/* deflate_stored.c -- store data without compression using deflation algorithm

 *

 * Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler

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

 */

#include "zbuild.h"

#include "deflate.h"

#include "deflate_p.h"

#include "functable.h"

/* ===========================================================================

 * Copy without compression as much as possible from the input stream, return

 * the current block state.

 *

 * In case deflateParams() is used to later switch to a non-zero compression

 * level, s->matches (otherwise unused when storing) keeps track of the number

 * of hash table slides to perform. If s->matches is 1, then one hash table

 * slide will be done when switching. If s->matches is 2, the maximum value

 * allowed here, then the hash table will be cleared, since two or more slides

 * is the same as a clear.

 *

 * deflate_stored() is written to minimize the number of times an input byte is

 * copied. It is most efficient with large input and output buffers, which

 * maximizes the opportunities to have a single copy from next_in to next_out.

 */

Z_INTERNAL block_state deflate_stored(deflate_state *s, int flush) {

    /* Smallest worthy block size when not flushing or finishing. By default

     * this is 32K. This can be as small as 507 bytes for memLevel == 1. For

     * large input and output buffers, the stored block size will be larger.

     */

    unsigned min_block = MIN(s->pending_buf_size - 5, s->w_size);

    /* Copy as many min_block or larger stored blocks directly to next_out as

     * possible. If flushing, copy the remaining available input to next_out as

     * stored blocks, if there is enough space.

     */

    unsigned len, left, have, last = 0;

    unsigned used = s->strm->avail_in;

    do {

        /* Set len to the maximum size block that we can copy directly with the

         * available input data and output space. Set left to how much of that

         * would be copied from what's left in the window.

         */

        len = MAX_STORED;       /* maximum deflate stored block length */

        have = (s->bi_valid + 42) >> 3;         /* number of header bytes */

        if (s->strm->avail_out < have)          /* need room for header */

            break;

            /* maximum stored block length that will fit in avail_out: */

        have = s->strm->avail_out - have;

        left = (int)s->strstart - s->block_start;    /* bytes left in window */

        if (len > (unsigned long)left + s->strm->avail_in)

            len = left + s->strm->avail_in;     /* limit len to the input */

        len = MIN(len, have);                   /* limit len to the output */

        /* If the stored block would be less than min_block in length, or if

         * unable to copy all of the available input when flushing, then try

         * copying to the window and the pending buffer instead. Also don't

         * write an empty block when flushing -- deflate() does that.

         */

        if (len < min_block && ((len == 0 && flush != Z_FINISH) || flush == Z_NO_FLUSH || len != left + s->strm->avail_in))

            break;

        /* Make a dummy stored block in pending to get the header bytes,

         * including any pending bits. This also updates the debugging counts.

         */

        last = flush == Z_FINISH && len == left + s->strm->avail_in ? 1 : 0;

        zng_tr_stored_block(s, (char *)0, 0L, last);

        /* Replace the lengths in the dummy stored block with len. */

        s->pending -= 4;

        put_short(s, (uint16_t)len);

        put_short(s, (uint16_t)~len);

        /* Write the stored block header bytes. */

        PREFIX(flush_pending)(s->strm);

        /* Update debugging counts for the data about to be copied. */

        cmpr_bits_add(s, len << 3);

        sent_bits_add(s, len << 3);

        /* Copy uncompressed bytes from the window to next_out. */

        if (left) {

            left = MIN(left, len);

            memcpy(s->strm->next_out, s->window + s->block_start, left);

            s->strm->next_out += left;

            s->strm->avail_out -= left;

            s->strm->total_out += left;

            s->block_start += (int)left;

            len -= left;

        }

        /* Copy uncompressed bytes directly from next_in to next_out, updating

         * the check value.

         */

        if (len) {

            PREFIX(read_buf)(s->strm, s->strm->next_out, len);

            s->strm->next_out += len;

            s->strm->avail_out -= len;

            s->strm->total_out += len;

        }

    } while (last == 0);

    /* Update the sliding window with the last s->w_size bytes of the copied

     * data, or append all of the copied data to the existing window if less

     * than s->w_size bytes were copied. Also update the number of bytes to

     * insert in the hash tables, in the event that deflateParams() switches to

     * a non-zero compression level.

     */

    used -= s->strm->avail_in;      /* number of input bytes directly copied */

    if (used) {

        /* If any input was used, then no unused input remains in the window,

         * therefore s->block_start == s->strstart.

         */

        if (used >= s->w_size) {    /* supplant the previous history */

            s->matches = 2;         /* clear hash */

            memcpy(s->window, s->strm->next_in - s->w_size, s->w_size);

            s->strstart = s->w_size;

            s->insert = s->strstart;

        } else {

            if (s->window_size - s->strstart <= used) {

                /* Slide the window down. */

                s->strstart -= s->w_size;

                memcpy(s->window, s->window + s->w_size, s->strstart);

                if (s->matches < 2)

                    s->matches++;   /* add a pending slide_hash() */

                s->insert = MIN(s->insert, s->strstart);

            }

            memcpy(s->window + s->strstart, s->strm->next_in - used, used);

            s->strstart += used;

            s->insert += MIN(used, s->w_size - s->insert);

        }

        s->block_start = (int)s->strstart;

    }

    s->high_water = MAX(s->high_water, s->strstart);

    /* If the last block was written to next_out, then done. */

    if (last)

        return finish_done;

    /* If flushing and all input has been consumed, then done. */

    if (flush != Z_NO_FLUSH && flush != Z_FINISH && s->strm->avail_in == 0 && (int)s->strstart == s->block_start)

        return block_done;

    /* Fill the window with any remaining input. */

    have = s->window_size - s->strstart;

    if (s->strm->avail_in > have && s->block_start >= (int)s->w_size) {

        /* Slide the window down. */

        s->block_start -= (int)s->w_size;

        s->strstart -= s->w_size;

        memcpy(s->window, s->window + s->w_size, s->strstart);

        if (s->matches < 2)

            s->matches++;           /* add a pending slide_hash() */

        have += s->w_size;          /* more space now */

        s->insert = MIN(s->insert, s->strstart);

    }

    have = MIN(have, s->strm->avail_in);

    if (have) {

        PREFIX(read_buf)(s->strm, s->window + s->strstart, have);

        s->strstart += have;

        s->insert += MIN(have, s->w_size - s->insert);

    }

    s->high_water = MAX(s->high_water, s->strstart);

    /* There was not enough avail_out to write a complete worthy or flushed

     * stored block to next_out. Write a stored block to pending instead, if we

     * have enough input for a worthy block, or if flushing and there is enough

     * room for the remaining input as a stored block in the pending buffer.

     */

    have = (s->bi_valid + 42) >> 3;         /* number of header bytes */

        /* maximum stored block length that will fit in pending: */

    have = MIN(s->pending_buf_size - have, MAX_STORED);

    min_block = MIN(have, s->w_size);

    left = (int)s->strstart - s->block_start;

    if (left >= min_block || ((left || flush == Z_FINISH) && flush != Z_NO_FLUSH && s->strm->avail_in == 0 && left <= have)) {

        len = MIN(left, have);

        last = flush == Z_FINISH && s->strm->avail_in == 0 && len == left ? 1 : 0;

        zng_tr_stored_block(s, (char *)s->window + s->block_start, len, last);

        s->block_start += (int)len;

        PREFIX(flush_pending)(s->strm);

    }

    /* We've done all we can with the available input and output. */

    return last ? finish_started : need_more;

}