# Streaming

## Stream JSON Lines

To stream JSON Lines, declare the return type and use `yield` to return the data.

```python
@app.get("/items/stream")
async def stream_items() -> AsyncIterable[Item]:
    for item in items:
        yield item
```

## Server-Sent Events (SSE)

To stream Server-Sent Events, use `response_class=EventSourceResponse` and `yield` items from the endpoint.

            response.off += n;
        } while (len > 0 && n == r);

        return (int) (fp - start);
    }

    /**
     * This stream class is unbuffered. Therefore this method will always
     * return 0 for streams connected to regular files. However, a
     * stream created from a Named Pipe this method will query the server using a
     * "peek named pipe" operation and return the number of available bytes

      check(!isLocallyInitiated) { "locally-initiated streams shouldn't have headers yet" }
      headersQueue += headers
    } else {
      check(isLocallyInitiated) { "remotely-initiated streams should have headers" }
    }
  }

  /**
   * Returns true if this stream is open. A stream is open until either:
   *
   *  * A `SYN_RESET` frame abnormally terminates the stream.

        newChunkedSink()
      }

      // Stream a request body of unknown length.
      contentLength != -1L -> {
        newKnownLengthSink()
      }

      // Stream a request body of a known length.
      else -> {
        // Stream a request body of a known length.
        throw IllegalStateException(
          "Cannot stream a request body without chunked encoding or a known content length!",

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *
   * @throws IllegalArgumentException if the stream consists of two or more elements.
   * @throws NullPointerException if any element in the stream is {@code null}.
   * @return {@code Optional.of(onlyElement)} if the stream has exactly one element (must not be

            assertNotNull(is1, "Default input stream should not be null");
            assertNotNull(is2, "Input stream with sharing should not be null");
            assertNotNull(is3, "Input stream with full params should not be null");
            assertSame(mockInputStream, is1, "Should return expected input stream");
            assertSame(mockInputStream, is2, "Should return expected input stream");

      Map<K, V> map, ObjectOutputStream stream) throws IOException {
    stream.writeInt(map.size());
    for (Map.Entry<K, V> entry : map.entrySet()) {
      stream.writeObject(entry.getKey());
      stream.writeObject(entry.getValue());
    }
  }

  /**
   * Populates a map by reading an input stream, as part of deserialization. See {@link #writeMap}
   * for the data format.
   */

     * element count in this stream does not have to be equal.
     */
    @Nonnull
    default Stream<P> problems() {
        Stream<P> result = Stream.empty();
        for (BuilderProblem.Severity severity : BuilderProblem.Severity.values()) {
            result = Stream.concat(result, problems(severity));
        }
        return result;
    }

    /**

        }
    }

    @Test
    public void testFileBasedCacheWithEmptyFile() throws IOException {
        tempFile = File.createTempFile("empty", ".tmp", Curl.tmpDir);
        // File is created but empty

        ContentCache cache = new ContentCache(tempFile);

        try (InputStream stream = cache.getInputStream()) {
            assertNotNull(stream);

                        return Collections.emptyList();
                    }

                    @Override
                    public Stream<Phase> allPhases() {
                        return Stream.concat(Stream.of(this), phases().stream().flatMap(Phase::allPhases));
                    }
                })
                .collect(Collectors.toList());
    }

    @Override