Add ability to use InputStream as source of RequestBody

BufferedInputStream is an InputStream that can be read several times.
Hence, provide a create methode for RequestBody that takes such stream as argument.

okhttp-tests/src/test/java/okhttp3/RequestTest.java

@@ -15,7 +15,10 @@
  */
 package okhttp3;
 
+import java.io.BufferedInputStream;
+import java.io.ByteArrayInputStream;
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.net.URI;
@@ -30,6 +33,9 @@
 import static org.junit.Assert.fail;
 
 public final class RequestTest {
+
+  private static final MediaType CONTENTTYPE_TEXT_PLAIN = MediaType.parse("text/plain");
+
   @Test public void string() throws Exception {
     MediaType contentType = MediaType.parse("text/plain; charset=utf-8");
     RequestBody body = RequestBody.create(contentType, "abc".getBytes(Util.UTF_8));
@@ -87,6 +93,38 @@ public final class RequestTest {
     assertEquals("Retransmit body", "616263", bodyToHex(body));
   }
 
+  @Test public void inputStreamFromFile() throws Exception {
+    File file = createFile("abc");
+    try (BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream(file))) {
+      RequestBody body = RequestBody.create(CONTENTTYPE_TEXT_PLAIN, inputStream);
+      checkRequestBodyFeatures(body, CONTENTTYPE_TEXT_PLAIN, 3, "616263");
+    }
+  }
+
+  @Test public void inputStreamFromByteArray() throws Exception {
+    byte[] bytes = "abc".getBytes(Util.UTF_8);
+    try (BufferedInputStream inputStream = new BufferedInputStream(new ByteArrayInputStream(bytes))) {
+      RequestBody body = RequestBody.create(CONTENTTYPE_TEXT_PLAIN, inputStream);
+      checkRequestBodyFeatures(body, CONTENTTYPE_TEXT_PLAIN, bytes.length, "616263");
+    }
+  }
+
+  private File createFile(String content) throws IOException {
+    File file = File.createTempFile("RequestTest", "tmp");
+    FileWriter writer = new FileWriter(file);
+    writer.write(content);
+    writer.close();
+
+    return file;
+  }
+
+  private void checkRequestBodyFeatures(RequestBody requestBody, MediaType expectedContentType, int expectedLength, String expectedBody) throws IOException {
+    assertEquals(expectedContentType, requestBody.contentType());
+    assertEquals(expectedLength, requestBody.contentLength());
+    assertEquals(expectedBody, bodyToHex(requestBody));
+    assertEquals("Retransmit body", expectedBody, bodyToHex(requestBody));
+  }
+
   /** Common verbs used for apis such as GitHub, AWS, and Google Cloud. */
   @Test public void crudVerbs() throws IOException {
     MediaType contentType = MediaType.parse("application/json");

okhttp/src/main/java/okhttp3/RequestBody.java

@@ -15,6 +15,7 @@
  */
 package okhttp3;
 
+import java.io.BufferedInputStream;
 import java.io.File;
 import java.io.IOException;
 import java.nio.charset.Charset;
@@ -25,6 +26,8 @@
 import okio.Okio;
 import okio.Source;
 
+import static java.util.Objects.requireNonNull;
+
 public abstract class RequestBody {
   /** Returns the Content-Type header for this body. */
   public abstract @Nullable MediaType contentType();
@@ -124,4 +127,38 @@ public static RequestBody create(final @Nullable MediaType contentType, final Fi
       }
     };
   }
+
+  /**
+   * Returns a new request body that transmits the content of an {@code inputStream}.
+   * Note that {@code RequestBody} is not responsible for closing the {@code inputStream}.
+   */
+  public static RequestBody create(final MediaType contentType,
+                                   final BufferedInputStream inputStream) {
+    if (inputStream == null) throw new NullPointerException("inputStream == null");
+
+    return new RequestBody() {
+      @Override public MediaType contentType() {
+        return contentType;
+      }
+
+      @Override public long contentLength() {
+        try {
+          return inputStream.available();
+        } catch (IOException e) {
+          //a IOException is sent if the input stream has been closed, i.e. no content to read.
+          return 0;
+        }
+      }
+
+      @Override public void writeTo(BufferedSink sink) throws IOException {
+        try {
+          inputStream.mark(0);
+          Source source = Okio.source(inputStream);
+          sink.writeAll(source);
+        } finally {
+          inputStream.reset();
+        }
+      }
+    };
+  }
 }