path: root/gs/src/sbhc.c

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/* sbhc.c */
/* Bounded Huffman code filters */
#include "memory_.h"
#include "stdio_.h"
#include "gdebug.h"
#include "strimpl.h"
#include "sbhc.h"
#include "shcgen.h"

/* ------ BoundedHuffmanEncode ------ */

private_st_BHCE_state();

#define ss ((stream_BHCE_state *)st)

/* Initialize BoundedHuffmanEncode filter. */
private int
s_BHCE_reinit(stream_state *st)
{	ss->encode.count = ss->definition.num_values;
	s_bhce_init_inline(ss);
	return 0;
}
private int
s_BHCE_init(register stream_state *st)
{	hce_code *encode = ss->encode.codes =
	  (hce_code *)gs_alloc_byte_array(st->memory,
		  			  ss->definition.num_values,
					  sizeof(hce_code), "BHCE encode");
	if ( encode == 0 )
	  return ERRC;			/****** WRONG ******/
	hc_make_encoding(encode, &ss->definition);
	return s_BHCE_reinit(st);
}

/* Release the filter. */
private void
s_BHCE_release(stream_state *st)
{	gs_free_object(st->memory, ss->encode.codes, "BHCE encode");
}

/* Process a buffer. */
private int
s_BHCE_process(stream_state *st, stream_cursor_read *pr,
  stream_cursor_write *pw, bool last)
{	const byte *p = pr->ptr;
	const byte *rlimit = pr->limit;
	byte *q = pw->ptr;
	byte *wlimit = pw->limit - (hc_bits_size >> 3);
	const hce_code *encode = ss->encode.codes;
	uint num_values = ss->definition.num_values;
	uint zero_runs = ss->EncodeZeroRuns;
	uint zero_max = num_values - zero_runs + (ss->EndOfData ? 0 : 1);
	uint zero_value = (zero_max > 1 ? 0 : 0x100);
	int zeros = ss->zeros;
	int status = 0;
	hce_declare_state;

	hce_load_state();
	while ( p < rlimit && q < wlimit )
	  {	uint value = *++p;
		const hce_code *cp;
		if ( value >= num_values )
		  {	status = ERRC;
			break;
		  }
		if ( value == zero_value )
		{	/* Accumulate a run of zeros. */
			++zeros;
			if ( zeros != zero_max )
			  continue;
			/* We've scanned the longest run we can encode. */
			cp = &encode[zeros - 2 + zero_runs];
			zeros = 0;
			hc_put_code((stream_hc_state *)ss, q, cp);
			continue;
		}
		/* Check whether we need to put out a zero run. */
		if ( zeros > 0 )
		{	--p;
			cp = (zeros == 1 ? &encode[0] :
			      &encode[zeros - 2 + zero_runs]);
			zeros = 0;
			hc_put_code((stream_hc_state *)ss, q, cp);
			continue;
		}
		cp = &encode[value];
		hc_put_code((stream_hc_state *)ss, q, cp);
	  }
	if ( q >= wlimit )
	  status = 1;
	wlimit = pw->limit;
	if ( last && status == 0 )
	  {	if ( zeros > 0 )
		  {	/* Put out a final run of zeros. */
			const hce_code *cp = (zeros == 1 ? &encode[0] :
					      &encode[zeros - 2 + zero_runs]);
			if ( !hce_bits_available(cp->code_length) )
			  status = 1;
			else
			  {	hc_put_code((stream_hc_state *)ss, q, cp);
				zeros = 0;
			  }
		  }
		if ( ss->EndOfData )
		  {	/* Put out the EOD code if we have room. */
			const hce_code *cp = &encode[num_values - 1];
			if ( !hce_bits_available(cp->code_length) )
			  status = 1;
			else
			  hc_put_code((stream_hc_state *)ss, q, cp);
		  }
		else
		  {	if ( q >= wlimit )
			  status = 1;
		  }
		if ( !status )
		  {	q = hc_put_last_bits((stream_hc_state *)ss, q);
			goto ns;
		  }
	  }
	hce_store_state();
ns:	pr->ptr = p;
	pw->ptr = q;
	ss->zeros = zeros;
	return (p == rlimit ? 0 : 1);
}

