diff --git a/src/solidity/astHelper.js b/src/solidity/astHelper.js
new file mode 100644
index 0000000000..a140bea55a
--- /dev/null
+++ b/src/solidity/astHelper.js
@@ -0,0 +1,64 @@
+'use strict'
+var AstWalker = require('../util/astWalker')
+
+/**
+  * return all contract definitions of the given @astList
+  *
+  * @param {Object} sourcesList - sources list (containing root AST node)
+  * @return {Object} - returns a mapping from AST node ids to AST nodes for the contracts
+  */
+function extractContractsDefinition (sourcesList) {
+  var ret = {
+    contractsIds: {},
+    contractsNames: {}
+  }
+  var walker = new AstWalker()
+  walker.walkAstList(sourcesList, { 'ContractDefinition': function (node) {
+    ret.contractsIds[node.id] = node
+    ret.contractsNames[node.attributes.name] = node.id
+    return false
+  }})
+  return ret
+}
+
+/**
+  * returns the linearized base contracts of the contract @arg id
+  *
+  * @param {Int} id - contract id to resolve
+  * @param {Map} contracts  - all contracts defined in the current context
+  * @return {Array} - array of base contracts in derived to base order as AST nodes.
+  */
+function getLinearizedBaseContracts (id, contracts) {
+  return contracts[id].attributes.linearizedBaseContracts.map(function (id) { return contracts[id] })
+}
+
+/**
+  * return state var and type definition of the given contract
+  *
+  * @param {String} contractName - contract for which state var should be resolved
+  * @param {Object} sourcesList - sources list (containing root AST node)
+  * @return {Array} - return an array of AST node of all state variables (including inherited) (this will include all enum/struct declarations)
+  */
+function extractStateVariables (contractName, sourcesList) {
+  var contracts = extractContractsDefinition(sourcesList)
+  var id = contracts.contractsNames[contractName]
+  if (id) {
+    var stateVar = []
+    var baseContracts = getLinearizedBaseContracts(id, contracts.contractsIds)
+    baseContracts.reverse()
+    for (var k in baseContracts) {
+      var ctr = baseContracts[k]
+      for (var i in ctr.children) {
+        stateVar.push(ctr.children[i])
+      }
+    }
+    return stateVar
+  }
+  return null
+}
+
+module.exports = {
+  extractStateVariables: extractStateVariables,
+  extractContractsDefinition: extractContractsDefinition,
+  getLinearizedBaseContracts: getLinearizedBaseContracts
+}
diff --git a/src/solidity/decodeInfo.js b/src/solidity/decodeInfo.js
new file mode 100644
index 0000000000..d08ba4fbd3
--- /dev/null
+++ b/src/solidity/decodeInfo.js
@@ -0,0 +1,353 @@
+'use strict'
+
+/**
+  * Uint decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function Uint (type) {
+  if (type.split(' ')) {
+    type = type.split(' ')[0]
+  }
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: parseInt(type.replace('uint', '')) / 8,
+    typeName: type,
+    name: 'uint'
+  }
+}
+
+/**
+  * Address decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function Address (type) {
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: 20,
+    typeName: 'address',
+    name: 'address'
+  }
+}
+
+/**
+  * Bool decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function Bool (type) {
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: 1,
+    typeName: 'bool',
+    name: 'bool'
+  }
+}
+
+/**
+  * DynamicByteArray decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function DynamicByteArray (type) {
+  return {
+    needsFreeStorageSlot: true,
+    storageBytes: 32,
+    typeName: 'bytes',
+    name: 'dynamicByteArray'
+  }
+}
+
+/**
+  * FixedByteArray decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function FixedByteArray (type) {
+  if (type.split(' ')) {
+    type = type.split(' ')[0]
+  }
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: parseInt(type.replace('bytes', '')),
+    typeName: type.split(' ')[0],
+    name: 'fixedByteArray'
+  }
+}
+
+/**
+  * Int decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function Int (type) {
+  if (type.split(' ')) {
+    type = type.split(' ')[0]
