ENH: Initial import from VTK

1 files changed, 875 insertions, 0 deletions

diff --git a/Utilities/cmzlib/gzio.c b/Utilities/cmzlib/gzio.c
new file mode 100644
index 0000000..0b779c8
--- /dev/null
+++ b/Utilities/cmzlib/gzio.c
@@ -0,0 +1,875 @@
+/* gzio.c -- IO on .gz files
+ * Copyright (C) 1995-2002 Jean-loup Gailly.
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ *
+ * Compile this file with -DNO_DEFLATE to avoid the compression code.
+ */
+
+/* @(#) $Id$ */
+
+#include <stdio.h>
+
+#include "zutil.h"
+
+struct internal_state {int dummy;}; /* for buggy compilers */
+
+#ifndef Z_BUFSIZE
+#  ifdef MAXSEG_64K
+#    define Z_BUFSIZE 4096 /* minimize memory usage for 16-bit DOS */
+#  else
+#    define Z_BUFSIZE 16384
+#  endif
+#endif
+#ifndef Z_PRINTF_BUFSIZE
+#  define Z_PRINTF_BUFSIZE 4096
+#endif
+
+#define ALLOC(size) malloc(size)
+#define TRYFREE(p) {if (p) free(p);}
+
+static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */
+
+/* gzip flag byte */
+#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
+#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
+#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
+#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
+#define COMMENT      0x10 /* bit 4 set: file comment present */
+#define RESERVED     0xE0 /* bits 5..7: reserved */
+
+typedef struct gz_stream {
+    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 */
+    char     *path;   /* path name for debugging only */
+    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) */
+} gz_stream;
+
+
+local gzFile gz_open      OF((const char *path, const char *mode, int  fd));
+local int do_flush        OF((gzFile file, int flush));
+local int    get_byte     OF((gz_stream *s));
+local void   check_header OF((gz_stream *s));
+local int    destroy      OF((gz_stream *s));
+local void   putLong      OF((FILE *file, uLong x));
+local uLong  getLong      OF((gz_stream *s));
+
+/* ===========================================================================
+     Opens a gzip (.gz) file for reading or writing. The mode parameter
+   is as in fopen ("rb" or "wb"). The file is given either by file descriptor
+   or path name (if fd == -1).
+     gz_open return 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).
+*/
+local gzFile gz_open (path, mode, fd)
+    const char *path;
+    const char *mode;
+    int  fd;
+{
+    int err;
+    int level = Z_DEFAULT_COMPRESSION; /* compression level */
+    int strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
+    char *p = (char*)mode;
+    gz_stream *s;
+    char fmode[80]; /* copy of mode, without the compression level */
+    char *m = fmode;
+
+    if (!path || !mode) return Z_NULL;
+
+    s = (gz_stream *)ALLOC(sizeof(gz_stream));
+    if (!s) return Z_NULL;
+
+    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;
+
+    s->path = (char*)ALLOC(strlen(path)+1);
+    if (s->path == NULL) {
+        return destroy(s), (gzFile)Z_NULL;
+    }
+    strcpy(s->path, path); /* do this early for debugging */
+
+    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') return destroy(s), (gzFile)Z_NULL;
+    
+    if (s->mode == 'w') {
+#ifdef NO_DEFLATE
+        err = Z_STREAM_ERROR;
+#else
+        err = deflateInit2(&(s->stream), level,
+                           Z_DEFLATED, -MAX_WBITS, DEF_MEM_LEVEL, strategy);
+        /* windowBits is passed < 0 to suppress zlib header */
+
+        s->stream.next_out = s->outbuf = (Byte*)ALLOC(Z_BUFSIZE);
+#endif
+        if (err != Z_OK || s->outbuf == Z_NULL) {
+            return destroy(s), (gzFile)Z_NULL;
+        }
+    } else {
+        s->stream.next_in  = s->inbuf = (Byte*)ALLOC(Z_BUFSIZE);
+
+        err = 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 (err != Z_OK || s->inbuf == Z_NULL) {
+            return destroy(s), (gzFile)Z_NULL;
+        }
+    }
+    s->stream.avail_out = Z_BUFSIZE;
+
+    errno = 0;
+    s->file = fd < 0 ? F_OPEN(path, fmode) : (FILE*)fdopen(fd, fmode);
+
+    if (s->file == NULL) {
+        return destroy(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", gz_magic[0], gz_magic[1],
+             Z_DEFLATED, 0 /*flags*/, 0,0,0,0 /*time*/, 0 /*xflags*/, 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 {
+        check_header(s); /* skip the .gz header */
+        s->startpos = (ftell(s->file) - s->stream.avail_in);
+    }
+    
+    return (gzFile)s;
+}
+
+/* ===========================================================================
+     Opens a gzip (.gz) file for reading or writing.
