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

 * Copyright (C) 2004-2026 Mark Adler

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

 */

#include "zbuild.h"

#include "zutil.h"

#include "zutil_p.h"

#include "gzguts.h"

#if defined(_WIN32)

#  define LSEEK _lseeki64

#else

#if defined(_LARGEFILE64_SOURCE) && _LFS64_LARGEFILE-0

#  define LSEEK lseek64

#else

#  define LSEEK lseek

#endif

#endif

/* Local functions */

static gzFile gz_state_init(void);

static void gz_reset(gz_state *);

static gzFile gz_open(const void *, int, const char *);

/* Initialize struct for gzFile state */

static gzFile gz_state_init(void) {

    /* allocate gzFile structure to return */

    gz_state *state = (gz_state *)zng_alloc(sizeof(gz_state));

    if (state == NULL)

        return NULL;

    state->strm.zalloc = NULL;

    state->strm.zfree = NULL;

    state->strm.opaque = NULL;

    state->strm.next_in = NULL;

    state->size = 0;

    state->want = GZBUFSIZE;

    state->in = NULL;

    state->out = NULL;

    state->direct = 0;

    state->mode = GZ_NONE;

    state->level = Z_DEFAULT_COMPRESSION;

    state->strategy = Z_DEFAULT_STRATEGY;

    state->msg = NULL;

    state->past = 0;

    state->skip = 0;

    return (gzFile)state;

}

void Z_INTERNAL gz_state_free(gz_state *state) {

    zng_free(state);

}

/* Reset gzip file state */

static void gz_reset(gz_state *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 */

    }

    else                            /* for writing ... */

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

    state->skip = 0;                /* no seek request pending */

    PREFIX(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 */

}

/* Allocate in/out buffers for gzFile */

int Z_INTERNAL gz_buffer_alloc(gz_state *state) {

    unsigned want = state->want;

    unsigned in_size = want, out_size = want;

    if (state->mode == GZ_WRITE) {

        in_size = want * 2; // double input buffer for compression (ref: gzprintf)

        if (state->direct)

            out_size = 0; // output buffer not needed in write + direct mode

    } else if (state->mode == GZ_READ) {

        out_size = want * 2;  // double output buffer for decompression

    }

    state->buffers = (unsigned char *)zng_alloc_aligned((in_size + out_size), 64);

    state->in = state->buffers;

    if (out_size) {

        state->out = state->buffers + (in_size); // Outbuffer goes after inbuffer

    }

    /* Return error if memory allocation failed */

    if (state->in == NULL || (out_size && state->out == NULL)) {

        gz_buffer_free(state);

        PREFIX(gz_error)(state, Z_MEM_ERROR, "out of memory");

        return -1;

    }

    state->size = want; // mark state as initialized

    return 0;

}

void Z_INTERNAL gz_buffer_free(gz_state *state) {

    zng_free_aligned(state->buffers);

    state->buffers = NULL;

    state->out = NULL;

    state->in = NULL;

    state->size = 0;

}

/* Open a gzip file either by name or file descriptor. */

static gzFile gz_open(const void *path, int fd, const char *mode) {

    gz_state *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 || mode == NULL)

        return NULL;

    /* Initialize gzFile state */

    state = (gz_state *)gz_state_init();

    if (state == NULL)

        return NULL;

    /* interpret mode */

    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 */

                gz_state_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 'G':

                state->direct = -1;

                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) {

        gz_state_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 */

            gz_state_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 */

        gz_state_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, (const wchar_t *)path, 0);

        if (len == (size_t)-1)

            len = 0;

    } else

#endif

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

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

    if (state->path == NULL) {

        gz_state_free(state);

        return NULL;

    }

#ifdef WIDECHAR

    if (fd == -2)

        if (len) {

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

        } else {

            *(state->path) = 0;

        }

    else

#endif

        (void)snprintf(state->path, len + 1, "%s", (const char *)path);

    /* 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 : (

#if defined(_WIN32)

        fd == -2 ? _wopen((const wchar_t *)path, oflag, 0666) :

#elif defined(__CYGWIN__)

        fd == -2 ? open(state->path, oflag, 0666) :

#endif

        open((const char *)path, oflag, 0666));

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

        free(state->path);

        gz_state_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 Z_EXPORT PREFIX(gzopen)(const char *path, const char *mode) {

    return gz_open(path, -1, mode);

