Log plain text bodies only

okhttp-logging-interceptor/src/main/java/okhttp3/logging/HttpLoggingInterceptor.java

@@ -15,6 +15,7 @@
  */
 package okhttp3.logging;
 
+import java.io.EOFException;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.nio.charset.UnsupportedCharsetException;
@@ -192,10 +193,14 @@ public final class HttpLoggingInterceptor implements Interceptor {
         }
 
         logger.log("");
-        logger.log(buffer.readString(charset));
-
-        logger.log("--> END " + request.method()
-            + " (" + requestBody.contentLength() + "-byte body)");
+        if (isPlaintext(buffer)) {
+          logger.log(buffer.readString(charset));
+          logger.log("--> END " + request.method()
+              + " (" + requestBody.contentLength() + "-byte body)");
+        } else {
+          logger.log("--> END " + request.method() + " (binary "
+              + requestBody.contentLength() + "-byte body omitted)");
+        }
       }
     }
 
@@ -239,6 +244,12 @@ public final class HttpLoggingInterceptor implements Interceptor {
           }
         }
 
+        if (!isPlaintext(buffer)) {
+          logger.log("");
+          logger.log("<-- END HTTP (binary " + buffer.size() + "-byte body omitted)");
+          return response;
+        }
+
         if (contentLength != 0) {
           logger.log("");
           logger.log(buffer.clone().readString(charset));
@@ -251,6 +262,29 @@ public final class HttpLoggingInterceptor implements Interceptor {
     return response;
   }
 
+  /**
+   * Returns true if the body in question probably contains human readable text. Uses a small sample
+   * of code points to detect unicode control characters commonly used in binary file signatures.
+   */
+  static boolean isPlaintext(Buffer buffer) throws EOFException {
+    try {
+      Buffer prefix = new Buffer();
+      long byteCount = buffer.size() < 64 ? buffer.size() : 64;
+      buffer.copyTo(prefix, 0, byteCount);
+      for (int i = 0; i < 16; i++) {
+        if (prefix.exhausted()) {
+          break;
+        }
+        if (Character.isISOControl(prefix.readUtf8CodePoint())) {
+          return false;
+        }
+      }
+      return true;
+    } catch (EOFException e) {
+      return false; // Truncated UTF-8 sequence.
+    }
+  }
+
   private boolean bodyEncoded(Headers headers) {
     String contentEncoding = headers.get("Content-Encoding");
     return contentEncoding != null && !contentEncoding.equalsIgnoreCase("identity");