+*/
+gzFile ZEXPORT gzopen (path, mode)
+    const char *path;
+    const char *mode;
+{
+    return gz_open (path, mode, -1);
+}
+
+/* ===========================================================================
+     Associate a gzFile with the file descriptor fd. fd is not dup'ed here
+   to mimic the behavio(u)r of fdopen.
+*/
+gzFile ZEXPORT gzdopen (fd, mode)
+    int fd;
+    const char *mode;
+{
+    char name[20];
+
+    if (fd < 0) return (gzFile)Z_NULL;
+    sprintf(name, "<fd:%d>", fd); /* for debugging */
+
+    return gz_open (name, mode, fd);
+}
+
+/* ===========================================================================
+ * Update the compression level and strategy
+ */
+int ZEXPORT gzsetparams (file, level, strategy)
+    gzFile file;
+    int level;
+    int strategy;
+{
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
+
+    /* Make room to allow flushing */
+    if (s->stream.avail_out == 0) {
+
+        s->stream.next_out = s->outbuf;
+        if (fwrite(s->outbuf, 1, Z_BUFSIZE, s->file) != Z_BUFSIZE) {
+            s->z_err = Z_ERRNO;
+        }
+        s->stream.avail_out = Z_BUFSIZE;
+    }
+
+    return deflateParams (&(s->stream), level, strategy);
+}
+
+/* ===========================================================================
+     Read a byte from a gz_stream; update next_in and avail_in. Return EOF
+   for end of file.
+   IN assertion: the stream s has been sucessfully opened for reading.
+*/
+local int get_byte(s)
+    gz_stream *s;
+{
+    if (s->z_eof) return EOF;
+    if (s->stream.avail_in == 0) {
+        errno = 0;
+        s->stream.avail_in = fread(s->inbuf, 1, Z_BUFSIZE, s->file);
+        if (s->stream.avail_in == 0) {
+            s->z_eof = 1;
+            if (ferror(s->file)) s->z_err = Z_ERRNO;
+            return EOF;
+        }
+        s->stream.next_in = s->inbuf;
+    }
+    s->stream.avail_in--;
+    return *(s->stream.next_in)++;
+}
+
+/* ===========================================================================
+      Check the gzip header of a gz_stream opened for reading. Set the stream
+    mode to transparent if the gzip magic header is not present; set 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.
+*/
+local void check_header(s)
+    gz_stream *s;
+{
+    int method; /* method byte */
+    int flags;  /* flags byte */
+    uInt len;
+    int c;
+
+    /* Check the gzip magic header */
+    for (len = 0; len < 2; len++) {
+        c = get_byte(s);
+        if (c != gz_magic[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 = get_byte(s);
+    flags = get_byte(s);
+    if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
+        s->z_err = Z_DATA_ERROR;
+        return;
+    }
+
+    /* Discard time, xflags and OS code: */
+    for (len = 0; len < 6; len++) (void)get_byte(s);
+
+    if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
+        len  =  (uInt)get_byte(s);
+        len += ((uInt)get_byte(s))<<8;
+        /* len is garbage if EOF but the loop below will quit anyway */
+        while (len-- != 0 && get_byte(s) != EOF) ;
+    }
+    if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
+        while ((c = get_byte(s)) != 0 && c != EOF) ;
+    }
+    if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
+        while ((c = get_byte(s)) != 0 && c != EOF) ;
+    }
+    if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
+        for (len = 0; len < 2; len++) (void)get_byte(s);
+    }
+    s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
+}
+
+ /* ===========================================================================
+ * Cleanup then free the given gz_stream. Return a zlib error code.
+   Try freeing in the reverse order of allocations.
+ */
+local int destroy (s)
+    gz_stream *s;
+{
+    int err = Z_OK;
+
+    if (!s) return Z_STREAM_ERROR;
+
+    TRYFREE(s->msg);
+
+    if (s->stream.state != NULL) {
+        if (s->mode == 'w') {
+#ifdef NO_DEFLATE
+            err = Z_STREAM_ERROR;
+#else
+            err = deflateEnd(&(s->stream));
+#endif
+        } else if (s->mode == 'r') {
+            err = inflateEnd(&(s->stream));
+        }
+    }
+    if (s->file != NULL && fclose(s->file)) {
+#ifdef ESPIPE
+        if (errno != ESPIPE) /* fclose is broken for pipes in HP/UX */
+#endif
+            err = Z_ERRNO;
+    }
+    if (s->z_err < 0) err = s->z_err;
+
+    TRYFREE(s->inbuf);
+    TRYFREE(s->outbuf);
+    TRYFREE(s->path);
+    TRYFREE(s);
+    return err;
+}
+
+/* ===========================================================================
+     Reads the given number of uncompressed bytes from the compressed file.
