encoding: encoding improvements for base128 varints.
This commit is contained in:
Christopher Jeffrey
parent
51cdd6156b
commit
5415147d4e
@ -12,6 +12,7 @@
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*/
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const {U64, I64} = require('./int64');
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const UINT128_MAX = U64.UINT64_MAX.shrn(7);
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const MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER;
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const encoding = exports;
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@ -345,9 +346,9 @@ encoding.readI53BE = function readI53BE(data, off) {
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*/
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encoding._writeI64 = function _writeI64(dst, num, off, be) {
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const negative = num < 0;
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const neg = num < 0;
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if (negative) {
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if (neg) {
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num = -num;
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num -= 1;
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}
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@ -357,7 +358,7 @@ encoding._writeI64 = function _writeI64(dst, num, off, be) {
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let hi = (num * (1 / 0x100000000)) | 0;
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let lo = num | 0;
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if (negative) {
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if (neg) {
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hi = ~hi;
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lo = ~lo;
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}
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@ -491,7 +492,7 @@ encoding.readI64BEN = function readI64BEN(data, off) {
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*/
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encoding.writeU64N = function writeU64N(dst, num, off) {
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enforce(!num.sign, off, 'Signed.');
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enforce(!num.sign, off, 'Signed');
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return num.writeLE(dst, off);
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};
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@ -504,7 +505,7 @@ encoding.writeU64N = function writeU64N(dst, num, off) {
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*/
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encoding.writeU64BEN = function writeU64BEN(dst, num, off) {
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enforce(!num.sign, off, 'Signed.');
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enforce(!num.sign, off, 'Signed');
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return num.writeBE(dst, off);
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};
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@ -517,7 +518,7 @@ encoding.writeU64BEN = function writeU64BEN(dst, num, off) {
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*/
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encoding.writeI64N = function writeI64N(dst, num, off) {
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enforce(num.sign, off, 'Not signed.');
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enforce(num.sign, off, 'Not signed');
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return num.writeLE(dst, off);
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};
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@ -530,7 +531,7 @@ encoding.writeI64N = function writeI64N(dst, num, off) {
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*/
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encoding.writeI64BEN = function writeI64BEN(dst, num, off) {
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enforce(num.sign, off, 'Not signed.');
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enforce(num.sign, off, 'Not signed');
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return num.writeBE(dst, off);
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};
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@ -682,9 +683,9 @@ encoding.readVarintN = function readVarintN(data, off) {
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*/
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encoding.writeVarintN = function writeVarintN(dst, num, off) {
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enforce(!num.sign, off, 'Signed.');
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enforce(!num.sign, off, 'Signed');
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if (num.gtn(0xffffffff)) {
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if (num.hi !== 0) {
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dst[off++] = 0xff;
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return encoding.writeU64N(dst, num, off);
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}
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@ -699,9 +700,9 @@ encoding.writeVarintN = function writeVarintN(dst, num, off) {
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*/
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encoding.sizeVarintN = function sizeVarintN(num) {
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enforce(!num.sign, 0, 'Signed.');
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enforce(!num.sign, 0, 'Signed');
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if (num.gtn(0xffffffff))
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if (num.hi !== 0)
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return 9;
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return encoding.sizeVarint(num.toInt());
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@ -724,13 +725,16 @@ encoding.readVarint2 = function readVarint2(data, off) {
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const ch = data[off++];
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size++;
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enforce(num < 0x3fffffffffff, off, 'Number exceeds 2^53-1');
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// Number.MAX_SAFE_INTEGER >>> 7
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enforce(num <= 0x3fffffffffff - (ch & 0x7f), off, 'Number exceeds 2^53-1');
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// num = (num << 7) | (ch & 0x7f);
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num = (num * 0x80) + (ch & 0x7f);
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if ((ch & 0x80) === 0)
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break;
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enforce(num !== MAX_SAFE_INTEGER, off, 'Number exceeds 2^53-1');
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num++;
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}
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@ -747,17 +751,19 @@ encoding.readVarint2 = function readVarint2(data, off) {
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encoding.writeVarint2 = function writeVarint2(dst, num, off) {
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const tmp = [];
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let len = 0;
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for (;;) {
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tmp[len] = (num & 0x7f) | (len ? 0x80 : 0x00);
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if (num <= 0x7f)
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break;
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// num = (num >>> 7) - 1;
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num = ((num - (num % 0x80)) / 0x80) - 1;
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len++;
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}
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assert(off + len <= dst.length, off);
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assert(off + len + 1 <= dst.length, off);
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do {
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dst[off++] = tmp[len];
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@ -800,6 +806,7 @@ encoding.sizeVarint2 = function sizeVarint2(num) {
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size++;
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if (num <= 0x7f)
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break;
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// num = (num >>> 7) - 1;
