awaforge

fontReader

AGPL-3.0-onlyRelease 2L4

Big-endian binary reader — SFNT / OpenType / WOFF / TrueType streams.

Module fontReader | Source packages/front/office/fonts/src/primitives/reader.js | Deps fontErrors, binaryReader, fontFixed | Worker-safe yes

Wraps a DataView over a Uint8Array and exposes typed reads (int / uint 8/16/24/32, Fixed, F2Dot14, tag, LONGDATETIME) plus cursor management (pos, seek, skip, peek, sub). Always BE — OpenType is big-endian throughout.

Resolve

const { BinaryReader, reader, sliceTable } = runtime.resolve('fontReader');
const r = reader(bytes);

sliceTable(bytes, offset, length) returns a bounds-checked, zero-copy Uint8Array view over bytes (a non-Uint8Array input throws ParseError('fonts/reader-input'), a range outside the buffer throws ParseError('fonts/reader-sub')).

API

Constructor

new BinaryReader(bytes, start?, length?) — throws ParseError if the input is not a Uint8Array or if start+length exceeds the buffer.

Properties

Property Type Description
pos number Current offset in the window.
length number Total size of the window.
eof boolean true when the cursor is at the end.

Methods

Method Signature Description
seek (p: number) => this Sets the cursor.
skip (n: number) => this Advances by n bytes.
peek (fn: (r) => T) => T Runs fn then restores the cursor.
sub (start, length) => BinaryReader Sub-reader, independent cursor.
readBytes (n) => Uint8Array Shared view of the buffer.
readBytesCopy (n) => Uint8Array Independent copy.
readUint8 / readInt8 () => number 1 byte.
readUint16 / readInt16 () => number 2 bytes BE.
readUint24 () => number 3 bytes BE.
readUint32 / readInt32 () => number 4 bytes BE.
readFixed () => number Fixed 16.16.
readF2Dot14 () => number F2Dot14.
readTag () => number uint32.
readLongDateTime () => number 64-bit seconds since 1904 (Number — ~2^53 precision).
readOffset16 / readOffset32 () => number Semantic aliases.

Examples

Simple parsing

const { reader } = runtime.resolve('fontReader');
const r = reader(bytes);
const version = r.readUint32();
const numTables = r.readUint16();
r.skip(6);

Sub-reader

const sub = r.sub(offset, length);
const x = sub.readUint16();   // r.pos unchanged

Peek

const next = r.peek(rr => rr.readUint32());
// r.pos stays where it was

Notes

  • All reads are BE — no endianness option, by OpenType design.
  • Out-of-bounds / EOF throws ParseError('fonts/reader-eof'|'fonts/reader-seek'|'fonts/reader-sub').
  • readBytes shares the source buffer — mutating the returned window affects the stream.
  • v1.0.0 migration: implementation delegated to @awacloud/fw/io/binary/reader.js. The fonts package's BinaryReader facade keeps the historical API (BE semantics, peek, sub, OT types) and translates fw's ContractError into typed fonts/reader-* ParseErrors; the original ContractError is kept as the cause of the ParseError.

See also