Exporting functions to compute SHA1 digests of files.

TODO: need to stich them all the way through various ActionInputFileCache
implementations!

--
MOS_MIGRATED_REVID=132685408

2 files changed, 28 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/vfs/FileSystem.java b/src/main/java/com/google/devtools/build/lib/vfs/FileSystem.java
index 3e3b94da63..e7f1fa2513 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/FileSystem.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/FileSystem.java
@@ -279,6 +279,20 @@ public abstract class FileSystem {
   }
 
   /**
+   * Returns the MD5 digest of the file denoted by {@code path}. See
+   * {@link Path#getMD5Digest} for specification.
+   */
+  protected byte[] getSHA1Digest(final Path path) throws IOException {
+    // Naive I/O implementation.  TODO(olaola): optimize!
+    return new ByteSource() {
+      @Override
+      public InputStream openStream() throws IOException {
+        return getInputStream(path);
+      }
+    }.hash(Hashing.sha1()).asBytes();
+  }
+
+  /**
    * Returns true if "path" denotes an existing symbolic link. See
    * {@link Path#isSymbolicLink} for specification.
    */
diff --git a/src/main/java/com/google/devtools/build/lib/vfs/Path.java b/src/main/java/com/google/devtools/build/lib/vfs/Path.java
index 657bb03c41..dbec227a22 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/Path.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/Path.java
@@ -995,6 +995,20 @@ public class Path implements Comparable<Path>, Serializable {
   }
 
   /**
+   * Returns the SHA1 digest of the file denoted by the current path, following
+   * symbolic links.
+   *
+   * <p>This method runs in O(n) time where n is the length of the file, but
+   * certain implementations may be much faster than the worst case.
+   *
+   * @return a new 20-byte array containing the file's SHA1 digest
+   * @throws IOException if the SHA1 digest could not be computed for any reason
+   */
+  public byte[] getSHA1Digest() throws IOException {
+    return fileSystem.getSHA1Digest(this);
+  }
+
+  /**
    * Opens the file denoted by this path, following symbolic links, for reading,
    * and returns an input stream to it.
    *