jdhuff.c

MCB2300_ucgui_LCD320240.rar LPC2368的uc/gui的移植

					if (bytes_in_buffer == 0)
					{
						if (!(*cinfo->src->fill_input_buffer) (cinfo))
						{
							return FALSE;
						}
						next_input_byte = cinfo->src->next_input_byte;
						bytes_in_buffer = cinfo->src->bytes_in_buffer;
					}
					bytes_in_buffer--;
					c = GETJOCTET(*next_input_byte++);
				}
				while (c == 0xFF);

				if (c == 0)
				{
					/* Found FF/00, which represents an FF data byte */
					c = 0xFF;
				}
				else
				{
					/* Oops, it's actually a marker indicating end of compressed data.
					   * Save the marker code for later use.
					   * Fine point: it might appear that we should save the marker into
					   * bitread working state, not straight into permanent state.  But
					   * once we have hit a marker, we cannot need to suspend within the
					   * current MCU, because we will read no more bytes from the data
					   * source.  So it is OK to update permanent state right away.
					   */
					cinfo->unread_marker = c;
					/* See if we need to insert some fake zero bits. */
					goto no_more_bytes;
				}
			}

			/* OK, load c into get_buffer */
			get_buffer = (get_buffer << 8) | c;
			bits_left += 8;
		} /* end while */
	}
	else
	{
		no_more_bytes:
		/* We get here if we've read the marker that terminates the compressed
		 * data segment.  There should be enough bits in the buffer register
		 * to satisfy the request; if so, no problem.
		 */
		if (nbits > bits_left)
		{
			/* Uh-oh.  Report corrupted data to user and stuff zeroes into
			 * the data stream, so that we can produce some kind of image.
			 * We use a nonvolatile flag to ensure that only one warning message
			 * appears per data segment.
			 */
			if (!cinfo->entropy->insufficient_data)
			{
				WARNMS(cinfo, JWRN_HIT_MARKER);
				cinfo->entropy->insufficient_data = TRUE;
			}
			/* Fill the buffer with zero bits */
			get_buffer <<= MIN_GET_BITS - bits_left;
			bits_left = MIN_GET_BITS;
		}
	}

	/* Unload the local registers */
	state->next_input_byte = next_input_byte;
	state->bytes_in_buffer = bytes_in_buffer;
	state->get_buffer = get_buffer;
	state->bits_left = bits_left;

	return TRUE;
}


/*
 * Out-of-line code for Huffman code decoding.
 * See jdhuff.h for info about usage.
 */

GLOBAL(int)
jpeg_huff_decode(bitread_working_state *state, register bit_buf_type get_buffer, register int bits_left, d_derived_tbl *htbl, int min_bits)
{
	register int l = min_bits;
	register INT32 code;

	/* HUFF_DECODE has determined that the code is at least min_bits */
	/* bits long, so fetch that many bits in one swoop. */

	CHECK_BIT_BUFFER(*state, l, return -1);
	code = GET_BITS(l);

	/* Collect the rest of the Huffman code one bit at a time. */
	/* This is per Figure F.16 in the JPEG spec. */

	while (code > htbl->maxcode[l])
	{
		code <<= 1;
		CHECK_BIT_BUFFER(*state, 1, return -1);
		code |= GET_BITS(1);
		l++;
	}

	/* Unload the local registers */
	state->get_buffer = get_buffer;
	state->bits_left = bits_left;

	/* With garbage input we may reach the sentinel value l = 17. */

	if (l > 16)
	{
		WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
		return 0;			/* fake a zero as the safest result */
	}

	return htbl->pub->huffval[(int) (code + htbl->valoffset[l])];
}


/*
 * Figure F.12: extend sign bit.
 * On some machines, a shift and add will be faster than a table lookup.
 */

#ifdef AVOID_TABLES

#define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))

#else

#define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

static const int extend_test[16] =   /* entry n is 2**(n-1) */
{ 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };

static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
{ 0, ((-1) << 1) + 1, ((-1) << 2) + 1, ((-1) << 3) + 1, ((-1) << 4) + 1,
((-1) << 5) + 1, ((-1) << 6) + 1, ((-1) << 7) + 1, ((-1) << 8) + 1,
((-1) << 9) + 1, ((-1) << 10) + 1, ((-1) << 11) + 1, ((-1) << 12) + 1,
((-1) << 13) + 1, ((-1) << 14) + 1, ((-1) << 15) + 1 };

#endif /* AVOID_TABLES */


/*
 * Check for a restart marker & resynchronize decoder.
 * Returns FALSE if must suspend.
 */

LOCAL(boolean)
process_restart(j_decompress_ptr cinfo)
{
	huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
	int ci;

	/* Throw away any unused bits remaining in bit buffer; */
	/* include any full bytes in next_marker's count of discarded bytes */
	cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
	entropy->bitstate.bits_left = 0;

	/* Advance past the RSTn marker */
	if (!(*cinfo->marker->read_restart_marker) (cinfo))
	{
		return FALSE;
	}

	/* Re-initialize DC predictions to 0 */
	for (ci = 0; ci < cinfo->comps_in_scan; ci++)
	{
		entropy->saved.last_dc_val[ci] = 0;
	}

