/*
  NrrdIO: stand-alone code for basic nrrd functionality
  Copyright (C) 2008, 2007, 2006, 2005  Gordon Kindlmann
  Copyright (C) 2004, 2003, 2002, 2001, 2000, 1999, 1998  University of Utah
 
  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any
  damages arising from the use of this software.
 
  Permission is granted to anyone to use this software for any
  purpose, including commercial applications, and to alter it and
  redistribute it freely, subject to the following restrictions:
 
  1. The origin of this software must not be misrepresented; you must
     not claim that you wrote the original software. If you use this
     software in a product, an acknowledgment in the product
     documentation would be appreciated but is not required.
 
  2. Altered source versions must be plainly marked as such, and must
     not be misrepresented as being the original software.
 
  3. This notice may not be removed or altered from any source distribution.
*/
/* 
  This file is a modified version of the 'gzio.c' and 'zutil.h' source
  files from the zlib 1.1.4 distribution.

  zlib.h -- interface of the 'zlib' general purpose compression library
  version 1.1.4, March 11th, 2002

  Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Jean-loup Gailly        Mark Adler
  jloup@gzip.org          madler@alumni.caltech.edu

  The data format used by the zlib library is described by RFCs (Request for
  Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt
  (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
*/

#if TEEM_ZLIB

#include "NrrdIO.h"
#include "privateNrrd.h"

#ifdef _WIN32 /* Window 95 & Windows NT */
#  define _NRRD_OS_CODE  0x0b
#endif

#if defined(MACOS) || defined(TARGET_OS_MAC) || defined(__APPLE_CC__)
#  define _NRRD_OS_CODE  0x07
#endif

#ifndef _NRRD_OS_CODE
#  define _NRRD_OS_CODE  0x03  /* assume Unix */
#endif

/* default memLevel */
#if MAX_MEM_LEVEL >= 8
#  define _NRRD_DEF_MEM_LEVEL 8
#else
#  define _NRRD_DEF_MEM_LEVEL  MAX_MEM_LEVEL
#endif

/* stream buffer size */
#define _NRRD_Z_BUFSIZE 16 * 1024

/* gzip flag byte */
#define _NRRD_ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define _NRRD_HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define _NRRD_EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define _NRRD_ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define _NRRD_COMMENT      0x10 /* bit 4 set: file comment present */
#define _NRRD_RESERVED     0xE0 /* bits 5..7: reserved */

typedef struct _NrrdGzStream {
  z_stream stream;
  int      z_err;   /* error code for last stream operation */
  int      z_eof;   /* set if end of input file */
  FILE     *file;   /* .gz file */
  Byte     *inbuf;  /* input buffer */
  Byte     *outbuf; /* output buffer */
  uLong    crc;     /* crc32 of uncompressed data */
  char     *msg;    /* error message */
  int      transparent; /* 1 if input file is not a .gz file */
  char     mode;    /* 'w' or 'r' */
  long     startpos; /* start of compressed data in file (header skipped) */
} _NrrdGzStream;

static int _nrrdGzMagic[2] = {0x1f, 0x8b}; /* gzip magic header */

/* zlib error messages */
static const char *_nrrdGzErrMsg[10] = {
  "need dictionary",     /* Z_NEED_DICT       2  */
  "stream end",          /* Z_STREAM_END      1  */
  "",                    /* Z_OK              0  */
  "file error",          /* Z_ERRNO         (-1) */
  "stream error",        /* Z_STREAM_ERROR  (-2) */
  "data error",          /* Z_DATA_ERROR    (-3) */
  "insufficient memory", /* Z_MEM_ERROR     (-4) */
  "buffer error",        /* Z_BUF_ERROR     (-5) */
  "incompatible version",/* Z_VERSION_ERROR (-6) */
  ""};

#define _NRRD_GZ_ERR_MSG(err) _nrrdGzErrMsg[Z_NEED_DICT-(err)]

