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OpenCV packaged with native libraries and loader for multiple platforms.
package nu.pattern;
import org.opencv.core.Core;
import sun.reflect.CallerSensitive;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.Pattern;
public class OpenCV {
private final static Logger logger = Logger.getLogger(OpenCV.class.getName());
static enum OS {
OSX("^[Mm]ac OS X$"),
LINUX("^[Ll]inux$"),
WINDOWS("^[Ww]indows.*");
private final Set patterns;
private OS(final String... patterns) {
this.patterns = new HashSet();
for (final String pattern : patterns) {
this.patterns.add(Pattern.compile(pattern));
}
}
private boolean is(final String id) {
for (final Pattern pattern : patterns) {
if (pattern.matcher(id).matches()) {
return true;
}
}
return false;
}
public static OS getCurrent() {
final String osName = System.getProperty("os.name");
for (final OS os : OS.values()) {
if (os.is(osName)) {
logger.log(Level.FINEST, "Current environment matches operating system descriptor \"{0}\".", os);
return os;
}
}
throw new UnsupportedOperationException(String.format("Operating system \"%s\" is not supported.", osName));
}
}
static enum Arch {
X86_32("i386", "i686"),
X86_64("amd64", "x86_64");
private final Set patterns;
private Arch(final String... patterns) {
this.patterns = new HashSet(Arrays.asList(patterns));
}
private boolean is(final String id) {
return patterns.contains(id);
}
public static Arch getCurrent() {
final String osArch = System.getProperty("os.arch");
for (final Arch arch : Arch.values()) {
if (arch.is(osArch)) {
logger.log(Level.FINEST, "Current environment matches architecture descriptor \"{0}\".", arch);
return arch;
}
}
throw new UnsupportedOperationException(String.format("Architecture \"%s\" is not supported.", osArch));
}
}
private static class UnsupportedPlatformException extends RuntimeException {
private UnsupportedPlatformException(final OS os, final Arch arch) {
super(String.format("Operating system \"%s\" and architecture \"%s\" are not supported.", os, arch));
}
}
private static class TemporaryDirectory {
final Path path;
public TemporaryDirectory() {
try {
path = Files.createTempDirectory("");
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public Path getPath() {
return path;
}
public TemporaryDirectory markDeleteOnExit() {
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
delete();
}
});
return this;
}
public void delete() {
if (!Files.exists(path)) {
return;
}
try {
Files.walkFileTree(path, new SimpleFileVisitor() {
@Override
public FileVisitResult postVisitDirectory(final Path dir, final IOException e)
throws IOException {
Files.deleteIfExists(dir);
return super.postVisitDirectory(dir, e);
}
@Override
public FileVisitResult visitFile(final Path file, final BasicFileAttributes attrs)
throws IOException {
Files.deleteIfExists(file);
return super.visitFile(file, attrs);
}
});
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
/**
* Exactly once per {@link ClassLoader}, attempt to load the native library (via {@link System#loadLibrary(String)} with {@link Core#NATIVE_LIBRARY_NAME}). If the first attempt fails, the native binary will be extracted from the classpath to a temporary location (which gets cleaned up on shutdown), that location is added to the {@code java.library.path} system property and {@link ClassLoader#usr_paths}, and then another call to load the library is made. Note this method uses reflection to gain access to private memory in {@link ClassLoader} as there's no documented method to augment the library path at runtime. Spurious calls are safe.
*/
public static void loadShared() {
SharedLoader.getInstance();
}
/**
* @see Initialization-on-demand holder idiom
*/
private static class SharedLoader {
private Path libraryPath;
private SharedLoader() {
try {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
logger.log(Level.FINEST, "Loaded existing OpenCV library \"{0}\" from library path.", Core.NATIVE_LIBRARY_NAME);
} catch (final UnsatisfiedLinkError ule) {
/* Only update the library path and load if the original error indicates it's missing from the library path. */
if (!String.format("no %s in java.library.path", Core.NATIVE_LIBRARY_NAME).equals(ule.getMessage())) {
logger.log(Level.FINEST, String.format("Encountered unexpected loading error."), ule);
throw ule;
}
/* Retain this path for cleaning up the library path later. */
this.libraryPath = extractNativeBinary();
addLibraryPath(libraryPath.getParent());
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
logger.log(Level.FINEST, "OpenCV library \"{0}\" loaded from extracted copy at \"{1}\".", new Object[]{Core.NATIVE_LIBRARY_NAME, System.mapLibraryName(Core.NATIVE_LIBRARY_NAME)});
}
}
/**
* Cleans up patches done to the environment.
*/
@Override
protected void finalize() throws Throwable {
super.finalize();
if (null == libraryPath) {
return;
}
removeLibraryPath(libraryPath.getParent());
}
private static class Holder {
private static final SharedLoader INSTANCE = new SharedLoader();
}
public static SharedLoader getInstance() {
return Holder.INSTANCE;
}
/**
* Adds the provided {@link Path}, normalized, to the {@link ClassLoader#usr_paths} array, as well as to the {@code java.library.path} system property. Uses the reflection API to make the field accessible, and may be unsafe in environments with a security policy.
