/* gzlib.c -- zlib functions common to reading and writing gzip files
 * Copyright (C) 2004, 2010, 2011, 2012, 2013 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "gzguts.h"

#if defined(_WIN32) && !defined(__BORLANDC__)
#  define LSEEK _lseeki64
#else
#if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0
#  define LSEEK lseek64
#else
#  define LSEEK lseek
#endif
#endif

#if defined UNDER_CE

/* Map the Windows error number in ERROR to a locale-dependent error message
   string and return a pointer to it.  Typically, the values for ERROR come
   from GetLastError.

   The string pointed to shall not be modified by the application, but may be
   overwritten by a subsequent call to gz_strwinerror

   The gz_strwinerror function does not change the current setting of
   GetLastError. */
char ZLIB_INTERNAL *gz_strwinerror (DWORD error)
{
   static char buf[1024];

   wchar_t *msgbuf;
   DWORD lasterr = GetLastError();
   DWORD chars = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM
         | FORMAT_MESSAGE_ALLOCATE_BUFFER,
         NULL,
         error,
         0, /* Default language */
         (LPVOID)&msgbuf,
         0,
         NULL);
   if (chars != 0) {
      /* If there is an \r\n appended, zap it.  */
      if (chars >= 2
            && msgbuf[chars - 2] == '\r' && msgbuf[chars - 1] == '\n') {
         chars -= 2;
         msgbuf[chars] = 0;
      }

      if (chars > sizeof (buf) - 1) {
         chars = sizeof (buf) - 1;
         msgbuf[chars] = 0;
      }

      wcstombs(buf, msgbuf, chars + 1);
      LocalFree(msgbuf);
   }
   else {
      sprintf(buf, "unknown win32 error (%ld)", error);
   }

   SetLastError(lasterr);
   return buf;
}

#endif /* UNDER_CE */

/* Reset gzip file state */
static void gz_reset(gz_statep state)
{
   state->x.have        = 0;       /* no output data available */
   if (state->mode == GZ_READ)     /* for reading ... */
   {
      state->eof        = 0;       /* not at end of file */
      state->past       = 0;       /* have not read past end yet */
      state->how        = LOOK;    /* look for gzip header */
   }
   state->seek          = 0;       /* no seek request pending */
   gz_error(state, Z_OK, NULL);    /* clear error */
   state->x.pos         = 0;       /* no uncompressed data yet */
   state->strm.avail_in = 0;       /* no input data yet */
}

/* Open a gzip file either by name or file descriptor. */
static gzFile gz_open(const void *path, int fd, const char *mode)
{
   int oflag;
   gz_statep state;
   size_t len;
#ifdef O_CLOEXEC
   int cloexec = 0;
#endif
#ifdef O_EXCL
   int exclusive = 0;
#endif

   /* check input */
   if (path == NULL)
      return NULL;

   /* allocate gzFile structure to return */
   state       = (gz_statep)malloc(sizeof(gz_state));
   if (state == NULL)
      return NULL;
   state->size = 0;            /* no buffers allocated yet */
   state->want = GZBUFSIZE;    /* requested buffer size */
   state->msg  = NULL;         /* no error message yet */

   /* interpret mode */
   state->mode     = GZ_NONE;
   state->level    = Z_DEFAULT_COMPRESSION;
   state->strategy = Z_DEFAULT_STRATEGY;
   state->direct   = 0;
   while (*mode)
   {
      if (*mode >= '0' && *mode <= '9')
         state->level = *mode - '0';
      else
         switch (*mode)
         {
            case 'r':
               state->mode = GZ_READ;
               break;
#ifndef NO_GZCOMPRESS
            case 'w':
               state->mode = GZ_WRITE;
               break;
            case 'a':
               state->mode = GZ_APPEND;
               break;
#endif
            case '+':       /* can't read and write at the same time */
               free(state);
               return NULL;
            case 'b':       /* ignore -- will request binary anyway */
               break;
#ifdef O_CLOEXEC
            case 'e':
               cloexec = 1;
               break;
#endif
#ifdef O_EXCL
            case 'x':
               exclusive = 1;
               break;
#endif
            case 'f':
               state->strategy = Z_FILTERED;
               break;
            case 'h':
               state->strategy = Z_HUFFMAN_ONLY;
               break;
            case 'R':
               state->strategy = Z_RLE;
               break;
            case 'F':
               state->strategy = Z_FIXED;
               break;
            case 'T':
               state->direct = 1;
               break;
            default:        /* could consider as an error, but just ignore */
               ;
         }
      mode++;
   }

