Complete b64Encoder.encode() method (requires testing)

src/root.zig

@@ -208,8 +208,32 @@ pub const b64Encoder = struct {
     }
 
     pub fn encode(self: Self) !void {
-        _ = self;
-        // todo
+        var len = 12;
+        const buf: [12]u8 = undefined;
+        while (len == 12) {
+            len = try self.reader.readAll(buf);
+            if (len == 12) {
+                const obuf: [16]u8 = undefined;
+                try self.alphabet.encodeChunksVectored(buf, &obuf);
+                try self.writer.writeAll(obuf);
+            } else {
+                for ([4]usize{ 0, 2, 5, 8 }) |start| {
+                    const end = start + 3;
+                    const ibuf: [3]u8 = buf[start..end];
+                    var obuf: [4]u8 = undefined;
+                    if (start == len - 1) {
+                        break;
+                    } else if (end <= len - 1) {
+                        self.alphabet.encodeChunk(ibuf, 3, &obuf);
+                        try self.writer.writeAll(obuf);
+                    } else {
+                        self.alphabet.encodeChunk(ibuf, len - 1 - start, &obuf);
+                        try self.writer.writeAll(obuf);
+                        break;
+                    }
+                }
+            }
+        }
     }
 };