sca_aux.c

Solaris操作系统下的过滤驱动程序, C源码程序.

/*
 * Copyright (c) 1997-2003 Erez Zadok
 * Copyright (c) 2001-2003 Stony Brook University
 * Copyright (c) 1997-2000 Columbia University
 *
 * For specific licensing information, see the COPYING file distributed with
 * this package, or get one from ftp://ftp.filesystems.org/pub/fist/COPYING.
 *
 * This Copyright notice must be kept intact and distributed with all
 * fistgen sources INCLUDING sources generated by fistgen.
 */
/*
 *  $Id: sca_aux.c,v 1.5 2002/12/27 20:19:06 ezk Exp $
 */
#include "sca_aux.h"

int chunksize = DEFAULT_CHUNK_SZ;  /* Size of an encoded chunk */
int do_fast_tails = 0;		   /* Use fast tail algorithm */

int encode_counter = 0;		/* Usage counters */
int decode_counter = 0;
int write_counter = 0;


int
get_page(int gzfd, struct fistfs_header *hdr, int pageno,
	 unsigned char **out, int *outlen)
{
  unsigned char *data = NULL;		/* mmap gzfd */
  struct stat sb;
  unsigned char *ptr;
  int len, rc=0, back;

  if (pageno < 0)
    return(-1);
  if (pageno > hdr->num_pages)
    return(-1);
  if (!(do_fast_tails) && (pageno == hdr->num_pages))
    return(-1);

  if ((fstat(gzfd,&sb)) < 0)
    return(-1);
  if ((data = mmap((void *)data,sb.st_size,PROT_READ,
		   MAP_PRIVATE,gzfd,0)) == NULL) {
    return(-1);
  }

  if (pageno == 0) {
    ptr = data;
    if (hdr->num_pages == 0) {
      len = sb.st_size;		/* Fast-tail append */
      rc = 1;
    } else {
      len = hdr->offsets[0];
    }
  } else {
    ptr = &(data[hdr->offsets[pageno-1]]);
    if (do_fast_tails && (pageno == hdr->num_pages)) { /* Possible fast tail */
      len = sb.st_size - hdr->offsets[pageno - 1];
      rc = 1;
    } else {
      len = hdr->offsets[pageno] - hdr->offsets[pageno-1];
    }
  }

  if (rc) {			/* Fast tail, already done */
    (*out) = (unsigned char *) malloc (len * sizeof(unsigned char));
    if ((*out) == NULL) {
      perror("malloc");
      return(-1);
    }
    memcpy(*out, ptr, len);
    *outlen = len;
  } else {
    if ((rc = sca_decode_page(ptr, len, out, &back)) < 0) {
      fprintf(stderr, "sca_decode_page returns %d\n", rc);
      return(-1);
    }
    *outlen = rc;
  }
  munmap(data, sb.st_size);
  return(*outlen);
}


int
put_page(int gzfd, struct fistfs_header *hdr, int pageno,
	 unsigned char *data, int datalen)
{
  unsigned char *encdata = NULL;	/* The new data to write */
  unsigned char *tmppage = NULL;	/* Temp page for shifting */
  int rc, curlen, delta, cnt, enclen, tmp;
  struct stat sb;

  write_counter++;

  if (fstat(gzfd, &sb) < 0) {
    return(-1);
  }

  if ((datalen < chunksize) &&
      (pageno == hdr->num_pages) &&
      (do_fast_tails)) {
    /* A fast tail, just write it at the end */
    if(pageno > 0) {
      cnt = hdr->offsets[hdr->num_pages-1];
      hdr->real_size -= (sb.st_size - cnt);
      hdr->real_size += datalen;
    }
    else {
      hdr->real_size = datalen;
      cnt = 0;
    }
    lseek(gzfd, cnt, SEEK_SET);	/* The beginning is the end */
    rc = 0; tmp = 0;
    while(tmp < datalen) {
      rc = write(gzfd, data, datalen);
      if (rc < 0) {
	return(-1);
      } else {
	tmp += rc;
      }
    }
    ftruncate(gzfd, cnt+datalen);
    return(0);
  }

  if ((enclen = sca_encode_page(data, datalen, &encdata, &enclen)) < 0) {
    return(enclen);
  }

  if (pageno < hdr->num_pages) { /* Replace an existing page */
    if ((tmppage = (unsigned char *) malloc(sizeof(unsigned char) * chunksize))
	== NULL) {
      return(-1);
    }

    if (pageno == 0) {	/* replace first page */
      curlen = hdr->offsets[0];
    } else {
      curlen = hdr->offsets[pageno] - hdr->offsets[pageno-1];
    }
    delta = curlen - enclen;	/* Positive, it got smaller, shift in
				   from here to end by delta bytes.
				   Negative, it got bigger, shift out
				   from end to here by delta bytes */

    /* Update size  */
    hdr->real_size -= delta;

