Apple-2-Tools/dmolony-DiskBrowser
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tidying

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This commit is contained in:
Denis Molony 2019-09-06 08:36:15 +10:00
parent 68a133b2b0
commit b7f9b73643
1 changed files with 11 additions and 10 deletions
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21
src/com/bytezone/diskbrowser/nib/DiskReaderGCR.java
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@ -41,15 +41,15 @@ public class DiskReaderGCR extends DiskReader
byte b1 = (byte) (d1 | ((d3 << 4) & 0xC0)); byte b1 = (byte) (d1 | ((d3 << 4) & 0xC0));
// calculate running checksums // calculate running checksums
outBuffer[outPtr++] = checksum (b0, checksums, 2, 0); outBuffer[outPtr++] = checksum (b0, checksums, 0);
outBuffer[outPtr++] = checksum (b1, checksums, 0, 1); outBuffer[outPtr++] = checksum (b1, checksums, 1);
if (outPtr == outBuffer.length) if (outPtr == outBuffer.length)
break; break;
byte d2 = byteTranslator.decode (inBuffer[inPtr++]); // translate byte d2 = byteTranslator.decode (inBuffer[inPtr++]); // translate
byte b2 = (byte) (d2 | (d3 << 6)); // reassemble byte b2 = (byte) (d2 | (d3 << 6)); // reassemble
outBuffer[outPtr++] = checksum (b2, checksums, 1, 2); // checksum outBuffer[outPtr++] = checksum (b2, checksums, 2); // checksum
} }
// decode four disk bytes into three checksum bytes // decode four disk bytes into three checksum bytes
@ -73,19 +73,20 @@ public class DiskReaderGCR extends DiskReader
} }
// ---------------------------------------------------------------------------------// // ---------------------------------------------------------------------------------//
private byte checksum (byte diskByte, int[] checksums, int current, int next) private byte checksum (byte diskByte, int[] checksums, int a)
// ---------------------------------------------------------------------------------// // ---------------------------------------------------------------------------------//
{ {
int val = (diskByte ^ checksums[current]) & 0xFF; int b = (a + 2) % 3;
checksums[next] += val; // prepare next checksum int val = (diskByte ^ checksums[b]) & 0xFF;
checksums[a] += val; // prepare next checksum
if (checksums[current] > 0xFF) // is there a carry? if (checksums[b] > 0xFF) // is there a carry?
{ {
++checksums[next]; // pass it on ++checksums[a]; // pass it on
checksums[current] &= 0xFF; // back to 8 bits checksums[b] &= 0xFF; // back to 8 bits
} }
return (byte) val; // converted data byte return (byte) val; // converted data byte
} }
// ---------------------------------------------------------------------------------// // ---------------------------------------------------------------------------------//