zu_file.cpp

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/**********************************************************************
zyGrib: meteorological GRIB file viewer
Copyright (C) 2008 - Jacques Zaninetti - http://www.zygrib.org
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
***********************************************************************/
 
#include "zu_file.h"
 
//----------------------------------------------------
int zu_can_read_file(const char *fname) {
  ZUFILE *f;
  f = zu_open(fname, "rb");
  if (f == nullptr) {
    return 0;
  } else {
    zu_close(f);
    return 1;
  }
}
 
//----------------------------------------------------
ZUFILE *zu_open(const char *fname, const char *mode, int type) {
  ZUFILE *f;
  char buf[16];
  if (!fname || strlen(fname) == 0) {
    return nullptr;
  }
  f = (ZUFILE *)malloc(sizeof(ZUFILE));
  if (!f) {
    return nullptr;
  }
 
  f->ok = 1;
  f->pos = 0;
  f->fname = strdup(fname);
 
  if (type == ZU_COMPRESS_AUTO) {
    char *p = strrchr(f->fname, '.');
    int i = 0;
    while (p != nullptr && *p != '\0' && i < 4) {
      buf[i] = tolower(*p);
      i++;
      p++;
    }
    buf[i] = '\0';
    if (!strcmp(buf, ".gz")) {
      f->type = ZU_COMPRESS_GZIP;
      // fprintf(stderr,"ZU_COMPRESS_GZIP\n");
    } else if (!strcmp(buf, ".bz2") || !strcmp(buf, ".bz")) {
      f->type = ZU_COMPRESS_BZIP;
      // fprintf(stderr,"ZU_COMPRESS_BZIP\n");
    } else {
      f->type = ZU_COMPRESS_NONE;
      // fprintf(stderr,"ZU_COMPRESS_NONE\n");
    }
  } else {
    f->type = type;
  }
 
  switch (f->type) {
    case ZU_COMPRESS_NONE:
      f->zfile = (void *)fopen(f->fname, mode);
      break;
    case ZU_COMPRESS_GZIP:
      f->zfile = (void *)gzopen(f->fname, mode);
      break;
    case ZU_COMPRESS_BZIP:
      f->faux = fopen(f->fname, mode);
      if (f->faux) {
        int bzerror = BZ_OK;
        f->zfile = (void *)BZ2_bzReadOpen(&bzerror, f->faux, 0, 0, nullptr, 0);
        if (bzerror != BZ_OK) {
          BZ2_bzReadClose(&bzerror, (BZFILE *)(f->zfile));
          fclose(f->faux);
          f->zfile = nullptr;
        }
      } else {
        f->zfile = nullptr;
      }
      break;
    default:
      f->zfile = nullptr;
  }
 
  if (f->zfile == nullptr) {
    free(f->fname);
    free(f);
    f = nullptr;
  }
 
  return f;
}
//----------------------------------------------------
int zu_read(ZUFILE *f, void *buf, long len) {
  int nb = 0;
  int bzerror = BZ_OK;
  switch (f->type) {
    case ZU_COMPRESS_NONE:
      nb = fread(buf, 1, len, (FILE *)(f->zfile));
      break;
    case ZU_COMPRESS_GZIP:
      nb = gzread((gzFile)(f->zfile), buf, len);
      break;
    case ZU_COMPRESS_BZIP:
      nb = BZ2_bzRead(&bzerror, (BZFILE *)(f->zfile), buf, len);
      break;
  }
  f->pos += nb;
  return nb;
}
 
//----------------------------------------------------
int zu_close(ZUFILE *f) {
  int bzerror = BZ_OK;
  if (f) {
    f->ok = 0;
    f->pos = 0;
    free(f->fname);
    if (f->zfile) {
      switch (f->type) {
        case ZU_COMPRESS_NONE:
          fclose((FILE *)(f->zfile));
          break;
        case ZU_COMPRESS_GZIP:
          gzclose((gzFile)(f->zfile));
          break;
        case ZU_COMPRESS_BZIP:
          BZ2_bzReadClose(&bzerror, (BZFILE *)(f->zfile));
          if (f->faux) {
            fclose(f->faux);
          }
          break;
      }
    }
    free(f);
  }
  return 0;
}
 
//----------------------------------------------------
long zu_tell(ZUFILE *f) { return f->pos; }
 
//----------------------------------------------------
long zu_filesize(ZUFILE *f) {
  long res = 0;
  FILE *ftmp = fopen(f->fname, "rb");
  if (ftmp) {
    fseek(ftmp, 0, SEEK_END);
    res = ftell(ftmp);
    fclose(ftmp);
  }
  return res;
}
 
//----------------------------------------------------
int zu_seek(ZUFILE *f, long offset, int whence) {
  int res = 0;
  int bzerror = BZ_OK;
  if (whence == SEEK_END) {
    return -1;  // TODO
  }
 
  switch (f->type) {  // SEEK_SET, SEEK_CUR
    case ZU_COMPRESS_NONE:
      res = fseek((FILE *)(f->zfile), offset, whence);
      f->pos = ftell((FILE *)(f->zfile));
      break;
    case ZU_COMPRESS_GZIP:
      if (whence == SEEK_SET) {
        res = gzseek((gzFile)(f->zfile), offset, whence);
      } else {  // !!! BUG with SEEK_CUR in ZLIB !!!
        int p1 = gztell((gzFile)(f->zfile));
        res = gzseek((gzFile)(f->zfile), p1 + offset, SEEK_SET);
      }
      f->pos = gztell((gzFile)(f->zfile));
      if (res >= 0) res = 0;
      break;
    case ZU_COMPRESS_BZIP:
      if (whence == SEEK_SET && offset >= f->pos) {
        res = zu_bzSeekForward(f, offset - f->pos);
      } else if (whence == SEEK_CUR) {
        res = zu_bzSeekForward(f, offset);
      } else {  // BAD : reopen file
        BZ2_bzReadClose(&bzerror, (BZFILE *)(f->zfile));
        bzerror = BZ_OK;
        rewind(f->faux);
        f->pos = 0;
        f->zfile = (void *)BZ2_bzReadOpen(&bzerror, f->faux, 0, 0, nullptr, 0);
        if (bzerror != BZ_OK) {
          BZ2_bzReadClose(&bzerror, (BZFILE *)(f->zfile));
          fclose(f->faux);
          f->zfile = nullptr;
          f->ok = 0;
        }
        res = zu_bzSeekForward(f, offset);
      }
      break;
  }
  return res;
}
 
//-----------------------------------------------------------------
int zu_bzSeekForward(ZUFILE *f, unsigned long nbytes_)
// for internal use
{
  unsigned long nbytes = nbytes_;
  char buf[ZU_BUFREADSIZE];
  unsigned long nbread = 0;
  int nb;
  int bzerror = BZ_OK;
  while (bzerror == BZ_OK && nbytes >= ZU_BUFREADSIZE) {
    nb = BZ2_bzRead(&bzerror, (BZFILE *)(f->zfile), buf, ZU_BUFREADSIZE);
    nbytes -= nb;
    nbread += nb;
  }
  if (bzerror == BZ_OK && nbytes > 0) {
    nb = BZ2_bzRead(&bzerror, (BZFILE *)(f->zfile), buf, nbytes);
    nbread += nb;
  }
  f->pos += nbread;
 
  return nbread == nbytes_ ? 0 : -1;
}
 
//-----------------------------------------------------------------
void zu_rewind(ZUFILE *f) { zu_seek(f, 0, SEEK_SET); }