+  }
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: parseInt(type.replace('int', '')) / 8,
+    typeName: type,
+    name: 'int'
+  }
+}
+
+/**
+  * StringType decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function StringType (type) {
+  return {
+    needsFreeStorageSlot: true,
+    storageBytes: 32,
+    typeName: 'string',
+    name: 'stringType'
+  }
+}
+
+/**
+  * ArrayType decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder, arraySize, subArray}
+  */
+function ArrayType (type, stateDefinitions) {
+  var arraySize
+  var storageBytes
+
+  var underlyingType = extractUnderlyingType(type)
+
+  arraySize = extractArraySize(type)
+  var dimensions = extractDimensions(type)
+  type = underlyingType + dimensions.join('')
+
+  var subArrayType = type.substring(0, type.lastIndexOf('['))
+  var subArray = null
+  if (subArrayType.indexOf('[') !== -1) {
+    subArray = decode(subArrayType, stateDefinitions)
+  }
+
+  underlyingType = decode(underlyingType, stateDefinitions)
+  storageBytes = underlyingType.storageBytes
+
+  if (arraySize === 'dynamic') {
+    storageBytes = 32
+  } else {
+    if (subArray) {
+      storageBytes = subArray.storageBytes // size on storage of one item of the array
+    }
+    storageBytes = Math.ceil(storageBytes * arraySize) // size on storage of one the whole array
+  }
+
+  return {
+    needsFreeStorageSlot: true,
+    storageBytes: storageBytes,
+    typeName: type,
+    arraySize: arraySize,
+    subArray: subArray,
+    name: 'arrayType'
+  }
+}
+
+/**
+  * Enum decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder}
+  */
+function Enum (type, stateDefinitions) {
+  var extracted = type.split(' ')
+  return {
+    needsFreeStorageSlot: false,
+    storageBytes: 1,
+    typeName: extracted[0] + ' ' + extracted[1],
+    enum: getEnum(type, stateDefinitions),
+    name: 'enum'
+  }
+}
+
+/**
+  * Struct decode the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @return {Object} returns decoded info about the current type: { needsFreeStorageSlot, storageBytes, typeName, decoder, members}
+  */
+function Struct (type, stateDefinitions) {
+  var extracted = type.split(' ')
+  type = extracted[0] + ' ' + extracted[1]
+  var membersDetails = getStructMembers(type, stateDefinitions)
+  return {
+    needsFreeStorageSlot: true,
+    storageBytes: membersDetails.storageBytes,
+    typeName: type,
+    members: membersDetails.members,
+    name: 'struct'
+  }
+}
+
+/**
+  * retrieve enum declaration of the given @arg type
+  *
+  * @param {String} type - type given by the AST
+  * @param {Object} stateDefinitions  - all state declarations given by the AST (including struct and enum type declaration)
+  * @return {Array} - containing all value declaration of the current enum type
+  */
+function getEnum (type, stateDefinitions) {
+  for (var k in stateDefinitions) {
+    var dec = stateDefinitions[k]
+    if (dec.name === 'EnumDefinition' && type.indexOf('enum ' + dec.attributes.name) === 0) {
+      return dec.children
+    }
+  }
+  return null
+}
+
+/**
+  * retrieve memebers declared in the given @arg tye
+  *
+  * @param {String} typeName - name of the struct type (e.g struct <name>)
+  * @param {Object} stateDefinitions  - all state definition given by the AST (including struct and enum type declaration)
+  * @return {Array} containing all members of the current struct type
+  */
+function getStructMembers (typeName, stateDefinitions) {
+  var members = []
+  var storageBytes = 0
+  for (var k in stateDefinitions) {
+    var dec = stateDefinitions[k]
+    if (dec.name === 'StructDefinition' && typeName.indexOf('struct ' + dec.attributes.name) === 0) {
+      for (var i in dec.children) {
+        var member = dec.children[i]
+        var decoded = decode(member.attributes.type, stateDefinitions)
+        members.push(decoded)
+        if (decoded.needsFreeStorageSlot) {
+          storageBytes = Math.ceil(storageBytes / 32) * 32
+        }
+        storageBytes += decoded.storageBytes
+      }
+      break
+    }
+  }
