/*
output.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.


Contains the code for actually outputting the assembled code
*/

//#include <ctype.h>
#include <errno.h>
#include <stdio.h>
//#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define __output_c_seen__
//#include "instab.h"
#include "lwasm.h"

void write_code_raw(asmstate_t *as, FILE *of);
void write_code_decb(asmstate_t *as, FILE *of);
void write_code_rawrel(asmstate_t *as, FILE *of);

// this prevents warnings about not using the return value of fwrite()
#define writebytes(s, l, c, f)	do { int r; r = fwrite((s), (l), (c), (f)); } while (0)

void lwasm_output(asmstate_t *as)
{
	FILE *of;
	
	if (as -> errorcount > 0)
	{
		fprintf(stderr, "Not doing output due to assembly errors.\n");
		return;
	}
	
	of = fopen(as -> outfile, "wb");
	if (!of)
	{
		fprintf(stderr, "Cannot open '%s' for output", as -> outfile);
		perror("");
		return;
	}

	switch (as -> outformat)
	{
	case OUTPUT_RAW:
		write_code_raw(as, of);
		break;
		
	case OUTPUT_DECB:
		write_code_decb(as, of);
		break;
		
	case OUTPUT_RAWREL:
		write_code_rawrel(as, of);
		break;
		
	default:
		fprintf(stderr, "BUG: unrecognized output format when generating output file\n");
		fclose(of);
		unlink(as -> outfile);
		return;
	}

	fclose(of);
}

/*
rawrel output treats an ORG directive as an offset from the start of the
file. Undefined results will occur if an ORG directive moves the output
pointer backward. This particular implementation uses "fseek" to handle
ORG requests and to skip over RMBs.

This simple brain damanged method simply does an fseek before outputting
each instruction.
*/
void write_code_rawrel(asmstate_t *as, FILE *of)
{
	lwasm_line_t *cl;
	
	for (cl = as -> lineshead; cl; cl = cl -> next)
	{
		if (cl -> codelen == 0)
			continue;
		
		fseek(of, cl -> codeaddr, SEEK_SET);
		writebytes(cl -> bytes, cl -> codelen, 1, of);
	}
}

/*
raw merely writes all the bytes directly to the file as is. ORG is just a
reference for the assembler to handle absolute references. Multiple ORG
statements will produce mostly useless results
*/
void write_code_raw(asmstate_t *as, FILE *of)
{
	lwasm_line_t *cl;
	
	for (cl = as -> lineshead; cl; cl = cl -> next)
	{
		if (cl -> nocodelen)
		{
			int i;
			for (i = 0; i < cl -> nocodelen; i++)
				writebytes("\0", 1, 1, of);
			continue;
		}
		writebytes(cl -> bytes, cl -> codelen, 1, of);
	}
}

void write_code_decb(asmstate_t *as, FILE *of)
{
	long preambloc;
	lwasm_line_t *cl;
	int blocklen = -1;
	int nextcalc = -1;
	unsigned char outbuf[5];
	
	for (cl = as -> lineshead; cl; cl = cl -> next)
	{
		if (cl -> nocodelen)
			continue;
		if (cl -> codeaddr != nextcalc && cl -> codelen > 0)
		{
			// need preamble here
			if (blocklen > 0)
			{
				// update previous preamble if needed
				fseek(of, preambloc, SEEK_SET);
				outbuf[0] = (blocklen >> 8) & 0xFF;
				outbuf[1] = blocklen & 0xFF;
				writebytes(outbuf, 2, 1, of);
				fseek(of, 0, SEEK_END);
			}
			blocklen = 0;
			nextcalc = cl -> codeaddr;
			outbuf[0] = 0x00;
			outbuf[1] = 0x00;
			outbuf[2] = 0x00;
			outbuf[3] = (nextcalc >> 8) & 0xFF;
			outbuf[4] = nextcalc & 0xFF;
			preambloc = ftell(of) + 1;
			writebytes(outbuf, 5, 1, of);
		}
		nextcalc += cl -> codelen;
		writebytes(cl -> bytes, cl -> codelen, 1, of);
		blocklen += cl -> codelen;
	}
	if (blocklen > 0)
	{
		fseek(of, preambloc, SEEK_SET);
		outbuf[0] = (blocklen >> 8) & 0xFF;
		outbuf[1] = blocklen & 0xFF;
		writebytes(outbuf, 2, 1, of);
		fseek(of, 0, SEEK_END);
	}
	
	// now write postamble
	outbuf[0] = 0xFF;
	outbuf[1] = 0x00;
	outbuf[2] = 0x00;
	outbuf[3] = (as -> execaddr >> 8) & 0xFF;
	outbuf[4] = (as -> execaddr) & 0xFF;
	writebytes(outbuf, 5, 1, of);
}