BREAKING(std): reorganization (#5087)

* Prepend underscores to private modules
* Remove collectUint8Arrays() It would be a misuse of Deno.iter()'s result.
* Move std/_util/async.ts to std/async
* Move std/util/sha*.ts to std/hash

2 files changed, 1871 insertions, 0 deletions

diff --git a/std/encoding/_yaml/loader/loader.ts b/std/encoding/_yaml/loader/loader.ts
new file mode 100644
index 000000000..f0d535624
--- /dev/null
+++ b/std/encoding/_yaml/loader/loader.ts
@@ -0,0 +1,1797 @@
+// Ported from js-yaml v3.13.1:
+// https://github.com/nodeca/js-yaml/commit/665aadda42349dcae869f12040d9b10ef18d12da
+// Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+/* eslint-disable max-len */
+
+import { YAMLError } from "../error.ts";
+import { Mark } from "../mark.ts";
+import { Type } from "../type.ts";
+import * as common from "../utils.ts";
+import { LoaderState, LoaderStateOptions, ResultType } from "./loader_state.ts";
+
+type Any = common.Any;
+type ArrayObject<T = Any> = common.ArrayObject<T>;
+
+const _hasOwnProperty = Object.prototype.hasOwnProperty;
+
+const CONTEXT_FLOW_IN = 1;
+const CONTEXT_FLOW_OUT = 2;
+const CONTEXT_BLOCK_IN = 3;
+const CONTEXT_BLOCK_OUT = 4;
+
+const CHOMPING_CLIP = 1;
+const CHOMPING_STRIP = 2;
+const CHOMPING_KEEP = 3;
+
+const PATTERN_NON_PRINTABLE = /[\x00-\x08\x0B\x0C\x0E-\x1F\x7F-\x84\x86-\x9F\uFFFE\uFFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?:[^\uD800-\uDBFF]|^)[\uDC00-\uDFFF]/;
+const PATTERN_NON_ASCII_LINE_BREAKS = /[\x85\u2028\u2029]/;
+const PATTERN_FLOW_INDICATORS = /[,\[\]\{\}]/;
+const PATTERN_TAG_HANDLE = /^(?:!|!!|![a-z\-]+!)$/i;
+/* eslint-disable-next-line max-len */
+const PATTERN_TAG_URI = /^(?:!|[^,\[\]\{\}])(?:%[0-9a-f]{2}|[0-9a-z\-#;\/\?:@&=\+\$,_\.!~\*'\(\)\[\]])*$/i;
+
+function _class(obj: unknown): string {
+  return Object.prototype.toString.call(obj);
+}
+
+function isEOL(c: number): boolean {
+  return c === 0x0a || /* LF */ c === 0x0d /* CR */;
+}
+
+function isWhiteSpace(c: number): boolean {
+  return c === 0x09 || /* Tab */ c === 0x20 /* Space */;
+}
+
+function isWsOrEol(c: number): boolean {
+  return (
+    c === 0x09 /* Tab */ ||
+    c === 0x20 /* Space */ ||
+    c === 0x0a /* LF */ ||
+    c === 0x0d /* CR */
+  );
+}
+
+function isFlowIndicator(c: number): boolean {
+  return (
+    c === 0x2c /* , */ ||
+    c === 0x5b /* [ */ ||
+    c === 0x5d /* ] */ ||
+    c === 0x7b /* { */ ||
+    c === 0x7d /* } */
+  );
+}
+
+function fromHexCode(c: number): number {
+  if (0x30 <= /* 0 */ c && c <= 0x39 /* 9 */) {
+    return c - 0x30;
+  }
+
+  const lc = c | 0x20;
+
+  if (0x61 <= /* a */ lc && lc <= 0x66 /* f */) {
+    return lc - 0x61 + 10;
+  }
+
+  return -1;
+}
+
+function escapedHexLen(c: number): number {
+  if (c === 0x78 /* x */) {
+    return 2;
+  }
+  if (c === 0x75 /* u */) {
+    return 4;
+  }
+  if (c === 0x55 /* U */) {
+    return 8;
+  }
+  return 0;
+}
+
+function fromDecimalCode(c: number): number {
+  if (0x30 <= /* 0 */ c && c <= 0x39 /* 9 */) {
+    return c - 0x30;
+  }
+
+  return -1;
+}
+
+function simpleEscapeSequence(c: number): string {
+  /* eslint:disable:prettier */
+  return c === 0x30 /* 0 */
+    ? "\x00"
+    : c === 0x61 /* a */
+    ? "\x07"
+    : c === 0x62 /* b */
+    ? "\x08"
+    : c === 0x74 /* t */
+    ? "\x09"
+    : c === 0x09 /* Tab */
+    ? "\x09"
+    : c === 0x6e /* n */
+    ? "\x0A"
+    : c === 0x76 /* v */
+    ? "\x0B"
+    : c === 0x66 /* f */
+    ? "\x0C"
+    : c === 0x72 /* r */
+    ? "\x0D"
+    : c === 0x65 /* e */
+    ? "\x1B"
+    : c === 0x20 /* Space */
+    ? " "
+    : c === 0x22 /* " */
+    ? "\x22"
+    : c === 0x2f /* / */
+    ? "/"
+    : c === 0x5c /* \ */
+    ? "\x5C"
+    : c === 0x4e /* N */
+    ? "\x85"
+    : c === 0x5f /* _ */
+    ? "\xA0"
+    : c === 0x4c /* L */
+    ? "\u2028"
+    : c === 0x50 /* P */
+    ? "\u2029"
+    : "";
+  /* eslint:enable:prettier */
+}
+
+function charFromCodepoint(c: number): string {
+  if (c <= 0xffff) {
+    return String.fromCharCode(c);
+  }
+  // Encode UTF-16 surrogate pair
+  // https://en.wikipedia.org/wiki/UTF-16#Code_points_U.2B010000_to_U.2B10FFFF
+  return String.fromCharCode(
+    ((c - 0x010000) >> 10) + 0xd800,
+    ((c - 0x010000) & 0x03ff) + 0xdc00
+  );
+}
+
+const simpleEscapeCheck = new Array(256); // integer, for fast access
+const simpleEscapeMap = new Array(256);
+for (let i = 0; i < 256; i++) {
+  simpleEscapeCheck[i] = simpleEscapeSequence(i) ? 1 : 0;
+  simpleEscapeMap[i] = simpleEscapeSequence(i);
+}
+
+function generateError(state: LoaderState, message: string): YAMLError {
+  return new YAMLError(
+    message,
+    new Mark(
+      state.filename as string,
+      state.input,
+      state.position,
+      state.line,
+      state.position - state.lineStart
+    )
+  );
+}
+
+function throwError(state: LoaderState, message: string): never {
+  throw generateError(state, message);
+}
+
+function throwWarning(state: LoaderState, message: string): void {
+  if (state.onWarning) {
+    state.onWarning.call(null, generateError(state, message));
+  }
+}
+
+interface DirectiveHandlers {
+  [directive: string]: (
+    state: LoaderState,
+    name: string,
+    ...args: string[]
+  ) => void;
+}
+
+const directiveHandlers: DirectiveHandlers = {
+  YAML(state, _name, ...args: string[]) {
+    if (state.version !== null) {
+      return throwError(state, "duplication of %YAML directive");
+    }
+
+    if (args.length !== 1) {
+      return throwError(state, "YAML directive accepts exactly one argument");
+    }
+
+    const match = /^([0-9]+)\.([0-9]+)$/.exec(args[0]);
+    if (match === null) {
+      return throwError(state, "ill-formed argument of the YAML directive");
+    }
+
+    const major = parseInt(match[1], 10);
+    const minor = parseInt(match[2], 10);
+    if (major !== 1) {
+      return throwError(state, "unacceptable YAML version of the document");
+    }
+
+    state.version = args[0];
+    state.checkLineBreaks = minor < 2;
+    if (minor !== 1 && minor !== 2) {
+      return throwWarning(state, "unsupported YAML version of the document");
+    }
+  },
+
+  TAG(state, _name, ...args: string[]): void {
