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Update DiskReaderGRC.java

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tidying
This commit is contained in:
Denis Molony 2019-09-05 07:14:35 +10:00
parent 19386e5c8e
commit 43cabfa7bb
1 changed files with 11 additions and 5 deletions
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16
src/com/bytezone/diskbrowser/nib/DiskReaderGRC.java
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@ -20,42 +20,48 @@ public class DiskReaderGRC extends DiskReader
{
byte[] outBuffer = new byte[BLOCK_SIZE * 2 + 12]; // 524 bytes
int outPtr = 0;
int[] checksums = new int[3];
// decode four disk bytes into three data bytes (175 * 3 - 1 = 524)
for (int j = 0; j < 175; j++)
{
checksums[0] = (checksums[0] & 0xFF) << 1; // ROL
if ((checksums[0] > 0xFF))
++checksums[0];
// 6&2 translation
byte d3 = byteTranslator.decode (buffer[ptr++]); // composite byte
byte d0 = byteTranslator.decode (buffer[ptr++]);
byte d1 = byteTranslator.decode (buffer[ptr++]);
// reassemble bytes
byte b0 = (byte) ((d0 & 0x3F) | ((d3 & 0x30) << 2));
byte b1 = (byte) ((d1 & 0x3F) | ((d3 & 0x0C) << 4));
// calculate running checksums
outBuffer[outPtr++] = checksum (b0, checksums, 0, 2);
outBuffer[outPtr++] = checksum (b1, checksums, 2, 1);
if (j < 174)
if (j < 174) // get fourth disk byte if we are not at the very end
{
byte d2 = byteTranslator.decode (buffer[ptr++]);
byte b2 = (byte) ((d2 & 0x3F) | ((d3 & 0x03) << 6));
outBuffer[outPtr++] = checksum (b2, checksums, 1, 0);
byte d2 = byteTranslator.decode (buffer[ptr++]); // translate
byte b2 = (byte) ((d2 & 0x3F) | ((d3 & 0x03) << 6)); // reassemble
outBuffer[outPtr++] = checksum (b2, checksums, 1, 0); // checksum
}
}
// decode four disk bytes into three data bytes
byte d3 = byteTranslator.decode (buffer[ptr++]); // composite byte
byte d0 = byteTranslator.decode (buffer[ptr++]);
byte d1 = byteTranslator.decode (buffer[ptr++]);
byte d2 = byteTranslator.decode (buffer[ptr++]);
// reassemble bytes
byte b0 = (byte) ((d0 & 0x3F) | ((d3 & 0x30) << 2));
byte b1 = (byte) ((d1 & 0x3F) | ((d3 & 0x0C) << 4));
byte b2 = (byte) ((d2 & 0x3F) | ((d3 & 0x03) << 6));
// compare disk checksums with calculated checksums
if ((checksums[0] & 0xFF) != (b2 & 0xFF) //
|| (checksums[1] & 0xFF) != (b1 & 0xFF) //
|| (checksums[2] & 0xFF) != (b0 & 0xFF))