1 | var opcodes = require('./opcodes.json')
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2 | var varuint = require('varuint-bitcoin')
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3 |
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4 | function pushDataSize (i) {
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5 | return i < opcodes.OP_PUSHDATA1 ? 1
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6 | : i <= 0xff ? 2
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7 | : i <= 0xffff ? 3
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8 | : 5
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9 | }
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10 |
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11 | function readPushDataInt (buffer, offset) {
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12 | var opcode = buffer.readUInt8(offset)
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13 | var number, size
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14 |
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15 |
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16 | if (opcode < opcodes.OP_PUSHDATA1) {
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17 | number = opcode
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18 | size = 1
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19 |
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20 |
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21 | } else if (opcode === opcodes.OP_PUSHDATA1) {
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22 | if (offset + 2 > buffer.length) return null
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23 | number = buffer.readUInt8(offset + 1)
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24 | size = 2
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25 |
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26 |
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27 | } else if (opcode === opcodes.OP_PUSHDATA2) {
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28 | if (offset + 3 > buffer.length) return null
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29 | number = buffer.readUInt16LE(offset + 1)
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30 | size = 3
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31 |
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32 |
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33 | } else {
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34 | if (offset + 5 > buffer.length) return null
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35 | if (opcode !== opcodes.OP_PUSHDATA4) throw new Error('Unexpected opcode')
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36 |
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37 | number = buffer.readUInt32LE(offset + 1)
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38 | size = 5
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39 | }
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40 |
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41 | return {
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42 | opcode: opcode,
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43 | number: number,
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44 | size: size
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45 | }
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46 | }
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47 |
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48 |
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49 | function verifuint (value, max) {
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50 | if (typeof value !== 'number') throw new Error('cannot write a non-number as a number')
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51 | if (value < 0) throw new Error('specified a negative value for writing an unsigned value')
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52 | if (value > max) throw new Error('RangeError: value out of range')
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53 | if (Math.floor(value) !== value) throw new Error('value has a fractional component')
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54 | }
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55 |
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56 | function readUInt64LE (buffer, offset) {
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57 | var a = buffer.readUInt32LE(offset)
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58 | var b = buffer.readUInt32LE(offset + 4)
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59 | b *= 0x100000000
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60 |
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61 | verifuint(b + a, 0x001fffffffffffff)
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62 |
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63 | return b + a
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64 | }
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65 |
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66 | function writePushDataInt (buffer, number, offset) {
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67 | var size = pushDataSize(number)
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68 |
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69 |
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70 | if (size === 1) {
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71 | buffer.writeUInt8(number, offset)
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72 |
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73 |
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74 | } else if (size === 2) {
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75 | buffer.writeUInt8(opcodes.OP_PUSHDATA1, offset)
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76 | buffer.writeUInt8(number, offset + 1)
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77 |
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78 |
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79 | } else if (size === 3) {
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80 | buffer.writeUInt8(opcodes.OP_PUSHDATA2, offset)
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81 | buffer.writeUInt16LE(number, offset + 1)
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82 |
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83 |
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84 | } else {
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85 | buffer.writeUInt8(opcodes.OP_PUSHDATA4, offset)
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86 | buffer.writeUInt32LE(number, offset + 1)
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87 | }
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88 |
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89 | return size
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90 | }
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91 |
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92 | function writeUInt64LE (buffer, value, offset) {
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93 | verifuint(value, 0x001fffffffffffff)
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94 |
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95 | buffer.writeInt32LE(value & -1, offset)
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96 | buffer.writeUInt32LE(Math.floor(value / 0x100000000), offset + 4)
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97 | return offset + 8
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98 | }
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99 |
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100 |
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101 | function readVarInt (buffer, offset) {
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102 | var result = varuint.decode(buffer, offset)
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103 |
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104 | return {
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105 | number: result,
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106 | size: varuint.decode.bytes
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107 | }
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108 | }
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109 |
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110 |
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111 | function writeVarInt (buffer, number, offset) {
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112 | varuint.encode(number, buffer, offset)
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113 | return varuint.encode.bytes
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114 | }
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115 |
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116 | module.exports = {
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117 | pushDataSize: pushDataSize,
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118 | readPushDataInt: readPushDataInt,
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119 | readUInt64LE: readUInt64LE,
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120 | readVarInt: readVarInt,
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121 | varIntBuffer: varuint.encode,
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122 | varIntSize: varuint.encodingLength,
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123 | writePushDataInt: writePushDataInt,
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124 | writeUInt64LE: writeUInt64LE,
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125 | writeVarInt: writeVarInt
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126 | }
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