# JSON Lines をストリームする { #stream-json-lines }

データのシーケンスを**「ストリーム」**で送りたい場合、**JSON Lines** を使って実現できます。

/// info | 情報

FastAPI 0.134.0 で追加されました。

///

## ストリームとは { #what-is-a-stream }

データを**ストリーミング**するとは、アイテムの全シーケンスが用意できるのを待たずに、アプリがデータアイテムの送信をクライアントに対して開始することを意味します。

つまり、最初のアイテムを送信し、クライアントはそれを受け取って処理を始めます。その間に、次のアイテムをまだ生成しているかもしれません。

```mermaid
sequenceDiagram
    participant App
    participant Client

def extract_code_includes(lines: list[str]) -> list[CodeIncludeInfo]:
    """
    Extract lines that contain code includes.

    Return list of CodeIncludeInfo, where each dict contains:
    - `line_no` - line number (1-based)
    - `line` - text of the line
    """

    includes: list[CodeIncludeInfo] = []
    for line_no, line in enumerate(lines, start=1):
        if CODE_INCLUDE_RE.match(line):

  private final char[] buf = cbuf.array();

  private final Queue<String> lines = new ArrayDeque<>();
  private final LineBuffer lineBuf =
      new LineBuffer() {
        @Override
        protected void handleLine(String line, String end) {
          lines.add(line);
        }
      };

  /** Creates a new instance that will read lines from the given {@code Readable} object. */
  public LineReader(Readable readable) {

        return String.join("\n", outputLines);
    }

    /** Squeeze multiple empty lines into a single line. */
    static List<String> skipBlanks(List<String> lines) {
        boolean skipNextEmpty = false;

        final List<String> output = new ArrayList<>(lines.size());

        for (final String line : lines) {
            if (line.isEmpty()) {
                if (skipNextEmpty) {
                    continue;

        errorLogFile.useLines { lines ->
            lines.drop(startLine).forEach { line ->
                if (line.isBlank() || line.startsWith(">")) return@useLines
                val regex = Regex("""\s*(api|implementation)\(([^)]+)\)\s*""")
                regex.find(line)?.let {
                    dependencies.add(replaceProjectDependency(line.trim()))
                }
            }
        }

 * <p>Several methods in this class, such as {@link #readLines()}, break the contents of the source
 * into lines. Like {@link BufferedReader}, these methods break lines on any of {@code \n}, {@code
 * \r} or {@code \r\n}, do not include the line separator in each line and do not consider there to
 * be an empty line at the end if the contents are terminated with a line separator.
 *

            if (line.isEmpty()) {
                continue;
            }
            if (false == line.startsWith(leadingSpaces)) {
                log.accept(lines.lastLineNumber, "snippet line should start with [" + leadingSpaces + "]");
                continue;
            }
            int width = line.length() - leadingSpaces.length();
            if (width > max) {

                }
                valueLines.add(line);
                while (!line.isEmpty() && contains(WHITE_SPACE, line.charAt(0))) {
                    line = line.substring(1, line.length());
                }
                buffer.append(line);
                if (!combine) {
                    break;
                }
            }
            return buffer.toString();

                }
                valueLines.add(line);
                while (!line.isEmpty() && contains(WHITE_SPACE, line.charAt(0))) {
                    line = line.substring(1, line.length());
                }
                buffer.append(line);
                if (!combine) {
                    break;
                }
            }
            return buffer.toString();

import (
	"iter"
	"unicode"
	"unicode/utf8"
)

// Lines returns an iterator over the newline-terminated lines in the byte slice s.
// The lines yielded by the iterator include their terminating newlines.
// If s is empty, the iterator yields no lines at all.
// If s does not end in a newline, the final yielded line will not end in a newline.
// It returns a single-use iterator.
func Lines(s []byte) iter.Seq[[]byte] {