ltx/src/parsers/ltx.js

<xml for="JavaScript">

import { EventEmitter } from "events";
import { unescapeXML } from "../escape.js";

const STATE_TEXT = 0;
const STATE_IGNORE_COMMENT = 1;
const STATE_IGNORE_INSTRUCTION = 2;
const STATE_TAG_NAME = 3;
const STATE_TAG = 4;
const STATE_ATTR_NAME = 5;
const STATE_ATTR_EQ = 6;
const STATE_ATTR_QUOT = 7;
const STATE_ATTR_VALUE = 8;
const STATE_CDATA = 9;
const STATE_IGNORE_CDATA = 10;

class SaxLtx extends EventEmitter {
  constructor() {
    super();
    let state = STATE_TEXT;
    let remainder;
    let parseRemainder;
    let tagName;
    let attrs;
    let endTag;
    let selfClosing;
    let attrQuote;
    let attrQuoteChar;
    let recordStart = 0;
    let attrName;

    this._handleTagOpening = function _handleTagOpening(
      endTag,
      tagName,
      attrs
    ) {
      if (!endTag) {
        this.emit("startElement", tagName, attrs);
        if (selfClosing) {
          this.emit("endElement", tagName, true);
        }
      } else {
        this.emit("endElement", tagName, false);
      }
    };

    this.write = function write(data) {
      if (typeof data !== "string") {
        data = data.toString();
      }
      let pos = 0;

      /* Anything from previous write()? */
      if (remainder) {
        data = remainder + data;
        pos += !parseRemainder ? remainder.length : 0;
        parseRemainder = false;
        remainder = null;
      }

      function endRecording() {
        if (typeof recordStart === "number") {
          const recorded = data.slice(recordStart, pos);
          recordStart = undefined;
          return recorded;
        }
      }

      for (; pos < data.length; pos++) {
        switch (state) {
          case STATE_TEXT: {
            // if we're looping through text, fast-forward using indexOf to
            // the next '<' character
            const lt = data.indexOf("<", pos);
            if (lt !== -1 && pos !== lt) {
              pos = lt;
            }

            break;
          }
          case STATE_ATTR_VALUE: {
            // if we're looping through an attribute, fast-forward using
            // indexOf to the next end quote character
            const quot = data.indexOf(attrQuoteChar, pos);
            if (quot !== -1) {
              pos = quot;
            }

            break;
          }
          case STATE_IGNORE_COMMENT: {
            // if we're looping through a comment, fast-forward using
            // indexOf to the first end-comment character
            const endcomment = data.indexOf("-->", pos);
            if (endcomment !== -1) {
              pos = endcomment + 2; // target the '>' character
            }

            break;
          }
          case STATE_IGNORE_CDATA: {
            // if we're looping through a CDATA, fast-forward using
            // indexOf to the first end-CDATA character ]]>
            const endCDATA = data.indexOf("]]>", pos);
            if (endCDATA !== -1) {
              pos = endCDATA + 2; // target the '>' character
            }

            break;
          }
          // No default
        }

        const c = data.charCodeAt(pos);
        switch (state) {
          case STATE_TEXT:
            if (c === 60 /* < */) {
              const text = endRecording();
              if (text) {
                this.emit("text", unescapeXML(text));
              }
              state = STATE_TAG_NAME;
              recordStart = pos + 1;
              attrs = {};
            }
            break;
          case STATE_CDATA:
            if (c === 93 /* ] */) {
              if (data.substr(pos + 1, 2) === "]>") {
                const cData = endRecording();
                if (cData) {
                  this.emit("text", cData);
                }
                state = STATE_TEXT;
              } else if (data.length < pos + 2) {
                parseRemainder = true;
                pos = data.length;
              }
            }
            break;
          case STATE_TAG_NAME:
            if (c === 47 /* / */ && recordStart === pos) {
              recordStart = pos + 1;
              endTag = true;
            } else if (c === 33 /* ! */) {
              if (data.substr(pos + 1, 7) === "[CDATA[") {
                recordStart = pos + 8;
                state = STATE_CDATA;
              } else if (
                data.length < pos + 8 &&
                "[CDATA[".startsWith(data.slice(pos + 1))
              ) {
                // We potentially have CDATA, but the chunk is ending; stop here and let the next write() decide
                parseRemainder = true;
                pos = data.length;
              } else {
                recordStart = undefined;
                state = STATE_IGNORE_COMMENT;
              }
            } else if (c === 63 /* ? */) {
              recordStart = undefined;
              state = STATE_IGNORE_INSTRUCTION;
            } else if (c <= 32 || c === 47 /* / */ || c === 62 /* > */) {
              tagName = endRecording();
              pos--;
              state = STATE_TAG;
            }
            break;
          case STATE_IGNORE_COMMENT:
            if (c === 62 /* > */) {
              const prevFirst = data.charCodeAt(pos - 1);
              const prevSecond = data.charCodeAt(pos - 2);
              if (
                (prevFirst === 45 /* - */ && prevSecond === 45) /* - */ ||
                (prevFirst === 93 /* ] */ && prevSecond === 93) /* ] */
              ) {
                state = STATE_TEXT;
              }
            }
            break;
          case STATE_IGNORE_INSTRUCTION:
            if (c === 62 /* > */) {
              const prev = data.charCodeAt(pos - 1);
              if (prev === 63 /* ? */) {
                state = STATE_TEXT;
              }
            }
            break;
          case STATE_TAG:
            if (c === 62 /* > */) {
              this._handleTagOpening(endTag, tagName, attrs);
              tagName = undefined;
              attrs = undefined;
              endTag = undefined;
              selfClosing = undefined;
              state = STATE_TEXT;
              recordStart = pos + 1;
            } else if (c === 47 /* / */) {
              selfClosing = true;
            } else if (c > 32) {
              recordStart = pos;
              state = STATE_ATTR_NAME;
            }
            break;
          case STATE_ATTR_NAME:
            if (c <= 32 || c === 61 /* = */) {
              attrName = endRecording();
              pos--;
              state = STATE_ATTR_EQ;
            }
            break;
          case STATE_ATTR_EQ:
            if (c === 61 /* = */) {
              state = STATE_ATTR_QUOT;
            }
            break;
          case STATE_ATTR_QUOT:
            if (c === 34 /* " */ || c === 39 /* ' */) {
              attrQuote = c;
              attrQuoteChar = c === 34 ? '"' : "'";
              state = STATE_ATTR_VALUE;
              recordStart = pos + 1;
            }
            break;
          case STATE_ATTR_VALUE:
            if (c === attrQuote) {
              const value = unescapeXML(endRecording());
              attrs[attrName] = value;
              attrName = undefined;
              state = STATE_TAG;
            }
            break;
        }
      }

      if (typeof recordStart === "number" && recordStart <= data.length) {
        remainder = data.slice(recordStart);
        recordStart = 0;
      }
    };
  }

  end(data) {
    if (data) {
      this.write(data);
    }

    /* Uh, yeah */
    this.write = function write() {};
  }
}

export default SaxLtx;