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Added 'Parse TCP' operation

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n1474335 2022-05-30 18:06:15 +01:00
parent 477e4a7421
commit a895d1d82a
14 changed files with 430 additions and 81 deletions
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34
src/core/lib/Stream.mjs
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@ -27,15 +27,17 @@ export default class Stream {
}
/**
* Get a number of bytes from the current position.
* Get a number of bytes from the current position, or all remaining bytes.
*
* @param {number} numBytes
* @param {number} [numBytes=null]
* @returns {Uint8Array}
*/
getBytes(numBytes) {
getBytes(numBytes=null) {
if (this.position > this.length) return undefined;
const newPosition = this.position + numBytes;
const newPosition = numBytes !== null ?
this.position + numBytes :
this.length;
const bytes = this.bytes.slice(this.position, newPosition);
this.position = newPosition;
this.bitPos = 0;
@ -91,34 +93,40 @@ export default class Stream {
}
/**
* Reads a number of bits from the buffer.
*
* @TODO Add endianness
* Reads a number of bits from the buffer in big or little endian.
*
* @param {number} numBits
* @param {string} [endianness="be"]
* @returns {number}
*/
readBits(numBits) {
readBits(numBits, endianness="be") {
if (this.position > this.length) return undefined;
let bitBuf = 0,
bitBufLen = 0;
// Add remaining bits from current byte
bitBuf = (this.bytes[this.position++] & bitMask(this.bitPos)) >>> this.bitPos;
bitBuf = this.bytes[this.position++] & bitMask(this.bitPos);
if (endianness !== "be") bitBuf >>>= this.bitPos;
bitBufLen = 8 - this.bitPos;
this.bitPos = 0;
// Not enough bits yet
while (bitBufLen < numBits) {
bitBuf |= this.bytes[this.position++] << bitBufLen;
if (endianness === "be")
bitBuf = (bitBuf << bitBufLen) | this.bytes[this.position++];
else
bitBuf |= this.bytes[this.position++] << bitBufLen;
bitBufLen += 8;
}
// Reverse back to numBits
if (bitBufLen > numBits) {
const excess = bitBufLen - numBits;
bitBuf &= (1 << numBits) - 1;
if (endianness === "be")
bitBuf >>>= excess;
else
bitBuf &= (1 << numBits) - 1;
bitBufLen -= excess;
this.position--;
this.bitPos = 8 - excess;
@ -133,7 +141,9 @@ export default class Stream {
* @returns {number} The bit mask
*/
function bitMask(bitPos) {
return 256 - (1 << bitPos);
return endianness === "be" ?
(1 << (8 - bitPos)) - 1 :
256 - (1 << bitPos);
}
}