+    if (args.length !== 2) {
+      return throwError(state, "TAG directive accepts exactly two arguments");
+    }
+
+    const handle = args[0];
+    const prefix = args[1];
+
+    if (!PATTERN_TAG_HANDLE.test(handle)) {
+      return throwError(
+        state,
+        "ill-formed tag handle (first argument) of the TAG directive"
+      );
+    }
+
+    if (_hasOwnProperty.call(state.tagMap, handle)) {
+      return throwError(
+        state,
+        `there is a previously declared suffix for "${handle}" tag handle`
+      );
+    }
+
+    if (!PATTERN_TAG_URI.test(prefix)) {
+      return throwError(
+        state,
+        "ill-formed tag prefix (second argument) of the TAG directive"
+      );
+    }
+
+    if (typeof state.tagMap === "undefined") {
+      state.tagMap = {};
+    }
+    state.tagMap[handle] = prefix;
+  },
+};
+
+function captureSegment(
+  state: LoaderState,
+  start: number,
+  end: number,
+  checkJson: boolean
+): void {
+  let result: string;
+  if (start < end) {
+    result = state.input.slice(start, end);
+
+    if (checkJson) {
+      for (
+        let position = 0, length = result.length;
+        position < length;
+        position++
+      ) {
+        const character = result.charCodeAt(position);
+        if (
+          !(character === 0x09 || (0x20 <= character && character <= 0x10ffff))
+        ) {
+          return throwError(state, "expected valid JSON character");
+        }
+      }
+    } else if (PATTERN_NON_PRINTABLE.test(result)) {
+      return throwError(state, "the stream contains non-printable characters");
+    }
+
+    state.result += result;
+  }
+}
+
+function mergeMappings(
+  state: LoaderState,
+  destination: ArrayObject,
+  source: ArrayObject,
+  overridableKeys: ArrayObject<boolean>
+): void {
+  if (!common.isObject(source)) {
+    return throwError(
+      state,
+      "cannot merge mappings; the provided source object is unacceptable"
+    );
+  }
+
+  const keys = Object.keys(source);
+  for (let i = 0, len = keys.length; i < len; i++) {
+    const key = keys[i];
+    if (!_hasOwnProperty.call(destination, key)) {
+      destination[key] = (source as ArrayObject)[key];
+      overridableKeys[key] = true;
+    }
+  }
+}
+
+function storeMappingPair(
+  state: LoaderState,
+  result: ArrayObject | null,
+  overridableKeys: ArrayObject<boolean>,
+  keyTag: string | null,
+  keyNode: Any,
+  valueNode: unknown,
+  startLine?: number,
+  startPos?: number
+): ArrayObject {
+  // The output is a plain object here, so keys can only be strings.
+  // We need to convert keyNode to a string, but doing so can hang the process
+  // (deeply nested arrays that explode exponentially using aliases).
+  if (Array.isArray(keyNode)) {
+    keyNode = Array.prototype.slice.call(keyNode);
+
+    for (let index = 0, quantity = keyNode.length; index < quantity; index++) {
+      if (Array.isArray(keyNode[index])) {
+        return throwError(state, "nested arrays are not supported inside keys");
+      }
+
+      if (
+        typeof keyNode === "object" &&
+        _class(keyNode[index]) === "[object Object]"
+      ) {
+        keyNode[index] = "[object Object]";
+      }
+    }
+  }
+
+  // Avoid code execution in load() via toString property
+  // (still use its own toString for arrays, timestamps,
+  // and whatever user schema extensions happen to have @@toStringTag)
+  if (typeof keyNode === "object" && _class(keyNode) === "[object Object]") {
+    keyNode = "[object Object]";
+  }
+
+  keyNode = String(keyNode);
+
+  if (result === null) {
+    result = {};
+  }
+
+  if (keyTag === "tag:yaml.org,2002:merge") {
+    if (Array.isArray(valueNode)) {
+      for (
+        let index = 0, quantity = valueNode.length;
+        index < quantity;
+        index++
+      ) {
+        mergeMappings(state, result, valueNode[index], overridableKeys);
+      }
+    } else {
+      mergeMappings(state, result, valueNode as ArrayObject, overridableKeys);
+    }
+  } else {
+    if (
+      !state.json &&
+      !_hasOwnProperty.call(overridableKeys, keyNode) &&
+      _hasOwnProperty.call(result, keyNode)
+    ) {
+      state.line = startLine || state.line;
+      state.position = startPos || state.position;
+      return throwError(state, "duplicated mapping key");
+    }
+    result[keyNode] = valueNode;
+    delete overridableKeys[keyNode];
+  }
+
+  return result;
+}
+
+function readLineBreak(state: LoaderState): void {
+  const ch = state.input.charCodeAt(state.position);
+
+  if (ch === 0x0a /* LF */) {
+    state.position++;
+  } else if (ch === 0x0d /* CR */) {
+    state.position++;
+    if (state.input.charCodeAt(state.position) === 0x0a /* LF */) {
+      state.position++;
+    }
+  } else {
+    return throwError(state, "a line break is expected");
+  }
+
+  state.line += 1;
+  state.lineStart = state.position;
+}
+
+function skipSeparationSpace(
+  state: LoaderState,
+  allowComments: boolean,
+  checkIndent: number
+): number {
+  let lineBreaks = 0,
+    ch = state.input.charCodeAt(state.position);
+
+  while (ch !== 0) {
+    while (isWhiteSpace(ch)) {
+      ch = state.input.charCodeAt(++state.position);
+    }
+
+    if (allowComments && ch === 0x23 /* # */) {
+      do {
+        ch = state.input.charCodeAt(++state.position);
+      } while (ch !== 0x0a && /* LF */ ch !== 0x0d && /* CR */ ch !== 0);
+    }
+
+    if (isEOL(ch)) {
+      readLineBreak(state);
+
+      ch = state.input.charCodeAt(state.position);
+      lineBreaks++;
+      state.lineIndent = 0;
+
+      while (ch === 0x20 /* Space */) {
+        state.lineIndent++;
+        ch = state.input.charCodeAt(++state.position);
+      }
+    } else {
+      break;
+    }
+  }
+
+  if (
+    checkIndent !== -1 &&
+    lineBreaks !== 0 &&
+    state.lineIndent < checkIndent
+  ) {
+    throwWarning(state, "deficient indentation");
+  }
+
+  return lineBreaks;
+}
+
+function testDocumentSeparator(state: LoaderState): boolean {
+  let _position = state.position;
+  let ch = state.input.charCodeAt(_position);
+
+  // Condition state.position === state.lineStart is tested
+  // in parent on each call, for efficiency. No needs to test here again.
