/* 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; }