+   gzread returns the number of bytes actually read (0 for end of file).
+*/
+int ZEXPORT gzread (file, buf, len)
+    gzFile file;
+    voidp buf;
+    unsigned len;
+{
+    gz_stream *s = (gz_stream*)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') return Z_STREAM_ERROR;
+
+    if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO) return -1;
+    if (s->z_err == Z_STREAM_END) 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) {
+                zmemcpy(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 -= fread(next_out, 1, s->stream.avail_out,
+                                             s->file);
+            }
+            len -= s->stream.avail_out;
+            s->stream.total_in  += (uLong)len;
+            s->stream.total_out += (uLong)len;
+            if (len == 0) s->z_eof = 1;
+            return (int)len;
+        }
+        if (s->stream.avail_in == 0 && !s->z_eof) {
+
+            errno = 0;
+            s->stream.avail_in = fread(s->inbuf, 1, 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 (getLong(s) != s->crc) {
+                s->z_err = Z_DATA_ERROR;
+            } else {
+                (void)getLong(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:
+                 */
+                check_header(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));
+
+    return (int)(len - s->stream.avail_out);
+}
+
+
+/* ===========================================================================
+      Reads one byte from the compressed file. gzgetc returns this byte
+   or -1 in case of end of file or error.
+*/
+int ZEXPORT gzgetc(file)
+    gzFile file;
+{
+    unsigned char c;
+
+    return gzread(file, &c, 1) == 1 ? c : -1;
+}
+
+
+/* ===========================================================================
+      Reads bytes from the compressed file until len-1 characters are
+   read, or a newline character is read and transferred to buf, or an
+   end-of-file condition is encountered.  The string is then terminated
+   with a null character.
+      gzgets returns buf, or Z_NULL in case of error.
+
+      The current implementation is not optimized at all.
+*/
+char * ZEXPORT gzgets(file, buf, len)
+    gzFile file;
+    char *buf;
+    int len;
+{
+    char *b = buf;
+    if (buf == Z_NULL || len <= 0) return Z_NULL;
+
+    while (--len > 0 && gzread(file, buf, 1) == 1 && *buf++ != '\n') ;
+    *buf = '\0';
+    return b == buf && len > 0 ? Z_NULL : b;
+}
+
+
+#ifndef NO_DEFLATE
+/* ===========================================================================
+     Writes the given number of uncompressed bytes into the compressed file.
+   gzwrite returns the number of bytes actually written (0 in case of error).
+*/
+int ZEXPORT gzwrite (file, buf, len)
+    gzFile file;
+    const voidp buf;
+    unsigned len;
+{
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
+
+    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, Z_BUFSIZE, s->file) != Z_BUFSIZE) {
+                s->z_err = Z_ERRNO;
+                break;
+            }
+            s->stream.avail_out = 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);
+
+    return (int)(len - s->stream.avail_in);
+}
+
+/* ===========================================================================
+     Converts, formats, and writes the args to the compressed file under
+   control of the format string, as in fprintf. gzprintf returns the number of
+   uncompressed bytes actually written (0 in case of error).
+*/
+#ifdef STDC
+#include <stdarg.h>
+
+int ZEXPORTVA gzprintf (gzFile file, const char *format, /* args */ ...)
+{
+    char buf[Z_PRINTF_BUFSIZE];
+    va_list va;
+    int len;
+
+    va_start(va, format);
+#ifdef HAS_vsnprintf
+    (void)vsnprintf(buf, sizeof(buf), format, va);
+#else
+    (void)vsprintf(buf, format, va);
+#endif
+    va_end(va);
+    len = strlen(buf); /* some *sprintf don't return the nb of bytes written */
+    if (len <= 0) return 0;
+
+    return gzwrite(file, buf, (unsigned)len);
+}
+#else /* not ANSI C */
+
+int ZEXPORTVA gzprintf (file, format, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10,
+                       a11, a12, a13, a14, a15, a16, a17, a18, a19, a20)
+    gzFile file;
+    const char *format;
+    int a1, a2, a3, a4, a5, a6, a7, a8, a9, a10,
+        a11, a12, a13, a14, a15, a16, a17, a18, a19, a20;
+{
+    char buf[Z_PRINTF_BUFSIZE];
+    int len;
+
+#ifdef HAS_snprintf
+    snprintf(buf, sizeof(buf), format, a1, a2, a3, a4, a5, a6, a7, a8,
+             a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
+#else
+    sprintf(buf, format, a1, a2, a3, a4, a5, a6, a7, a8,
+            a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
+#endif
+    len = strlen(buf); /* old sprintf doesn't return the nb of bytes written */
+    if (len <= 0) return 0;
+
+    return gzwrite(file, buf, len);
+}
+#endif
+
+/* ===========================================================================
+      Writes c, converted to an unsigned char, into the compressed file.
