path: root/lib/zlib_inflate/inflate.c

/* inflate.c -- zlib decompression
 * Copyright (C) 1995-2005 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 *
 * Based on zlib 1.2.3 but modified for the Linux Kernel by
 * Richard Purdie <richard@openedhand.com>
 *
 * Changes mainly for static instead of dynamic memory allocation
 *
 */

#include <linux/zutil.h>
#include "inftrees.h"
#include "inflate.h"
#include "inffast.h"
#include "infutil.h"

/* architecture-specific bits */
#ifdef CONFIG_ZLIB_DFLTCC
#  include "../zlib_dfltcc/dfltcc.h"
#else
#define INFLATE_RESET_HOOK(strm) do {} while (0)
#define INFLATE_TYPEDO_HOOK(strm, flush) do {} while (0)
#define INFLATE_NEED_UPDATEWINDOW(strm) 1
#define INFLATE_NEED_CHECKSUM(strm) 1
#endif

int zlib_inflate_workspacesize(void)
{
    return sizeof(struct inflate_workspace);
}

int zlib_inflateReset(z_streamp strm)
{
    struct inflate_state *state;

    if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
    state = (struct inflate_state *)strm->state;
    strm->total_in = strm->total_out = state->total = 0;
    strm->msg = NULL;
    strm->adler = 1;        /* to support ill-conceived Java test suite */
    state->mode = HEAD;
    state->last = 0;
    state->havedict = 0;
    state->dmax = 32768U;
    state->hold = 0;
    state->bits = 0;
    state->lencode = state->distcode = state->next = state->codes;

    /* Initialise Window */
    state->wsize = 1U << state->wbits;
    state->write = 0;
    state->whave = 0;

    INFLATE_RESET_HOOK(strm);
    return Z_OK;
}

int zlib_inflateInit2(z_streamp strm, int windowBits)
{
    struct inflate_state *state;

    if (strm == NULL) return Z_STREAM_ERROR;
    strm->msg = NULL;                 /* in case we return an error */

    state = &WS(strm)->inflate_state;
    strm->state = (struct internal_state *)state;

    if (windowBits < 0) {
        state->wrap = 0;
        windowBits = -windowBits;
    }
    else {
        state->wrap = (windowBits >> 4) + 1;
    }
    if (windowBits < 8 || windowBits > 15) {
        return Z_STREAM_ERROR;
    }
    state->wbits = (unsigned)windowBits;
#ifdef CONFIG_ZLIB_DFLTCC
    /*
     * DFLTCC requires the window to be page aligned.
     * Thus, we overallocate and take the aligned portion of the buffer.
     */
    state->window = PTR_ALIGN(&WS(strm)->working_window[0], PAGE_SIZE);
#else
    state->window = &WS(strm)->working_window[0];
#endif

    return zlib_inflateReset(strm);
}

/*
   Return state with length and distance decoding tables and index sizes set to
   fixed code decoding.  This returns fixed tables from inffixed.h.
 */
static void zlib_fixedtables(struct inflate_state *state)
{
#   include "inffixed.h"
    state->lencode = lenfix;
    state->lenbits = 9;
    state->distcode = distfix;
    state->distbits = 5;
}


/*
   Update the window with the last wsize (normally 32K) bytes written before
   returning. This is only called when a window is already in use, or when
   output has been written during this inflate call, but the end of the deflate
   stream has not been reached yet. It is also called to window dictionary data
   when a dictionary is loaded.

   Providing output buffers larger than 32K to inflate() should provide a speed
   advantage, since only the last 32K of output is copied to the sliding window
   upon return from inflate(), and since all distances after the first 32K of
   output will fall in the output data, making match copies simpler and faster.
   The advantage may be dependent on the size of the processor's data caches.
 */
static void zlib_updatewindow(z_streamp strm, unsigned out)
{
    struct inflate_state *state;
    unsigned copy, dist;

    state = (struct inflate_state *)strm->state;

    /* copy state->wsize or less output bytes into the circular window */
    copy = out - strm->avail_out;
    if (copy >= state->wsize) {
        memcpy(state->window, strm->next_out - state->wsize, state->wsize);
        state->write = 0;
        state->whave = state->wsize;
    }
    else {
        dist = state->wsize - state->write;
        if (dist > copy) dist = copy;
        memcpy(state->window + state->write, strm->next_out - copy, dist);
        copy -= dist;
        if (copy) {
            memcpy(state->window, strm->next_out - copy, copy);
            state->write = copy;
            state->whave = state->wsize;
        }
        else {
            state->write += dist;
            if (state->write == state->wsize) state->write = 0;
            if (state->whave < state->wsize) state->whave += dist;
        }
    }
}


/*
 * At the end of a Deflate-compressed PPP packet, we expect to have seen
 * a `stored' block type value but not the (zero) length bytes.
 */
/*
   Returns true if inflate is currently at the end of a block generated by
   Z_SYNC_FLUSH or Z_FULL_FLUSH. This function is used by one PPP
   implementation to provide an additional safety check. PPP uses
   Z_SYNC_FLUSH but removes the length bytes of the resulting empty stored
   block. When decompressing, PPP checks that at the end of input packet,
   inflate is waiting for these length bytes.
 */
static int zlib_inflateSyncPacket(z_streamp strm)
{
    struct inflate_state *state;

    if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
    state = (struct inflate_state *)strm->state;

    if (state->mode == STORED && state->bits == 0) {
	state->mode = TYPE;
        return Z_OK;
    }
    return Z_DATA_ERROR;
}

/* Macros for inflate(): */

/* check function to use adler32() for zlib or crc32() for gzip */
#define UPDATE(check, buf, len) zlib_adler32(check, buf, len)

/* Load registers with state in inflate() for speed */
#define LOAD() \
    do { \
        put = strm->next_out; \
        left = strm->avail_out; \