jpc_mqenc.c

用C语言实现的JPEG编码

/*
 * Copyright (c) 1999-2000 Image Power, Inc. and the University of
 *   British Columbia.
 * Copyright (c) 2001-2003 Michael David Adams.
 * All rights reserved.
 */

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 */

/*
 * MQ Arithmetic Encoder
 *
 * $Id$
 */

/******************************************************************************\
* Includes.
\******************************************************************************/

#include <assert.h>
#include <stdlib.h>

#include "jasper/jas_stream.h"
#include "jasper/jas_malloc.h"
#include "jasper/jas_math.h"
#include "jasper/jas_debug.h"

#include "jpc_mqenc.h"

/******************************************************************************\
* Macros
\******************************************************************************/

#if defined(DEBUG)
#define	JPC_MQENC_CALL(n, x) \
	((jas_getdbglevel() >= (n)) ? ((void)(x)) : ((void)0))
#else
#define	JPC_MQENC_CALL(n, x)
#endif

#define	jpc_mqenc_codemps9(areg, creg, ctreg, curctx, enc) \
{ \
	jpc_mqstate_t *state = *(curctx); \
	(areg) -= state->qeval; \
	if (!((areg) & 0x8000)) { \
		if ((areg) < state->qeval) { \
			(areg) = state->qeval; \
		} else { \
			(creg) += state->qeval; \
		} \
		*(curctx) = state->nmps; \
		jpc_mqenc_renorme((areg), (creg), (ctreg), (enc)); \
	} else { \
		(creg) += state->qeval; \
	} \
}

#define	jpc_mqenc_codelps2(areg, creg, ctreg, curctx, enc) \
{ \
	jpc_mqstate_t *state = *(curctx); \
	(areg) -= state->qeval; \
	if ((areg) < state->qeval) { \
		(creg) += state->qeval; \
	} else { \
		(areg) = state->qeval; \
	} \
	*(curctx) = state->nlps; \
	jpc_mqenc_renorme((areg), (creg), (ctreg), (enc)); \
}

#define	jpc_mqenc_renorme(areg, creg, ctreg, enc) \
{ \
	do { \
		(areg) <<= 1; \
		(creg) <<= 1; \
		if (!--(ctreg)) { \
			jpc_mqenc_byteout((areg), (creg), (ctreg), (enc)); \
		} \
	} while (!((areg) & 0x8000)); \
}

#define	jpc_mqenc_byteout(areg, creg, ctreg, enc) \
{ \
	if ((enc)->outbuf != 0xff) { \
		if ((creg) & 0x8000000) { \
			if (++((enc)->outbuf) == 0xff) { \
				(creg) &= 0x7ffffff; \
				jpc_mqenc_byteout2(enc); \
				enc->outbuf = ((creg) >> 20) & 0xff; \
				(creg) &= 0xfffff; \
				(ctreg) = 7; \
			} else { \
				jpc_mqenc_byteout2(enc); \
				enc->outbuf = ((creg) >> 19) & 0xff; \
				(creg) &= 0x7ffff; \
				(ctreg) = 8; \
			} \
		} else { \
			jpc_mqenc_byteout2(enc); \
			(enc)->outbuf = ((creg) >> 19) & 0xff; \
			(creg) &= 0x7ffff; \
			(ctreg) = 8; \
		} \
	} else { \
		jpc_mqenc_byteout2(enc); \
		(enc)->outbuf = ((creg) >> 20) & 0xff; \
		(creg) &= 0xfffff; \
		(ctreg) = 7; \
	} \
}

#define	jpc_mqenc_byteout2(enc) \
{ \
	if (enc->outbuf >= 0) { \
		if (jas_stream_putc(enc->out, (unsigned char)enc->outbuf) == EOF) { \
			enc->err |= 1; \
		} \
	} \
	enc->lastbyte = enc->outbuf; \
}

/******************************************************************************\
* Local function protoypes.
\******************************************************************************/

static void jpc_mqenc_setbits(jpc_mqenc_t *mqenc);

/******************************************************************************\
* Code for creation and destruction of encoder.
\******************************************************************************/

/* Create a MQ encoder. */

jpc_mqenc_t *jpc_mqenc_create(int maxctxs, jas_stream_t *out)
{
	jpc_mqenc_t *mqenc;

	/* Allocate memory for the MQ encoder. */
	if (!(mqenc = jas_malloc(sizeof(jpc_mqenc_t)))) {
		goto error;
	}
	mqenc->out = out;
	mqenc->maxctxs = maxctxs;

	/* Allocate memory for the per-context state information. */
	if (!(mqenc->ctxs = jas_malloc(mqenc->maxctxs * sizeof(jpc_mqstate_t *)))) {
		goto error;
	}

	/* Set the current context to the first one. */
	mqenc->curctx = mqenc->ctxs;

	jpc_mqenc_init(mqenc);

	/* Initialize the per-context state information to something sane. */
	jpc_mqenc_setctxs(mqenc, 0, 0);

	return mqenc;

error:
	if (mqenc) {
		jpc_mqenc_destroy(mqenc);
	}
	return 0;
}

/* Destroy a MQ encoder. */

void jpc_mqenc_destroy(jpc_mqenc_t *mqenc)
{
	if (mqenc->ctxs) {
		jas_free(mqenc->ctxs);
	}
	jas_free(mqenc);
}

/******************************************************************************\
* State initialization code.
\******************************************************************************/