/* some forward declarations for things in this file */
static void _nrrdGzCheckHeader(_NrrdGzStream *s);
static int _nrrdGzDestroy(_NrrdGzStream *s);
static int _nrrdGzDoFlush(gzFile file, int flush);
static void _nrrdGzPutLong(FILE *file, uLong x);
static uLong _nrrdGzGetLong(_NrrdGzStream *s);

/*
** _nrrdGzOpen()
**
** Opens a gzip (.gz) file for reading or writing. The mode parameter
** is like in fopen ("rb" or "wb"). The file represented by the FILE* pointer
** should be open already with the same mode.  The mode parameter can also be
** used to specify the compression level "[0-9]" and strategy "[f|h]".
**
** The compression level must be between 0 and 9: 1 gives best speed,
** 9 gives best compression, 0 gives no compression at all (the input data
** is simply copied a block at a time). The default level is 6.
**
** The strategy parameter is used to tune the compression algorithm. Use
** "f" for data produced by a filter (or predictor), or "h" to force Huffman
** encoding only (no string match). Filtered data consists mostly of small
** values with a somewhat random distribution. In this case, the compression
** algorithm is tuned to compress them better. The effect of "f" is to force
** more Huffman coding and less string matching; it is somewhat intermediate
** between the default and Huffman. The strategy parameter only affects the
** compression ratio but not the correctness of the compressed output even
** if it is not set appropriately.
**
** The complete syntax for the mode parameter is: "(r|w[a])[0-9][f|h]".
** 
** Returns Z_NULL if the file could not be opened or if there was
** insufficient memory to allocate the (de)compression state; errno
** can be checked to distinguish the two cases (if errno is zero, the
** zlib error is Z_MEM_ERROR).
*/
gzFile
_nrrdGzOpen(FILE* fd, const char* mode) {
  static const char me[]="_nrrdGzOpen";
  int error;
  int level = Z_DEFAULT_COMPRESSION; /* compression level */
  int strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
  char *p = (char*)mode;
  _NrrdGzStream *s;
  char fmode[AIR_STRLEN_MED]; /* copy of mode, without the compression level */
  char *m = fmode;
    
  if (!mode) {
    biffAddf(NRRD, "%s: no file mode specified", me);
    return Z_NULL;
  }
  /* allocate stream struct */
  s = (_NrrdGzStream *)calloc(1, sizeof(_NrrdGzStream));
  if (!s) {
    biffAddf(NRRD, "%s: failed to allocate stream buffer", me);
    return Z_NULL;
  }
  /* initialize stream struct */
  s->stream.zalloc = (alloc_func)0;
  s->stream.zfree = (free_func)0;
  s->stream.opaque = (voidpf)0;
  s->stream.next_in = s->inbuf = Z_NULL;
  s->stream.next_out = s->outbuf = Z_NULL;
  s->stream.avail_in = s->stream.avail_out = 0;
  s->file = NULL;
  s->z_err = Z_OK;
  s->z_eof = 0;
  s->crc = crc32(0L, Z_NULL, 0);
  s->msg = NULL;
  s->transparent = 0;
  /* parse mode flag */
  s->mode = '\0';
  do {
    if (*p == 'r') s->mode = 'r';
    if (*p == 'w' || *p == 'a') s->mode = 'w';
    if (*p >= '0' && *p <= '9') {
      level = *p - '0';
    } else if (*p == 'f') {
      strategy = Z_FILTERED;
    } else if (*p == 'h') {
      strategy = Z_HUFFMAN_ONLY;
    } else {
      *m++ = *p; /* copy the mode */
    }
  } while (*p++ && m != fmode + sizeof(fmode));
  if (s->mode == '\0') {
    biffAddf(NRRD, "%s: invalid file mode", me);
    return _nrrdGzDestroy(s), (gzFile)Z_NULL;
  }
  
  if (s->mode == 'w') {
    error = deflateInit2(&(s->stream), level,
                         Z_DEFLATED, -MAX_WBITS, _NRRD_DEF_MEM_LEVEL, 
                         strategy);
    /* windowBits is passed < 0 to suppress zlib header */

