bufferutils: add PUSHDATA implementation

src/bufferutils.js

@@ -1,4 +1,46 @@
 var assert = require('assert')
+var opcodes = require('./opcodes')
+
+function pushDataSize(i) {
+  return i < opcodes.OP_PUSHDATA1 ? 1
+    : i < 0xff        ? 2
+    : i < 0xffff      ? 3
+    :                   5
+}
+
+function readPushDataInt(buffer, offset) {
+  var opcode = buffer.readUInt8(offset)
+  var number, size
+
+  // ~6 bit
+  if (opcode < opcodes.OP_PUSHDATA1) {
+    number = opcode
+    size = 1
+
+  // 8 bit
+  } else if (opcode === opcodes.OP_PUSHDATA1) {
+    number = buffer.readUInt8(offset + 1)
+    size = 2
+
+  // 16 bit
+  } else if (opcode === opcodes.OP_PUSHDATA2) {
+    number = buffer.readUInt16LE(offset + 1)
+    size = 3
+
+  // 32 bit
+  } else {
+    assert.equal(opcode, opcodes.OP_PUSHDATA4, 'Unexpected opcode')
+
+    number = buffer.readUInt32LE(offset + 1)
+    size = 5
+
+  }
+
+  return {
+    number: number,
+    size: size
+  }
+}
 
 function readUInt64LE(buffer, offset) {
   var a = buffer.readUInt32LE(offset)
@@ -16,17 +58,17 @@ function readVarInt(buffer, offset) {
   var t = buffer.readUInt8(offset)
   var number, size
 
-  // 8-bit
+  // 8 bit
   if (t < 253) {
     number = t
     size = 1
 
-  // 16-bit
+  // 16 bit
   } else if (t < 254) {
     number = buffer.readUInt16LE(offset + 1)
     size = 3
 
-  // 32-bit
+  // 32 bit
   } else if (t < 255) {
     number = buffer.readUInt32LE(offset + 1)
     size = 5
@@ -43,6 +85,37 @@ function readVarInt(buffer, offset) {
   }
 }
 
+function writePushDataInt(buffer, number, offset) {
+  var size = pushDataSize(number)
+
+  // ~6 bit
+  if (size === 1) {
+    buffer.writeUInt8(number, offset)
+
+  // 8 bit
+  } else if (size === 2) {
+    buffer.writeUInt8(opcodes.OP_PUSHDATA1, offset)
+    buffer.writeUInt8(number, offset + 1)
+
+  // 16 bit
+  } else if (size === 3) {
+    buffer.writeUInt8(opcodes.OP_PUSHDATA2, offset)
+    buffer.writeUInt16LE(number, offset + 1)
+
+  // 32 bit
+  } else {
+    // Javascript Safe Integer limitation
+    // assert(Number.isSafeInteger(value), 'value must be < 2^53')
+    assert(number < 0x0020000000000000, 'value must be < 2^53')
+
+    buffer.writeUInt8(opcodes.OP_PUSHDATA4, offset)
+    buffer.writeUInt32LE(number, offset + 1)
+
+  }
+
+  return size
+}
+
 function writeUInt64LE(buffer, value, offset) {
   // Javascript Safe Integer limitation
   // assert(Number.isSafeInteger(value), 'value must be < 2^53')
@@ -86,9 +159,12 @@ function writeVarInt(buffer, number, offset) {
 }
 
 module.exports = {
+  pushDataSize: pushDataSize,
+  readPushDataInt: readPushDataInt,
   readUInt64LE: readUInt64LE,
   readVarInt: readVarInt,
   varIntSize: varIntSize,
+  writePushDataInt: writePushDataInt,
   writeUInt64LE: writeUInt64LE,
   writeVarInt: writeVarInt
 }

test/bufferutils.js

@@ -4,6 +4,32 @@ var bufferutils = require('../src/bufferutils')
 var fixtures = require('./fixtures/buffer.json')
 
