muddle/src/zscii.c

/*
 *	Copyright (c) 2024 Scott Duensing, scott@kangaroopunch.com
 *
 *	Permission is hereby granted, free of charge, to any person obtaining a copy
 *	of this software and associated documentation files (the "Software"), to deal
 *	in the Software without restriction, including without limitation the rights
 *	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *	copies of the Software, and to permit persons to whom the Software is
 *	furnished to do so, subject to the following conditions:
 *
 *	The above copyright notice and this permission notice shall be included in
 *	all copies or substantial portions of the Software.
 *
 *	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 *	SOFTWARE.
 */


#include "zscii.h"
#include "portme.h"
#include "messages.h"
#include "story.h"
#include "state.h"
#include "memory.h"
#include "text.h"


char zsciiDecodeChar(uint16_t z) {
	char c = 0;

	//***TODO*** V6+ has more codes.

	if ((z >= 32) && (z <= 126)) {
		c = z;  // ASCII
	} else if (z == 13) {
		c = '\n';
	} else if ((z >= 155) && (z <= 251)) {
		c = '?';  //***TODO*** Extended ZSCII
	}

	return c;
}


uint32_t zsciiPrint(uint32_t zstr, bool abbr) {
	uint16_t code           = 0;
	uint8_t  alphabet       = 0;
	uint8_t  useAbbrTable   = 0;
	uint8_t  zsciiCollector = 0;
	uint16_t zsciiCode      = 0;
	uint32_t decodedChars   = 0;
	uint32_t pc             = zstr;
	char     printVal       = 0;
	uint32_t index;
	uint32_t ptr;
	uint16_t abbrAddr;
	uint32_t abbrDecodedChars;
	int8_t   i;
	uint8_t  ch;
	int16_t  newShift;

	do {
		code = ZPEEKW(pc);
		pc += 2;

		// Characters are 5 bits each, packed three to a 16-bit word.
		for (i=10; i>=0; i-=5) {

			newShift = 0;
			printVal = 0;
			ch       = ((code >> i) & 0x1f);

			if (zsciiCollector) {
				if (zsciiCollector == 2) {
					zsciiCode |= ((uint16_t)ch) << 5;
				} else {
					zsciiCode |= ((uint16_t)ch);
				}

				zsciiCollector--;

				if (!zsciiCollector) {
					printVal = zsciiDecodeChar(zsciiCode);
					if (printVal) {
						decodedChars++;
						textCharPrint(printVal);
					}
					alphabet     = 0;
					useAbbrTable = 0;
					zsciiCode    = 0;
				}  // !zsciiCollector

				continue;

			} else if (useAbbrTable) {  // zsciiCollector

				if (abbr) portDie(MSG_INT_NO_ABBR);

				index    = ((32 * (((uint32_t)useAbbrTable) - 1)) + (uint32_t)ch);
				ptr      = storyAbbreviationTableAddress() + (index * 2);
				abbrAddr = ZPEEKW(ptr);
				ptr += 2;

				decodedChars += zsciiPrint(abbrAddr * 2, true);

				useAbbrTable = 0;
				alphabet = 0;  //***FIXME*** Version 3+ has no shift-lock but V1 needs it.

				continue;

			}  // useAbbrTable

			switch (ch) {
				case 0:
					printVal = ' ';
					break;

				case 1:
					if (storyVersion() == 1) {
						printVal = '\n';
					} else {
						useAbbrTable = 1;
					}
					break;

				case 2:
				case 3:
					if (storyVersion() <= 2) {
						portDie(MSG_INT_V12_SHIFT);
					} else {
						useAbbrTable = ch;
					}
					break;

				case 4:
				case 5:
					if (storyVersion() <= 2) {
						portDie(MSG_INT_V12_SHIFT_LOCK);
					} else {
						newShift = 1;
						alphabet = ch - 3;
					}
					break;

				default:
					if ((ch == 6) && (alphabet == 2)) {
						zsciiCollector = 2;
					} else {
						printVal = __state.alphabetTable[(alphabet * 26) + (ch - 6)];
					}
					break;
			}

			if (printVal) {
				decodedChars++;
				textCharPrint(printVal);
			}

			if (alphabet && !newShift) alphabet = 0;

		} // for

		// There is no NULL terminator, you look for a word with the top bit set.
	} while ((code & (1 << 15)) == 0);

	return pc - zstr;
}