/* Initialize the coding state of a MQ encoder. */

void jpc_mqenc_init(jpc_mqenc_t *mqenc)
{
	mqenc->areg = 0x8000;
	mqenc->outbuf = -1;
	mqenc->creg = 0;
	mqenc->ctreg = 12;
	mqenc->lastbyte = -1;
	mqenc->err = 0;
}

/* Initialize one or more contexts. */

void jpc_mqenc_setctxs(jpc_mqenc_t *mqenc, int numctxs, jpc_mqctx_t *ctxs)
{
	jpc_mqstate_t **ctx;
	int n;

	ctx = mqenc->ctxs;
	n = JAS_MIN(mqenc->maxctxs, numctxs);
	while (--n >= 0) {
		*ctx = &jpc_mqstates[2 * ctxs->ind + ctxs->mps];
		++ctx;
		++ctxs;
	}
	n = mqenc->maxctxs - numctxs;
	while (--n >= 0) {
		*ctx = &jpc_mqstates[0];
		++ctx;
	}

}

/* Get the coding state for a MQ encoder. */

void jpc_mqenc_getstate(jpc_mqenc_t *mqenc, jpc_mqencstate_t *state)
{
	state->areg = mqenc->areg;
	state->creg = mqenc->creg;
	state->ctreg = mqenc->ctreg;
	state->lastbyte = mqenc->lastbyte;
}

/******************************************************************************\
* Code for coding symbols.
\******************************************************************************/

/* Encode a bit. */

int jpc_mqenc_putbit_func(jpc_mqenc_t *mqenc, int bit)
{
	const jpc_mqstate_t *state;
	JAS_DBGLOG(100, ("jpc_mqenc_putbit(%p, %d)\n", mqenc, bit));
	JPC_MQENC_CALL(100, jpc_mqenc_dump(mqenc, stderr));

	state = *(mqenc->curctx);

	if (state->mps == bit) {
		/* Apply the CODEMPS algorithm as defined in the standard. */
		mqenc->areg -= state->qeval;
		if (!(mqenc->areg & 0x8000)) {
			jpc_mqenc_codemps2(mqenc);
		} else {
			mqenc->creg += state->qeval;
		}
	} else {
		/* Apply the CODELPS algorithm as defined in the standard. */
		jpc_mqenc_codelps2(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc->curctx, mqenc);
	}

	return jpc_mqenc_error(mqenc) ? (-1) : 0;
}

int jpc_mqenc_codemps2(jpc_mqenc_t *mqenc)
{
	/* Note: This function only performs part of the work associated with
	the CODEMPS algorithm from the standard.  Some of the work is also
	performed by the caller. */

	jpc_mqstate_t *state = *(mqenc->curctx);
	if (mqenc->areg < state->qeval) {
		mqenc->areg = state->qeval;
	} else {
		mqenc->creg += state->qeval;
	}
	*mqenc->curctx = state->nmps;
	jpc_mqenc_renorme(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc);
	return jpc_mqenc_error(mqenc) ? (-1) : 0;
}

int jpc_mqenc_codelps(jpc_mqenc_t *mqenc)
{
	jpc_mqenc_codelps2(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc->curctx, mqenc);
	return jpc_mqenc_error(mqenc) ? (-1) : 0;
}

/******************************************************************************\
* Miscellaneous code.
\******************************************************************************/

/* Terminate the code word. */

int jpc_mqenc_flush(jpc_mqenc_t *mqenc, int termmode)
{
	int_fast16_t k;

	switch (termmode) {
	case JPC_MQENC_PTERM:
		k = 11 - mqenc->ctreg + 1;
		while (k > 0) {
			mqenc->creg <<= mqenc->ctreg;
			mqenc->ctreg = 0;
			jpc_mqenc_byteout(mqenc->areg, mqenc->creg, mqenc->ctreg,
			  mqenc);
			k -= mqenc->ctreg;
		}
		if (mqenc->outbuf != 0xff) {
			jpc_mqenc_byteout(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc);
		}
		break;
	case JPC_MQENC_DEFTERM:
		jpc_mqenc_setbits(mqenc);
		mqenc->creg <<= mqenc->ctreg;
		jpc_mqenc_byteout(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc);
		mqenc->creg <<= mqenc->ctreg;
		jpc_mqenc_byteout(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc);
		if (mqenc->outbuf != 0xff) {
			jpc_mqenc_byteout(mqenc->areg, mqenc->creg, mqenc->ctreg, mqenc);
		}
		break;
	default:
		abort();
		break;
	}
	return 0;
}

static void jpc_mqenc_setbits(jpc_mqenc_t *mqenc)
{
	uint_fast32_t tmp = mqenc->creg + mqenc->areg;
	mqenc->creg |= 0xffff;
	if (mqenc->creg >= tmp) {
		mqenc->creg -= 0x8000;
	}
}

/* Dump a MQ encoder to a stream for debugging. */

int jpc_mqenc_dump(jpc_mqenc_t *mqenc, FILE *out)
{
	fprintf(out, "AREG = %08x, CREG = %08x, CTREG = %d\n",
	  mqenc->areg, mqenc->creg, mqenc->ctreg);
	fprintf(out, "IND = %02d, MPS = %d, QEVAL = %04x\n",
	  *mqenc->curctx - jpc_mqstates, (*mqenc->curctx)->mps,
	  (*mqenc->curctx)->qeval);
	return 0;
}