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All cases mutate, so R/W lock is redundant and complicates things

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comp500
2019-06-01 12:37:01 +01:00
parent f76a3d2d62
commit 86c2349fd3
1 changed files with 9 additions and 20 deletions
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29
src/main/java/link/infra/packwiz/installer/request/handlers/RequestHandlerZip.java
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@@ -8,6 +8,7 @@ import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
@@ -19,14 +20,14 @@ public abstract class RequestHandlerZip extends RequestHandlerHTTP {
private final ZipInputStream zis;
private final Map<URI, byte[]> readFiles = new HashMap<URI, byte[]>();
// Write lock implies access to ZipInputStream - only 1 thread must read at a time!
final ReentrantReadWriteLock filesLock = new ReentrantReadWriteLock();
final ReentrantLock filesLock = new ReentrantLock();
private ZipEntry entry;
public ZipReader(InputStream zip) {
zis = new ZipInputStream(zip);
}
// File write lock must be obtained before calling this function
// File lock must be obtained before calling this function
private byte[] readCurrFile() throws IOException {
byte[] bytes = new byte[(int) entry.getSize()];
DataInputStream dis = new DataInputStream(zis);
@@ -34,7 +35,7 @@ public abstract class RequestHandlerZip extends RequestHandlerHTTP {
return bytes;
}
// File write lock must be obtained before calling this function
// File lock must be obtained before calling this function
private byte[] findFile(URI loc) throws IOException, URISyntaxException {
while (true) {
entry = zis.getNextEntry();
@@ -51,28 +52,16 @@ public abstract class RequestHandlerZip extends RequestHandlerHTTP {
}
public InputStream getFileInputStream(URI loc) throws Exception {
filesLock.readLock().lock();
byte[] file = readFiles.get(loc);
filesLock.readLock().unlock();
filesLock.lock();
// Assume files are only read once, allow GC by removing
byte[] file = readFiles.remove(loc);
if (file != null) {
// Assume files are only read once, allow GC
filesLock.writeLock().lock();
readFiles.remove(loc);
filesLock.writeLock().unlock();
return new ByteArrayInputStream(file);
}
filesLock.writeLock().lock();
// Test again after receiving write lock
file = readFiles.get(loc);
if (file != null) {
// Assume files are only read once, allow GC
readFiles.remove(loc);
filesLock.writeLock().unlock();
filesLock.unlock();
return new ByteArrayInputStream(file);
}
file = findFile(loc);
filesLock.writeLock().unlock();
filesLock.unlock();
if (file != null) {
return new ByteArrayInputStream(file);
}