/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2003-2008 H. Peter Anvin - All Rights Reserved
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <syslinux/zio.h>

#include "file.h"
#include "zlib.h"

/*
 * zopen.c
 *
 * Open an ordinary file, possibly compressed; if so, insert
 * an appropriate decompressor.
 */

int __file_get_block(struct file_info *fp);
int __file_close(struct file_info *fp);

static ssize_t gzip_file_read(struct file_info *, void *, size_t);
static int gzip_file_close(struct file_info *);

static const struct input_dev gzip_file_dev = {
  .dev_magic = __DEV_MAGIC,
  .flags     = __DEV_FILE | __DEV_INPUT,
  .fileflags = O_RDONLY,
  .read      = gzip_file_read,
  .close     = gzip_file_close,
  .open      = NULL,
};

static int gzip_file_init(struct file_info *fp)
{
  z_streamp zs = calloc(1, sizeof(z_stream));

  if (!zs)
    return -1;

  fp->i.pvt = zs;

  zs->next_in  = (void *)fp->i.datap;
  zs->avail_in = fp->i.nbytes;

  if (inflateInit2(zs, 15+32) != Z_OK) {
    errno = EIO;
    return -1;
  }

  fp->iop = &gzip_file_dev;
  fp->i.length = -1;		/* Unknown */

  return 0;
}

static ssize_t gzip_file_read(struct file_info *fp, void *ptr, size_t n)
{
  z_streamp zs = fp->i.pvt;
  int rv;
  ssize_t bytes;
  ssize_t nout = 0;
  unsigned char *p = ptr;

  while ( n ) {
    zs->next_out = p;
    zs->avail_out = n;

    if (!zs->avail_in && fp->i.filedes) {
      if (__file_get_block(fp))
	return nout ? nout : -1;

      zs->next_in = (void *)fp->i.datap;
      zs->avail_in = fp->i.nbytes;
    }

    rv = inflate(zs, Z_SYNC_FLUSH);

    bytes = n - zs->avail_out;
    nout += bytes;
    p += bytes;
    n -= bytes;

    switch (rv) {
    case Z_DATA_ERROR:
    case Z_NEED_DICT:
    case Z_BUF_ERROR:
    case Z_STREAM_ERROR:
    default:
      errno = EIO;
      return nout ? nout : -1;
    case Z_MEM_ERROR:
      errno = ENOMEM;
      return nout ? nout : -1;
    case Z_STREAM_END:
      return nout;
    case Z_OK:
      break;
    }
  }

  return nout;
}

static int gzip_file_close(struct file_info *fp)
{
  z_streamp zs = fp->i.pvt;

  inflateEnd(zs);
  free(zs);
  return __file_close(fp);
}

int zopen(const char *pathname, int flags, ...)
{
  int fd, rv;
  struct file_info *fp;

  /* We don't actually give a hoot about the creation bits... */
  fd = open(pathname, flags, 0);

  if ( fd < 0 )
    return -1;

  fp = &__file_info[fd];

  /* Need to get the first block into the buffer, but not consumed */
  if ( __file_get_block(fp) )
    goto err;

  if (fp->i.nbytes >= 14 &&
      (uint8_t)fp->i.buf[0] == 037 &&
      (uint8_t)fp->i.buf[1] == 0213 && /* gzip */
      fp->i.buf[2] == 8) /* deflate */
    rv = gzip_file_init(fp);
  else
    rv = 0;			/* Plain file */

  if (!rv)
    return fd;

 err:
  close(fd);
  return -1;
}
