1 files changed, 304 insertions, 0 deletions
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
new file mode 100644
index 0000000000..72aad9b0c9
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
@@ -0,0 +1,304 @@
+/*
+ * Copyright (C) 2016, 2021 Christian Halstrick <christian.halstrick@sap.com> and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.lfs;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.io.UnsupportedEncodingException;
+import java.util.Locale;
+import java.util.Objects;
+
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
+import org.eclipse.jgit.lfs.lib.Constants;
+import org.eclipse.jgit.lfs.lib.LongObjectId;
+import org.eclipse.jgit.util.IO;
+
+/**
+ * Represents an LFS pointer file
+ *
+ * @since 4.6
+ */
+public class LfsPointer implements Comparable<LfsPointer> {
+	/**
+	 * The version of the LfsPointer file format
+	 */
+	public static final String VERSION = "https://git-lfs.github.com/spec/v1"; //$NON-NLS-1$
+
+	/**
+	 * The version of the LfsPointer file format using legacy URL
+	 * @since 4.7
+	 */
+	public static final String VERSION_LEGACY = "https://hawser.github.com/spec/v1"; //$NON-NLS-1$
+
+	/**
+	 * Don't inspect files that are larger than this threshold to avoid
+	 * excessive reading. No pointer file should be larger than this.
+	 * @since 4.11
+	 */
+	public static final int SIZE_THRESHOLD = 200;
+
+	/**
+	 * The name of the hash function as used in the pointer files. This will
+	 * evaluate to "sha256"
+	 */
+	public static final String HASH_FUNCTION_NAME = Constants.LONG_HASH_FUNCTION
+			.toLowerCase(Locale.ROOT).replace("-", ""); //$NON-NLS-1$ //$NON-NLS-2$
+
+	/**
+	 * {@link #SIZE_THRESHOLD} is too low; with lfs extensions a LFS pointer can
+	 * be larger. But 8kB should be more than enough.
+	 */
+	static final int FULL_SIZE_THRESHOLD = 8 * 1024;
+
+	private final AnyLongObjectId oid;
+
+	private final long size;
+
+	/**
+	 * <p>Constructor for LfsPointer.</p>
+	 *
+	 * @param oid
+	 *            the id of the content
+	 * @param size
+	 *            the size of the content
+	 */
+	public LfsPointer(AnyLongObjectId oid, long size) {
+		this.oid = oid;
+		this.size = size;
+	}
+
+	/**
+	 * <p>Getter for the field <code>oid</code>.</p>
+	 *
+	 * @return the id of the content
+	 */
+	public AnyLongObjectId getOid() {
+		return oid;
+	}
+
+	/**
+	 * <p>Getter for the field <code>size</code>.</p>
+	 *
+	 * @return the size of the content
+	 */
+	public long getSize() {
+		return size;
+	}
+
+	/**
+	 * Encode this object into the LFS format defined by {@link #VERSION}
+	 *
+	 * @param out
+	 *            the {@link java.io.OutputStream} into which the encoded data should be
+	 *            written
+	 */
+	public void encode(OutputStream out) {
+		try (PrintStream ps = new PrintStream(out, false,
+				UTF_8.name())) {
+			ps.print("version "); //$NON-NLS-1$
+			ps.print(VERSION + "\n"); //$NON-NLS-1$
+			ps.print("oid " + HASH_FUNCTION_NAME + ":"); //$NON-NLS-1$ //$NON-NLS-2$
+			ps.print(oid.name() + "\n"); //$NON-NLS-1$
+			ps.print("size "); //$NON-NLS-1$
+			ps.print(size + "\n"); //$NON-NLS-1$
+		} catch (UnsupportedEncodingException e) {
+			// should not happen, we are using a standard charset
+		}
+	}
+
+	/**
+	 * Try to parse the data provided by an InputStream to the format defined by
+	 * {@link #VERSION}. If the given stream supports mark and reset as
+	 * indicated by {@link InputStream#markSupported()}, its input position will
+	 * be reset if the stream content is not actually a LFS pointer (i.e., when
+	 * {@code null} is returned). If the stream content is an invalid LFS
+	 * pointer or the given stream does not support mark/reset, the input
+	 * position may not be reset.
+	 *
+	 * @param in
+	 *            the {@link java.io.InputStream} from where to read the data
+	 * @return an {@link org.eclipse.jgit.lfs.LfsPointer} or {@code null} if the
+	 *         stream was not parseable as LfsPointer
+	 * @throws java.io.IOException
+	 *             if an IO error occurred
+	 */
+	@Nullable
+	public static LfsPointer parseLfsPointer(InputStream in)
+			throws IOException {
+		if (in.markSupported()) {
+			return parse(in);
+		}
+		// Fallback; note that while parse() resets its input stream, that won't
+		// reset "in".
+		return parse(new BufferedInputStream(in));
+	}
+
+	@Nullable
+	private static LfsPointer parse(InputStream in)
+			throws IOException {
+		if (!in.markSupported()) {
+			// No translation; internal error
+			throw new IllegalArgumentException(
+					"LFS pointer parsing needs InputStream.markSupported() == true"); //$NON-NLS-1$
+		}
+		// Try reading only a short block first.