    s->stream.next_out = s->outbuf = (Byte*)calloc(1, _NRRD_Z_BUFSIZE);
    if (error != Z_OK || s->outbuf == Z_NULL) {
      biffAddf(NRRD, "%s: stream init failed", me);
      return _nrrdGzDestroy(s), (gzFile)Z_NULL;
    }
  } else {
    s->stream.next_in  = s->inbuf = (Byte*)calloc(1, _NRRD_Z_BUFSIZE);

    error = inflateInit2(&(s->stream), -MAX_WBITS);
    /* windowBits is passed < 0 to tell that there is no zlib header.
     * Note that in this case inflate *requires* an extra "dummy" byte
     * after the compressed stream in order to complete decompression and
     * return Z_STREAM_END. Here the gzip CRC32 ensures that 4 bytes are
     * present after the compressed stream.
     */
    if (error != Z_OK || s->inbuf == Z_NULL) {
      biffAddf(NRRD, "%s: stream init failed", me);
      return _nrrdGzDestroy(s), (gzFile)Z_NULL;
    }
  }
  s->stream.avail_out = _NRRD_Z_BUFSIZE;
  errno = 0;
  s->file = fd;
  if (s->file == NULL) {
    biffAddf(NRRD, "%s: null file pointer", me);
    return _nrrdGzDestroy(s), (gzFile)Z_NULL;
  }
  if (s->mode == 'w') {
    /* Write a very simple .gz header: */
    fprintf(s->file, "%c%c%c%c%c%c%c%c%c%c", _nrrdGzMagic[0], _nrrdGzMagic[1],
            Z_DEFLATED, 
            0 /*flags*/, 
            0,0,0,0 /*time*/, 
            0 /*xflags*/, 
            _NRRD_OS_CODE);
    s->startpos = 10L;
    /* We use 10L instead of ftell(s->file) to because ftell causes an
     * fflush on some systems. This version of the library doesn't use
     * startpos anyway in write mode, so this initialization is not
     * necessary.
     */
  } else {
    _nrrdGzCheckHeader(s); /* skip the .gz header */
    s->startpos = (ftell(s->file) - s->stream.avail_in);
  }
  return (gzFile)s;
}

/*
** _nrrdGzClose()
**
** Flushes all pending output if necessary, closes the compressed file
** and deallocates the (de)compression state.
*/
int
_nrrdGzClose (gzFile file) {
  static const char me[]="_nrrdGzClose";
  int error;
  _NrrdGzStream *s = (_NrrdGzStream*)file;

  if (s == NULL) {
    biffAddf(NRRD, "%s: invalid stream", me);
    return 1;
  }
  if (s->mode == 'w') {
    error = _nrrdGzDoFlush(file, Z_FINISH);
    if (error != Z_OK) {
      biffAddf(NRRD, "%s: failed to flush pending data", me);
      return _nrrdGzDestroy((_NrrdGzStream*)file);
    }
    _nrrdGzPutLong(s->file, s->crc);
    _nrrdGzPutLong(s->file, s->stream.total_in);
  }
  return _nrrdGzDestroy((_NrrdGzStream*)file);
}

/*
** _nrrdGzRead()
**
** Reads the given number of uncompressed bytes from the compressed file.
** Returns the number of bytes actually read (0 for end of file).
*/
int
_nrrdGzRead(gzFile file, voidp buf, unsigned int len, unsigned int* read) {
  static const char me[]="_nrrdGzRead";
  _NrrdGzStream *s = (_NrrdGzStream*)file;
  Bytef *start = (Bytef*)buf; /* starting point for crc computation */
  Byte  *next_out; /* == stream.next_out but not forced far (for MSDOS) */

  if (s == NULL || s->mode != 'r') {
    biffAddf(NRRD, "%s: invalid stream or file mode", me);
    *read = 0;
    return 1;
  }