}

#ifdef ZLIB_COMPAT

gzFile Z_EXPORT PREFIX4(gzopen)(const char *path, const char *mode) {

    return gz_open(path, -1, mode);

}

#endif

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

gzFile Z_EXPORT PREFIX(gzdopen)(int fd, const char *mode) {

    gzFile gz;

    char path[32];         /* identifier for error messages */

    if (fd == -1)

        return NULL;

    (void)snprintf(path, 32, "<fd:%d>", fd); /* for debugging */

    gz = gz_open(path, fd, mode);

    return gz;

}

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

#ifdef WIDECHAR

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

    return gz_open(path, -2, mode);

}

#endif

z_int32_t Z_EXPORT PREFIX(gzclose)(gzFile file) {

#ifndef NO_GZCOMPRESS

    gz_state *state;

    if (file == NULL)

        return Z_STREAM_ERROR;

    state = (gz_state *)file;

    return state->mode == GZ_READ ? PREFIX(gzclose_r)(file) : PREFIX(gzclose_w)(file);

#else

    return PREFIX(gzclose_r)(file);

#endif

}

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

z_int32_t Z_EXPORT PREFIX(gzbuffer)(gzFile file, z_uint32_t size) {

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return -1;

    state = (gz_state *)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 > GZBUFSIZE_MAX) {

#ifdef ZLIB_COMPAT

        size = GZBUFSIZE_MAX;   /* silently clamp to stay compatible with zlib */

#else

        PREFIX(gz_error)(state, Z_MEM_ERROR, "out of memory");

        return -1;              /* too large */

#endif

    }

    if (size < 8)

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

    state->want = size;

    return 0;

}

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

z_int32_t Z_EXPORT PREFIX(gzrewind)(gzFile file) {

    gz_state *state;

    /* get internal structure */

    if (file == NULL)

        return -1;

    state = (gz_state *)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 Z_EXPORT PREFIX4(gzseek)(gzFile file, z_off64_t offset, int whence) {

    unsigned n;

    z_off64_t ret;

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return -1;

    state = (gz_state *)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;

        PREFIX(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 (PREFIX(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 -- */

#ifdef ZLIB_COMPAT

z_off_t Z_EXPORT PREFIX(gzseek)(gzFile file, z_off_t offset, int whence) {

    z_off64_t ret;

    ret = PREFIX4(gzseek)(file, (z_off64_t)offset, whence);

    return ret == (z_off_t)ret ? (z_off_t)ret : -1;

}

#endif

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

z_off64_t Z_EXPORT PREFIX4(gztell)(gzFile file) {

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return -1;

    state = (gz_state *)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 -- */

#ifdef ZLIB_COMPAT

z_off_t Z_EXPORT PREFIX(gztell)(gzFile file) {

    z_off64_t ret;

    ret = PREFIX4(gztell)(file);

    return ret == (z_off_t)ret ? (z_off_t)ret : -1;

}

#endif

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

z_off64_t Z_EXPORT PREFIX4(gzoffset)(gzFile file) {

    z_off64_t offset;

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return -1;

    state = (gz_state *)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 -- */

#ifdef ZLIB_COMPAT

z_off_t Z_EXPORT PREFIX(gzoffset)(gzFile file) {

    z_off64_t ret;

    ret = PREFIX4(gzoffset)(file);

    return ret == (z_off_t)ret ? (z_off_t)ret : -1;

}

#endif

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

z_int32_t Z_EXPORT PREFIX(gzeof)(gzFile file) {

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return 0;

    state = (gz_state *)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 * Z_EXPORT PREFIX(gzerror)(gzFile file, z_int32_t *errnum) {

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return NULL;

    state = (gz_state *)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 Z_EXPORT PREFIX(gzclearerr)(gzFile file) {

    gz_state *state;

    /* get internal structure and check integrity */

    if (file == NULL)

        return;

    state = (gz_state *)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;

    }

    PREFIX(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 Z_INTERNAL PREFIX(gz_error)(gz_state *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 = malloc(strlen(state->path) + strlen(msg) + 3)) == NULL) {

        state->err = Z_MEM_ERROR;

        return;

    }

    (void)snprintf(state->msg, strlen(state->path) + strlen(msg) + 3, "%s%s%s", state->path, ": ", msg);

}

#ifdef ZLIB_COMPAT

unsigned Z_INTERNAL gz_intmax(void) {

    return INT_MAX;

}

#endif