+  return {
+    members: members,
+    storageBytes: storageBytes
+  }
+}
+
+/**
+  * return the size of the current array
+  *
+  * @param {String} typeName - short type ( e.g uint[][4] )
+  * @return {String|Int} return 'dynamic' if dynamic array | return size of the array
+  */
+function extractArraySize (typeName) {
+  if (typeName.indexOf('[') !== -1) {
+    var squareBracket = /\[([0-9]+|\s*)\]/g
+    var dim = typeName.match(squareBracket)
+    var size = dim[dim.length - 1]
+    if (size === '[]') {
+      return 'dynamic'
+    } else {
+      return parseInt(dim[dim.length - 1].replace('[', '').replace(']'))
+    }
+  }
+}
+
+/**
+  * extract the underlying type
+  *
+  * @param {String} fullType - type given by the AST (ex: uint[2] storage ref[2])
+  * @return {String} return the first part of the full type. don not keep the array declaration ( uint[2] storage ref[2] will return uint)
+  */
+function extractUnderlyingType (fullType) {
+  var splitted = fullType.split(' ')
+  if (fullType.indexOf('enum') === 0 || fullType.indexOf('struct') === 0) {
+    return splitted[0] + ' ' + splitted[1]
+  }
+  if (splitted.length > 0) {
+    fullType = splitted[0]
+  }
+  if (fullType[fullType.length - 1] === ']') {
+    return fullType.substring(0, fullType.indexOf('['))
+  }
+  return fullType
+}
+
+/**
+  * get the array dimensions
+  *
+  * @param {String} fullType - type given by the AST
+  * @return {Array} containing all the dimensions and size of the array (e.g ['[3]', '[]'] )
+  */
+function extractDimensions (fullType) {
+  var ret = []
+  if (fullType.indexOf('[') !== -1) {
+    var squareBracket = /\[([0-9]+|\s*)\]/g
+    var dim = fullType.match(squareBracket)
+    return dim
+  }
+  return ret
+}
+
+/**
+  * parse the full type
+  *
+  * @param {String} fullType - type given by the AST (ex: uint[2] storage ref[2])
+  * @return {String} returns the token type (used to instanciate the right decoder) (uint[2] storage ref[2] will return 'array', uint256 will return uintX)
+  */
+function extractTokenType (fullType) {
+  if (fullType.indexOf('[') !== -1) {
+    return 'array'
+  }
+  if (fullType.indexOf(' ') !== -1) {
+    fullType = fullType.split(' ')[0]
+  }
+  var char = fullType.indexOf('bytes') === 0 ? 'X' : ''
+  return fullType.replace(/[0-9]+/g, char)
+}
+
+/**
+  * parse the type and return an object representing the type
+  *
+  * @param {Object} type - type name given by the ast node
+  * @param {Object} stateDefinitions - all state stateDefinitions given by the AST (including struct and enum type declaration)
+  * @return {Object} - return the corresponding decoder
+  */
+function decode (type, stateDefinitions) {
+  var decodeInfos = {
+    'address': Address,
+    'array': ArrayType,
+    'bool': Bool,
+    'bytes': DynamicByteArray,
+    'bytesX': FixedByteArray,
+    'enum': Enum,
+    'string': StringType,
+    'struct': Struct,
+    'int': Int,
+    'uint': Uint
+  }
+  var currentType = extractTokenType(type)
+  return decodeInfos[currentType](type, stateDefinitions)
+}
+
+module.exports = {
+  decode: decode,
+  Uint: Uint,
+  Address: Address,
+  Bool: Bool,
+  DynamicByteArray: DynamicByteArray,
+  FixedByteArray: FixedByteArray,
+  Int: Int,
+  StringType: StringType,
+  ArrayType: ArrayType,
+  Enum: Enum,
+  Struct: Struct
+}
diff --git a/src/util/astWalker.js b/src/util/astWalker.js
index ffd02819c1..38dc3f9337 100644
--- a/src/util/astWalker.js
+++ b/src/util/astWalker.js
@@ -30,6 +30,19 @@ AstWalker.prototype.walk = function (ast, callback) {
   }
 }
 
+/**
+ +  * walk the given @astList
+ +  *
+ +  * @param {Object} sourcesList - sources list (containing root AST node)
+ +  * @param {Function} - callback used by AstWalker to compute response
+ +  */
+AstWalker.prototype.walkAstList = function (sourcesList, callback) {
+  var walker = new AstWalker()
+  for (var k in sourcesList) {
+    walker.walk(sourcesList[k].AST, callback)
+  }
+}
+
 function manageCallBack (node, callback) {
   if (node.name in callback) {
     return callback[node.name](node)