+  if (
+    (ch === 0x2d || /* - */ ch === 0x2e) /* . */ &&
+    ch === state.input.charCodeAt(_position + 1) &&
+    ch === state.input.charCodeAt(_position + 2)
+  ) {
+    _position += 3;
+
+    ch = state.input.charCodeAt(_position);
+
+    if (ch === 0 || isWsOrEol(ch)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+function writeFoldedLines(state: LoaderState, count: number): void {
+  if (count === 1) {
+    state.result += " ";
+  } else if (count > 1) {
+    state.result += common.repeat("\n", count - 1);
+  }
+}
+
+function readPlainScalar(
+  state: LoaderState,
+  nodeIndent: number,
+  withinFlowCollection: boolean
+): boolean {
+  const kind = state.kind;
+  const result = state.result;
+  let ch = state.input.charCodeAt(state.position);
+
+  if (
+    isWsOrEol(ch) ||
+    isFlowIndicator(ch) ||
+    ch === 0x23 /* # */ ||
+    ch === 0x26 /* & */ ||
+    ch === 0x2a /* * */ ||
+    ch === 0x21 /* ! */ ||
+    ch === 0x7c /* | */ ||
+    ch === 0x3e /* > */ ||
+    ch === 0x27 /* ' */ ||
+    ch === 0x22 /* " */ ||
+    ch === 0x25 /* % */ ||
+    ch === 0x40 /* @ */ ||
+    ch === 0x60 /* ` */
+  ) {
+    return false;
+  }
+
+  let following: number;
+  if (ch === 0x3f || /* ? */ ch === 0x2d /* - */) {
+    following = state.input.charCodeAt(state.position + 1);
+
+    if (
+      isWsOrEol(following) ||
+      (withinFlowCollection && isFlowIndicator(following))
+    ) {
+      return false;
+    }
+  }
+
+  state.kind = "scalar";
+  state.result = "";
+  let captureEnd: number,
+    captureStart = (captureEnd = state.position);
+  let hasPendingContent = false;
+  let line = 0;
+  while (ch !== 0) {
+    if (ch === 0x3a /* : */) {
+      following = state.input.charCodeAt(state.position + 1);
+
+      if (
+        isWsOrEol(following) ||
+        (withinFlowCollection && isFlowIndicator(following))
+      ) {
+        break;
+      }
+    } else if (ch === 0x23 /* # */) {
+      const preceding = state.input.charCodeAt(state.position - 1);
+
+      if (isWsOrEol(preceding)) {
+        break;
+      }
+    } else if (
+      (state.position === state.lineStart && testDocumentSeparator(state)) ||
+      (withinFlowCollection && isFlowIndicator(ch))
+    ) {
+      break;
+    } else if (isEOL(ch)) {
+      line = state.line;
+      const lineStart = state.lineStart;
+      const lineIndent = state.lineIndent;
+      skipSeparationSpace(state, false, -1);
+
+      if (state.lineIndent >= nodeIndent) {
+        hasPendingContent = true;
+        ch = state.input.charCodeAt(state.position);
+        continue;
+      } else {
+        state.position = captureEnd;
+        state.line = line;
+        state.lineStart = lineStart;
+        state.lineIndent = lineIndent;
+        break;
+      }
+    }
+
+    if (hasPendingContent) {
+      captureSegment(state, captureStart, captureEnd, false);
+      writeFoldedLines(state, state.line - line);
+      captureStart = captureEnd = state.position;
+      hasPendingContent = false;
+    }
+
+    if (!isWhiteSpace(ch)) {
+      captureEnd = state.position + 1;
+    }
+
+    ch = state.input.charCodeAt(++state.position);
+  }
+
+  captureSegment(state, captureStart, captureEnd, false);
+
+  if (state.result) {
+    return true;
+  }
+
+  state.kind = kind;
+  state.result = result;
+  return false;
+}
+
+function readSingleQuotedScalar(
+  state: LoaderState,
+  nodeIndent: number
+): boolean {
+  let ch, captureStart, captureEnd;
+
+  ch = state.input.charCodeAt(state.position);
+
+  if (ch !== 0x27 /* ' */) {
+    return false;
+  }
+
+  state.kind = "scalar";
+  state.result = "";
+  state.position++;
+  captureStart = captureEnd = state.position;
+
+  while ((ch = state.input.charCodeAt(state.position)) !== 0) {
+    if (ch === 0x27 /* ' */) {
+      captureSegment(state, captureStart, state.position, true);
+      ch = state.input.charCodeAt(++state.position);
+
+      if (ch === 0x27 /* ' */) {
+        captureStart = state.position;
+        state.position++;
+        captureEnd = state.position;
+      } else {
+        return true;
+      }
+    } else if (isEOL(ch)) {
+      captureSegment(state, captureStart, captureEnd, true);
+      writeFoldedLines(state, skipSeparationSpace(state, false, nodeIndent));
+      captureStart = captureEnd = state.position;
+    } else if (
+      state.position === state.lineStart &&
+      testDocumentSeparator(state)
+    ) {
+      return throwError(
+        state,
+        "unexpected end of the document within a single quoted scalar"
+      );
+    } else {
+      state.position++;
+      captureEnd = state.position;
+    }
+  }
+
+  return throwError(
+    state,
+    "unexpected end of the stream within a single quoted scalar"
+  );
+}
+
+function readDoubleQuotedScalar(
+  state: LoaderState,
+  nodeIndent: number
+): boolean {
+  let ch = state.input.charCodeAt(state.position);
+
+  if (ch !== 0x22 /* " */) {
+    return false;
+  }
+
+  state.kind = "scalar";
+  state.result = "";
+  state.position++;
+  let captureEnd: number,
+    captureStart = (captureEnd = state.position);
+  let tmp: number;
+  while ((ch = state.input.charCodeAt(state.position)) !== 0) {
+    if (ch === 0x22 /* " */) {
+      captureSegment(state, captureStart, state.position, true);
+      state.position++;
+      return true;
+    }
+    if (ch === 0x5c /* \ */) {
+      captureSegment(state, captureStart, state.position, true);
+      ch = state.input.charCodeAt(++state.position);
+
+      if (isEOL(ch)) {
+        skipSeparationSpace(state, false, nodeIndent);
+
+        // TODO: rework to inline fn with no type cast?