+   gzputc returns the value that was written, or -1 in case of error.
+*/
+int ZEXPORT gzputc(file, c)
+    gzFile file;
+    int c;
+{
+    unsigned char cc = (unsigned char) c; /* required for big endian systems */
+
+    return gzwrite(file, &cc, 1) == 1 ? (int)cc : -1;
+}
+
+
+/* ===========================================================================
+      Writes the given null-terminated string to the compressed file, excluding
+   the terminating null character.
+      gzputs returns the number of characters written, or -1 in case of error.
+*/
+int ZEXPORT gzputs(file, s)
+    gzFile file;
+    const char *s;
+{
+    return gzwrite(file, (char*)s, (unsigned)strlen(s));
+}
+
+
+/* ===========================================================================
+     Flushes all pending output into the compressed file. The parameter
+   flush is as in the deflate() function.
+*/
+local int do_flush (file, flush)
+    gzFile file;
+    int flush;
+{
+    uInt len;
+    int done = 0;
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
+
+    s->stream.avail_in = 0; /* should be zero already anyway */
+
+    for (;;) {
+        len = 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 = 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;
+}
+
+int ZEXPORT gzflush (file, flush)
+     gzFile file;
+     int flush;
+{
+    gz_stream *s = (gz_stream*)file;
+    int err = do_flush (file, flush);
+
+    if (err) return err;
+    fflush(s->file);
+    return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
+}
+#endif /* NO_DEFLATE */
+
+/* ===========================================================================
+      Sets the starting position for the next gzread or gzwrite on the given
+   compressed file. The offset represents a number of bytes in the
+      gzseek returns the resulting offset location as measured in bytes from
+   the beginning of the uncompressed stream, or -1 in case of error.
+      SEEK_END is not implemented, returns error.
+      In this version of the library, gzseek can be extremely slow.
+*/
+z_off_t ZEXPORT gzseek (file, offset, whence)
+    gzFile file;
+    z_off_t offset;
+    int whence;
+{
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL || whence == SEEK_END ||
+        s->z_err == Z_ERRNO || s->z_err == Z_DATA_ERROR) {
+        return -1L;
+    }
+    
+    if (s->mode == 'w') {
+#ifdef NO_DEFLATE
+        return -1L;
+#else
+        if (whence == SEEK_SET) {
+            offset -= s->stream.total_in;
+        }
+        if (offset < 0) return -1L;
+
+        /* At this point, offset is the number of zero bytes to write. */
+        if (s->inbuf == Z_NULL) {
+            s->inbuf = (Byte*)ALLOC(Z_BUFSIZE); /* for seeking */
+            zmemzero(s->inbuf, Z_BUFSIZE);
+        }
+        while (offset > 0)  {
+            uInt size = Z_BUFSIZE;
+            if (offset < Z_BUFSIZE) size = (uInt)offset;
+
+            size = gzwrite(file, s->inbuf, size);
+            if (size == 0) return -1L;
+
+            offset -= size;
+        }
+        return (z_off_t)s->stream.total_in;
+#endif
+    }
+    /* Rest of function is for reading only */
+
+    /* compute absolute position */
+    if (whence == SEEK_CUR) {
+        offset += s->stream.total_out;
+    }
+    if (offset < 0) return -1L;
+
+    if (s->transparent) {
+        /* map to fseek */
+        s->stream.avail_in = 0;
+        s->stream.next_in = s->inbuf;
+        if (fseek(s->file, offset, SEEK_SET) < 0) return -1L;
+
+        s->stream.total_in = s->stream.total_out = (uLong)offset;
+        return offset;
+    }
+
+    /* For a negative seek, rewind and use positive seek */
+    if ((uLong)offset >= s->stream.total_out) {
+        offset -= s->stream.total_out;
+    } else if (gzrewind(file) < 0) {
+        return -1L;
+    }
+    /* offset is now the number of bytes to skip. */
+
+    if (offset != 0 && s->outbuf == Z_NULL) {
+        s->outbuf = (Byte*)ALLOC(Z_BUFSIZE);
+    }
+    while (offset > 0)  {
+        int size = Z_BUFSIZE;
+        if (offset < Z_BUFSIZE) size = (int)offset;
+
+        size = gzread(file, s->outbuf, (uInt)size);
+        if (size <= 0) return -1L;
+        offset -= size;
+    }
+    return (z_off_t)s->stream.total_out;
+}
+
+/* ===========================================================================
+     Rewinds input file. 
