    /* 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

    /* Local functions */
    local void gz_reset OF((gz_statep));
    local gzFile gz_open OF((const void *, int, const char *));

    #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 (error)
         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 */
    local void gz_reset(state)
        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. */
    local gzFile gz_open(path, fd, mode)
        const void *path;
        int fd;
        const char *mode;
    {
        gz_statep state;
        size_t len;
        int oflag;
    #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, 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, 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
            strcpy(state->path, 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(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;
    }

    /* -- see zlib.h -- */
    gzFile ZEXPORT gzopen(path, mode)
        const char *path;
        const char *mode;
    {
        return gz_open(path, -1, mode);
    }

    /* -- see zlib.h -- */
    gzFile ZEXPORT gzopen64(path, mode)
        const char *path;
        const char *mode;
    {
        return gz_open(path, -1, mode);
    }

    /* -- see zlib.h -- */
    gzFile ZEXPORT gzdopen(fd, mode)
        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;
    }

    /* -- see zlib.h -- */
    #ifdef _WIN32
    gzFile ZEXPORT gzopen_w(path, mode)
        const wchar_t *path;
        const char *mode;
    {
        return gz_open(path, -2, mode);
    }
    #endif

    /* -- see zlib.h -- */
    int ZEXPORT gzbuffer(file, size)
        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;
    }

    /* -- see zlib.h -- */
    int ZEXPORT gzrewind(file)
        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;
    }

    /* -- see zlib.h -- */
    z_off64_t ZEXPORT gzseek64(file, offset, whence)
        gzFile file;
        z_off64_t offset;
        int whence;
    {
        unsigned n;
        z_off64_t ret;
        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 == COPY &&
                state->x.pos + offset >= 0) {
            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;
    }

    /* -- see zlib.h -- */
    z_off_t ZEXPORT gzseek(file, offset, whence)
        gzFile file;
        z_off_t offset;
        int whence;
    {
        z_off64_t ret;

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

    /* -- see zlib.h -- */
    z_off64_t ZEXPORT gztell64(file)
        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);
    }

    /* -- see zlib.h -- */
    z_off_t ZEXPORT gztell(file)
        gzFile file;
    {
        z_off64_t ret;

        ret = gztell64(file);
        return ret == (z_off_t)ret ? (z_off_t)ret : -1;
    }

    /* -- see zlib.h -- */
    z_off64_t ZEXPORT gzoffset64(file)
        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;
    }

    /* -- see zlib.h -- */
    z_off_t ZEXPORT gzoffset(file)
        gzFile file;
    {
        z_off64_t ret;

        ret = gzoffset64(file);
        return ret == (z_off_t)ret ? (z_off_t)ret : -1;
    }

    /* -- see zlib.h -- */
    int ZEXPORT gzeof(file)
        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;
    }

    /* -- see zlib.h -- */
    const char * ZEXPORT gzerror(file, errnum)
        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);
    }

    /* -- see zlib.h -- */
    void ZEXPORT gzclearerr(file)
        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(state, err, msg)
        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
        strcpy(state->msg, state->path);
        strcat(state->msg, ": ");
        strcat(state->msg, msg);
    #endif
        return;
    }

    #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()
    {
        unsigned p, q;

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