add convenience method for files to FileMagic

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1830782 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 19 insertions, 0 deletions

diff --git a/src/java/org/apache/poi/poifs/filesystem/FileMagic.java b/src/java/org/apache/poi/poifs/filesystem/FileMagic.java
index 765cf6e323..4ac616082e 100644
--- a/src/java/org/apache/poi/poifs/filesystem/FileMagic.java
+++ b/src/java/org/apache/poi/poifs/filesystem/FileMagic.java
@@ -22,6 +22,8 @@ import static org.apache.poi.poifs.common.POIFSConstants.RAW_XML_FILE_HEADER;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import java.io.BufferedInputStream;
+import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
@@ -117,6 +119,23 @@ public enum FileMagic {
         return UNKNOWN;
     }
 
+
+    /**
+     * Get the file magic of the supplied {@link File}<p>
+     *
+     * Even if this method returns {@link FileMagic#UNKNOWN} it could potentially mean,
+     *  that the ZIP stream has leading junk bytes
+     *
+     * @param inp a file to be identified
+     */
+    public static FileMagic valueOf(final File inp) throws IOException {
+        try (FileInputStream fis = new FileInputStream(inp)) {
+            final byte[] data = IOUtils.toByteArray(fis, 8);
+            return FileMagic.valueOf(data);
+        }
+    }
+
+
     /**
      * Get the file magic of the supplied InputStream (which MUST
      *  support mark and reset).<p>