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Bug 520257: Avoid touching file with unchanged content

Browse source 
When creating the settings.xml, avoid writing to the file unless
the contents have actually changed. This avoids a resource delta
that caused unneeded rebuilds.

Change-Id: I83cea84e96d006f99a1c264f283d4bba4ad68784
This commit is contained in:
Jonah Graham 2017-07-28 10:53:01 +01:00
parent 594e65c8c0
commit 7f3b2120fe
1 changed files with 29 additions and 2 deletions
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31
core/org.eclipse.cdt.core/utils/org/eclipse/cdt/internal/core/XmlUtil.java
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@ -19,6 +19,7 @@ import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.util.Arrays;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
@ -384,10 +385,14 @@ public class XmlUtil {
String utfString = new String(toByteArray(doc), ENCODING_UTF_8);
String lineSeparator = Util.getLineSeparator(file);
utfString = XmlUtil.replaceLineSeparatorInternal(utfString, lineSeparator);
InputStream input = new ByteArrayInputStream(utfString.getBytes(ENCODING_UTF_8));
byte[] newContents = utfString.getBytes(ENCODING_UTF_8);
InputStream input = new ByteArrayInputStream(newContents);
if (file.exists()) {
file.setContents(input, IResource.FORCE, null);
byte[] existingContents = readFile(file);
if (!Arrays.equals(existingContents, newContents)) {
file.setContents(input, IResource.FORCE, null);
}
} else {
file.create(input, IResource.FORCE, null);
}
@ -395,6 +400,28 @@ public class XmlUtil {
}
}
/**
* Read whole file, returning null on any error.
*/
private static byte[] readFile(IFile file) {
try (InputStream is = file.getContents(true)) {
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[4096];
while ((nRead = is.read(data)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush();
return buffer.toByteArray();
} catch (IOException | CoreException e) {
return null;
}
}
/**
* Serialize XML Document into a string.
*