    /* Do shifting as appropriate */
    if (delta > 0) {
      tmp = lseek(gzfd, hdr->offsets[pageno], SEEK_SET);
      while (tmp<sb.st_size) {
	rc = read(gzfd, tmppage, chunksize);
	lseek(gzfd, tmp-delta, SEEK_SET);
	write(gzfd, tmppage, rc);
	tmp += rc;
	lseek(gzfd, tmp, SEEK_SET);
      }
      ftruncate(gzfd, sb.st_size-delta);
    } else if (delta < 0) {
      tmp = sb.st_size - hdr->offsets[pageno];
      while (tmp > 0) {
	if (tmp > chunksize) {
	  lseek(gzfd, hdr->offsets[pageno] + tmp - chunksize, SEEK_SET);
	  rc = read(gzfd, tmppage, chunksize);
	  lseek(gzfd,hdr->offsets[pageno] + tmp + - chunksize +(-delta),
		SEEK_SET);
	  write(gzfd, tmppage, rc);
	} else {
	  lseek(gzfd, hdr->offsets[pageno], SEEK_SET);
	  rc = read(gzfd, tmppage, tmp);
	  lseek(gzfd, hdr->offsets[pageno] + (-delta), SEEK_SET);
	  write(gzfd, tmppage, tmp);
	}
	tmp -= chunksize;
      }
    } /* Else it happens to fit exactly! no shifting necessary! */

    /* Update index table */
    for (tmp=pageno; tmp<hdr->num_pages; tmp++) {
      hdr->offsets[tmp] -= delta;
    }

    lseek(gzfd, hdr->offsets[pageno-1], SEEK_SET); /* move to correct offset */
    free(tmppage);
  } else {			/* Add a new page somewhere later in the
				   file */
    delta = pageno - hdr->num_pages;

    hdr->real_size += datalen;

    hdr->num_pages += (delta + 1);
    if ((hdr->offsets = realloc(hdr->offsets, (hdr->num_pages * sizeof(off_t))))
	== NULL) {
      return(-1);
    }

    for(; delta>0; delta--) {
      /* Insert an empty page and an index entry for same */
      fprintf(stderr, "Should insert an empty page here\n");
      return(-1);		/* For now */
    }

    if (hdr->num_pages == 1) {
      hdr->offsets[pageno] = enclen;
      lseek(gzfd, 0, SEEK_SET);
    } else {
      hdr->offsets[pageno] = enclen + hdr->offsets[pageno-1];
      lseek(gzfd, hdr->offsets[pageno-1], SEEK_SET);
    }
  }

  cnt = 0;
  while(cnt < enclen) {
    rc = write(gzfd, encdata, enclen);
    if (rc > 0) {
      cnt+=rc;
    } else {
      /* Write error */
      return(-1);
    }
  }

  free(encdata);		/* This was malloc'ed for us */
  return(0);
}


int
read_idx(char *filename, struct fistfs_header *hdr)
{
  int fd, i;

  if (filename == NULL)
    return(-1);
  if ((fd = open(filename, O_RDONLY)) < 0) {
    return(-1);
  }

  if ((read(fd, &(hdr->num_pages), sizeof(off_t))) < (sizeof(off_t))) {
    fprintf(stderr, "Short read from index file!\n");
    return(-1);
  }

  hdr->flags = hdr->num_pages & 0xfff00000;
  hdr->num_pages &= 0xfffff;

  if ((read(fd, &(hdr->real_size), sizeof(off_t))) < (sizeof(off_t))) {
    fprintf(stderr, "Short read from index file!\n");
    return(-1);
  }

  hdr->offsets = (off_t *) malloc(sizeof(off_t) * hdr->num_pages);
  if (hdr->offsets == NULL) {
    return(-1);
  }

  for(i=0; i<hdr->num_pages; i++) {
    if((read(fd, &(hdr->offsets[i]), sizeof(off_t))) != (sizeof(off_t))) {
      fprintf(stderr, "Short read from index file!\n");
      return(-1);
    }
  }
  close(fd);
  return(hdr->num_pages);
}


int
write_idx(char *filename, struct fistfs_header *hdr)
{
  int fd, i;

  if ((fd = open(filename, O_RDWR|O_CREAT|O_TRUNC, 0600)) < 0)
    return(-1);

  if(write(fd, &(hdr->num_pages), sizeof(int)) != (sizeof(int))) {
    fprintf(stderr, "Short write to index file!\n");
    return(-1);
  }

  if(write(fd, &(hdr->real_size), sizeof(int)) != (sizeof(int))) {
    fprintf(stderr, "Short write to index file!\n");
    return(-1);
  }

  for(i=0; i<hdr->num_pages; i++) {
    if(write(fd, &(hdr->offsets[i]), sizeof(off_t)) != (sizeof(off_t))) {
      fprintf(stderr, "Short write to index file!\n");
      return(-1);
    }
  }

  close(fd);
  return(hdr->num_pages);
}