119 lines
3.3 KiB
JavaScript
119 lines
3.3 KiB
JavaScript
import { Token, Type } from './token.js'
|
|
import { assertEnoughData, decodeErrPrefix } from './common.js'
|
|
import * as uint from './0uint.js'
|
|
import { encodeBytes } from './2bytes.js'
|
|
|
|
const textDecoder = new TextDecoder()
|
|
|
|
// Threshold for ASCII fast-path vs TextDecoder. Short ASCII strings (common for
|
|
// map keys) are faster to decode with a simple loop than TextDecoder overhead.
|
|
const ASCII_THRESHOLD = 32
|
|
|
|
/**
|
|
* @typedef {import('../interface').ByteWriter} ByteWriter
|
|
* @typedef {import('../interface').DecodeOptions} DecodeOptions
|
|
*/
|
|
|
|
/**
|
|
* Decode UTF-8 bytes to string. For short ASCII strings (common case for map keys),
|
|
* a simple loop is faster than TextDecoder.
|
|
* @param {Uint8Array} bytes
|
|
* @param {number} start
|
|
* @param {number} end
|
|
* @returns {string}
|
|
*/
|
|
function toStr (bytes, start, end) {
|
|
const len = end - start
|
|
if (len < ASCII_THRESHOLD) {
|
|
let str = ''
|
|
for (let i = start; i < end; i++) {
|
|
const c = bytes[i]
|
|
if (c & 0x80) { // non-ASCII, fall back to TextDecoder
|
|
return textDecoder.decode(bytes.subarray(start, end))
|
|
}
|
|
str += String.fromCharCode(c)
|
|
}
|
|
return str
|
|
}
|
|
return textDecoder.decode(bytes.subarray(start, end))
|
|
}
|
|
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} prefix
|
|
* @param {number} length
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
function toToken (data, pos, prefix, length, options) {
|
|
const totLength = prefix + length
|
|
assertEnoughData(data, pos, totLength)
|
|
const tok = new Token(Type.string, toStr(data, pos + prefix, pos + totLength), totLength)
|
|
if (options.retainStringBytes === true) {
|
|
tok.byteValue = data.slice(pos + prefix, pos + totLength)
|
|
}
|
|
return tok
|
|
}
|
|
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} minor
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
export function decodeStringCompact (data, pos, minor, options) {
|
|
return toToken(data, pos, 1, minor, options)
|
|
}
|
|
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} _minor
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
export function decodeString8 (data, pos, _minor, options) {
|
|
return toToken(data, pos, 2, uint.readUint8(data, pos + 1, options), options)
|
|
}
|
|
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} _minor
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
export function decodeString16 (data, pos, _minor, options) {
|
|
return toToken(data, pos, 3, uint.readUint16(data, pos + 1, options), options)
|
|
}
|
|
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} _minor
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
export function decodeString32 (data, pos, _minor, options) {
|
|
return toToken(data, pos, 5, uint.readUint32(data, pos + 1, options), options)
|
|
}
|
|
|
|
// TODO: maybe we shouldn't support this ..
|
|
/**
|
|
* @param {Uint8Array} data
|
|
* @param {number} pos
|
|
* @param {number} _minor
|
|
* @param {DecodeOptions} options
|
|
* @returns {Token}
|
|
*/
|
|
export function decodeString64 (data, pos, _minor, options) {
|
|
const l = uint.readUint64(data, pos + 1, options)
|
|
if (typeof l === 'bigint') {
|
|
throw new Error(`${decodeErrPrefix} 64-bit integer string lengths not supported`)
|
|
}
|
|
return toToken(data, pos, 9, l, options)
|
|
}
|
|
|
|
export const encodeString = encodeBytes
|