  if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO) {
    biffAddf(NRRD, "%s: data read error", me);
    *read = 0;
    return 1;
  }

  if (s->z_err == Z_STREAM_END) {
    *read = 0;
    return 0;  /* EOF */
  }

  next_out = (Byte*)buf;
  s->stream.next_out = (Bytef*)buf;
  s->stream.avail_out = len;

  while (s->stream.avail_out != 0) {

    if (s->transparent) {
      /* Copy first the lookahead bytes: */
      uInt n = s->stream.avail_in;
      if (n > s->stream.avail_out) n = s->stream.avail_out;
      if (n > 0) {
        memcpy(s->stream.next_out, s->stream.next_in, n);
        next_out += n;
        s->stream.next_out = next_out;
        s->stream.next_in   += n;
        s->stream.avail_out -= n;
        s->stream.avail_in  -= n;
      }
      if (s->stream.avail_out > 0) {
        s->stream.avail_out -= (uInt)fread(next_out, 1, s->stream.avail_out,
                                           s->file);
      }
      len -= s->stream.avail_out;
      s->stream.total_in  += len;
      s->stream.total_out += len;
      if (len == 0) s->z_eof = 1;
      *read = len;
      return 0;
    }
    if (s->stream.avail_in == 0 && !s->z_eof) {

      errno = 0;
      s->stream.avail_in = (uInt)fread(s->inbuf, 1, _NRRD_Z_BUFSIZE, s->file);
      if (s->stream.avail_in == 0) {
        s->z_eof = 1;
        if (ferror(s->file)) {
          s->z_err = Z_ERRNO;
          break;
        }
      }
      s->stream.next_in = s->inbuf;
    }
    s->z_err = inflate(&(s->stream), Z_NO_FLUSH);

    if (s->z_err == Z_STREAM_END) {
      /* Check CRC and original size */
      s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));
      start = s->stream.next_out;

      if (_nrrdGzGetLong(s) != s->crc) {
        s->z_err = Z_DATA_ERROR;
      } else {
        (void)_nrrdGzGetLong(s);
        /* The uncompressed length returned by above getlong() may
         * be different from s->stream.total_out) in case of
         * concatenated .gz files. Check for such files:
         */
        _nrrdGzCheckHeader(s);
        if (s->z_err == Z_OK) {
          uLong total_in = s->stream.total_in;
          uLong total_out = s->stream.total_out;

          inflateReset(&(s->stream));
          s->stream.total_in = total_in;
          s->stream.total_out = total_out;
          s->crc = crc32(0L, Z_NULL, 0);
        }
      }
    }
    if (s->z_err != Z_OK || s->z_eof) break;
  }
  s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));

  *read = len - s->stream.avail_out;
  return 0;
}

/*
** _nrrdGzWrite()
**
** Writes the given number of uncompressed bytes into the compressed file.
** Returns the number of bytes actually written (0 in case of error).
*/
int
_nrrdGzWrite(gzFile file, const voidp buf, unsigned int len,
             unsigned int* written) {
  static const char me[]="_nrrdGzWrite";
  _NrrdGzStream *s = (_NrrdGzStream*)file;

  if (s == NULL || s->mode != 'w') {
    biffAddf(NRRD, "%s: invalid stream or file mode", me);
    *written = 0;
    return 1;
  }

  s->stream.next_in = (Bytef*)buf;
  s->stream.avail_in = len;

  while (s->stream.avail_in != 0) {
    if (s->stream.avail_out == 0) {
      s->stream.next_out = s->outbuf;
      if (fwrite(s->outbuf, 1, _NRRD_Z_BUFSIZE, s->file) != _NRRD_Z_BUFSIZE) {
        s->z_err = Z_ERRNO;
        biffAddf(NRRD, "%s: failed to write to file", me);
        break;
      }
      s->stream.avail_out = _NRRD_Z_BUFSIZE;
    }
    s->z_err = deflate(&(s->stream), Z_NO_FLUSH);
    if (s->z_err != Z_OK) break;
  }
  s->crc = crc32(s->crc, (const Bytef *)buf, len);