+		in.mark(SIZE_THRESHOLD);
+		byte[] preamble = new byte[SIZE_THRESHOLD];
+		int length = IO.readFully(in, preamble, 0);
+		if (length < preamble.length || in.read() < 0) {
+			// We have the whole file. Try to parse a pointer from it.
+			try (BufferedReader r = new BufferedReader(new InputStreamReader(
+					new ByteArrayInputStream(preamble, 0, length), UTF_8))) {
+				LfsPointer ptr = parse(r);
+				if (ptr == null) {
+					in.reset();
+				}
+				return ptr;
+			}
+		}
+		// Longer than SIZE_THRESHOLD: expect "version" to be the first line.
+		boolean hasVersion = checkVersion(preamble);
+		in.reset();
+		if (!hasVersion) {
+			return null;
+		}
+		in.mark(FULL_SIZE_THRESHOLD);
+		byte[] fullPointer = new byte[FULL_SIZE_THRESHOLD];
+		length = IO.readFully(in, fullPointer, 0);
+		if (length == fullPointer.length && in.read() >= 0) {
+			in.reset();
+			return null; // Too long.
+		}
+		try (BufferedReader r = new BufferedReader(new InputStreamReader(
+				new ByteArrayInputStream(fullPointer, 0, length), UTF_8))) {
+			LfsPointer ptr = parse(r);
+			if (ptr == null) {
+				in.reset();
+			}
+			return ptr;
+		}
+	}
+
+	private static LfsPointer parse(BufferedReader r) throws IOException {
+		boolean versionLine = false;
+		LongObjectId id = null;
+		long sz = -1;
+		// This parsing is a bit too general if we go by the spec at
+		// https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
+		// Comment lines are not mentioned in the spec, the "version" line
+		// MUST be the first, and keys are ordered alphabetically.
+		for (String s = r.readLine(); s != null; s = r.readLine()) {
+			if (s.startsWith("#") || s.length() == 0) { //$NON-NLS-1$
+				continue;
+			} else if (s.startsWith("version")) { //$NON-NLS-1$
+				if (versionLine || !checkVersionLine(s)) {
+					return null; // Not a LFS pointer
+				}
+				versionLine = true;
+			} else {
+				try {
+					if (s.startsWith("oid sha256:")) { //$NON-NLS-1$
+						if (id != null) {
+							return null; // Not a LFS pointer
+						}
+						id = LongObjectId.fromString(s.substring(11).trim());
+					} else if (s.startsWith("size")) { //$NON-NLS-1$
+						if (sz > 0 || s.length() < 5 || s.charAt(4) != ' ') {
+							return null; // Not a LFS pointer
+						}
+						sz = Long.parseLong(s.substring(5).trim());
+					}
+				} catch (RuntimeException e) {
+					// We could not parse the line. If we have a version
+					// already, this is a corrupt LFS pointer. Otherwise it
+					// is just not an LFS pointer.
+					if (versionLine) {
+						throw e;
+					}
+					return null;
+				}
+			}
+			if (versionLine && id != null && sz > -1) {
+				return new LfsPointer(id, sz);
+			}
+		}
+		return null;
+	}
+
+	private static boolean checkVersion(byte[] data) {
+		// According to the spec at
+		// https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
+		// it MUST always be the first line.
+		try (BufferedReader r = new BufferedReader(
+				new InputStreamReader(new ByteArrayInputStream(data), UTF_8))) {
+			String s = r.readLine();
+			if (s != null && s.startsWith("version")) { //$NON-NLS-1$
+				return checkVersionLine(s);
+			}
+		} catch (IOException e) {
+			// Doesn't occur, we're reading from a byte array!
+		}
+		return false;
+	}
+
+	private static boolean checkVersionLine(String s) {
+		if (s.length() < 8 || s.charAt(7) != ' ') {
+			return false; // Not a valid LFS pointer version line
+		}
+		String rest = s.substring(8).trim();
+		return VERSION.equals(rest) || VERSION_LEGACY.equals(rest);
+	}
+
+	@Override
+	public String toString() {
+		return "LfsPointer: oid=" + oid.name() + ", size=" //$NON-NLS-1$ //$NON-NLS-2$
+				+ size;
+	}
+
+	/**
+	 * @since 4.11
+	 */
+	@Override
+	public int compareTo(LfsPointer o) {
+		int x = getOid().compareTo(o.getOid());
+		if (x != 0) {
+			return x;
+		}
+
+		return Long.compare(getSize(), o.getSize());
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(getOid()) * 31 + Long.hashCode(getSize());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) {
+			return true;
+		}
+		if (!(obj instanceof LfsPointer)) {
+			return false;
+		}
+		LfsPointer other = (LfsPointer) obj;
+		return Objects.equals(getOid(), other.getOid())
+				&& getSize() == other.getSize();
+	}
+}