 describe('bufferutils', function() {
+  describe('pushDataSize', function() {
+    it('matches test vectors', function() {
+      fixtures.valid.forEach(function(f) {
+        if (!f.hexPD) return
+
+        var size = bufferutils.pushDataSize(f.dec)
+
+        assert.equal(size, f.hexPD.length / 2)
+      })
+    })
+  })
+
+  describe('readPushDataInt', function() {
+    it('matches test vectors', function() {
+      fixtures.valid.forEach(function(f) {
+        if (!f.hexPD) return
+
+        var buffer = new Buffer(f.hexPD, 'hex')
+        var d = bufferutils.readPushDataInt(buffer, 0)
+
+        assert.equal(d.number, f.dec)
+        assert.equal(d.size, buffer.length)
+      })
+    })
+  })
+
   describe('readUInt64LE', function() {
     it('matches test vectors', function() {
       fixtures.valid.forEach(function(f) {
@@ -30,14 +56,38 @@ describe('bufferutils', function() {
   describe('varIntSize', function() {
     it('matches test vectors', function() {
       fixtures.valid.forEach(function(f) {
-        var number = parseInt(f.dec)
+        var size = bufferutils.varIntSize(f.dec)
-        var size = bufferutils.varIntSize(number)
 
         assert.equal(size, f.hexVI.length / 2)
       })
     })
   })
 
+  describe('writePushDataInt', function() {
+    it('matches test vectors', function() {
+      fixtures.valid.forEach(function(f, i) {
+        if (!f.hexPD) return
+
+        var buffer = new Buffer(5)
+        buffer.fill(0)
+
+        var n = bufferutils.writePushDataInt(buffer, f.dec, 0)
+        assert.equal(buffer.slice(0, n).toString('hex'), f.hexPD)
+      })
+    })
+
+    fixtures.invalid.forEach(function(f) {
+      it('throws on ' + f.description, function() {
+        var buffer = new Buffer(5)
+        buffer.fill(0)
+
+        assert.throws(function() {
+          bufferutils.writePushDataInt(buffer, f.dec, 0)
+        }, /value must be < 2\^53/)
+      })
+    })
+  })
+
   describe('writeUInt64LE', function() {
     it('matches test vectors', function() {
       fixtures.valid.forEach(function(f) {
@@ -51,12 +101,12 @@ describe('bufferutils', function() {
 
     fixtures.invalid.forEach(function(f) {
       it('throws on ' + f.description, function() {
-        assert.throws(function() {
         var buffer = new Buffer(8)
         buffer.fill(0)
 
+        assert.throws(function() {
           bufferutils.writeUInt64LE(buffer, f.dec, 0)
-        })
+        }, /value must be < 2\^53/)
       })
     })
   })
@@ -74,12 +124,12 @@ describe('bufferutils', function() {
 
     fixtures.invalid.forEach(function(f) {
       it('throws on ' + f.description, function() {
-        assert.throws(function() {
         var buffer = new Buffer(9)
         buffer.fill(0)
 
+        assert.throws(function() {
           bufferutils.writeVarInt(buffer, f.dec, 0)
-        })
+        }, /value must be < 2\^53/)
       })
     })
   })

test/fixtures/buffer.json

@@ -3,47 +3,56 @@
     {
       "dec": 0,
       "hex64": "0000000000000000",
-      "hexVI": "00"
+      "hexVI": "00",
+      "hexPD": "00"
     },
     {
       "dec": 1,
       "hex64": "0100000000000000",
-      "hexVI": "01"
+      "hexVI": "01",
+      "hexPD": "01"
     },
     {
       "dec": 252,
       "hex64": "fc00000000000000",
-      "hexVI": "fc"
+      "hexVI": "fc",
+      "hexPD": "4cfc"
     },
     {
       "dec": 253,
       "hex64": "fd00000000000000",
-      "hexVI": "fdfd00"
+      "hexVI": "fdfd00",
+      "hexPD": "4cfd"
     },
     {
       "dec": 254,
       "hex64": "fe00000000000000",
-      "hexVI": "fdfe00"
+      "hexVI": "fdfe00",
+      "hexPD": "4cfe"
     },
     {
       "dec": 65535,
       "hex64": "ffff000000000000",
-      "hexVI": "fdffff"
+      "hexVI": "fdffff",
+      "hexPD": "4effff0000"
     },
     {
       "dec": 65536,
       "hex64": "0000010000000000",
-      "hexVI": "fe00000100"
+      "hexVI": "fe00000100",
+      "hexPD": "4e00000100"
     },
     {
       "dec": 65537,
       "hex64": "0100010000000000",
-      "hexVI": "fe01000100"
+      "hexVI": "fe01000100",
+      "hexPD": "4e01000100"
     },
     {
       "dec": 4294967295,
       "hex64": "ffffffff00000000",
-      "hexVI": "feffffffff"
+      "hexVI": "feffffffff",
+      "hexPD": "4effffffff"
     },
     {
       "dec": 4294967296,