/* gzlib.c -- zlib functions common to reading and writing gzip files

 * Copyright (C) 2004-2025 Mark Adler

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

#include "gzguts.h"

#if defined(__DJGPP__)

#  define LSEEK llseek

#elif defined(_WIN32) && !defined(__BORLANDC__) && !defined(UNDER_CE)

#  define LSEEK _lseeki64

#elif defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0

#  define LSEEK lseek64

#else

#  define LSEEK lseek

#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);       /* assumes buf is big enough */

        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(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->junk = -1;           /* mark first member */

    }

    else                            /* for writing ... */

        state->reset = 0;           /* no deflateReset pending */

    state->again = 0;               /* no stalled i/o yet */

    state->skip = 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(const void *path, int fd, const char *mode) {

    gz_statep state;

    z_size_t len;

    int oflag = 0;

#ifdef O_EXCL

    int exclusive = 0;

#endif

    /* check input */

    if (path == NULL || mode == 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->err = Z_OK;          /* no error yet */

    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':

                oflag |= O_CLOEXEC;

                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 'G':

                state->direct = -1;

                break;

#ifdef O_NONBLOCK

            case 'N':

                oflag |= O_NONBLOCK;

                break;

#endif

            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;

    }

    /* direct is 0, 1 if "T", or -1 if "G" (last "G" or "T" wins) */

    if (state->mode == GZ_READ) {

        if (state->direct == 1) {

            /* can't force a transparent read */

            free(state);

            return NULL;

        }

        if (state->direct == 0)

            /* default when reading is auto-detect of gzip vs. transparent --

               start with a transparent assumption in case of an empty file */

            state->direct = 1;

    }

    else if (state->direct == -1) {

        /* "G" has no meaning when writing -- disallow it */

        free(state);

        return NULL;

    }

    /* if reading, direct == 1 for auto-detect, -1 for gzip only; if writing or

       appending, direct == 0 for gzip, 1 for transparent (copy in to out) */

    /* save the path name for error messages */

#ifdef WIDECHAR

    if (fd == -2)

        len = wcstombs(NULL, path, 0);

    else

#endif

        len = strlen((const char *)path);

    state->path = (char *)malloc(len + 1);

    if (state->path == NULL) {

        free(state);

        return NULL;

    }

#ifdef WIDECHAR

    if (fd == -2) {

        if (len)

            wcstombs(state->path, path, len + 1);

        else

            *(state->path) = 0;

    }

    else

#endif

    {

#if !defined(NO_snprintf) && !defined(NO_vsnprintf)

        (void)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

        (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) */

    if (fd == -1)

        state->fd = open((const char *)path, oflag, 0666);

#ifdef WIDECHAR

    else if (fd == -2)

        state->fd = _wopen(path, oflag, _S_IREAD | _S_IWRITE);

#endif

    else {

#ifdef O_NONBLOCK

        if (oflag & O_NONBLOCK)

            fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);

#endif

#ifdef O_CLOEXEC

        if (oflag & O_CLOEXEC)

            fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | O_CLOEXEC);

#endif

        state->fd = fd;

    }

    if (state->fd == -1) {

        free(state->path);

        free(state);

        return NULL;

    }

    if (state->mode == GZ_APPEND) {

        LSEEK(state->fd, 0, SEEK_END);  /* so gzoffset() is correct */

        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(const char *path, const char *mode) {

    return gz_open(path, -1, mode);

}

/* -- see zlib.h -- */

gzFile ZEXPORT gzopen64(const char *path, const char *mode) {

    return gz_open(path, -1, mode);

}

/* -- see zlib.h -- */

gzFile ZEXPORT 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)

    (void)snprintf(path, 7 + 3 * sizeof(int), "<fd:%d>", fd);

#else

    sprintf(path, "<fd:%d>", fd);   /* for debugging */

#endif

    gz = gz_open(path, fd, mode);

    free(path);

    return gz;

}

/* -- see zlib.h -- */

#ifdef WIDECHAR

gzFile ZEXPORT gzopen_w(const wchar_t *path, const char *mode) {

    return gz_open(path, -2, mode);

}

#endif

/* -- see zlib.h -- */

int ZEXPORT 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 << 1) < size)

        return -1;              /* need to be able to double it */

    if (size < 8)

        size = 8;               /* needed to behave well with flushing */

    state->want = size;

    return 0;

}

/* -- see zlib.h -- */

int ZEXPORT 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;

}

/* -- see zlib.h -- */

z_off64_t ZEXPORT gzseek64(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 {

        offset += state->past ? 0 : state->skip;

        state->skip = 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 - (z_off64_t)state->x.have, SEEK_CUR);

        if (ret == -1)

            return -1;

        state->x.have = 0;

        state->eof = 0;

        state->past = 0;

        state->skip = 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) */

    state->skip = offset;

    return state->x.pos + offset;

}

/* -- see zlib.h -- */

z_off_t ZEXPORT gzseek(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(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->past ? 0 : state->skip);

}

/* -- see zlib.h -- */

z_off_t ZEXPORT gztell(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(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(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(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(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(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->again)

        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)

    (void)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

}

/* 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) {

#ifdef INT_MAX

    return INT_MAX;

#else

    unsigned p = 1, q;

    do {

        q = p;

        p <<= 1;

        p++;

    } while (p > q);

    return q >> 1;

#endif

}