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sad attempt to complete alt2 checksum

This commit is contained in:
a33b 2020-12-26 07:00:45 -07:00
parent 6335c8f351
commit 68f8c51677
2 changed files with 55 additions and 2 deletions
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32
src/main/java/com/romraider/maps/checksum/CalculateALT2.java
View File

@ -45,15 +45,43 @@ public final class CalculateALT2 implements Calculator {
int sumt = 0;
int xort = 0;
int dw = 0;
for (int i = range.get(START); i < range.get(END); i += 4) {
for (int i = range.get(START) + 4; i < range.get(END); i += 4) {
if ((i == range.get(SUMLOC))
|| (i == range.get(XORLOC)
|| (i == range.get(SKIPLOC)))) continue;
dw = (int)parseByteValue(binData, Settings.Endian.BIG, i, 4, true);
dw = (int)parseByteValue(binData, Settings.Endian.BIG, i, 4, true); //this works, but shouldn't it be unsigned?
sumt += dw;
xort ^= dw;
}
results.put(SUMT, sumt);
results.put(XORT, xort);
//need to save SUMT and XORT before doing 16bit checksums
short sumCAL = 0;
short sumCODE = 0;
short d = 0;
for (int i = range.get(START) + 2; i < range.get(SKIPLOC); i += 2) {
if (i == range.get(SUMLOC)){
dw = results.get(SUMT);
sumCAL += (short)((dw >> 16) & 0xffff);
sumCAL += (short)(dw & 0xffff);
i += 2; //skip over final 2 bytes of SUMT
continue;
}
if (i == range.get(XORLOC)){
dw = results.get(XORT);
sumCAL += (short)((dw >> 16) & 0xffff);
sumCAL += (short)(dw & 0xffff);
i += 2; //skip over final 2 bytes of XORT
continue;
}
d = (short)parseByteValue(binData, Settings.Endian.BIG, i, 2, false);
sumCAL += d;
}
for (int i = range.get(SKIPLOC) + 2; i < range.get(END); i += 2) {
d = (short)parseByteValue(binData, Settings.Endian.BIG, i, 2, false);
sumCODE += d;
}
results.put(START, (int)sumCAL); //will this work casting as int?
results.put(SKIPLOC, (int)sumCODE); //will this work casting as int?
}
}

25
src/main/java/com/romraider/maps/checksum/ChecksumALT2.java
View File

@ -19,8 +19,12 @@
package com.romraider.maps.checksum;
import static com.romraider.xml.RomAttributeParser.parseByteValue;
import static com.romraider.xml.RomAttributeParser.parseIntegerValue;
import java.util.Map;
import com.romraider.Settings;
import com.romraider.util.HexUtil;
/**
@ -29,6 +33,8 @@ import com.romraider.util.HexUtil;
*/
public final class ChecksumALT2 extends NissanChecksum {
protected static final String SKIPLOC = "skiploc";
public static final String SUMCAL = "sumcal";
public static final String SUMCODE = "sumcode";
public ChecksumALT2() {
calculator = new CalculateALT2();
@ -42,5 +48,24 @@ public final class ChecksumALT2 extends NissanChecksum {
else {
range.put(SKIPLOC, 0x20000);
}
//override start for ALT2
range.put(START, 0x8200);
}
// Validate the 16 bit chks as well
public boolean validate(byte[] binData) {
calculator.calculate(range, binData, results);
final boolean valid =
(results.get(SUMT) == (int)parseByteValue(binData, Settings.Endian.BIG, range.get(SUMLOC), 4, true)) &&
(results.get(XORT) == (int)parseByteValue(binData, Settings.Endian.BIG, range.get(XORLOC), 4, true)) &&
(results.get(SUMCAL) == (short)parseByteValue(binData, Settings.Endian.BIG, range.get(START), 2, false)) &&
(results.get(SUMCODE) == (short)parseByteValue(binData, Settings.Endian.BIG, range.get(SKIPLOC), 2, false));
return valid;
}
public void update(byte[] binData) {
super.update(binData);
System.arraycopy(parseIntegerValue(results.get(SUMCAL), Settings.Endian.BIG, 2), 0, binData, range.get(START), 2);
System.arraycopy(parseIntegerValue(results.get(SUMCODE), Settings.Endian.BIG, 2), 0, binData, range.get(SKIPLOC), 2);
}
}