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num = ((num - (num % 0x80)) / 0x80) - 1;
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}
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@ -824,11 +831,14 @@ encoding.readVarint2N = function readVarint2N(data, off) {
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const ch = data[off++];
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size++;
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num.iushln(7).iaddn(ch & 0x7f);
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enforce(num.lte(UINT128_MAX), off, 'Number exceeds 2^64-1');
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num.ishln(7).iorn(ch & 0x7f);
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if ((ch & 0x80) === 0)
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break;
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enforce(!num.eq(U64.UINT64_MAX), off, 'Number exceeds 2^64-1');
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num.iaddn(1);
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}
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@ -844,25 +854,26 @@ encoding.readVarint2N = function readVarint2N(data, off) {
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*/
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encoding.writeVarint2N = function writeVarint2N(dst, num, off) {
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enforce(!num.sign, off, 'Signed.');
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enforce(!num.sign, off, 'Signed');
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if (num.hi === 0)
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return encoding.writeVarint2(dst, num.toInt(), off);
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const tmp = [];
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let len = 0;
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num = num.clone();
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const tmp = [];
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let len = 0;
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for (;;) {
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tmp[len] = num.andln(0x7f) | (len ? 0x80 : 0x00);
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if (num.lten(0x7f))
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break;
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num.iushrn(7).isubn(1);
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num.ishrn(7).isubn(1);
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len++;
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}
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enforce(off + len <= dst.length, off, 'Out of bounds write');
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enforce(off + len + 1 <= dst.length, off, 'Out of bounds write');
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do {
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dst[off++] = tmp[len];
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@ -878,7 +889,7 @@ encoding.writeVarint2N = function writeVarint2N(dst, num, off) {
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*/
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encoding.sizeVarint2N = function sizeVarint2N(num) {
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enforce(!num.sign, 0, 'Signed.');
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enforce(!num.sign, 0, 'Signed');
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if (num.hi === 0)
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return encoding.sizeVarint2(num.toInt());
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@ -891,7 +902,7 @@ encoding.sizeVarint2N = function sizeVarint2N(num) {
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size++;
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if (num.lten(0x7f))
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break;
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num.iushrn(7).isubn(1);
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num.ishrn(7).isubn(1);
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}
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return size;
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@ -128,54 +128,54 @@ describe('Utils', function() {
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* 2^32: [0x8E 0xFE 0xFE 0xFF 0x00]
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*/
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let b = Buffer.allocUnsafe(1);
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let b = Buffer.alloc(1, 0xff);
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encoding.writeVarint2(b, 0, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 0);
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assert.deepEqual(b, [0]);
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b = Buffer.allocUnsafe(1);
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b = Buffer.alloc(1, 0xff);
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encoding.writeVarint2(b, 1, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 1);
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assert.deepEqual(b, [1]);
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b = Buffer.allocUnsafe(1);
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b = Buffer.alloc(1, 0xff);
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encoding.writeVarint2(b, 127, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 127);
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assert.deepEqual(b, [0x7f]);
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b = Buffer.allocUnsafe(2);
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b = Buffer.alloc(2, 0xff);
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encoding.writeVarint2(b, 128, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 128);
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assert.deepEqual(b, [0x80, 0x00]);
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b = Buffer.allocUnsafe(2);
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b = Buffer.alloc(2, 0xff);
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encoding.writeVarint2(b, 255, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 255);
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assert.deepEqual(b, [0x80, 0x7f]);
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b = Buffer.allocUnsafe(2);
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b = Buffer.alloc(2, 0xff);
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encoding.writeVarint2(b, 16383, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 16383);
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assert.deepEqual(b, [0xfe, 0x7f]);
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b = Buffer.allocUnsafe(2);
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b = Buffer.alloc(2, 0xff);
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encoding.writeVarint2(b, 16384, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 16384);
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assert.deepEqual(b, [0xff, 0x00]);
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b = Buffer.allocUnsafe(3);
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b = Buffer.alloc(3, 0xff);
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encoding.writeVarint2(b, 16511, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 16511);
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assert.deepEqual(b.slice(0, 2), [0xff, 0x7f]);
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// assert.deepEqual(b, [0x80, 0xff, 0x7f]);
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assert.deepEqual(b, [0xff, 0x7f, 0x00]);
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b = Buffer.allocUnsafe(3);
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b = Buffer.alloc(3, 0xff);
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encoding.writeVarint2(b, 65535, 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, 65535);
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// assert.deepEqual(b, [0x82, 0xfd, 0x7f]);
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assert.deepEqual(b, [0x82, 0xfe, 0x7f]);
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// assert.deepEqual(b, [0x82, 0xfd, 0x7f]);
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b = Buffer.allocUnsafe(5);
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b = Buffer.alloc(5, 0xff);
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encoding.writeVarint2(b, Math.pow(2, 32), 0);
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assert.strictEqual(encoding.readVarint2(b, 0).value, Math.pow(2, 32));
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assert.deepEqual(b, [0x8e, 0xfe, 0xfe, 0xff, 0x00]);
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