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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.node.admin.task.util.file;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.time.Instant;
import java.util.Optional;
/**
* A snapshot of the attributes of the file for a given path, and file content if it is a regular file.
*
* @author hakonhall
*/
public class FileSnapshot {
private final Path path;
private final Optional<FileAttributes> attributes;
private final Optional<byte[]> content;
public static FileSnapshot forPath(Path path) { return forNonExistingFile(path).snapshot(); }
/** Guaranteed to not throw any exceptions. */
public static FileSnapshot forNonExistingFile(Path path) {
return new FileSnapshot(path, Optional.empty(), Optional.empty());
}
private static FileSnapshot forRegularFile(Path path, FileAttributes attributes, byte[] content) {
if (!attributes.isRegularFile()) throw new IllegalArgumentException(path + " is not a regular file");
return new FileSnapshot(path, Optional.of(attributes), Optional.of(content));
}
private static FileSnapshot forOtherFile(Path path, FileAttributes attributes) {
if (attributes.isRegularFile()) throw new IllegalArgumentException(path + " is a regular file");
return new FileSnapshot(path, Optional.of(attributes), Optional.empty());
}
private FileSnapshot(Path path, Optional<FileAttributes> attributes, Optional<byte[]> content) {
this.path = path;
this.attributes = attributes;
this.content = content;
}
public Path path() { return path; }
/** Whether there was a file (or directory) at path. */
public boolean exists() { return attributes.isPresent(); }
/** Returns the file attributes if the file exists. */
public Optional<FileAttributes> attributes() { return attributes; }
/** Returns the file content if the file exists and is a regular file. */
public Optional<byte[]> content() { return content; }
/** Returns the file UTF-8 content if it exists and is a regular file. */
public Optional<String> utf8Content() { return content.map(c -> new String(c, StandardCharsets.UTF_8)); }
/** Returns an up-to-date snapshot of the path, possibly {@code this} if last modified time has not changed. */
public FileSnapshot snapshot() {
Optional<FileAttributes> currentAttributes = new UnixPath(path).getAttributesIfExists();
if (currentAttributes.isPresent()) {
// 'this' may still be valid, depending on last modified times.
if (attributes.isPresent()) {
Instant previousModifiedTime = attributes.get().lastModifiedTime();
Instant currentModifiedTime = currentAttributes.get().lastModifiedTime();
if (currentModifiedTime.compareTo(previousModifiedTime) <= 0) {
return this;
}
}
if (currentAttributes.get().isRegularFile()) {
Optional<byte[]> content = IOExceptionUtil.ifExists(() -> Files.readAllBytes(path));
return content.map(bytes -> FileSnapshot.forRegularFile(path, currentAttributes.get(), bytes))
// File was removed after getting attributes and before getting content.
.orElseGet(() -> FileSnapshot.forNonExistingFile(path));
} else {
return FileSnapshot.forOtherFile(path, currentAttributes.get());
}
} else {
return attributes.isPresent() ? FileSnapshot.forNonExistingFile(path) : this /* avoid allocation */;
}
}
}
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