/* gzread.c -- zlib functions for reading gzip files
 * Copyright (C) 2004, 2005, 2010, 2011, 2012, 2013 Mark Adler
 * Copyright (C) 2004, 2005, 2010, 2011, 2012, 2013, 2016 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "gzguts.h"

/* Local functions */
local int gz_load OF((gz_statep, unsigned char *, unsigned, unsigned *));
local int gz_avail OF((gz_statep));
local int gz_look OF((gz_statep));
local int gz_decomp OF((gz_statep));
local int gz_fetch OF((gz_statep));
local int gz_skip OF((gz_statep, z_off64_t));
local z_size_t gz_read OF((gz_statep, voidp, z_size_t));

/* Use read() to load a buffer -- return -1 on error, otherwise 0.  Read from
   state->fd, and update state->eof, state->err, and state->msg as appropriate.
   This function needs to loop on read(), since read() is not guaranteed to
   read the number of bytes requested, depending on the type of descriptor. */
local int gz_load(state, buf, len, have)
    gz_statep state;
    unsigned char *buf;
    unsigned len;
    unsigned *have;
{
    int ret;
    unsigned get, max = ((unsigned)-1 >> 2) + 1;

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

    /* 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);
            free(state->out);
            if (state->in != NULL)
                free(state->in);
            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;

            /* get more output, looking for header if required */
            if (gz_fetch(state) == -1)
                return -1;
        }
    return 0;
}

/* -- see zlib.h -- */
int ZEXPORT gzread(file, buf, len)
    gzFile file;
/* Read len bytes into buf from file, or less than len up to the end of the
   input.  Return the number of bytes read.  If zero is returned, either the
   end of file was reached, or there was an error.  state->err must be
   consulted in that case to determine which. */
local z_size_t gz_read(state, buf, len)
    gz_statep state;
    voidp buf;
    unsigned len;
    z_size_t len;
{
    z_size_t got;
    unsigned got, n;
    unsigned 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;
            return 0;
    }

    /* get len bytes to buf, or less than len if at the end */
    got = 0;
    do {
        /* set n to the maximum amount of len that fits in an unsigned int */
        n = -1;
        if (n > len)
            n = len;

        /* first just try copying data from the output buffer */
        if (state->x.have) {
            if (state->x.have < n)
            n = state->x.have > len ? len : state->x.have;
                n = 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) {
        else if (state->eof && state->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)) {
        else if (state->how == LOOK || n < (state->size << 1)) {
            /* get more output, looking for header if required */
            if (gz_fetch(state) == -1)
                return -1;
                return 0;
            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;
            if (gz_load(state, (unsigned char *)buf, n, &n) == -1)
                return 0;
        }

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

/* -- see zlib.h -- */
int ZEXPORT gzread(file, buf, len)
    gzFile file;
    voidp buf;
    unsigned len;
{
    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;

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

    /* read len or fewer bytes to buf */
    len = gz_read(state, buf, len);

    /* check for an error */
    if (len == 0 && state->err != Z_OK && state->err != Z_BUF_ERROR)
        return -1;

    /* return the number of bytes read (this is assured to fit in an int) */
    return (int)len;
}

/* -- see zlib.h -- */
z_size_t ZEXPORT gzfread(buf, size, nitems, file)
    voidp buf;
    z_size_t size;
    z_size_t nitems;
    gzFile file;
{
    z_size_t len;
    gz_statep state;

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

    /* compute bytes to read -- error on overflow */
    len = nitems * size;
    if (size && len / size != nitems) {
        gz_error(state, Z_STREAM_ERROR, "request does not fit in a size_t");
        return 0;
    }

    /* read len or fewer bytes to buf, return the number of full items read */
    return len ? gz_read(state, buf, len) / size : 0;
}

/* -- see zlib.h -- */
#ifdef Z_PREFIX_SET
#  undef z_gzgetc
#else
#  undef gzgetc

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

int ZEXPORT gzgetc_(file)
gzFile file;
{
    return gzgetc(file);

    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.next[0] = (unsigned char)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)) {

        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.next[0] = (unsigned char)c;
    state->x.pos--;
    state->past = 0;
    return c;
}

/* -- see zlib.h -- */
char * ZEXPORT gzgets(file, buf, len)