+      } else if (ch < 256 && simpleEscapeCheck[ch]) {
+        state.result += simpleEscapeMap[ch];
+        state.position++;
+      } else if ((tmp = escapedHexLen(ch)) > 0) {
+        let hexLength = tmp;
+        let hexResult = 0;
+
+        for (; hexLength > 0; hexLength--) {
+          ch = state.input.charCodeAt(++state.position);
+
+          if ((tmp = fromHexCode(ch)) >= 0) {
+            hexResult = (hexResult << 4) + tmp;
+          } else {
+            return throwError(state, "expected hexadecimal character");
+          }
+        }
+
+        state.result += charFromCodepoint(hexResult);
+
+        state.position++;
+      } else {
+        return throwError(state, "unknown escape sequence");
+      }
+
+      captureStart = captureEnd = state.position;
+    } else if (isEOL(ch)) {
+      captureSegment(state, captureStart, captureEnd, true);
+      writeFoldedLines(state, skipSeparationSpace(state, false, nodeIndent));
+      captureStart = captureEnd = state.position;
+    } else if (
+      state.position === state.lineStart &&
+      testDocumentSeparator(state)
+    ) {
+      return throwError(
+        state,
+        "unexpected end of the document within a double quoted scalar"
+      );
+    } else {
+      state.position++;
+      captureEnd = state.position;
+    }
+  }
+
+  return throwError(
+    state,
+    "unexpected end of the stream within a double quoted scalar"
+  );
+}
+
+function readFlowCollection(state: LoaderState, nodeIndent: number): boolean {
+  let ch = state.input.charCodeAt(state.position);
+  let terminator: number;
+  let isMapping = true;
+  let result: ResultType = {};
+  if (ch === 0x5b /* [ */) {
+    terminator = 0x5d; /* ] */
+    isMapping = false;
+    result = [];
+  } else if (ch === 0x7b /* { */) {
+    terminator = 0x7d; /* } */
+  } else {
+    return false;
+  }
+
+  if (
+    state.anchor !== null &&
+    typeof state.anchor != "undefined" &&
+    typeof state.anchorMap != "undefined"
+  ) {
+    state.anchorMap[state.anchor] = result;
+  }
+
+  ch = state.input.charCodeAt(++state.position);
+
+  const tag = state.tag,
+    anchor = state.anchor;
+  let readNext = true;
+  let valueNode,
+    keyNode,
+    keyTag: string | null = (keyNode = valueNode = null),
+    isExplicitPair: boolean,
+    isPair = (isExplicitPair = false);
+  let following = 0,
+    line = 0;
+  const overridableKeys: ArrayObject<boolean> = {};
+  while (ch !== 0) {
+    skipSeparationSpace(state, true, nodeIndent);
+
+    ch = state.input.charCodeAt(state.position);
+
+    if (ch === terminator) {
+      state.position++;
+      state.tag = tag;
+      state.anchor = anchor;
+      state.kind = isMapping ? "mapping" : "sequence";
+      state.result = result;
+      return true;
+    }
+    if (!readNext) {
+      return throwError(state, "missed comma between flow collection entries");
+    }
+
+    keyTag = keyNode = valueNode = null;
+    isPair = isExplicitPair = false;
+
+    if (ch === 0x3f /* ? */) {
+      following = state.input.charCodeAt(state.position + 1);
+
+      if (isWsOrEol(following)) {
+        isPair = isExplicitPair = true;
+        state.position++;
+        skipSeparationSpace(state, true, nodeIndent);
+      }
+    }
+
+    line = state.line;
+    // eslint-disable-next-line @typescript-eslint/no-use-before-define
+    composeNode(state, nodeIndent, CONTEXT_FLOW_IN, false, true);
+    keyTag = state.tag || null;
+    keyNode = state.result;
+    skipSeparationSpace(state, true, nodeIndent);
+
+    ch = state.input.charCodeAt(state.position);
+
+    if ((isExplicitPair || state.line === line) && ch === 0x3a /* : */) {
+      isPair = true;
+      ch = state.input.charCodeAt(++state.position);
+      skipSeparationSpace(state, true, nodeIndent);
+      // eslint-disable-next-line @typescript-eslint/no-use-before-define
+      composeNode(state, nodeIndent, CONTEXT_FLOW_IN, false, true);
+      valueNode = state.result;
+    }
+
+    if (isMapping) {
+      storeMappingPair(
+        state,
+        result,
+        overridableKeys,
+        keyTag,
+        keyNode,
+        valueNode
+      );
+    } else if (isPair) {
+      (result as Array<{}>).push(
+        storeMappingPair(
+          state,
+          null,
+          overridableKeys,
+          keyTag,
+          keyNode,
+          valueNode
+        )
+      );
+    } else {
+      (result as ResultType[]).push(keyNode as ResultType);
+    }
+
+    skipSeparationSpace(state, true, nodeIndent);
+
+    ch = state.input.charCodeAt(state.position);
+
+    if (ch === 0x2c /* , */) {
+      readNext = true;
+      ch = state.input.charCodeAt(++state.position);
+    } else {
+      readNext = false;
+    }
+  }
+
+  return throwError(
+    state,
+    "unexpected end of the stream within a flow collection"
+  );
+}
+
+function readBlockScalar(state: LoaderState, nodeIndent: number): boolean {
+  let chomping = CHOMPING_CLIP,
+    didReadContent = false,
+    detectedIndent = false,
+    textIndent = nodeIndent,
+    emptyLines = 0,
+    atMoreIndented = false;
+
+  let ch = state.input.charCodeAt(state.position);
+
+  let folding = false;
+  if (ch === 0x7c /* | */) {
+    folding = false;
+  } else if (ch === 0x3e /* > */) {
+    folding = true;
+  } else {
+    return false;
+  }
+
+  state.kind = "scalar";
+  state.result = "";
+
+  let tmp = 0;
+  while (ch !== 0) {
+    ch = state.input.charCodeAt(++state.position);
+
+    if (ch === 0x2b || /* + */ ch === 0x2d /* - */) {
+      if (CHOMPING_CLIP === chomping) {
+        chomping = ch === 0x2b /* + */ ? CHOMPING_KEEP : CHOMPING_STRIP;
+      } else {
+        return throwError(state, "repeat of a chomping mode identifier");
+      }
+    } else if ((tmp = fromDecimalCode(ch)) >= 0) {
+      if (tmp === 0) {
+        return throwError(
+          state,
+          "bad explicit indentation width of a block scalar; it cannot be less than one"
+        );
+      } else if (!detectedIndent) {
+        textIndent = nodeIndent + tmp - 1;
+        detectedIndent = true;
+      } else {
+        return throwError(state, "repeat of an indentation width identifier");
+      }
+    } else {
+      break;
+    }
+  }
+
+  if (isWhiteSpace(ch)) {
+    do {
+      ch = state.input.charCodeAt(++state.position);
+    } while (isWhiteSpace(ch));
+
+    if (ch === 0x23 /* # */) {
+      do {
+        ch = state.input.charCodeAt(++state.position);
+      } while (!isEOL(ch) && ch !== 0);
+    }
+  }
+
+  while (ch !== 0) {
+    readLineBreak(state);
+    state.lineIndent = 0;
+
+    ch = state.input.charCodeAt(state.position);
+
+    while (
+      (!detectedIndent || state.lineIndent < textIndent) &&
+      ch === 0x20 /* Space */
+    ) {
+      state.lineIndent++;
+      ch = state.input.charCodeAt(++state.position);
+    }
+
+    if (!detectedIndent && state.lineIndent > textIndent) {
+      textIndent = state.lineIndent;
+    }
+
+    if (isEOL(ch)) {
+      emptyLines++;
+      continue;
+    }
+
+    // End of the scalar.
