1 files changed, 101 insertions, 0 deletions
diff --git a/pg/src/main/java/org/spongycastle/openpgp/SXprUtils.java b/pg/src/main/java/org/spongycastle/openpgp/SXprUtils.java
new file mode 100644
index 00000000..0da315ec
--- /dev/null
+++ b/pg/src/main/java/org/spongycastle/openpgp/SXprUtils.java
@@ -0,0 +1,101 @@
+package org.spongycastle.openpgp;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.spongycastle.bcpg.HashAlgorithmTags;
+import org.spongycastle.bcpg.S2K;
+import org.spongycastle.util.io.Streams;
+
+/**
+ * Utility functions for looking a S-expression keys. This class will move when it finds a better home!
+ * <p>
+ * Format documented here:
+ * http://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=agent/keyformat.txt;h=42c4b1f06faf1bbe71ffadc2fee0fad6bec91a97;hb=refs/heads/master
+ * </p>
+ */
+class SXprUtils
+{
+    private static int readLength(InputStream in, int ch)
+        throws IOException
+    {
+        int len = ch - '0';
+
+        while ((ch = in.read()) >= 0 && ch != ':')
+        {
+            len = len * 10 + ch - '0';
+        }
+
+        return len;
+    }
+
+    static String readString(InputStream in, int ch)
+        throws IOException
+    {
+        int len = readLength(in, ch);
+
+        char[] chars = new char[len];
+
+        for (int i = 0; i != chars.length; i++)
+        {
+            chars[i] = (char)in.read();
+        }
+
+        return new String(chars);
+    }
+
+    static byte[] readBytes(InputStream in, int ch)
+        throws IOException
+    {
+        int len = readLength(in, ch);
+
+        byte[] data = new byte[len];
+
+        Streams.readFully(in, data);
+
+        return data;
+    }
+
+    static S2K parseS2K(InputStream in)
+        throws IOException
+    {
+        skipOpenParenthesis(in);
+
+        String alg = readString(in, in.read());
+        byte[] iv = readBytes(in, in.read());
+        final long iterationCount = Long.parseLong(readString(in, in.read()));
+
+        skipCloseParenthesis(in);
+
+        // we have to return the actual iteration count provided.
+        S2K s2k = new S2K(HashAlgorithmTags.SHA1, iv, (int)iterationCount)
+        {
+            public long getIterationCount()
+            {
+                return iterationCount;
+            }
+        };
+
+        return s2k;
+    }
+
+    static void skipOpenParenthesis(InputStream in)
+        throws IOException
+    {
+        int ch = in.read();
+        if (ch != '(')
+        {
+            throw new IOException("unknown character encountered");
+        }
+    }
+
+    static void skipCloseParenthesis(InputStream in)
+        throws IOException
+    {
+        int ch = in.read();
+        if (ch != ')')
+        {
+            throw new IOException("unknown character encountered");
+        }
+    }
+}