From fe7fc036ca0f7769fd9b9b771a92a303a323e8ee Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Mon, 3 Jun 2024 15:49:02 -0400
Subject: unprotbas: split off utility functions/etc to bas.c.

---
 bas.c | 183 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 183 insertions(+)
 create mode 100644 bas.c

(limited to 'bas.c')

diff --git a/bas.c b/bas.c
new file mode 100644
index 0000000..64c4f3f
--- /dev/null
+++ b/bas.c
@@ -0,0 +1,183 @@
+/* bas.c - API for writing standalone programs that deal with
+	tokenized Atari 8-bit BASIC program. */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <time.h>
+
+#include "bas.h"
+
+int verbose = 0;
+unsigned short lomem;
+unsigned short vntp;
+unsigned short vntd;
+unsigned short vvtp;
+unsigned short stmtab;
+unsigned short stmcur;
+unsigned short starp;
+unsigned short codestart;
+unsigned short code_end;
+unsigned short vnstart;
+unsigned short vvstart;
+int filelen;
+const char *self;
+unsigned char program[BUFSIZE];
+FILE *input_file;
+FILE *output_file;
+
+void die(const char *msg) {
+	fprintf(stderr, "%s: %s\n", self, msg);
+	exit(1);
+}
+
+/* read entire file into memory */
+int readfile(void) {
+	int got = fread(program, 1, BUFSIZE - 1, input_file);
+	if(verbose) fprintf(stderr, "Read %d bytes.\n", got);
+	if(!feof(input_file))
+		fprintf(stderr, "Warning: file is >64KB, way too big for a BASIC program.\n");
+	else if(got > MAX_PROG_SIZE)
+		fprintf(stderr, "Warning: file is %d bytes, suspiciously large for a BASIC program.\n", got);
+	fclose(input_file);
+	if(got < MIN_PROG_SIZE)
+		die("File too short to be a BASIC program (truncated?)\n");
+	return got;
+}
+
+/* get a 16-bit value from the file, in 6502 LSB/MSB order. */
+unsigned short getword(int addr) {
+	return program[addr] | (program[addr + 1] << 8);
+}
+
+void setword(int addr, int value) {
+	program[addr] = value & 0xff;
+	program[addr + 1] = value >> 8;
+}
+
+void dump_header_vars(void) {
+	fprintf(stderr, "LOMEM  $%04x    VNTP $%04x   VNTD $%04x  VVTP $%04x\n", lomem, vntp, vntd, vvtp);
+	fprintf(stderr, "STMTAB $%04x  STMCUR $%04x  STARP $%04x\n", stmtab, stmcur, starp);
+	fprintf(stderr, "vnstart $%04x, vvstart $%04x, codestart $%04x, code_end $%04x\n", vnstart, vvstart, codestart, code_end);
+}
+
+void parse_header(void) {
+	lomem = getword(0);
+	vntp = getword(2);
+	vntd = getword(4);
+	vvtp = getword(6);
+	stmtab = getword(8);
+	stmcur = getword(10);
+	starp = getword(12);
+	codestart = stmtab - TBL_OFFSET - (vntp - 256);
+	vnstart = vntp - TBL_OFFSET;
+	vvstart = vvtp - TBL_OFFSET;
+	code_end = starp - TBL_OFFSET;
+
+	if(filelen < code_end) {
+		fprintf(stderr, "Warning: file is truncated: %d bytes, should be %d.\n", filelen, code_end);
+	}
+
+	if(verbose) dump_header_vars();
+}
+
+void update_header(void) {
+	setword(0, lomem);
+	setword(2, vntp);
+	setword(4, vntd);
+	setword(6, vvtp);
+	setword(8, stmtab);
+	setword(10, stmcur);
+	setword(12, starp);
+}
+
+/* sometimes the variable name table isn't large enough to hold
+	the generated variable names. move_code() makes more space,
+	by moving the rest of the program (including the variable value
+	table) up in memory. */
+void move_code(int offset) {
+	unsigned char *dest = program + vvstart + offset;
+
+	if(dest < program || ((filelen + offset) > (BUFSIZE - 1))) {
+		die("Attempt to move memory out of range; corrupt header bytes?\n");
+	}
+
+	memmove(dest, program + vvstart, filelen);
+
+	vntd += offset;
+	vvtp += offset;
+	stmtab += offset;
+	stmcur += offset;
+	starp += offset;
+	update_header();
+	parse_header();
+	filelen += offset;
+}
+
+void adjust_vntable_size(int oldsize, int newsize) {
+	int move_by;
+	if(oldsize != newsize) {
+		move_by = newsize - oldsize;
+		if(verbose) fprintf(stderr,
+				"Need %d bytes for vntable, have %d, moving VVTP by %d to $%04x.\n",
+				newsize, oldsize, move_by, vvtp + move_by);
+		move_code(move_by);
+	}
+}
+
+void invalid_args(const char *arg) {
+	fprintf(stderr, "%s: Invalid argument '%s'.\n\n", self, arg);
+	exit(1);
+}
+
+FILE *open_file(const char *name, const char *mode) {
+	FILE *fp;
+	if(!(fp = fopen(name, mode))) {
+		perror(name);
+		exit(1);
+	}
+	return fp;
+}
+
+void open_input(const char *name) {
+	if(!name) {
+		if(isatty(fileno(stdin))) {
+			die("Can't read binary data from the terminal.");
+		}
+		if(freopen(NULL, "rb", stdin)) {
+			input_file = stdin;
+			return;
+		} else {
+			perror("stdin");
+			exit(1);
+		}
+	}
+
+	input_file = open_file(name, "rb");
+}
+
+void open_output(const char *name) {
+	if(!name || (strcmp(name, "-") == 0)) {
+		if(isatty(fileno(stdout))) {
+			die("Refusing to write binary data to the terminal.");
+		}
+		if(freopen(NULL, "wb", stdout)) {
+			output_file = stdout;
+			return;
+		} else {
+			perror("stdout");
+			exit(1);
+		}
+	}
+	output_file = open_file(name, "wb");
+}
+
+extern void set_self(const char *argv0) {
+	char *p;
+
+	self = argv0;
+	p = strrchr(self, '/');
+	if(p) self = p + 1;
+}
-- 
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