   /* must provide an "r", "w", or "a" */
   if (state->mode == GZ_NONE)
   {
      free(state);
      return NULL;
   }

   /* can't force transparent read */
   if (state->mode == GZ_READ)
   {
      if (state->direct)
      {
         free(state);
         return NULL;
      }
      state->direct = 1;      /* for empty file */
   }

   /* save the path name for error messages */
#ifdef _WIN32
   if (fd == -2)
   {
      len = wcstombs(NULL, (const wchar_t*)path, 0);
      if (len == (size_t)-1)
         len = 0;
   }
   else
#endif
      len = strlen((const char *)path);
   state->path = (char *)malloc(len + 1);
   if (state->path == NULL)
   {
      free(state);
      return NULL;
   }
#ifdef _WIN32
   if (fd == -2)
      if (len)
         wcstombs(state->path, (const wchar_t*)path, len + 1);
      else
         *(state->path) = 0;
   else
#endif
#if !defined(NO_snprintf) && !defined(NO_vsnprintf)
      snprintf(state->path, len + 1, "%s", (const char *)path);
#else
   strlcpy(state->path, path, sizeof(state->path));
#endif

   /* compute the flags for open() */
   oflag =
#ifdef O_LARGEFILE
      O_LARGEFILE |
#endif
#ifdef O_BINARY
      O_BINARY |
#endif
#ifdef O_CLOEXEC
      (cloexec ? O_CLOEXEC : 0) |
#endif
      (state->mode == GZ_READ ?
       O_RDONLY :
       (O_WRONLY | O_CREAT |
#ifdef O_EXCL
        (exclusive ? O_EXCL : 0) |
#endif
        (state->mode == GZ_WRITE ?
         O_TRUNC :
         O_APPEND)));

   /* open the file with the appropriate flags (or just use fd) */
   state->fd = fd > -1 ? fd : (
#ifdef _WIN32
         fd == -2 ? _wopen((const wchar_t*)path, oflag, 0666) :
#endif
         open((const char *)path, oflag, 0666));
   if (state->fd == -1) {
      free(state->path);
      free(state);
      return NULL;
   }
   if (state->mode == GZ_APPEND)
      state->mode = GZ_WRITE;         /* simplify later checks */

   /* save the current position for rewinding (only if reading) */
   if (state->mode == GZ_READ)
   {
      state->start = LSEEK(state->fd, 0, SEEK_CUR);
      if (state->start == -1) state->start = 0;
   }

   /* initialize stream */
   gz_reset(state);

   /* return stream */
   return (gzFile)state;
}

gzFile gzopen(const char *path, const char *mode)
{
   return gz_open(path, -1, mode);
}

gzFile gzopen64(const char *path, const char *mode)
{
   return gz_open(path, -1, mode);
}

gzFile gzdopen(int fd, const char *mode)
{
   char *path;         /* identifier for error messages */
   gzFile gz;

   if (fd == -1 || (path = (char *)malloc(7 + 3 * sizeof(int))) == NULL)
      return NULL;
#if !defined(NO_snprintf) && !defined(NO_vsnprintf)
   snprintf(path, 7 + 3 * sizeof(int), "<fd:%d>", fd); /* for debugging */
#else
   sprintf(path, "<fd:%d>", fd);   /* for debugging */
#endif
   gz = gz_open(path, fd, mode);
   free(path);
   return gz;
}

