Merge pull request #37028 from overleaf/em-bibtex-stream-parser

[web] add a streaming bibtex parser

GitOrigin-RevId: 5397ba546a3d5b3436a80eab0467244969b280d0

services/web/shared/bibtex/parser/bibtex-char-codes.mts

@@ -0,0 +1,49 @@
+import { isBibtexIdentifierContinuationChar } from '../bibtex-identifier.mts'
+
+export const TAB = 0x09
+export const LINE_FEED = 0x0a
+export const CARRIAGE_RETURN = 0x0d
+export const SPACE = 0x20
+export const QUOTE = 0x22
+export const HASH = 0x23
+export const PERCENT = 0x25
+export const OPEN_PAREN = 0x28
+export const CLOSE_PAREN = 0x29
+export const COMMA = 0x2c
+export const EQUALS = 0x3d
+export const AT = 0x40
+export const OPEN_BRACE = 0x7b
+export const CLOSE_BRACE = 0x7d
+
+// Derived from the shared predicate rather than restated, so the character-code
+// variants below cannot drift from it.
+const ASCII_ALLOWED = Uint8Array.from({ length: 0x80 }, (_, code) =>
+  isBibtexIdentifierContinuationChar(String.fromCharCode(code)) ? 1 : 0
+)
+
+/**
+ * Character-code variant of isBibtexIdentifierContinuationChar. Every
+ * forbidden character is ASCII, so anything above is allowed, including the
+ * surrogate halves of an astral character.
+ */
+export function isBibtexIdentifierCharCode(code: number): boolean {
+  return code > 0x7f || ASCII_ALLOWED[code] === 1
+}
+
+/** Character-code variant of isBibtexIdentifierStartChar. */
+export function isBibtexIdentifierStartCharCode(code: number): boolean {
+  return isBibtexIdentifierCharCode(code) && !isDigitCode(code)
+}
+
+export function isDigitCode(code: number): boolean {
+  return code >= 0x30 && code <= 0x39
+}
+
+export function isWhitespaceCode(code: number): boolean {
+  return (
+    code === SPACE ||
+    code === LINE_FEED ||
+    code === TAB ||
+    code === CARRIAGE_RETURN
+  )
+}