+    if (state.lineIndent < textIndent) {
+      // Perform the chomping.
+      if (chomping === CHOMPING_KEEP) {
+        state.result += common.repeat(
+          "\n",
+          didReadContent ? 1 + emptyLines : emptyLines
+        );
+      } else if (chomping === CHOMPING_CLIP) {
+        if (didReadContent) {
+          // i.e. only if the scalar is not empty.
+          state.result += "\n";
+        }
+      }
+
+      // Break this `while` cycle and go to the funciton's epilogue.
+      break;
+    }
+
+    // Folded style: use fancy rules to handle line breaks.
+    if (folding) {
+      // Lines starting with white space characters (more-indented lines) are not folded.
+      if (isWhiteSpace(ch)) {
+        atMoreIndented = true;
+        // except for the first content line (cf. Example 8.1)
+        state.result += common.repeat(
+          "\n",
+          didReadContent ? 1 + emptyLines : emptyLines
+        );
+
+        // End of more-indented block.
+      } else if (atMoreIndented) {
+        atMoreIndented = false;
+        state.result += common.repeat("\n", emptyLines + 1);
+
+        // Just one line break - perceive as the same line.
+      } else if (emptyLines === 0) {
+        if (didReadContent) {
+          // i.e. only if we have already read some scalar content.
+          state.result += " ";
+        }
+
+        // Several line breaks - perceive as different lines.
+      } else {
+        state.result += common.repeat("\n", emptyLines);
+      }
+
+      // Literal style: just add exact number of line breaks between content lines.
+    } else {
+      // Keep all line breaks except the header line break.
+      state.result += common.repeat(
+        "\n",
+        didReadContent ? 1 + emptyLines : emptyLines
+      );
+    }
+
+    didReadContent = true;
+    detectedIndent = true;
+    emptyLines = 0;
+    const captureStart = state.position;
+
+    while (!isEOL(ch) && ch !== 0) {
+      ch = state.input.charCodeAt(++state.position);
+    }
+
+    captureSegment(state, captureStart, state.position, false);
+  }
+
+  return true;
+}
+
+function readBlockSequence(state: LoaderState, nodeIndent: number): boolean {
+  let line: number,
+    following: number,
+    detected = false,
+    ch: number;
+  const tag = state.tag,
+    anchor = state.anchor,
+    result: unknown[] = [];
+
+  if (
+    state.anchor !== null &&
+    typeof state.anchor !== "undefined" &&
+    typeof state.anchorMap !== "undefined"
+  ) {
+    state.anchorMap[state.anchor] = result;
+  }
+
+  ch = state.input.charCodeAt(state.position);
+
+  while (ch !== 0) {
+    if (ch !== 0x2d /* - */) {
+      break;
+    }
+
+    following = state.input.charCodeAt(state.position + 1);
+
+    if (!isWsOrEol(following)) {
+      break;
+    }
+
+    detected = true;
+    state.position++;
+
+    if (skipSeparationSpace(state, true, -1)) {
+      if (state.lineIndent <= nodeIndent) {
+        result.push(null);
+        ch = state.input.charCodeAt(state.position);
+        continue;
+      }
+    }
+
+    line = state.line;
+    // eslint-disable-next-line @typescript-eslint/no-use-before-define
+    composeNode(state, nodeIndent, CONTEXT_BLOCK_IN, false, true);
+    result.push(state.result);
+    skipSeparationSpace(state, true, -1);
+
+    ch = state.input.charCodeAt(state.position);
+
+    if ((state.line === line || state.lineIndent > nodeIndent) && ch !== 0) {
+      return throwError(state, "bad indentation of a sequence entry");
+    } else if (state.lineIndent < nodeIndent) {
+      break;
+    }
+  }
+
+  if (detected) {
+    state.tag = tag;
+    state.anchor = anchor;
+    state.kind = "sequence";
+    state.result = result;
+    return true;
+  }
+  return false;
+}
+
+function readBlockMapping(
+  state: LoaderState,
+  nodeIndent: number,
+  flowIndent: number
+): boolean {
+  const tag = state.tag,
+    anchor = state.anchor,
+    result = {},
+    overridableKeys = {};
+  let following: number,
+    allowCompact = false,
+    line: number,
+    pos: number,
+    keyTag = null,
+    keyNode = null,
+    valueNode = null,
+    atExplicitKey = false,
+    detected = false,
+    ch: number;
+
+  if (
+    state.anchor !== null &&
+    typeof state.anchor !== "undefined" &&
+    typeof state.anchorMap !== "undefined"
+  ) {
+    state.anchorMap[state.anchor] = result;
+  }
+
+  ch = state.input.charCodeAt(state.position);
+
+  while (ch !== 0) {
+    following = state.input.charCodeAt(state.position + 1);
+    line = state.line; // Save the current line.
+    pos = state.position;
+
+    //
+    // Explicit notation case. There are two separate blocks:
+    // first for the key (denoted by "?") and second for the value (denoted by ":")
+    //
+    if ((ch === 0x3f || /* ? */ ch === 0x3a) && /* : */ isWsOrEol(following)) {
+      if (ch === 0x3f /* ? */) {
+        if (atExplicitKey) {
+          storeMappingPair(
+            state,
+            result,
+            overridableKeys,
+            keyTag as string,
+            keyNode,
+            null
+          );
+          keyTag = keyNode = valueNode = null;
+        }
+
+        detected = true;
+        atExplicitKey = true;
+        allowCompact = true;
+      } else if (atExplicitKey) {
+        // i.e. 0x3A/* : */ === character after the explicit key.
+        atExplicitKey = false;
+        allowCompact = true;
+      } else {
+        return throwError(
+          state,
+          "incomplete explicit mapping pair; a key node is missed; or followed by a non-tabulated empty line"
+        );
+      }
+
+      state.position += 1;
+      ch = following;
+
+      //
+      // Implicit notation case. Flow-style node as the key first, then ":", and the value.
+      //
+      // eslint-disable-next-line @typescript-eslint/no-use-before-define
+    } else if (composeNode(state, flowIndent, CONTEXT_FLOW_OUT, false, true)) {
+      if (state.line === line) {
+        ch = state.input.charCodeAt(state.position);
+
+        while (isWhiteSpace(ch)) {
+          ch = state.input.charCodeAt(++state.position);
+        }
+
+        if (ch === 0x3a /* : */) {
+          ch = state.input.charCodeAt(++state.position);
+
+          if (!isWsOrEol(ch)) {
+            return throwError(
+              state,
+              "a whitespace character is expected after the key-value separator within a block mapping"
+            );
+          }
+
+          if (atExplicitKey) {
+            storeMappingPair(
+              state,
+              result,
+              overridableKeys,
+              keyTag as string,
+              keyNode,
+              null
+            );
+            keyTag = keyNode = valueNode = null;
+          }
+
+          detected = true;
+          atExplicitKey = false;
+          allowCompact = false;
+          keyTag = state.tag;
+          keyNode = state.result;
+        } else if (detected) {
+          return throwError(
+            state,
+            "can not read an implicit mapping pair; a colon is missed"
+          );
+        } else {
+          state.tag = tag;
+          state.anchor = anchor;
+          return true; // Keep the result of `composeNode`.