  *written = len - s->stream.avail_in;
  return 0;
}

/*
** _nrrdGzGetByte()
**
** Reads a byte from a _NrrdGzStream. Updates next_in and avail_in.
** Returns EOF for end of file.
** IN assertion: the stream s has been sucessfully opened for reading.
*/
static int
_nrrdGzGetByte(_NrrdGzStream *s) {
  static const char me[]="_nrrdGzGetByte";

  if (s->z_eof) return EOF;
  if (s->stream.avail_in == 0) {
    errno = 0;
    s->stream.avail_in = (uInt)fread(s->inbuf, 1, _NRRD_Z_BUFSIZE, s->file);
    if (s->stream.avail_in == 0) {
      s->z_eof = 1;
      if (ferror(s->file)) {
        biffAddf(NRRD, "%s: failed to read from file", me);
        s->z_err = Z_ERRNO;
      }
      return EOF;
    }
    s->stream.next_in = s->inbuf;
  }
  s->stream.avail_in--;
  return *(s->stream.next_in)++;
}

/*
******** _nrrdGzCheckHeader()
**
** Checks the gzip header of a _NrrdGzStream opened for reading. Sets
** the stream mode to transparent if the gzip magic header is not
** present; sets s->err to Z_DATA_ERROR if the magic header is present
** but the rest of the header is incorrect.
** IN assertion: the stream s has already been created sucessfully;
** s->stream.avail_in is zero for the first time, but may be non-zero
** for concatenated .gz files.
*/
static void
_nrrdGzCheckHeader(_NrrdGzStream *s) {
  static const char me[]="_nrrdGzCheckHeader";
  int method; /* method byte */
  int flags;  /* flags byte */
  uInt len;
  int c;

  /* Check the gzip magic header */
  for (len = 0; len < 2; len++) {
    c = _nrrdGzGetByte(s);
    if (c != _nrrdGzMagic[len]) {
      if (len != 0) s->stream.avail_in++, s->stream.next_in--;
      if (c != EOF) {
        s->stream.avail_in++, s->stream.next_in--;
        s->transparent = 1;
      }
      s->z_err = s->stream.avail_in != 0 ? Z_OK : Z_STREAM_END;
      return;
    }
  }
  method = _nrrdGzGetByte(s);
  flags = _nrrdGzGetByte(s);
  if (method != Z_DEFLATED || (flags & _NRRD_RESERVED) != 0) {
    biffAddf(NRRD, "%s: gzip compression method is not deflate", me);
    s->z_err = Z_DATA_ERROR;
    return;
  }

  /* Discard time, xflags and OS code: */
  for (len = 0; len < 6; len++) (void)_nrrdGzGetByte(s);

  if ((flags & _NRRD_EXTRA_FIELD) != 0) { /* skip the extra field */
    len  =  (uInt)_nrrdGzGetByte(s);
    len += ((uInt)_nrrdGzGetByte(s))<<8;
    /* len is garbage if EOF but the loop below will quit anyway */
    while (len-- != 0 && _nrrdGzGetByte(s) != EOF) ;
  }
  if ((flags & _NRRD_ORIG_NAME) != 0) { /* skip the original file name */
    while ((c = _nrrdGzGetByte(s)) != 0 && c != EOF) ;
  }
  if ((flags & _NRRD_COMMENT) != 0) {   /* skip the .gz file comment */
    while ((c = _nrrdGzGetByte(s)) != 0 && c != EOF) ;
  }
  if ((flags & _NRRD_HEAD_CRC) != 0) {  /* skip the header crc */
    for (len = 0; len < 2; len++) (void)_nrrdGzGetByte(s);
  }
  s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
}

