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support BN in bufferwriter 

So that the precision of writing a variable sized integer is sufficient.
This commit is contained in:
Ryan X. Charles 2014-08-20 12:52:37 -07:00
parent cde44d689c
commit 912bed1d9c
2 changed files with 70 additions and 14 deletions
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47
lib/bufferwriter.js
View File

@ -1,3 +1,5 @@
var BN = require('./bn');
var BufferWriter = function BufferWriter(bufs) {
if (!(this instanceof BufferWriter))
return new BufferReader(buf);
@ -48,21 +50,17 @@ BufferWriter.prototype.writeUInt32LE = function(n) {
return this;
};
//TODO: What if n is so large that it loses precision?
BufferWriter.prototype.writeUInt64BE = function(n) {
var buf = new Buffer(8);
buf.writeInt32BE(n & -1, 4);
buf.writeUInt32BE(Math.floor(n / 0x100000000), 0);
BufferWriter.prototype.writeUInt64BEBN = function(bn) {
var buf = bn.toBuffer({size: 8});
this.write(buf);
return this;
};
//TODO: What if n is so large that it loses precision?
BufferWriter.prototype.writeUInt64LE = function(n) {
var buf = new Buffer(8);
buf.writeInt32LE(n & -1, 0);
buf.writeUInt32LE(Math.floor(n / 0x100000000), 4);
this.write(buf);
BufferWriter.prototype.writeUInt64LEBN = function(bn) {
var buf = bn.toBuffer({size: 8});
var reversebuf = new Buffer(Array.apply(new Array(), buf).reverse());
this.write(reversebuf);
return this;
};
@ -72,6 +70,12 @@ BufferWriter.prototype.writeVarInt = function(n) {
return this;
};
BufferWriter.prototype.writeVarIntBN = function(bn) {
var buf = BufferWriter.varIntBufBN(bn);
this.write(buf);
return this;
};
//TODO: What if n is so large that it loses precision?
BufferWriter.varIntBuf = function(n) {
var buf = undefined;
@ -95,4 +99,27 @@ BufferWriter.varIntBuf = function(n) {
return buf;
};
BufferWriter.varIntBufBN = function(bn) {
var buf = undefined;
var n = bn.toNumber();
if (n < 253) {
buf = new Buffer(1);
buf.writeUInt8(n, 0);
} else if (n < 0x10000) {
buf = new Buffer(1 + 2);
buf.writeUInt8(253, 0);
buf.writeUInt16LE(n, 1);
} else if (n < 0x100000000) {
buf = new Buffer(1 + 4);
buf.writeUInt8(254, 0);
buf.writeUInt32LE(n, 1);
} else {
var bw = new BufferWriter();
bw.writeUInt8(255);
bw.writeUInt64LEBN(bn);
var buf = bw.concat();
}
return buf;
};
module.exports = BufferWriter;

37
test/test.bufferwriter.js
View File

@ -1,4 +1,5 @@
var BufferWriter = require('../lib/bufferwriter');
var BN = require('../lib/bn');
var should = require('chai').should();
describe('BufferWriter', function() {
@ -75,20 +76,20 @@ describe('BufferWriter', function() {
});
describe('#writeUInt64BE', function() {
describe('#writeUInt64BEBN', function() {
it('should write 1', function() {
var bw = new BufferWriter();
bw.writeUInt64BE(1).concat().toString('hex').should.equal('0000000000000001');
bw.writeUInt64BEBN(BN(1)).concat().toString('hex').should.equal('0000000000000001');
});
});
describe('#writeUInt64LE', function() {
describe('#writeUInt64LEBN', function() {
it('should write 1', function() {
var bw = new BufferWriter();
bw.writeUInt64LE(1).concat().toString('hex').should.equal('0100000000000000');
bw.writeUInt64LEBN(BN(1)).concat().toString('hex').should.equal('0100000000000000');
});
});
@ -121,4 +122,32 @@ describe('BufferWriter', function() {
});
describe('#writeVarIntBN', function() {
it('should write a 1 byte varInt', function() {
var bw = new BufferWriter();
bw.writeVarIntBN(BN(1));
bw.concat().length.should.equal(1);
});
it('should write a 3 byte varInt', function() {
var bw = new BufferWriter();
bw.writeVarIntBN(BN(1000));
bw.concat().length.should.equal(3);
});
it('should write a 5 byte varInt', function() {
var bw = new BufferWriter();
bw.writeVarIntBN(BN(Math.pow(2, 16 + 1)));
bw.concat().length.should.equal(5);
});
it('should write a 9 byte varInt', function() {
var bw = new BufferWriter();
bw.writeVarIntBN(BN(Math.pow(2, 32 + 1)));
bw.concat().length.should.equal(9);
});
});
});