+        }
+      } else if (detected) {
+        return throwError(
+          state,
+          "can not read a block mapping entry; a multiline key may not be an implicit key"
+        );
+      } else {
+        state.tag = tag;
+        state.anchor = anchor;
+        return true; // Keep the result of `composeNode`.
+      }
+    } else {
+      break; // Reading is done. Go to the epilogue.
+    }
+
+    //
+    // Common reading code for both explicit and implicit notations.
+    //
+    if (state.line === line || state.lineIndent > nodeIndent) {
+      if (
+        // eslint-disable-next-line @typescript-eslint/no-use-before-define
+        composeNode(state, nodeIndent, CONTEXT_BLOCK_OUT, true, allowCompact)
+      ) {
+        if (atExplicitKey) {
+          keyNode = state.result;
+        } else {
+          valueNode = state.result;
+        }
+      }
+
+      if (!atExplicitKey) {
+        storeMappingPair(
+          state,
+          result,
+          overridableKeys,
+          keyTag as string,
+          keyNode,
+          valueNode,
+          line,
+          pos
+        );
+        keyTag = keyNode = valueNode = null;
+      }
+
+      skipSeparationSpace(state, true, -1);
+      ch = state.input.charCodeAt(state.position);
+    }
+
+    if (state.lineIndent > nodeIndent && ch !== 0) {
+      return throwError(state, "bad indentation of a mapping entry");
+    } else if (state.lineIndent < nodeIndent) {
+      break;
+    }
+  }
+
+  //
+  // Epilogue.
+  //
+
+  // Special case: last mapping's node contains only the key in explicit notation.
+  if (atExplicitKey) {
+    storeMappingPair(
+      state,
+      result,
+      overridableKeys,
+      keyTag as string,
+      keyNode,
+      null
+    );
+  }
+
+  // Expose the resulting mapping.
+  if (detected) {
+    state.tag = tag;
+    state.anchor = anchor;
+    state.kind = "mapping";
+    state.result = result;
+  }
+
+  return detected;
+}
+
+function readTagProperty(state: LoaderState): boolean {
+  let position: number,
+    isVerbatim = false,
+    isNamed = false,
+    tagHandle = "",
+    tagName: string,
+    ch: number;
+
+  ch = state.input.charCodeAt(state.position);
+
+  if (ch !== 0x21 /* ! */) return false;
+
+  if (state.tag !== null) {
+    return throwError(state, "duplication of a tag property");
+  }
+
+  ch = state.input.charCodeAt(++state.position);
+
+  if (ch === 0x3c /* < */) {
+    isVerbatim = true;
+    ch = state.input.charCodeAt(++state.position);
+  } else if (ch === 0x21 /* ! */) {
+    isNamed = true;
+    tagHandle = "!!";
+    ch = state.input.charCodeAt(++state.position);
+  } else {
+    tagHandle = "!";
+  }
+
+  position = state.position;
+
+  if (isVerbatim) {
+    do {
+      ch = state.input.charCodeAt(++state.position);
+    } while (ch !== 0 && ch !== 0x3e /* > */);
+
+    if (state.position < state.length) {
+      tagName = state.input.slice(position, state.position);
+      ch = state.input.charCodeAt(++state.position);
+    } else {
+      return throwError(
+        state,
+        "unexpected end of the stream within a verbatim tag"
+      );
+    }
+  } else {
+    while (ch !== 0 && !isWsOrEol(ch)) {
+      if (ch === 0x21 /* ! */) {
+        if (!isNamed) {
+          tagHandle = state.input.slice(position - 1, state.position + 1);
+
+          if (!PATTERN_TAG_HANDLE.test(tagHandle)) {
+            return throwError(
+              state,
+              "named tag handle cannot contain such characters"
+            );
+          }
+
+          isNamed = true;
+          position = state.position + 1;
+        } else {
+          return throwError(
+            state,
+            "tag suffix cannot contain exclamation marks"
+          );
+        }
+      }
+
+      ch = state.input.charCodeAt(++state.position);
+    }
+
+    tagName = state.input.slice(position, state.position);
+
+    if (PATTERN_FLOW_INDICATORS.test(tagName)) {
+      return throwError(
+        state,
+        "tag suffix cannot contain flow indicator characters"
+      );
+    }
+  }
+
+  if (tagName && !PATTERN_TAG_URI.test(tagName)) {
+    return throwError(
+      state,
+      `tag name cannot contain such characters: ${tagName}`
+    );
+  }
+
+  if (isVerbatim) {
+    state.tag = tagName;
+  } else if (
+    typeof state.tagMap !== "undefined" &&
+    _hasOwnProperty.call(state.tagMap, tagHandle)
+  ) {
+    state.tag = state.tagMap[tagHandle] + tagName;
+  } else if (tagHandle === "!") {
+    state.tag = `!${tagName}`;
+  } else if (tagHandle === "!!") {
+    state.tag = `tag:yaml.org,2002:${tagName}`;
+  } else {
+    return throwError(state, `undeclared tag handle "${tagHandle}"`);
+  }
+
+  return true;
+}
+
+function readAnchorProperty(state: LoaderState): boolean {
+  let ch = state.input.charCodeAt(state.position);
+  if (ch !== 0x26 /* & */) return false;
+
+  if (state.anchor !== null) {
+    return throwError(state, "duplication of an anchor property");
+  }
+  ch = state.input.charCodeAt(++state.position);
+
+  const position = state.position;
+  while (ch !== 0 && !isWsOrEol(ch) && !isFlowIndicator(ch)) {
+    ch = state.input.charCodeAt(++state.position);
+  }
+
+  if (state.position === position) {
+    return throwError(
+      state,
+      "name of an anchor node must contain at least one character"
+    );
+  }
+
+  state.anchor = state.input.slice(position, state.position);
+  return true;
+}
+
+function readAlias(state: LoaderState): boolean {
+  let ch = state.input.charCodeAt(state.position);
+
+  if (ch !== 0x2a /* * */) return false;
+
+  ch = state.input.charCodeAt(++state.position);
+  const _position = state.position;
+
+  while (ch !== 0 && !isWsOrEol(ch) && !isFlowIndicator(ch)) {
+    ch = state.input.charCodeAt(++state.position);
+  }
+
+  if (state.position === _position) {
+    return throwError(
+      state,
+      "name of an alias node must contain at least one character"
+    );
+  }
+
+  const alias = state.input.slice(_position, state.position);
+  if (
+    typeof state.anchorMap !== "undefined" &&
+    !state.anchorMap.hasOwnProperty(alias)
+  ) {
+    return throwError(state, `unidentified alias "${alias}"`);
+  }
+
+  if (typeof state.anchorMap !== "undefined") {
+    state.result = state.anchorMap[alias];
+  }
+  skipSeparationSpace(state, true, -1);
+  return true;
+}
+
+function composeNode(
+  state: LoaderState,
+  parentIndent: number,
+  nodeContext: number,
+  allowToSeek: boolean,