*
* @see Adding new paths for native libraries at runtime in Java
*/
private static void addLibraryPath(final Path path) {
final String normalizedPath = path.normalize().toString();
try {
final Field field = ClassLoader.class.getDeclaredField("usr_paths");
field.setAccessible(true);
final Set userPaths = new HashSet<>(Arrays.asList((String[]) field.get(null)));
userPaths.add(normalizedPath);
field.set(null, userPaths.toArray(new String[userPaths.size()]));
System.setProperty("java.library.path", System.getProperty("java.library.path") + File.pathSeparator + normalizedPath);
logger.log(Level.FINEST, "System library path now \"{0}\".", System.getProperty("java.library.path"));
} catch (IllegalAccessException e) {
throw new RuntimeException("Failed to get permissions to set library path");
} catch (NoSuchFieldException e) {
throw new RuntimeException("Failed to get field handle to set library path");
}
}
/**
* Removes the provided {@link Path}, normalized, from the {@link ClassLoader#usr_paths} array, as well as to the {@code java.library.path} system property. Uses the reflection API to make the field accessible, and may be unsafe in environments with a security policy.
*/
private static void removeLibraryPath(final Path path) {
final String normalizedPath = path.normalize().toString();
try {
final Field field = ClassLoader.class.getDeclaredField("usr_paths");
field.setAccessible(true);
final Set userPaths = new HashSet<>(Arrays.asList((String[]) field.get(null)));
userPaths.remove(normalizedPath);
field.set(null, userPaths.toArray(new String[userPaths.size()]));
System.setProperty("java.library.path", System.getProperty("java.library.path").replace(File.pathSeparator + path.normalize().toString(), ""));
} catch (IllegalAccessException e) {
throw new RuntimeException("Failed to get permissions to set library path");
} catch (NoSuchFieldException e) {
throw new RuntimeException("Failed to get field handle to set library path");
}
}
}
/**
* Exactly once per {@link ClassLoader}, extract the native binary from the classpath to a temporary location (which gets cleaned up on shutdown), and load that binary (via {@link System#load(String)}). Spurious calls are safe.
*/
public static void loadLocally() {
LocalLoader.getInstance();
}
private static class LocalLoader {
private LocalLoader() {
/* Retain this path for cleaning up later. */
final Path libraryPath = extractNativeBinary();
System.load(libraryPath.normalize().toString());
logger.log(Level.FINEST, "OpenCV library \"{0}\" loaded from extracted copy at \"{1}\".", new Object[]{Core.NATIVE_LIBRARY_NAME, System.mapLibraryName(Core.NATIVE_LIBRARY_NAME)});
}
private static class Holder {
private static final LocalLoader INSTANCE = new LocalLoader();
}
public static LocalLoader getInstance() {
return Holder.INSTANCE;
}
}
/**
* Selects the appropriate packaged binary, extracts it to a temporary location (which gets deleted when the JVM shuts down), and returns a {@link Path} to that file.
*/
@CallerSensitive
private static Path extractNativeBinary() {
final OS os = OS.getCurrent();
final Arch arch = Arch.getCurrent();
return extractNativeBinary(os, arch);
}
/**
* Extracts the packaged binary for the specified platform to a temporary location (which gets deleted when the JVM shuts down), and returns a {@link Path} to that file.
*/
private static Path extractNativeBinary(final OS os, final Arch arch) {
final String location;
switch (os) {
case LINUX:
switch (arch) {
case X86_32:
location = "/nu/pattern/opencv/linux/x86_32/libopencv_java2411.so";
break;
case X86_64:
location = "/nu/pattern/opencv/linux/x86_64/libopencv_java2411.so";
break;
default:
throw new UnsupportedPlatformException(os, arch);
}
break;
case OSX:
switch (arch) {
case X86_64:
location = "/nu/pattern/opencv/osx/x86_64/libopencv_java2411.dylib";
break;
default:
throw new UnsupportedPlatformException(os, arch);
}
break;
case WINDOWS:
switch (arch) {
case X86_32:
location = "/nu/pattern/opencv/windows/x86_32/opencv_java2411.dll";
break;
case X86_64:
location = "/nu/pattern/opencv/windows/x86_64/opencv_java2411.dll";
break;
default:
throw new UnsupportedPlatformException(os, arch);
}
break;
default:
throw new UnsupportedPlatformException(os, arch);
}
logger.log(Level.FINEST, "Selected native binary \"{0}\".", location);
final InputStream binary = OpenCV.class.getResourceAsStream(location);
final Path destination = new TemporaryDirectory().markDeleteOnExit().getPath().resolve("./" + location).normalize();
try {
logger.log(Level.FINEST, "Copying native binary to \"{0}\".", destination);
Files.createDirectories(destination.getParent());
Files.copy(binary, destination);
} catch (final IOException ioe) {
throw new IllegalStateException(String.format("Error writing native library to \"%s\".", destination), ioe);
}
logger.log(Level.FINEST, "Extracted native binary to \"{0}\".", destination);
return destination;
}
}
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