefined data, but it *is* readable */
	  /* oh no, it contains ZEROD data per definition...
	     this is really important */
	  if(clusterd) /*clusterd==NULL means read_ahead - don't do anything*/
	         memset(clusterd,0,dblsb->s_sectperclust*SECTOR_SIZE);
	  LOG_CLUST("DMSDOS: lost cluster %d detected\n",clusternr);
	  return 0; /* yes, has length zero */
	}
	
        sector=mde.sector_minus_1+1;
        nr_of_sectors=mde.size_lo_minus_1+1;/* real sectors on disk */
        if(nr_of_sectors>dblsb->s_sectperclust)
        { printk(KERN_WARNING "DMSDOS: read_cluster: mdfat sectors > sectperclust, cutting\n");
          nr_of_sectors=dblsb->s_sectperclust;
        }
        
        if(clusterd==NULL)
        { /* read-ahead */
          dblspace_reada(sb,sector,nr_of_sectors);
          return 0;
        }
        
#ifdef DMSDOS_CONFIG_DRVSP3
        if(mde.unknown&2)
        { /* we suppose this bit indicates a fragmented cluster */
          /* this is *not sure* and may be awfully wrong - reports
             whether success or not are welcome
          */
          
          LOG_CLUST("DMSDOS: cluster %d has unknown bit #1 set. Assuming fragmented cluster.\n",
                 clusternr);
          
          if(mde.flags&1) /* not compressed */
          { LOG_CLUST("DMSDOS: uncompressed fragmented cluster\n");
            i=read_fragments(sb,&mde,clusterd);
            if(i<0)
            { printk(KERN_ERR "DMSDOS: read_fragments failed!\n");
              return i;
            }
          }
          else
          { LOG_CLUST("DMSDOS: compressed fragmented cluster\n");
            membytes=SECTOR_SIZE*dblsb->s_sectperclust;
            
            clusterk=(unsigned char*)MALLOC(membytes);
            if(clusterk==NULL)
            { printk(KERN_ERR "DMSDOS: no memory for decompression!\n");
              return -2;
            }
            /* returns length in bytes */
            i=read_fragments(sb,&mde,clusterk);
            if(i<0)
            { printk(KERN_ERR "DMSDOS: read_fragments failed!\n"); 
              return i;
            }
            /* correct wrong size_lo information (sq_dec needs it) */
            if(i>0)mde.size_lo_minus_1=(i-1)/SECTOR_SIZE;
            i=dbl_decompress(clusterd,clusterk,&mde);
           
            FREE(clusterk);
           
            if(i)
            { printk(KERN_ERR "DMSDOS: decompression of cluster %d in CVF failed.\n",
                    clusternr);
              return i;
            }
            
          }
        
          /* the slack must be zerod out */
          if(mde.size_hi_minus_1+1<dblsb->s_sectperclust)
          { memset(clusterd+(mde.size_hi_minus_1+1)*SECTOR_SIZE,0,
                  (dblsb->s_sectperclust-mde.size_hi_minus_1-1)*
                                                              SECTOR_SIZE);
          }
        
	  return (mde.size_hi_minus_1+1)*SECTOR_SIZE;
          
        } /* end of read routine for fragmented cluster */
#endif

        if(mde.flags&1)
        {  /* cluster is not compressed */
	   for(i=0;i<nr_of_sectors;++i)
	   {  bh=raw_bread(sb,sector+i);
	      if(bh==NULL)return -EIO;
	      memcpy(&clusterd[i*SECTOR_SIZE],bh->b_data,SECTOR_SIZE);
	      raw_brelse(sb,bh);
	   }
        }
        else
        {  /* cluster is compressed */
           
           membytes=SECTOR_SIZE*nr_of_sectors;
           
           clusterk=(unsigned char*)MALLOC(membytes);
           if(clusterk==NULL)
           { printk(KERN_ERR "DMSDOS: no memory for decompression!\n");
             return -2;
           }
           
           for(i=0;i<nr_of_sectors;++i)
	   {  bh=raw_bread(sb,sector+i);
	      if(bh==NULL)
	      { FREE(clusterk);
	        return -EIO;
	      }
	      memcpy(&clusterk[i*SECTOR_SIZE],bh->b_data,SECTOR_SIZE);
	      raw_brelse(sb,bh);
	   }
	   
           i=dbl_decompress(clusterd,clusterk,&mde);
           
           FREE(clusterk);
           
           if(i)
           { printk(KERN_ERR "DMSDOS: decompression of cluster %d in CVF failed.\n",
                    clusternr);
             return i;
           }
           
        }

        /* the slack must be zerod out */
        if(mde.size_hi_minus_1+1<dblsb->s_sectperclust)
        { memset(clusterd+(mde.size_hi_minus_1+1)*SECTOR_SIZE,0,
                  (dblsb->s_sectperclust-mde.size_hi_minus_1-1)*
                                                              SECTOR_SIZE);
        }
        
	return (mde.size_hi_minus_1+1)*SECTOR_SIZE;
}
#endif

/* read a complete file cluster and decompress it if necessary; 
   it must be able to read directories
   this function is unable to read cluster 0 (CVF root directory) */
/* returns cluster length in bytes or error (<0) */
/* this function is a generic wrapper */
int dmsdos_read_cluster(struct super_block*sb,
                        unsigned char*clusterd, int clusternr)
{ int ret;
  Dblsb*dblsb=MSDOS_SB(sb)->private_data;
         
  LOG_CLUST("DMSDOS: read_cluster %d\n",clusternr);

  switch(dblsb->s_cvf_version)
  {
#ifdef DMSDOS_CONFIG_DBL  
    case DBLSP:
    case DRVSP:
    case DRVSP3:
      ret=dbl_read_cluster(sb,clusterd,clusternr);
      break;
#endif
#ifdef DMSDOS_CONFIG_STAC
    case STAC3:
    case STAC4:
      ret=stac_read_cluster(sb,clusterd,clusternr);
      break;
#endif
    default:
      printk(KERN_ERR "DMSDOS: read_cluster: illegal cvf version flag!\n");
      ret=-EIO;
  }
  
  return ret;
}