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CLK/Analyser/Static/Commodore/File.cpp

48 lines
1.4 KiB
C++

//
// File.cpp
// Clock Signal
//
// Created by Thomas Harte on 10/09/2016.
// Copyright 2016 Thomas Harte. All rights reserved.
//
#include "File.hpp"
bool Analyser::Static::Commodore::File::is_basic() {
// BASIC files are always relocatable (?)
if(type != File::RelocatableProgram) return false;
uint16_t line_address = starting_address;
int line_number = -1;
// decide whether this is a BASIC file based on the proposition that:
// (1) they're always relocatable; and
// (2) they have a per-line structure of:
// [4 bytes: address of start of next line]
// [4 bytes: this line number]
// ... null-terminated code ...
// (with a next line address of 0000 indicating end of program)
while(1) {
if(size_t(line_address - starting_address) + 1 >= data.size()) break;
uint16_t next_line_address = data[line_address - starting_address];
next_line_address |= data[line_address - starting_address + 1] << 8;
if(!next_line_address) {
return true;
}
if(next_line_address < line_address + 5) break;
if(size_t(line_address - starting_address) + 3 >= data.size()) break;
uint16_t next_line_number = data[line_address - starting_address + 2];
next_line_number |= data[line_address - starting_address + 3] << 8;
if(next_line_number <= line_number) break;
line_number = uint16_t(next_line_number);
line_address = next_line_address;
}
return false;
}