Add an example sha256FileHex().

README.md

@@ -16,7 +16,7 @@ Note that IANAC (I am not a cryptologist), so this will surely be flawed in some
   Supports certificates signed with RSASSA-PSS!
   Still need support for X.500 names (AttributeValueAssertions with well-known object identifiers).
   Right now, only common name (2.5.4.3), country (2.5.4.6) and organization (2.5.4.10) are supported.
-  No specific v3 extensions support yet. Need to implement some standard and well-known types. 
+  No specific v3 extensions support yet. Need to implement some standard and well-known types.
   UTCTime is not finished
 * Removed erroneous and unnecessary dependency from api to impl module
 

examples/de/dlkw/ccrypto/examples/digest.ceylon

@@ -2,6 +2,12 @@ import de.dlkw.ccrypto.svc {
     sha256,
     sha1
 }
+import import ceylon.file {
+    Path
+}
+import ceylon.buffer.base {
+    base16String
+}
 
 "Illustrates the use of SHA-256."
 shared void runDigestSha256() {
@@ -10,6 +16,30 @@ shared void runDigestSha256() {
     Byte[] digest = digester.digest({#63.byte});
 }
 
+"Given a file, return its sha256sum in hex form."
+String? sha256FileHex(Path filePath) {
+    value digester = sha256();
+    Byte[] sha256sum;
+    if (is File file = filePath.resource) {
+        try (reader = file.Reader()) {
+            Integer bufferSize = 64 * 1024;
+            Integer remainingSize = file.size % bufferSize;
+            variable Integer parts = file.size / bufferSize;
+            variable Byte[] bytes;
+            while (parts > 0) {
+                bytes = reader.readBytes(bufferSize);
+                digester.update(bytes);
+                parts--;
+            }
+            Byte[] remainder = reader.readBytes(remainingSize);
+            sha256sum = digester.digest(remainder);
+        }
+        return base16String.encode(sha256sum);
+    } else {
+        return null;
+    }
+}
+
 "Illustrates the use of SHA-1."
 shared void runDigestSha1() {
     value digester = sha1();

examples/de/dlkw/ccrypto/examples/module.ceylon

@@ -3,7 +3,8 @@ module de.dlkw.ccrypto.examples "0.0.2" {
 
     // will not be needed once finished, temporary hack to initialize a key pair.
     import de.dlkw.ccrypto.impl "0.0.2";
-    
+
     import ceylon.buffer "1.2.2";
+    import ceylon.file "1.2.2";
     import ceylon.random "1.2.2";
 }