awaforge

pdfAscii85

AGPL-3.0-onlyRelease 2L4

ASCII85Decode ISO 32000-2 §7.4.3 — base 85, 5 chars ↔ 4 bytes.

Module pdfAscii85 | Source packages/front/office/pdf/src/syntax/filters/ascii85.js | Deps pdfErrors | Worker-safe yes

Five ASCII characters in the !..u range decode to 4 binary bytes, interpreted as a big-endian 32-bit integer in base 85. The special character z stands for 4 zero bytes and may appear only at a group boundary. The stream is terminated by ~>. The final group may be 2..4 characters, decoding to 1..3 trailing bytes (padded with u = 84, keeping count - 1 bytes). Whitespace is ignored.

Resolve

const a85 = runtime.resolve('pdfAscii85');
// Returns: { decode, encode }

API

Method Signature Returns
decode (bytes: Uint8Array) => Uint8Array Binary bytes.
encode (bytes: Uint8Array) => Uint8Array ASCII85 plus the ~> EOD.

Examples

Decode

const a85 = runtime.resolve('pdfAscii85');
const src = new TextEncoder().encode('87cURD]j~>');
const out = a85.decode(src);
new TextDecoder().decode(out);   // 'Hello'

Zero group (z)

a85.decode(new TextEncoder().encode('z~>'));   // [0,0,0,0]

Round trip with a tail

const bin = new Uint8Array([1, 2, 3]);         // 3 bytes → 4 chars + ~>
const enc = a85.encode(bin);
const back = a85.decode(enc);
// back equals bin.

Errors

Code Class When
pdf/ascii85/bad-input ParseError Argument is not a Uint8Array.
pdf/ascii85/bad-eod ParseError ~ not followed by >.
pdf/ascii85/bad-z ParseError z inside a group (count !== 0).
pdf/ascii85/bad-digit ParseError Character outside !..u, not whitespace, not z/~.

See also