#undef ss

/* Stream template */
const stream_template s_BHCE_template =
{	&st_BHCE_state, s_BHCE_init, s_BHCE_process,
	1, hc_bits_size >> 3, s_BHCE_release, NULL, s_BHCE_reinit
};

/* ------ BoundedHuffmanDecode ------ */

private_st_BHCD_state();

#define ss ((stream_BHCD_state *)st)

#define hcd_initial_bits 7		/* arbitrary, >= 1 and <= 8 */

/* Initialize BoundedHuffmanDecode filter. */
private int
s_BHCD_reinit(stream_state *st)
{	ss->decode.count = ss->definition.num_values;
	s_bhcd_init_inline(ss);
	return 0;
}
private int
s_BHCD_init(register stream_state *st)
{	uint initial_bits = ss->decode.initial_bits =
	  min(hcd_initial_bits, ss->definition.num_counts);
	uint dsize = hc_sizeof_decoding(&ss->definition, initial_bits);
	hcd_code *decode = ss->decode.codes =
	  (hcd_code *)gs_alloc_byte_array(st->memory, dsize,
					  sizeof(hcd_code), "BHCD decode");
	if ( decode == 0 )
	  return ERRC;			/****** WRONG ******/
	hc_make_decoding(decode, &ss->definition, initial_bits);
	return s_BHCD_reinit(st);
}

/* Release the filter. */
private void
s_BHCD_release(stream_state *st)
{	gs_free_object(st->memory, ss->decode.codes, "BHCD decode");
}

/* Process a buffer. */
private int
s_BHCD_process(stream_state *st, stream_cursor_read *pr,
  stream_cursor_write *pw, bool last)
{	bhcd_declare_state;
	byte *q = pw->ptr;
	byte *wlimit = pw->limit;
	const hcd_code *decode = ss->decode.codes;
	uint initial_bits = ss->decode.initial_bits;
	uint zero_runs = ss->EncodeZeroRuns;
	int status = 0;
	int eod = (ss->EndOfData ? ss->definition.num_values - 1 : -1);

	bhcd_load_state();
z:	for ( ; zeros > 0; --zeros )
	{	if ( q >= wlimit )
		{	status = 1;
			goto out;
		}
		*++q = 0;
	}
	for ( ; ; )
	  {	const hcd_code *cp;
		int clen;
		hcd_ensure_bits(initial_bits, x1);
		cp = &decode[hcd_peek_var_bits(initial_bits)];
w1:		if ( q >= wlimit )
		  {	status = 1;
			break;
		  }
		if ( (clen = cp->code_length) > initial_bits )
		  {	if ( !hcd_bits_available(clen) )
			  {	/* We don't have enough bits for */
				/* all possible codes that begin this way, */
				/* but we might have enough for */
				/* the next code. */
				/****** NOT IMPLEMENTED YET ******/
			    break;
			  }
			clen -= initial_bits;
			hcd_skip_bits(initial_bits);
			hcd_ensure_bits(clen, out);	/* can't exit */
			cp = &decode[cp->value + hcd_peek_var_bits(clen)];
			hcd_skip_bits(cp->code_length);
		  }
		else
		  {	hcd_skip_bits(clen);
		  }
		if ( cp->value >= zero_runs )
		{	if ( cp->value == eod )
			  {	status = EOFC;
				goto out;
			  }
			/* This code represents a run of zeros, */
			/* not a single output value. */
			zeros = cp->value - zero_runs + 2;
			goto z;
		}
		*++q = cp->value;
		continue;
			/* We don't have enough bits for all possible */
			/* codes, but we might have enough for */
			/* the next code. */
x1:		cp = &decode[(bits & ((1 << bits_left) - 1)) <<
			     (initial_bits - bits_left)];
		if ( (clen = cp->code_length) <= bits_left )
		  goto w1;
		break;
	  }
out:	bhcd_store_state();
	pw->ptr = q;
	return status;
}

#undef ss

/* Stream template */
const stream_template s_BHCD_template =
{	&st_BHCD_state, s_BHCD_init, s_BHCD_process, 1, 1, s_BHCD_release,
	NULL, s_BHCD_reinit
};