	/* Reset restart counter */
	entropy->restarts_to_go = cinfo->restart_interval;

	/* Reset out-of-data flag, unless read_restart_marker left us smack up
	 * against a marker.  In that case we will end up treating the next data
	 * segment as empty, and we can avoid producing bogus output pixels by
	 * leaving the flag set.
	 */
	if (cinfo->unread_marker == 0)
	{
		entropy->pub.insufficient_data = FALSE;
	}

	return TRUE;
}


/*
 * Decode and return one MCU's worth of Huffman-compressed coefficients.
 * The coefficients are reordered from zigzag order into natural array order,
 * but are not dequantized.
 *
 * The i'th block of the MCU is stored into the block pointed to by
 * MCU_data[i].  WE ASSUME THIS AREA HAS BEEN ZEROED BY THE CALLER.
 * (Wholesale zeroing is usually a little faster than retail...)
 *
 * Returns FALSE if data source requested suspension.  In that case no
 * changes have been made to permanent state.  (Exception: some output
 * coefficients may already have been assigned.  This is harmless for
 * this module, since we'll just re-assign them on the next call.)
 */

METHODDEF(boolean)
decode_mcu(j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
{
	huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
	int blkn;
	BITREAD_STATE_VARS;
	savable_state state;

	/* Process restart marker if needed; may have to suspend */
	if (cinfo->restart_interval)
	{
		if (entropy->restarts_to_go == 0)
		{
			if (!process_restart(cinfo))
			{
				return FALSE;
			}
		}
	}

	/* If we've run out of data, just leave the MCU set to zeroes.
	 * This way, we return uniform gray for the remainder of the segment.
	 */
	if (!entropy->pub.insufficient_data)
	{
		/* Load up working state */
		BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
		ASSIGN_STATE(state, entropy->saved);

		/* Outer loop handles each block in the MCU */

		for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
		{
			JBLOCKROW block = MCU_data[blkn];
			d_derived_tbl * dctbl = entropy->dc_cur_tbls[blkn];
			d_derived_tbl * actbl = entropy->ac_cur_tbls[blkn];
			register int s, k, r;

			/* Decode a single block's worth of coefficients */

			/* Section F.2.2.1: decode the DC coefficient difference */
			HUFF_DECODE(s, br_state, dctbl, return FALSE, label1);
			if (s)
			{
				CHECK_BIT_BUFFER(br_state, s, return FALSE);
				r = GET_BITS(s);
				s = HUFF_EXTEND(r, s);
			}

			if (entropy->dc_needed[blkn])
			{
				/* Convert DC difference to actual value, update last_dc_val */
				int ci = cinfo->MCU_membership[blkn];
				s += state.last_dc_val[ci];
				state.last_dc_val[ci] = s;
				/* Output the DC coefficient (assumes jpeg_natural_order[0] = 0) */
				(*block)[0] = (JCOEF) s;
			}

			if (entropy->ac_needed[blkn])
			{
				/* Section F.2.2.2: decode the AC coefficients */
				/* Since zeroes are skipped, output area must be cleared beforehand */
				for (k = 1; k < DCTSIZE2; k++)
				{
					HUFF_DECODE(s, br_state, actbl, return FALSE, label2);

					r = s >> 4;
					s &= 15;

					if (s)
					{
						k += r;
						CHECK_BIT_BUFFER(br_state, s, return FALSE);
						r = GET_BITS(s);
						s = HUFF_EXTEND(r, s);
						/* Output coefficient in natural (dezigzagged) order.
						   * Note: the extra entries in jpeg_natural_order[] will save us
						   * if k >= DCTSIZE2, which could happen if the data is corrupted.
						   */
						(*block)[jpeg_natural_order[k]] = (JCOEF) s;
					}
					else
					{
						if (r != 15)
						{
							break;
						}
						k += 15;
					}
				}
			}
			else
			{
				/* Section F.2.2.2: decode the AC coefficients */
				/* In this path we just discard the values */
				for (k = 1; k < DCTSIZE2; k++)
				{
					HUFF_DECODE(s, br_state, actbl, return FALSE, label3);

					r = s >> 4;
					s &= 15;

					if (s)
					{
						k += r;
						CHECK_BIT_BUFFER(br_state, s, return FALSE);
						DROP_BITS(s);
					}
					else
					{
						if (r != 15)
						{
							break;
						}
						k += 15;
					}
				}
			}
		}

		/* Completed MCU, so update state */
		BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
		ASSIGN_STATE(entropy->saved, state);
	}

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
}


/*
 * Module initialization routine for Huffman entropy decoding.
 */

GLOBAL(void)
jinit_huff_decoder(j_decompress_ptr cinfo)
{
	huff_entropy_ptr entropy;
	int i;

	entropy = (huff_entropy_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(huff_entropy_decoder));
	cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
	entropy->pub.start_pass = start_pass_huff_decoder;
	entropy->pub.decode_mcu = decode_mcu;

	/* Mark tables unallocated */
	for (i = 0; i < NUM_HUFF_TBLS; i++)
	{
		entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
	}
}