gzread.c File Reference

#include "gzguts.h"

Include dependency graph for gzread.c:

Functions
static int gz_load	OF ((gz_statep, unsigned char *, unsigned, unsigned *))
static int gz_avail	OF ((gz_statep))
static int gz_skip	OF ((gz_statep, z_off64_t))
static int	gz_load (gz_statep state, unsigned char *buf, unsigned len, unsigned *have)
static int	gz_avail (gz_statep state)
static int	gz_look (gz_statep state)
static int	gz_decomp (gz_statep state)
static int	gz_fetch (gz_statep state)
static int	gz_skip (gz_statep state, z_off64_t len)
int ZEXPORT	gzread (gzFile file, voidp buf, unsigned len)
int ZEXPORT	gzgetc (gzFile file)
int ZEXPORT	gzgetc_ (gzFile file)
int ZEXPORT	gzungetc (int c, gzFile file)
char *ZEXPORT	gzgets (gzFile file, char *buf, int len)
int ZEXPORT	gzdirect (gzFile file)
int ZEXPORT	gzclose_r (gzFile file)

Function Documentation

static int gz_load OF ( (gz_statep, unsigned char *, unsigned, unsigned *)  )

static

static int gz_avail OF ( (gz_statep)  )

static

static int gz_skip OF ( (gz_statep, z_off64_t)  )

static

static int gz_load ( gz_statep  state, unsigned char *  buf, unsigned  len, unsigned *  have  )

static

{
    int ret;

    *have = 0;
    do {
        ret = read(state->fd, buf + *have, len - *have);
        if (ret <= 0)
            break;
        *have += ret;
    } while (*have < len);
    if (ret < 0) {
        gz_error(state, Z_ERRNO, zstrerror());
        return -1;
    }
    if (ret == 0)
        state->eof = 1;
    return 0;
}

static int gz_avail ( gz_statep  state )

static

{
    unsigned got;
    z_streamp strm = &(state->strm);

    if (state->err != Z_OK && state->err != Z_BUF_ERROR)
        return -1;
    if (state->eof == 0) {
        if (strm->avail_in) {       /* copy what's there to the start */
            unsigned char *p = state->in;
            unsigned const char *q = strm->next_in;
            unsigned n = strm->avail_in;
            do {
                *p++ = *q++;
            } while (--n);
        }
        if (gz_load(state, state->in + strm->avail_in,
                    state->size - strm->avail_in, &got) == -1)
            return -1;
        strm->avail_in += got;
        strm->next_in = state->in;
    }
    return 0;
}

static int gz_look ( gz_statep  state )

static

{
    z_streamp strm = &(state->strm);

    /* allocate read buffers and inflate memory */
    if (state->size == 0) {
        /* allocate buffers */
        state->in = (unsigned char *)malloc(state->want);
        state->out = (unsigned char *)malloc(state->want << 1);
        if (state->in == NULL || state->out == NULL) {
            if (state->out != NULL)
                free(state->out);
            if (state->in != NULL)
                free(state->in);
            gz_error(state, Z_MEM_ERROR, "out of memory");
            return -1;
        }
        state->size = state->want;

        /* allocate inflate memory */
        state->strm.zalloc = Z_NULL;
        state->strm.zfree = Z_NULL;
        state->strm.opaque = Z_NULL;
        state->strm.avail_in = 0;
        state->strm.next_in = Z_NULL;
        if (inflateInit2(&(state->strm), 15 + 16) != Z_OK) {    /* gunzip */
            free(state->out);
            free(state->in);
            state->size = 0;
            gz_error(state, Z_MEM_ERROR, "out of memory");
            return -1;
        }
    }

    /* get at least the magic bytes in the input buffer */
    if (strm->avail_in < 2) {
        if (gz_avail(state) == -1)
            return -1;
        if (strm->avail_in == 0)
            return 0;
    }

    /* look for gzip magic bytes -- if there, do gzip decoding (note: there is
       a logical dilemma here when considering the case of a partially written
       gzip file, to wit, if a single 31 byte is written, then we cannot tell
       whether this is a single-byte file, or just a partially written gzip
       file -- for here we assume that if a gzip file is being written, then
       the header will be written in a single operation, so that reading a
       single byte is sufficient indication that it is not a gzip file) */
    if (strm->avail_in > 1 &&
            strm->next_in[0] == 31 && strm->next_in[1] == 139) {
        inflateReset(strm);
        state->how = GZIP;
        state->direct = 0;
        return 0;
    }

    /* no gzip header -- if we were decoding gzip before, then this is trailing
       garbage.  Ignore the trailing garbage and finish. */
    if (state->direct == 0) {
        strm->avail_in = 0;
        state->eof = 1;
        state->x.have = 0;
        return 0;
    }

    /* doing raw i/o, copy any leftover input to output -- this assumes that
       the output buffer is larger than the input buffer, which also assures
       space for gzungetc() */
    state->x.next = state->out;
    if (strm->avail_in) {
        memcpy(state->x.next, strm->next_in, strm->avail_in);
        state->x.have = strm->avail_in;
        strm->avail_in = 0;
    }
    state->how = COPY;
    state->direct = 1;
    return 0;
}

static int gz_decomp ( gz_statep  state )

static

{
    int ret = Z_OK;
    unsigned had;
    z_streamp strm = &(state->strm);