#ifdef _WIN32
gzFile gzopen_w(const wchar_t *path, const char *mode)
{
   return gz_open(path, -2, mode);
}
#endif

int gzbuffer(gzFile file, unsigned size)
{
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return -1;
   state = (gz_statep)file;
   if (state->mode != GZ_READ && state->mode != GZ_WRITE)
      return -1;

   /* make sure we haven't already allocated memory */
   if (state->size != 0)
      return -1;

   /* check and set requested size */
   if (size < 2)
      size = 2;               /* need two bytes to check magic header */
   state->want = size;
   return 0;
}

int gzrewind(gzFile file)
{
   gz_statep state;

   /* get internal structure */
   if (file == NULL)
      return -1;
   state = (gz_statep)file;

   /* check that we're reading and that there's no error */
   if (
             state->mode != GZ_READ ||
         (   state->err  != Z_OK 
          && state->err  != Z_BUF_ERROR))
      return -1;

   /* back up and start over */
   if (LSEEK(state->fd, state->start, SEEK_SET) == -1)
      return -1;
   gz_reset(state);
   return 0;
}

z_off64_t gzseek64(gzFile file, z_off64_t offset, int whence)
{
   unsigned n;
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return -1;
   state = (gz_statep)file;
   if (  state->mode != GZ_READ && 
         state->mode != GZ_WRITE)
      return -1;

   /* check that there's no error */
   if (  state->err != Z_OK && 
         state->err != Z_BUF_ERROR)
      return -1;

   /* can only seek from start or relative to current position */
   if (  whence != SEEK_SET && 
         whence != SEEK_CUR)
      return -1;

   /* normalize offset to a SEEK_CUR specification */
   if (whence == SEEK_SET)
      offset -= state->x.pos;
   else if (state->seek)
      offset += state->skip;
   state->seek = 0;

   /* if within raw area while reading, just go there */
   if (  state->mode == GZ_READ   && 
         state->how  == MODE_COPY &&
         state->x.pos + offset >= 0)
   {
      z_off64_t ret         = LSEEK(
            state->fd, offset - state->x.have, SEEK_CUR);
      if (ret == -1)
         return -1;
      state->x.have         = 0;
      state->eof            = 0;
      state->past           = 0;
      state->seek           = 0;
      gz_error(state, Z_OK, NULL);
      state->strm.avail_in  = 0;
      state->x.pos         += offset;
      return state->x.pos;
   }

   /* calculate skip amount, rewinding if 
    * needed for back seek when reading */
   if (offset < 0)
   {
      if (state->mode != GZ_READ)         /* writing -- can't go backwards */
         return -1;
      offset += state->x.pos;
      if (offset < 0)                     /* before start of file! */
         return -1;
      if (gzrewind(file) == -1)           /* rewind, then skip to offset */
         return -1;
   }

   /* if reading, skip what's in output buffer (one less gzgetc() check) */
   if (state->mode == GZ_READ)
   {
      n = GT_OFF(state->x.have) || (z_off64_t)state->x.have > offset ?
         (unsigned)offset : state->x.have;
      state->x.have -= n;
      state->x.next += n;
      state->x.pos  += n;
      offset        -= n;
   }

   /* request skip (if not zero) */
   if (offset)
   {
      state->seek = 1;
      state->skip = offset;
   }
   return state->x.pos + offset;
}

z_off_t gzseek(gzFile file, z_off_t offset, int whence)
{
   z_off64_t ret = gzseek64(file, (z_off64_t)offset, whence);
   return ret == (z_off_t)ret ? (z_off_t)ret : -1;
}

z_off64_t gztell64(gzFile file)
{
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return -1;
   state = (gz_statep)file;
   if (  state->mode != GZ_READ && 
         state->mode != GZ_WRITE)
      return -1;

   /* return position */
   return state->x.pos + (state->seek ? state->skip : 0);
}

z_off_t gztell(gzFile file)
{
   z_off64_t ret = gztell64(file);
   return ret == (z_off_t)ret ? (z_off_t)ret : -1;
}

z_off64_t gzoffset64(gzFile file)
{
   z_off64_t offset;
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return -1;
   state = (gz_statep)file;
   if (state->mode != GZ_READ && state->mode != GZ_WRITE)
      return -1;