+*/
+int ZEXPORT gzrewind (file)
+    gzFile file;
+{
+    gz_stream *s = (gz_stream*)file;
+    
+    if (s == NULL || s->mode != 'r') return -1;
+
+    s->z_err = Z_OK;
+    s->z_eof = 0;
+    s->stream.avail_in = 0;
+    s->stream.next_in = s->inbuf;
+    s->crc = crc32(0L, Z_NULL, 0);
+        
+    if (s->startpos == 0) { /* not a compressed file */
+        rewind(s->file);
+        return 0;
+    }
+
+    (void) inflateReset(&s->stream);
+    return fseek(s->file, s->startpos, SEEK_SET);
+}
+
+/* ===========================================================================
+     Returns the starting position for the next gzread or gzwrite on the
+   given compressed file. This position represents a number of bytes in the
+   uncompressed data stream.
+*/
+z_off_t ZEXPORT gztell (file)
+    gzFile file;
+{
+    return gzseek(file, 0L, SEEK_CUR);
+}
+
+/* ===========================================================================
+     Returns 1 when EOF has previously been detected reading the given
+   input stream, otherwise zero.
+*/
+int ZEXPORT gzeof (file)
+    gzFile file;
+{
+    gz_stream *s = (gz_stream*)file;
+    
+    return (s == NULL || s->mode != 'r') ? 0 : s->z_eof;
+}
+
+/* ===========================================================================
+   Outputs a long in LSB order to the given file
+*/
+local void putLong (file, x)
+    FILE *file;
+    uLong x;
+{
+    int n;
+    for (n = 0; n < 4; n++) {
+        fputc((int)(x & 0xff), file);
+        x >>= 8;
+    }
+}
+
+/* ===========================================================================
+   Reads a long in LSB order from the given gz_stream. Sets z_err in case
+   of error.
+*/
+local uLong getLong (s)
+    gz_stream *s;
+{
+    uLong x = (uLong)get_byte(s);
+    int c;
+
+    x += ((uLong)get_byte(s))<<8;
+    x += ((uLong)get_byte(s))<<16;
+    c = get_byte(s);
+    if (c == EOF) s->z_err = Z_DATA_ERROR;
+    x += ((uLong)c)<<24;
+    return x;
+}
+
+/* ===========================================================================
+     Flushes all pending output if necessary, closes the compressed file
+   and deallocates all the (de)compression state.
+*/
+int ZEXPORT gzclose (file)
+    gzFile file;
+{
+    int err;
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL) return Z_STREAM_ERROR;
+
+    if (s->mode == 'w') {
+#ifdef NO_DEFLATE
+        return Z_STREAM_ERROR;
+#else
+        err = do_flush (file, Z_FINISH);
+        if (err != Z_OK) return destroy((gz_stream*)file);
+
+        putLong (s->file, s->crc);
+        putLong (s->file, s->stream.total_in);
+#endif
+    }
+    return destroy((gz_stream*)file);
+}
+
+/* ===========================================================================
+     Returns the error message for the last error which occured on the
+   given compressed file. errnum is set to zlib error number. If an
+   error occured in the file system and not in the compression library,
+   errnum is set to Z_ERRNO and the application may consult errno
+   to get the exact error code.
+*/
+const char*  ZEXPORT gzerror (file, errnum)
+    gzFile file;
+    int *errnum;
+{
+    char *m;
+    gz_stream *s = (gz_stream*)file;
+
+    if (s == NULL) {
+        *errnum = Z_STREAM_ERROR;
+        return (const char*)ERR_MSG(Z_STREAM_ERROR);
+    }
+    *errnum = s->z_err;
+    if (*errnum == Z_OK) return (const char*)"";
+
+    m =  (char*)(*errnum == Z_ERRNO ? zstrerror(errno) : s->stream.msg);
+
+    if (m == NULL || *m == '\0') m = (char*)ERR_MSG(s->z_err);
+
+    TRYFREE(s->msg);
+    s->msg = (char*)ALLOC(strlen(s->path) + strlen(m) + 3);
+    strcpy(s->msg, s->path);
+    strcat(s->msg, ": ");
+    strcat(s->msg, m);
+    return (const char*)s->msg;
+}