    /* fill output buffer up to end of deflate stream */
    had = strm->avail_out;
    do {
        /* get more input for inflate() */
        if (strm->avail_in == 0 && gz_avail(state) == -1)
            return -1;
        if (strm->avail_in == 0) {
            gz_error(state, Z_BUF_ERROR, "unexpected end of file");
            break;
        }

        /* decompress and handle errors */
        ret = inflate(strm, Z_NO_FLUSH);
        if (ret == Z_STREAM_ERROR || ret == Z_NEED_DICT) {
            gz_error(state, Z_STREAM_ERROR,
                     "internal error: inflate stream corrupt");
            return -1;
        }
        if (ret == Z_MEM_ERROR) {
            gz_error(state, Z_MEM_ERROR, "out of memory");
            return -1;
        }
        if (ret == Z_DATA_ERROR) {              /* deflate stream invalid */
            gz_error(state, Z_DATA_ERROR,
                     strm->msg == NULL ? "compressed data error" : strm->msg);
            return -1;
        }
    } while (strm->avail_out && ret != Z_STREAM_END);

    /* update available output */
    state->x.have = had - strm->avail_out;
    state->x.next = strm->next_out - state->x.have;

    /* if the gzip stream completed successfully, look for another */
    if (ret == Z_STREAM_END)
        state->how = LOOK;

    /* good decompression */
    return 0;
}

static int gz_fetch ( gz_statep  state )

static

{
    z_streamp strm = &(state->strm);

    do {
        switch(state->how) {
        case LOOK:      /* -> LOOK, COPY (only if never GZIP), or GZIP */
            if (gz_look(state) == -1)
                return -1;
            if (state->how == LOOK)
                return 0;
            break;
        case COPY:      /* -> COPY */
            if (gz_load(state, state->out, state->size << 1, &(state->x.have))
                    == -1)
                return -1;
            state->x.next = state->out;
            return 0;
        case GZIP:      /* -> GZIP or LOOK (if end of gzip stream) */
            strm->avail_out = state->size << 1;
            strm->next_out = state->out;
            if (gz_decomp(state) == -1)
                return -1;
        }
    } while (state->x.have == 0 && (!state->eof || strm->avail_in));
    return 0;
}

static int gz_skip ( gz_statep  state, z_off64_t  len  )

static

{
    unsigned n;

    /* skip over len bytes or reach end-of-file, whichever comes first */
    while (len)
        /* skip over whatever is in output buffer */
        if (state->x.have) {
            n = GT_OFF(state->x.have) || (z_off64_t)state->x.have > len ?
                (unsigned)len : state->x.have;
            state->x.have -= n;
            state->x.next += n;
            state->x.pos += n;
            len -= n;
        }

        /* output buffer empty -- return if we're at the end of the input */
        else if (state->eof && state->strm.avail_in == 0)
            break;

        /* need more data to skip -- load up output buffer */
        else {
            /* get more output, looking for header if required */
            if (gz_fetch(state) == -1)
                return -1;
        }
    return 0;
}

int ZEXPORT gzread	(	gzFile	file,
		voidp	buf,
		unsigned	len
	)

{
    unsigned got, n;
    gz_statep state;
    z_streamp strm;

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

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

    /* since an int is returned, make sure len fits in one, otherwise return
       with an error (this avoids the flaw in the interface) */
    if ((int)len < 0) {
        gz_error(state, Z_DATA_ERROR, "requested length does not fit in int");
        return -1;
    }

    /* if len is zero, avoid unnecessary operations */
    if (len == 0)
        return 0;

    /* process a skip request */
    if (state->seek) {
        state->seek = 0;
        if (gz_skip(state, state->skip) == -1)
            return -1;
    }

    /* get len bytes to buf, or less than len if at the end */
    got = 0;
    do {
        /* first just try copying data from the output buffer */
        if (state->x.have) {
            n = state->x.have > len ? len : state->x.have;
            memcpy(buf, state->x.next, n);
            state->x.next += n;
            state->x.have -= n;
        }

        /* output buffer empty -- return if we're at the end of the input */
        else if (state->eof && strm->avail_in == 0) {
            state->past = 1;        /* tried to read past end */
            break;
        }

        /* need output data -- for small len or new stream load up our output
           buffer */
        else if (state->how == LOOK || len < (state->size << 1)) {
            /* get more output, looking for header if required */
            if (gz_fetch(state) == -1)
                return -1;
            continue;       /* no progress yet -- go back to copy above */
            /* the copy above assures that we will leave with space in the
               output buffer, allowing at least one gzungetc() to succeed */
        }

        /* large len -- read directly into user buffer */
        else if (state->how == COPY) {      /* read directly */
            if (gz_load(state, (unsigned char *)buf, len, &n) == -1)
                return -1;
        }

        /* large len -- decompress directly into user buffer */
        else {  /* state->how == GZIP */
            strm->avail_out = len;
            strm->next_out = (unsigned char *)buf;
            if (gz_decomp(state) == -1)
                return -1;
            n = state->x.have;
            state->x.have = 0;
        }