   /* compute and return effective offset in file */
   offset = LSEEK(state->fd, 0, SEEK_CUR);
   if (offset == -1)
      return -1;
   if (state->mode == GZ_READ)             /* reading */
      offset -= state->strm.avail_in;     /* don't count buffered input */
   return offset;
}

z_off_t gzoffset(gzFile file)
{
   z_off64_t ret = gzoffset64(file);
   return ret == (z_off_t)ret ? (z_off_t)ret : -1;
}

int gzeof(gzFile file)
{
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return 0;
   state = (gz_statep)file;
   if (  state->mode != GZ_READ && 
         state->mode != GZ_WRITE)
      return 0;

   /* return end-of-file state */
   return state->mode == GZ_READ ? state->past : 0;
}

const char * gzerror(gzFile file, int *errnum)
{
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return NULL;
   state = (gz_statep)file;

   if (  state->mode != GZ_READ && 
         state->mode != GZ_WRITE)
      return NULL;

   /* return error information */
   if (errnum != NULL)
      *errnum = state->err;
   return state->err == Z_MEM_ERROR ? "out of memory" :
      (state->msg == NULL ? "" : state->msg);
}

void gzclearerr(gzFile file)
{
   gz_statep state;

   /* get internal structure and check integrity */
   if (file == NULL)
      return;
   state = (gz_statep)file;

   if (  state->mode != GZ_READ && 
         state->mode != GZ_WRITE)
      return;

   /* clear error and end-of-file */
   if (state->mode == GZ_READ)
   {
      state->eof  = 0;
      state->past = 0;
   }
   gz_error(state, Z_OK, NULL);
}

/* Create an error message in allocated memory and set state->err and
   state->msg accordingly.  Free any previous error message already there.  Do
   not try to free or allocate space if the error is Z_MEM_ERROR (out of
   memory).  Simply save the error message as a static string.  If there is an
   allocation failure constructing the error message, then convert the error to
   out of memory. */
void ZLIB_INTERNAL gz_error(gz_statep state, int err, const char *msg)
{
   /* free previously allocated message and clear */
   if (state->msg != NULL)
   {
      if (state->err != Z_MEM_ERROR)
         free(state->msg);
      state->msg = NULL;
   }

   /* if fatal, set state->x.have to 0 so that the gzgetc() macro fails */
   if (err != Z_OK && err != Z_BUF_ERROR)
      state->x.have = 0;

   /* set error code, and if no message, then done */
   state->err = err;
   if (msg == NULL)
      return;

   /* for an out of memory error, return literal string when requested */
   if (err == Z_MEM_ERROR)
      return;

   /* construct error message with path */
   if ((state->msg = (char *)malloc(strlen(state->path) + strlen(msg) + 3)) ==
         NULL)
   {
      state->err = Z_MEM_ERROR;
      return;
   }
#if !defined(NO_snprintf) && !defined(NO_vsnprintf)
   snprintf(state->msg, strlen(state->path) + strlen(msg) + 3,
         "%s%s%s", state->path, ": ", msg);
#else
   strlcpy(state->msg, state->path, sizeof(state->msg));
   strlcat(state->msg, ": ", sizeof(state->msg));
   strlcat(state->msg, msg, sizeof(state->msg));
#endif
}

#ifndef INT_MAX
/* portably return maximum value for an int (when limits.h presumed not
   available) -- we need to do this to cover cases where 2's complement not
   used, since C standard permits 1's complement and sign-bit representations,
   otherwise we could just use ((unsigned)-1) >> 1 */
unsigned ZLIB_INTERNAL gz_intmax(void)
{
   unsigned p, q;

   p = 1;
   do {
      q = p;
      p <<= 1;
      p++;
   } while (p > q);
   return q >> 1;
}
#endif
