// Copyright 2012 The Obvious Corporation.
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/*
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* leb: LEB128 utilities.
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*/
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/*
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* Modules used
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*/
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"use strict";
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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exports.default = void 0;
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var _long = _interopRequireDefault(require("@xtuc/long"));
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var bits = _interopRequireWildcard(require("./bits"));
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var bufs = _interopRequireWildcard(require("./bufs"));
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function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) { var desc = Object.defineProperty && Object.getOwnPropertyDescriptor ? Object.getOwnPropertyDescriptor(obj, key) : {}; if (desc.get || desc.set) { Object.defineProperty(newObj, key, desc); } else { newObj[key] = obj[key]; } } } } newObj.default = obj; return newObj; } }
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function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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/*
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* Module variables
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*/
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/** The minimum possible 32-bit signed int. */
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var MIN_INT32 = -0x80000000;
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/** The maximum possible 32-bit signed int. */
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var MAX_INT32 = 0x7fffffff;
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/** The maximum possible 32-bit unsigned int. */
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var MAX_UINT32 = 0xffffffff;
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/** The minimum possible 64-bit signed int. */
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// const MIN_INT64 = -0x8000000000000000;
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/**
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* The maximum possible 64-bit signed int that is representable as a
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* JavaScript number.
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*/
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// const MAX_INT64 = 0x7ffffffffffffc00;
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/**
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* The maximum possible 64-bit unsigned int that is representable as a
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* JavaScript number.
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*/
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// const MAX_UINT64 = 0xfffffffffffff800;
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/*
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* Helper functions
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*/
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/**
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* Determines the number of bits required to encode the number
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* represented in the given buffer as a signed value. The buffer is
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* taken to represent a signed number in little-endian form.
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*
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* The number of bits to encode is the (zero-based) bit number of the
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* highest-order non-sign-matching bit, plus two. For example:
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*
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* 11111011 01110101
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* high low
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*
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* The sign bit here is 1 (that is, it's a negative number). The highest
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* bit number that doesn't match the sign is bit #10 (where the lowest-order
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* bit is bit #0). So, we have to encode at least 12 bits total.
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*
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* As a special degenerate case, the numbers 0 and -1 each require just one bit.
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*/
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function signedBitCount(buffer) {
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return bits.highOrder(bits.getSign(buffer) ^ 1, buffer) + 2;
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}
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/**
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* Determines the number of bits required to encode the number
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* represented in the given buffer as an unsigned value. The buffer is
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* taken to represent an unsigned number in little-endian form.
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*
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* The number of bits to encode is the (zero-based) bit number of the
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* highest-order 1 bit, plus one. For example:
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*
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* 00011000 01010011
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* high low
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*
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* The highest-order 1 bit here is bit #12 (where the lowest-order bit
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* is bit #0). So, we have to encode at least 13 bits total.
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*
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* As a special degenerate case, the number 0 requires 1 bit.
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*/
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function unsignedBitCount(buffer) {
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var result = bits.highOrder(1, buffer) + 1;
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return result ? result : 1;
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}
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/**
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* Common encoder for both signed and unsigned ints. This takes a
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* bigint-ish buffer, returning an LEB128-encoded buffer.
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*/
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function encodeBufferCommon(buffer, signed) {
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var signBit;
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var bitCount;
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if (signed) {
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signBit = bits.getSign(buffer);
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bitCount = signedBitCount(buffer);
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} else {
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signBit = 0;
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bitCount = unsignedBitCount(buffer);
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}
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var byteCount = Math.ceil(bitCount / 7);
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var result = bufs.alloc(byteCount);
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for (var i = 0; i < byteCount; i++) {
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var payload = bits.extract(buffer, i * 7, 7, signBit);
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result[i] = payload | 0x80;
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} // Mask off the top bit of the last byte, to indicate the end of the
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// encoding.
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result[byteCount - 1] &= 0x7f;
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return result;
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}
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/**
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* Gets the byte-length of the value encoded in the given buffer at
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* the given index.
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*/
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function encodedLength(encodedBuffer, index) {
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var result = 0;
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while (encodedBuffer[index + result] >= 0x80) {
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result++;
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}
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result++; // to account for the last byte
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if (index + result > encodedBuffer.length) {// FIXME(sven): seems to cause false positives
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// throw new Error("integer representation too long");
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}
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return result;
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}
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/**
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* Common decoder for both signed and unsigned ints. This takes an
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* LEB128-encoded buffer, returning a bigint-ish buffer.