/*
** _nrrdGzDestroy()
**
** Cleans up then free the given _NrrdGzStream. Returns a zlib error code.
** Try freeing in the reverse order of allocations.  FILE* s->file is not
** closed.  Because we didn't allocate it, we shouldn't delete it.
*/
static int
_nrrdGzDestroy(_NrrdGzStream *s) {
  static const char me[]="_nrrdGzDestroy";
  int error = Z_OK;

  if (s == NULL) {
    biffAddf(NRRD, "%s: invalid stream", me);
    return 1;
  }
  s->msg = (char *)airFree(s->msg);
  if (s->stream.state != NULL) {
    if (s->mode == 'w') {
      error = deflateEnd(&(s->stream));
    } else if (s->mode == 'r') {
      error = inflateEnd(&(s->stream));
    }
  }
  if (error != Z_OK) {
    biffAddf(NRRD, "%s: %s", me, _NRRD_GZ_ERR_MSG(error));
  }
  if (s->z_err < 0) error = s->z_err;
  if (error != Z_OK) {
    biffAddf(NRRD, "%s: %s", me, _NRRD_GZ_ERR_MSG(error));
  }
  s->inbuf = (Byte *)airFree(s->inbuf);
  s->outbuf = (Byte *)airFree(s->outbuf);
  airFree(s);   /* avoiding unused value warnings, no NULL set */
  return error != Z_OK;
}

/*
** _nrrdGzDoFlush()
**
** Flushes all pending output into the compressed file. The parameter
** flush is the same as in the deflate() function.
*/
static int
_nrrdGzDoFlush(gzFile file, int flush) {
  static const char me[]="_nrrdGzDoFlush";
  uInt len;
  int done = 0;
  _NrrdGzStream *s = (_NrrdGzStream*)file;

  if (s == NULL || s->mode != 'w') {
    biffAddf(NRRD, "%s: invalid stream or file mode", me);
    return Z_STREAM_ERROR;
  }
  
  s->stream.avail_in = 0; /* should be zero already anyway */

  for (;;) {
    len = _NRRD_Z_BUFSIZE - s->stream.avail_out;

    if (len != 0) {
      if ((uInt)fwrite(s->outbuf, 1, len, s->file) != len) {
        s->z_err = Z_ERRNO;
        return Z_ERRNO;
      }
      s->stream.next_out = s->outbuf;
      s->stream.avail_out = _NRRD_Z_BUFSIZE;
    }
    if (done) break;
    s->z_err = deflate(&(s->stream), flush);

    /* Ignore the second of two consecutive flushes: */
    if (len == 0 && s->z_err == Z_BUF_ERROR) s->z_err = Z_OK;

    /* deflate has finished flushing only when it hasn't used up
     * all the available space in the output buffer: 
     */
    done = (s->stream.avail_out != 0 || s->z_err == Z_STREAM_END);
 
    if (s->z_err != Z_OK && s->z_err != Z_STREAM_END) break;
  }
  return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
}

/*
** _nrrdGzPutLong()
**
** Outputs a long in LSB order to the given file.
*/
static void
_nrrdGzPutLong(FILE* file, uLong x) {
  int n;
  for (n = 0; n < 4; n++) {
    fputc((int)(x & 0xff), file);
    x >>= 8;
  }
}

/*
** _nrrdGzGetLong()
**
** Reads a long in LSB order from the given _NrrdGzStream.
** Sets z_err in case of error.
*/
static uLong
_nrrdGzGetLong(_NrrdGzStream *s) {
  uLong x = (uLong)_nrrdGzGetByte(s);
  int c;

  x += ((uLong)_nrrdGzGetByte(s))<<8;
  x += ((uLong)_nrrdGzGetByte(s))<<16;
  c = _nrrdGzGetByte(s);
  if (c == EOF) s->z_err = Z_DATA_ERROR;
  x += ((uLong)c)<<24;
  return x;
}

#endif /* TEEM_ZLIB */

/*
** random symbol to have in object file, even when Zlib not enabled 
*/
int
_nrrdGzDummySymbol(void) {
  return 42;
}