First commit

node_modules/@ldapjs/dn/lib/utils/parse-string/read-escape-sequence.js

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+'use strict'
+
+/**
+ * @typedef ReadEscapeSequenceResult
+ * @property {number} endPos The position in the buffer that marks the end of
+ * the escape sequence.
+ * @property {Buffer} parsed The parsed escape sequence as a buffer of bytes.
+ */
+
+/**
+ * Read an escape sequence from a buffer. It reads until no escape sequences
+ * are found. Thus, a sequence of escape sequences will all be parsed at once
+ * and returned as a single result.
+ *
+ * @example A Single ASCII Sequence
+ * const toParse = Buffer.from('foo\\#bar', 'utf8')
+ * const {parsed, endPos} = readEscapeSequence({
+ *   searchBuffer: toParse,
+ *   startPos: 3
+ * })
+ * // => parsed = '#', endPos = 5
+ *
+ * @example Multiple ASCII Sequences In Succession
+ * const toParse = Buffer.from('foo\\#\\!bar', 'utf8')
+ * const {parsed, endPos} = readEscapeSequence({
+ *   searchBuffer: toParse,
+ *   startPos: 3
+ * })
+ * // => parsed = '#!', endPos = 7
+ *
+ * @param searchBuffer
+ * @param startPos
+ *
+ * @returns {ReadEscapeSequenceResult}
+ *
+ * @throws When an escaped sequence is not a valid hexadecimal value.
+ */
+module.exports = function readEscapeSequence ({ searchBuffer, startPos }) {
+  // This is very similar to the `readEscapedCharacters` algorithm in
+  // the `utils/escape-filter-value` in `@ldapjs/filter`. The difference being
+  // that here we want to interpret the escape sequence instead of return it
+  // as a string to be embedded in an "escaped" string.
+  // https://github.com/ldapjs/filter/blob/1423612/lib/utils/escape-filter-value.js
+
+  let pos = startPos
+  const buf = []
+
+  while (pos < searchBuffer.byteLength) {
+    const char = searchBuffer[pos]
+    const nextChar = searchBuffer[pos + 1]
+
+    if (char !== 0x5c) {
+      // End of sequence reached.
+      break
+    }
+
+    const strHexCode = String.fromCharCode(nextChar) +
+      String.fromCharCode(searchBuffer[pos + 2])
+    const hexCode = parseInt(strHexCode, 16)
+    if (Number.isNaN(hexCode) === true) {
+      if (nextChar >= 0x00 && nextChar <= 0x7f) {
+        // Sequence is a single escaped ASCII character
+        buf.push(nextChar)
+        pos += 2
+        continue
+      } else {
+        throw Error('invalid hex code in escape sequence')
+      }
+    }
+
+    if (hexCode >= 0xc0 && hexCode <= 0xdf) {
+      // Sequence is a 2-byte utf-8 character.
+      const secondByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 4]) +
+        String.fromCharCode(searchBuffer[pos + 5]),
+        16
+      )
+      buf.push(hexCode)
+      buf.push(secondByte)
+      pos += 6
+      continue
+    }
+
+    if (hexCode >= 0xe0 && hexCode <= 0xef) {
+      // Sequence is a 3-byte utf-8 character.
+      const secondByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 4]) +
+        String.fromCharCode(searchBuffer[pos + 5]),
+        16
+      )
+      const thirdByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 7]) +
+        String.fromCharCode(searchBuffer[pos + 8]),
+        16
+      )
+      buf.push(hexCode)
+      buf.push(secondByte)
+      buf.push(thirdByte)
+      pos += 9
+      continue
+    }
+
+    if (hexCode >= 0xf0 && hexCode <= 0xf7) {
+      // Sequence is a 4-byte utf-8 character.
+      const secondByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 4]) +
+        String.fromCharCode(searchBuffer[pos + 5]),
+        16
+      )
+      const thirdByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 7]) +
+        String.fromCharCode(searchBuffer[pos + 8]),
+        16
+      )
+      const fourthByte = parseInt(
+        String.fromCharCode(searchBuffer[pos + 10]) +
+        String.fromCharCode(searchBuffer[pos + 11]),
+        16
+      )
+      buf.push(hexCode)
+      buf.push(secondByte)
+      buf.push(thirdByte)
+      buf.push(fourthByte)
+      pos += 12
+      continue
+    }
+
+    // The escaped character should be a single hex value.
+    buf.push(hexCode)
+    pos += 3
+  }
+
+  return {
+    endPos: pos,
+    parsed: Buffer.from(buf)
+  }
+}