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*/
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function decodeBufferCommon(encodedBuffer, index, signed) {
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index = index === undefined ? 0 : index;
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var length = encodedLength(encodedBuffer, index);
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var bitLength = length * 7;
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var byteLength = Math.ceil(bitLength / 8);
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var result = bufs.alloc(byteLength);
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var outIndex = 0;
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while (length > 0) {
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bits.inject(result, outIndex, 7, encodedBuffer[index]);
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outIndex += 7;
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index++;
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length--;
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}
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var signBit;
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var signByte;
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if (signed) {
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// Sign-extend the last byte.
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var lastByte = result[byteLength - 1];
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var endBit = outIndex % 8;
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if (endBit !== 0) {
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var shift = 32 - endBit; // 32 because JS bit ops work on 32-bit ints.
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lastByte = result[byteLength - 1] = lastByte << shift >> shift & 0xff;
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}
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signBit = lastByte >> 7;
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signByte = signBit * 0xff;
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} else {
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signBit = 0;
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signByte = 0;
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} // Slice off any superfluous bytes, that is, ones that add no meaningful
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// bits (because the value would be the same if they were removed).
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while (byteLength > 1 && result[byteLength - 1] === signByte && (!signed || result[byteLength - 2] >> 7 === signBit)) {
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byteLength--;
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}
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result = bufs.resize(result, byteLength);
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return {
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value: result,
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nextIndex: index
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};
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}
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/*
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* Exported bindings
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*/
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function encodeIntBuffer(buffer) {
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return encodeBufferCommon(buffer, true);
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}
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function decodeIntBuffer(encodedBuffer, index) {
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return decodeBufferCommon(encodedBuffer, index, true);
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}
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function encodeInt32(num) {
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var buf = bufs.alloc(4);
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buf.writeInt32LE(num, 0);
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var result = encodeIntBuffer(buf);
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bufs.free(buf);
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return result;
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}
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function decodeInt32(encodedBuffer, index) {
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var result = decodeIntBuffer(encodedBuffer, index);
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var parsed = bufs.readInt(result.value);
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var value = parsed.value;
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bufs.free(result.value);
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if (value < MIN_INT32 || value > MAX_INT32) {
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throw new Error("integer too large");
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}
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return {
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value: value,
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nextIndex: result.nextIndex
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};
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}
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function encodeInt64(num) {
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var buf = bufs.alloc(8);
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bufs.writeInt64(num, buf);
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var result = encodeIntBuffer(buf);
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bufs.free(buf);
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return result;
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}
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function decodeInt64(encodedBuffer, index) {
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var result = decodeIntBuffer(encodedBuffer, index);
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var value = _long.default.fromBytesLE(result.value, false);
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bufs.free(result.value);
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return {
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value: value,
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nextIndex: result.nextIndex,
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lossy: false
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};
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}
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function encodeUIntBuffer(buffer) {
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return encodeBufferCommon(buffer, false);
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}
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function decodeUIntBuffer(encodedBuffer, index) {
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return decodeBufferCommon(encodedBuffer, index, false);
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}
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function encodeUInt32(num) {
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var buf = bufs.alloc(4);
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buf.writeUInt32LE(num, 0);
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var result = encodeUIntBuffer(buf);
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bufs.free(buf);
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return result;
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}
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function decodeUInt32(encodedBuffer, index) {
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var result = decodeUIntBuffer(encodedBuffer, index);
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var parsed = bufs.readUInt(result.value);
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var value = parsed.value;
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bufs.free(result.value);
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if (value > MAX_UINT32) {
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throw new Error("integer too large");
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}
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return {
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value: value,
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nextIndex: result.nextIndex
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};
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}
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function encodeUInt64(num) {
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var buf = bufs.alloc(8);
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bufs.writeUInt64(num, buf);
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var result = encodeUIntBuffer(buf);
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bufs.free(buf);
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return result;
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}
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function decodeUInt64(encodedBuffer, index) {
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var result = decodeUIntBuffer(encodedBuffer, index);
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var value = _long.default.fromBytesLE(result.value, true);
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bufs.free(result.value);
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return {
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value: value,
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nextIndex: result.nextIndex,
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lossy: false
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};
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}
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var _default = {
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decodeInt32: decodeInt32,
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decodeInt64: decodeInt64,
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decodeIntBuffer: decodeIntBuffer,
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decodeUInt32: decodeUInt32,
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decodeUInt64: decodeUInt64,
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decodeUIntBuffer: decodeUIntBuffer,
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encodeInt32: encodeInt32,
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encodeInt64: encodeInt64,
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encodeIntBuffer: encodeIntBuffer,
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encodeUInt32: encodeUInt32,
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encodeUInt64: encodeUInt64,
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encodeUIntBuffer: encodeUIntBuffer
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};
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exports.default = _default;
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