        /* update progress */
        len -= n;
        buf = (char *)buf + n;
        got += n;
        state->x.pos += n;
    } while (len);

    /* return number of bytes read into user buffer (will fit in int) */
    return (int)got;
}

int ZEXPORT gzgetc

(

gzFile

file

)

{
    int ret;
    unsigned char buf[1];
    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 (serious) error */
    if (state->mode != GZ_READ ||
        (state->err != Z_OK && state->err != Z_BUF_ERROR))
        return -1;

    /* try output buffer (no need to check for skip request) */
    if (state->x.have) {
        state->x.have--;
        state->x.pos++;
        return *(state->x.next)++;
    }

    /* nothing there -- try gzread() */
    ret = gzread(file, buf, 1);
    return ret < 1 ? -1 : buf[0];
}

int ZEXPORT gzgetc_

(

gzFile

file

)

{
    return gzgetc(file);
}

int ZEXPORT gzungetc	(	int	c,
		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 (serious) error */
    if (state->mode != GZ_READ ||
        (state->err != Z_OK && state->err != Z_BUF_ERROR))
        return -1;

    /* process a skip request */
    if (state->seek) {
        state->seek = 0;
        if (gz_skip(state, state->skip) == -1)
            return -1;
    }

    /* can't push EOF */
    if (c < 0)
        return -1;

    /* if output buffer empty, put byte at end (allows more pushing) */
    if (state->x.have == 0) {
        state->x.have = 1;
        state->x.next = state->out + (state->size << 1) - 1;
        state->x.next[0] = c;
        state->x.pos--;
        state->past = 0;
        return c;
    }

    /* if no room, give up (must have already done a gzungetc()) */
    if (state->x.have == (state->size << 1)) {
        gz_error(state, Z_DATA_ERROR, "out of room to push characters");
        return -1;
    }

    /* slide output data if needed and insert byte before existing data */
    if (state->x.next == state->out) {
        unsigned char *src = state->out + state->x.have;
        unsigned char *dest = state->out + (state->size << 1);
        while (src > state->out)
            *--dest = *--src;
        state->x.next = dest;
    }
    state->x.have++;
    state->x.next--;
    state->x.next[0] = c;
    state->x.pos--;
    state->past = 0;
    return c;
}

char* ZEXPORT gzgets	(	gzFile	file,
		char *	buf,
		int	len
	)

{
    unsigned left, n;
    char *str;
    unsigned char *eol;
    gz_statep state;

    /* check parameters and get internal structure */
    if (file == NULL || buf == NULL || len < 1)
        return NULL;
    state = (gz_statep)file;

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

    /* process a skip request */
    if (state->seek) {
        state->seek = 0;
        if (gz_skip(state, state->skip) == -1)
            return NULL;
    }

    /* copy output bytes up to new line or len - 1, whichever comes first --
       append a terminating zero to the string (we don't check for a zero in
       the contents, let the user worry about that) */
    str = buf;
    left = (unsigned)len - 1;
    if (left) do {
        /* assure that something is in the output buffer */
        if (state->x.have == 0 && gz_fetch(state) == -1)
            return NULL;                /* error */
        if (state->x.have == 0) {       /* end of file */
            state->past = 1;            /* read past end */
            break;                      /* return what we have */
        }

        /* look for end-of-line in current output buffer */
        n = state->x.have > left ? left : state->x.have;
        eol = (unsigned char *)memchr(state->x.next, '\n', n);
        if (eol != NULL)
            n = (unsigned)(eol - state->x.next) + 1;

        /* copy through end-of-line, or remainder if not found */
        memcpy(buf, state->x.next, n);
        state->x.have -= n;
        state->x.next += n;
        state->x.pos += n;
        left -= n;
        buf += n;
    } while (left && eol == NULL);

    /* return terminated string, or if nothing, end of file */
    if (buf == str)
        return NULL;
    buf[0] = 0;
    return str;
}

int ZEXPORT gzdirect

(

gzFile

file

)

{
    gz_statep state;

    /* get internal structure */
    if (file == NULL)
        return 0;
    state = (gz_statep)file;

    /* if the state is not known, but we can find out, then do so (this is
       mainly for right after a gzopen() or gzdopen()) */
    if (state->mode == GZ_READ && state->how == LOOK && state->x.have == 0)
        (void)gz_look(state);

    /* return 1 if transparent, 0 if processing a gzip stream */
    return state->direct;
}

int ZEXPORT gzclose_r

(

gzFile

file

)

{
    int ret, err;
    gz_statep state;

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

    /* check that we're reading */
    if (state->mode != GZ_READ)
        return Z_STREAM_ERROR;

    /* free memory and close file */
    if (state->size) {
        inflateEnd(&(state->strm));
        free(state->out);
        free(state->in);
    }
    err = state->err == Z_BUF_ERROR ? Z_BUF_ERROR : Z_OK;
    gz_error(state, Z_OK, NULL);
    free(state->path);
    ret = close(state->fd);
    free(state);
    return ret ? Z_ERRNO : err;
}