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TMC-IOENC: Refactored Decoder to use ByteBuffer instead of byte[] for better readability/simpler code.

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Harald Kuhr
2013-09-08 13:39:13 +02:00
parent 9a27f62dec
commit f2ff00580a
9 changed files with 102 additions and 126 deletions
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28
imageio/imageio-tiff/src/main/java/com/twelvemonkeys/imageio/plugins/tiff/LZWDecoder.java
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@@ -33,6 +33,7 @@ import com.twelvemonkeys.io.enc.Decoder;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
/**
* Lempel–Ziv–Welch (LZW) decompression. LZW is a universal loss-less data compression algorithm
@@ -94,10 +95,9 @@ abstract class LZWDecoder implements Decoder {
maxString = 1;
}
public int decode(final InputStream stream, final byte[] buffer) throws IOException {
public int decode(final InputStream stream, final ByteBuffer buffer) throws IOException {
// Adapted from the pseudo-code example found in the TIFF 6.0 Specification, 1992.
// See Section 13: "LZW Compression"/"LZW Decoding", page 61+
int bufferPos = 0;
int code;
while ((code = getNextCode(stream)) != EOI_CODE) {
@@ -109,30 +109,30 @@ abstract class LZWDecoder implements Decoder {
break;
}
bufferPos += table[code].writeTo(buffer, bufferPos);
table[code].writeTo(buffer);
}
else {
if (isInTable(code)) {
bufferPos += table[code].writeTo(buffer, bufferPos);
table[code].writeTo(buffer);
addStringToTable(table[oldCode].concatenate(table[code].firstChar));
}
else {
String outString = table[oldCode].concatenate(table[oldCode].firstChar);
bufferPos += outString.writeTo(buffer, bufferPos);
outString.writeTo(buffer);
addStringToTable(outString);
}
}
oldCode = code;
if (bufferPos >= buffer.length - maxString - 1) {
if (buffer.remaining() < maxString + 1) {
// Buffer full, stop decoding for now
break;
}
}
return bufferPos;
return buffer.position();
}
private void addStringToTable(final String string) throws IOException {
@@ -301,24 +301,24 @@ abstract class LZWDecoder implements Decoder {
return new String(firstChar, this.firstChar, length + 1, this);
}
public final int writeTo(final byte[] buffer, final int offset) {
public final void writeTo(final ByteBuffer buffer) {
if (length == 0) {
return 0;
return;
}
else if (length == 1) {
buffer[offset] = value;
return 1;
if (length == 1) {
buffer.put(value);
}
else {
String e = this;
final int offset = buffer.position();
for (int i = length - 1; i >= 0; i--) {
buffer[offset + i] = e.value;
buffer.put(offset + i, e.value);
e = e.previous;
}
return length;
buffer.position(offset + length);
}
}
}