writer: use 100kb pool for sighashing.

lib/primitives/outpoint.js

@@ -8,7 +8,7 @@
 
 const assert = require('assert');
 const util = require('../utils/util');
-const StaticWriter = require('../utils/writer');
+const StaticWriter = require('../utils/staticwriter');
 const BufferReader = require('../utils/reader');
 const encoding = require('../utils/encoding');
 

lib/primitives/tx.js

@@ -451,7 +451,7 @@ TX.prototype.signatureHashV0 = function signatureHashV0(index, prev, type) {
 
   // Calculate buffer size.
   const size = this.hashSize(index, prev, type);
-  const bw = new StaticWriter(size);
+  const bw = StaticWriter.pool(size);
 
   bw.writeU32(this.version);
 
@@ -615,7 +615,7 @@ TX.prototype.signatureHashV1 = function signatureHashV1(index, prev, value, type
     if (this._hashPrevouts) {
       prevouts = this._hashPrevouts;
     } else {
-      const bw = new StaticWriter(this.inputs.length * 36);
+      const bw = StaticWriter.pool(this.inputs.length * 36);
 
       for (const input of this.inputs)
         input.prevout.toWriter(bw);
@@ -633,7 +633,7 @@ TX.prototype.signatureHashV1 = function signatureHashV1(index, prev, value, type
     if (this._hashSequence) {
       sequences = this._hashSequence;
     } else {
-      const bw = new StaticWriter(this.inputs.length * 4);
+      const bw = StaticWriter.pool(this.inputs.length * 4);
 
       for (const input of this.inputs)
         bw.writeU32(input.sequence);
@@ -655,7 +655,7 @@ TX.prototype.signatureHashV1 = function signatureHashV1(index, prev, value, type
       for (const output of this.outputs)
         size += output.getSize();
 
-      const bw = new StaticWriter(size);
+      const bw = StaticWriter.pool(size);
 
       for (const output of this.outputs)
         output.toWriter(bw);
@@ -673,7 +673,7 @@ TX.prototype.signatureHashV1 = function signatureHashV1(index, prev, value, type
   }
 
   const size = 156 + prev.getVarSize();
-  const bw = new StaticWriter(size);
+  const bw = StaticWriter.pool(size);
 
   bw.writeU32(this.version);
   bw.writeBytes(prevouts);

lib/utils/reader.js

@@ -10,7 +10,8 @@
 const assert = require('assert');
 const encoding = require('./encoding');
 const digest = require('../crypto/digest');
-const EMPTY_BUFFER = Buffer.alloc(0);
+
+const EMPTY = Buffer.alloc(0);
 
 /**
  * An object that allows reading of buffers in a sane manner.
@@ -145,7 +146,7 @@ BufferReader.prototype.endData = function endData(zeroCopy) {
  */
 
 BufferReader.prototype.destroy = function destroy() {
-  this.data = EMPTY_BUFFER;
+  this.data = EMPTY;
   this.offset = 0;
   this.stack.length = 0;
 };

lib/utils/staticwriter.js

@@ -9,7 +9,9 @@
 const assert = require('assert');
 const encoding = require('./encoding');
 const digest = require('../crypto/digest');
-const EMPTY_BUFFER = Buffer.alloc(0);
+
+const POOL = Buffer.allocUnsafeSlow(100 * 1024);
+const EMPTY = Buffer.alloc(0);
 
 /**
  * Statically allocated buffer writer.
@@ -22,24 +24,34 @@ function StaticWriter(size) {
   if (!(this instanceof StaticWriter))
     return new StaticWriter(size);
 
-  this.data = Buffer.allocUnsafe(size);
+  this.data = size ? Buffer.allocUnsafe(size) : EMPTY;
   this.offset = 0;
 }
 
+/**
+ * Allocate writer from preallocated 100kb pool.
+ * @param {Number} size
+ * @returns {StaticWriter}
+ */
+
+StaticWriter.pool = function pool(size) {
+  if (size <= POOL.length) {
+    const bw = new StaticWriter(0);
+    bw.data = POOL.slice(0, size);
+    return bw;
+  }
+  return new StaticWriter(size);
+};
+
 /**
  * Allocate and render the final buffer.
- * @param {Boolean?} keep - Do not destroy the writer.
  * @returns {Buffer} Rendered buffer.
  */
 
-StaticWriter.prototype.render = function render(keep) {
+StaticWriter.prototype.render = function render() {
   const data = this.data;
-
   assert(this.offset === data.length);
-
-  if (!keep)
-    this.destroy();
-
+  this.destroy();
   return data;
 };
 
@@ -66,7 +78,7 @@ StaticWriter.prototype.seek = function seek(offset) {
  */
 
 StaticWriter.prototype.destroy = function destroy() {
-  this.data = EMPTY_BUFFER;
+  this.data = EMPTY;
   this.offset = 0;
 };
 

lib/utils/writer.js

@@ -71,11 +71,10 @@ function BufferWriter() {
 
 /**
  * Allocate and render the final buffer.
- * @param {Boolean?} keep - Do not destroy the writer.
  * @returns {Buffer} Rendered buffer.
  */
 
-BufferWriter.prototype.render = function render(keep) {
+BufferWriter.prototype.render = function render() {
   const data = Buffer.allocUnsafe(this.offset);
   let off = 0;
 
@@ -183,8 +182,7 @@ BufferWriter.prototype.render = function render(keep) {
 
   assert(off === data.length);
 
-  if (!keep)
-    this.destroy();
+  this.destroy();
 
   return data;
 };