+  allowCompact: boolean
+): boolean {
+  let allowBlockScalars: boolean,
+    allowBlockCollections: boolean,
+    indentStatus = 1, // 1: this>parent, 0: this=parent, -1: this<parent
+    atNewLine = false,
+    hasContent = false,
+    type: Type,
+    flowIndent: number,
+    blockIndent: number;
+
+  if (state.listener && state.listener !== null) {
+    state.listener("open", state);
+  }
+
+  state.tag = null;
+  state.anchor = null;
+  state.kind = null;
+  state.result = null;
+
+  const allowBlockStyles = (allowBlockScalars = allowBlockCollections =
+    CONTEXT_BLOCK_OUT === nodeContext || CONTEXT_BLOCK_IN === nodeContext);
+
+  if (allowToSeek) {
+    if (skipSeparationSpace(state, true, -1)) {
+      atNewLine = true;
+
+      if (state.lineIndent > parentIndent) {
+        indentStatus = 1;
+      } else if (state.lineIndent === parentIndent) {
+        indentStatus = 0;
+      } else if (state.lineIndent < parentIndent) {
+        indentStatus = -1;
+      }
+    }
+  }
+
+  if (indentStatus === 1) {
+    while (readTagProperty(state) || readAnchorProperty(state)) {
+      if (skipSeparationSpace(state, true, -1)) {
+        atNewLine = true;
+        allowBlockCollections = allowBlockStyles;
+
+        if (state.lineIndent > parentIndent) {
+          indentStatus = 1;
+        } else if (state.lineIndent === parentIndent) {
+          indentStatus = 0;
+        } else if (state.lineIndent < parentIndent) {
+          indentStatus = -1;
+        }
+      } else {
+        allowBlockCollections = false;
+      }
+    }
+  }
+
+  if (allowBlockCollections) {
+    allowBlockCollections = atNewLine || allowCompact;
+  }
+
+  if (indentStatus === 1 || CONTEXT_BLOCK_OUT === nodeContext) {
+    const cond =
+      CONTEXT_FLOW_IN === nodeContext || CONTEXT_FLOW_OUT === nodeContext;
+    flowIndent = cond ? parentIndent : parentIndent + 1;
+
+    blockIndent = state.position - state.lineStart;
+
+    if (indentStatus === 1) {
+      if (
+        (allowBlockCollections &&
+          (readBlockSequence(state, blockIndent) ||
+            readBlockMapping(state, blockIndent, flowIndent))) ||
+        readFlowCollection(state, flowIndent)
+      ) {
+        hasContent = true;
+      } else {
+        if (
+          (allowBlockScalars && readBlockScalar(state, flowIndent)) ||
+          readSingleQuotedScalar(state, flowIndent) ||
+          readDoubleQuotedScalar(state, flowIndent)
+        ) {
+          hasContent = true;
+        } else if (readAlias(state)) {
+          hasContent = true;
+
+          if (state.tag !== null || state.anchor !== null) {
+            return throwError(
+              state,
+              "alias node should not have Any properties"
+            );
+          }
+        } else if (
+          readPlainScalar(state, flowIndent, CONTEXT_FLOW_IN === nodeContext)
+        ) {
+          hasContent = true;
+
+          if (state.tag === null) {
+            state.tag = "?";
+          }
+        }
+
+        if (state.anchor !== null && typeof state.anchorMap !== "undefined") {
+          state.anchorMap[state.anchor] = state.result;
+        }
+      }
+    } else if (indentStatus === 0) {
+      // Special case: block sequences are allowed to have same indentation level as the parent.
+      // http://www.yaml.org/spec/1.2/spec.html#id2799784
+      hasContent =
+        allowBlockCollections && readBlockSequence(state, blockIndent);
+    }
+  }
+
+  if (state.tag !== null && state.tag !== "!") {
+    if (state.tag === "?") {
+      for (
+        let typeIndex = 0, typeQuantity = state.implicitTypes.length;
+        typeIndex < typeQuantity;
+        typeIndex++
+      ) {
+        type = state.implicitTypes[typeIndex];
+
+        // Implicit resolving is not allowed for non-scalar types, and '?'
+        // non-specific tag is only assigned to plain scalars. So, it isn't
+        // needed to check for 'kind' conformity.
+
+        if (type.resolve(state.result)) {
+          // `state.result` updated in resolver if matched
+          state.result = type.construct(state.result);
+          state.tag = type.tag;
+          if (state.anchor !== null && typeof state.anchorMap !== "undefined") {
+            state.anchorMap[state.anchor] = state.result;
+          }
+          break;
+        }
+      }
+    } else if (
+      _hasOwnProperty.call(state.typeMap[state.kind || "fallback"], state.tag)
+    ) {
+      type = state.typeMap[state.kind || "fallback"][state.tag];
+
+      if (state.result !== null && type.kind !== state.kind) {
+        return throwError(
+          state,
+          `unacceptable node kind for !<${state.tag}> tag; it should be "${type.kind}", not "${state.kind}"`
+        );
+      }
+
+      if (!type.resolve(state.result)) {
+        // `state.result` updated in resolver if matched
+        return throwError(
+          state,
+          `cannot resolve a node with !<${state.tag}> explicit tag`
+        );
+      } else {
+        state.result = type.construct(state.result);
+        if (state.anchor !== null && typeof state.anchorMap !== "undefined") {
+          state.anchorMap[state.anchor] = state.result;
+        }
+      }
+    } else {
+      return throwError(state, `unknown tag !<${state.tag}>`);
+    }
+  }
+
+  if (state.listener && state.listener !== null) {
+    state.listener("close", state);
+  }
+  return state.tag !== null || state.anchor !== null || hasContent;
+}
+
+function readDocument(state: LoaderState): void {
+  const documentStart = state.position;
+  let position: number,
+    directiveName: string,
+    directiveArgs: string[],
+    hasDirectives = false,
+    ch: number;
+
+  state.version = null;
+  state.checkLineBreaks = state.legacy;
+  state.tagMap = {};
+  state.anchorMap = {};
+
+  while ((ch = state.input.charCodeAt(state.position)) !== 0) {
+    skipSeparationSpace(state, true, -1);
+
+    ch = state.input.charCodeAt(state.position);
+
+    if (state.lineIndent > 0 || ch !== 0x25 /* % */) {
+      break;
+    }
+
+    hasDirectives = true;
+    ch = state.input.charCodeAt(++state.position);
+    position = state.position;
+
+    while (ch !== 0 && !isWsOrEol(ch)) {
+      ch = state.input.charCodeAt(++state.position);
+    }
+
+    directiveName = state.input.slice(position, state.position);
+    directiveArgs = [];
+
+    if (directiveName.length < 1) {
+      return throwError(
+        state,
+        "directive name must not be less than one character in length"
+      );
+    }
+
+    while (ch !== 0) {
+      while (isWhiteSpace(ch)) {
+        ch = state.input.charCodeAt(++state.position);
+      }
+
+      if (ch === 0x23 /* # */) {
+        do {
+          ch = state.input.charCodeAt(++state.position);
+        } while (ch !== 0 && !isEOL(ch));
+        break;
+      }
+
+      if (isEOL(ch)) break;
+
+      position = state.position;
+
+      while (ch !== 0 && !isWsOrEol(ch)) {
+        ch = state.input.charCodeAt(++state.position);
+      }
+
+      directiveArgs.push(state.input.slice(position, state.position));
+    }
+
+    if (ch !== 0) readLineBreak(state);
+
+    if (_hasOwnProperty.call(directiveHandlers, directiveName)) {
+      directiveHandlers[directiveName](state, directiveName, ...directiveArgs);
+    } else {
+      throwWarning(state, `unknown document directive "${directiveName}"`);
+    }
+  }
+
+  skipSeparationSpace(state, true, -1);
+
+  if (
+    state.lineIndent === 0 &&
+    state.input.charCodeAt(state.position) === 0x2d /* - */ &&
+    state.input.charCodeAt(state.position + 1) === 0x2d /* - */ &&
+    state.input.charCodeAt(state.position + 2) === 0x2d /* - */
+  ) {
+    state.position += 3;
+    skipSeparationSpace(state, true, -1);
+  } else if (hasDirectives) {
+    return throwError(state, "directives end mark is expected");
+  }
+
+  composeNode(state, state.lineIndent - 1, CONTEXT_BLOCK_OUT, false, true);
+  skipSeparationSpace(state, true, -1);
+
+  if (
+    state.checkLineBreaks &&
+    PATTERN_NON_ASCII_LINE_BREAKS.test(
+      state.input.slice(documentStart, state.position)
+    )
+  ) {
+    throwWarning(state, "non-ASCII line breaks are interpreted as content");
+  }
+
+  state.documents.push(state.result);
+
+  if (state.position === state.lineStart && testDocumentSeparator(state)) {
+    if (state.input.charCodeAt(state.position) === 0x2e /* . */) {
+      state.position += 3;
+      skipSeparationSpace(state, true, -1);
+    }
+    return;
+  }
+
+  if (state.position < state.length - 1) {
+    return throwError(
+      state,
+      "end of the stream or a document separator is expected"
+    );
+  } else {
+    return;
+  }
+}
+
+function loadDocuments(input: string, options?: LoaderStateOptions): unknown[] {
+  input = String(input);
+  options = options || {};
+
+  if (input.length !== 0) {
+    // Add tailing `\n` if not exists
+    if (
+      input.charCodeAt(input.length - 1) !== 0x0a /* LF */ &&
+      input.charCodeAt(input.length - 1) !== 0x0d /* CR */
+    ) {
+      input += "\n";
+    }
+
+    // Strip BOM
+    if (input.charCodeAt(0) === 0xfeff) {
+      input = input.slice(1);
+    }
+  }
+
+  const state = new LoaderState(input, options);
+
+  // Use 0 as string terminator. That significantly simplifies bounds check.
+  state.input += "\0";
+
+  while (state.input.charCodeAt(state.position) === 0x20 /* Space */) {
+    state.lineIndent += 1;
+    state.position += 1;
+  }
+
+  while (state.position < state.length - 1) {
+    readDocument(state);
+  }
+
+  return state.documents;
+}
+
+export type CbFunction = (doc: unknown) => void;
+function isCbFunction(fn: unknown): fn is CbFunction {
+  return typeof fn === "function";
+}
+
+export function loadAll<T extends CbFunction | LoaderStateOptions>(
+  input: string,
+  iteratorOrOption?: T,
+  options?: LoaderStateOptions
+): T extends CbFunction ? void : unknown[] {
+  if (!isCbFunction(iteratorOrOption)) {
+    return loadDocuments(input, iteratorOrOption as LoaderStateOptions) as Any;
+  }
+
+  const documents = loadDocuments(input, options);
+  const iterator = iteratorOrOption;
+  for (let index = 0, length = documents.length; index < length; index++) {
+    iterator(documents[index]);
+  }
+
+  return void 0 as Any;
+}
+
+export function load(input: string, options?: LoaderStateOptions): unknown {
+  const documents = loadDocuments(input, options);
+
+  if (documents.length === 0) {
+    return;
+  }
+  if (documents.length === 1) {
+    return documents[0];
+  }
+  throw new YAMLError(
+    "expected a single document in the stream, but found more"
+  );
+}
diff --git a/std/encoding/_yaml/loader/loader_state.ts b/std/encoding/_yaml/loader/loader_state.ts
new file mode 100644
index 000000000..ca50fcaf1
--- /dev/null
+++ b/std/encoding/_yaml/loader/loader_state.ts
@@ -0,0 +1,74 @@
+// Ported from js-yaml v3.13.1:
+// https://github.com/nodeca/js-yaml/commit/665aadda42349dcae869f12040d9b10ef18d12da
+// Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { YAMLError } from "../error.ts";
+import { Schema, SchemaDefinition, TypeMap } from "../schema.ts";
+import { State } from "../state.ts";
+import { Type } from "../type.ts";
+import { Any, ArrayObject } from "../utils.ts";
+
+export interface LoaderStateOptions {
+  legacy?: boolean;
+  listener?: ((...args: Any[]) => void) | null;
+  /** string to be used as a file path in error/warning messages. */
+  filename?: string;
+  /** specifies a schema to use. */
+  schema?: SchemaDefinition;
+  /** compatibility with JSON.parse behaviour. */
+  json?: boolean;
+  /** function to call on warning messages. */
+  onWarning?(this: null, e?: YAMLError): void;
+}
+
+export type ResultType = [] | {} | string;
+
+export class LoaderState extends State {
+  public documents: Any[] = [];
+  public length: number;
+  public lineIndent = 0;
+  public lineStart = 0;
+  public position = 0;
+  public line = 0;
+  public filename?: string;
+  public onWarning?: (...args: Any[]) => void;
+  public legacy: boolean;
+  public json: boolean;
+  public listener?: ((...args: Any[]) => void) | null;
+  public implicitTypes: Type[];
+  public typeMap: TypeMap;
+
+  public version?: string | null;
+  public checkLineBreaks?: boolean;
+  public tagMap?: ArrayObject;
+  public anchorMap?: ArrayObject;
+  public tag?: string | null;
+  public anchor?: string | null;
+  public kind?: string | null;
+  public result: ResultType | null = "";
+
+  constructor(
+    public input: string,
+    {
+      filename,
+      schema,
+      onWarning,
+      legacy = false,
+      json = false,
+      listener = null,
+    }: LoaderStateOptions
+  ) {
+    super(schema);
+    this.filename = filename;
+    this.onWarning = onWarning;
+    this.legacy = legacy;
+    this.json = json;
+    this.listener = listener;
+
+    this.implicitTypes = (this.schema as Schema).compiledImplicit;
+    this.typeMap = (this.schema as Schema).compiledTypeMap;
+
+    this.length = input.length;
+  }
+}