From 8b76861318b402923c77b2f55f64be54734a8cc9 Mon Sep 17 00:00:00 2001
From: cdetrio <cdetrio@gmail.com>
Date: Tue, 2 May 2017 12:18:08 -0400
Subject: [PATCH 01/11] initial support for mapping types

---
 src/helpers/traceHelper.js       |  4 ++
 src/solidity/decodeInfo.js       | 19 +++++++--
 src/solidity/types/Mapping.js    | 52 ++++++++++++++++++++++--
 src/solidity/types/StringType.js |  2 +-
 src/trace/traceAnalyser.js       | 16 ++++++++
 src/trace/traceCache.js          | 14 +++++++
 src/ui/SolidityState.js          | 68 ++++++++++++++++++++++++++++++--
 src/ui/SolidityTypeFormatter.js  |  9 ++++-
 8 files changed, 170 insertions(+), 14 deletions(-)

diff --git a/src/helpers/traceHelper.js b/src/helpers/traceHelper.js
index 8d2a560d3..6e66c6cbd 100644
--- a/src/helpers/traceHelper.js
+++ b/src/helpers/traceHelper.js
@@ -37,6 +37,10 @@ module.exports = {
     return step.op === 'SSTORE'
   },
 
+  isSHA3Instruction: function (step) {
+    return step.op === 'SHA3'
+  },
+
   newContextStorage: function (step) {
     return step.op === 'CREATE' || step.op === 'CALL'
   },
diff --git a/src/solidity/decodeInfo.js b/src/solidity/decodeInfo.js
index aaee05cd7..4dbd1d341 100644
--- a/src/solidity/decodeInfo.js
+++ b/src/solidity/decodeInfo.js
@@ -19,8 +19,19 @@ var util = require('./types/util')
   * @param {String} type - type given by the AST
   * @return {Object} returns decoded info about the current type: { storageBytes, typeName}
   */
-function mapping (type) {
-  return new MappingType()
+function mapping (type, stateDefinitions, contractName) {
+  var match = type.match(/mapping\((.*?)( =>)? (.*)\)$/)
+  var keyTypeName = match[1]
+  var valueTypeName = match[3]
+
+  var keyType = parseType(keyTypeName, stateDefinitions, contractName, 'storage')
+  var valueType = parseType(valueTypeName, stateDefinitions, contractName, 'storage')
+
+  var underlyingTypes = {
+    'keyType': keyType,
+    'valueType': valueType
+  }
+  return new MappingType(underlyingTypes, 'location', util.removeLocation(type))
 }
 
 /**
@@ -179,7 +190,7 @@ function struct (type, stateDefinitions, contractName, location) {
     if (!location) {
       location = match[2].trim()
     }
-    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName, location) // type is used to extract the ast struct definition
+    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName) // type is used to extract the ast struct definition
     if (!memberDetails) return null
     return new StructType(memberDetails, location, match[1])
   } else {
@@ -222,7 +233,7 @@ function getEnum (type, stateDefinitions, contractName) {
   * @param {String} location - location of the data (storage ref| storage pointer| memory| calldata)
   * @return {Array} containing all members of the current struct type
   */
-function getStructMembers (type, stateDefinitions, contractName, location) {
+function getStructMembers (type, stateDefinitions, contractName) {
   var split = type.split('.')
   if (!split.length) {
     type = contractName + '.' + type
diff --git a/src/solidity/types/Mapping.js b/src/solidity/types/Mapping.js
index e61df4720..0e62012af 100644
--- a/src/solidity/types/Mapping.js
+++ b/src/solidity/types/Mapping.js
@@ -1,20 +1,41 @@
 'use strict'
 var RefType = require('./RefType')
+var ethutil = require('ethereumjs-util')
 
 class Mapping extends RefType {
-  constructor () {
-    super(1, 32, 'mapping', 'storage')
+  constructor (underlyingTypes, location, fullType) {
+    super(1, 32, fullType, 'storage')
+    this.keyType = underlyingTypes.keyType
+    this.valueType = underlyingTypes.valueType
+  }
+
+  setMappingElements (mappingKeyPreimages) {
+    this.preimages = mappingKeyPreimages
   }
 
   async decodeFromStorage (location, storageResolver) {
+    // location.offset should always be 0 for a mapping (?? double check)
+
+    var ret = {}
+    for (var i in this.preimages) {
+      var preimage = this.preimages[i]
+      var mapLocation = getMappingLocation(preimage, location.slot)
+      var globalLocation = {
+        offset: location.offset,
+        slot: mapLocation
+      }
+      ret[preimage] = await this.valueType.decodeFromStorage(globalLocation, storageResolver)
+    }
+
     return {
-      value: '<not implemented>',
-      length: '0x',
+      value: ret,
       type: this.typeName
     }
   }
 
   decodeFromMemoryInternal (offset, memory) {
+    // mappings can only exist in storage and not in memory
+    // so this should never be called
     return {
       value: '<not implemented>',
       length: '0x',
@@ -23,4 +44,27 @@ class Mapping extends RefType {
   }
 }
 
+function getMappingLocation (key, position) {
+  // mapping storage location decribed at http://solidity.readthedocs.io/en/develop/miscellaneous.html#layout-of-state-variables-in-storage
+  // > the value corresponding to a mapping key k is located at keccak256(k . p) where . is concatenation.
+
+  // key should be a hex string, and position an int
+  var mappingK = ethutil.toBuffer('0x' + key)
+  mappingK = ethutil.setLengthLeft(mappingK, 32)
+  var mappingP = ethutil.intToBuffer(position)
+  mappingP = ethutil.setLengthLeft(mappingP, 32)
+  var mappingKeyBuf = concatTypedArrays(mappingK, mappingP)
+  var mappingKeyPreimage = '0x' + mappingKeyBuf.toString('hex')
+  var mappingStorageLocation = ethutil.sha3(mappingKeyPreimage)
+  mappingStorageLocation = new ethutil.BN(mappingStorageLocation, 16)
+  return mappingStorageLocation
+}
+
+function concatTypedArrays (a, b) { // a, b TypedArray of same type
+  let c = new (a.constructor)(a.length + b.length)
+  c.set(a, 0)
+  c.set(b, a.length)
+  return c
+}
+
 module.exports = Mapping
diff --git a/src/solidity/types/StringType.js b/src/solidity/types/StringType.js
index f21eac4a5..a74b6745a 100644
--- a/src/solidity/types/StringType.js
+++ b/src/solidity/types/StringType.js
@@ -40,7 +40,7 @@ function format (decoded) {
   var value = decoded.value
   value = value.replace('0x', '').replace(/(..)/g, '%$1')
   var ret = {
-    length: decoded.length,
+    // length: decoded.length, // unneeded, only dynamicBytes uses length
     raw: decoded.value,
     type: 'string'
   }
diff --git a/src/trace/traceAnalyser.js b/src/trace/traceAnalyser.js
index 66aefa2c5..2dd60fbad 100644
--- a/src/trace/traceAnalyser.js
+++ b/src/trace/traceAnalyser.js
@@ -1,5 +1,6 @@
 'use strict'
 var traceHelper = require('../helpers/traceHelper')
+var ethutil = require('ethereumjs-util')
 
 function TraceAnalyser (_cache) {
   this.traceCache = _cache
@@ -71,6 +72,18 @@ TraceAnalyser.prototype.buildMemory = function (index, step) {
   }
 }
 
+function getSha3Input (stack, memory) {
+  var memoryStart = stack[stack.length - 1]
+  var memoryLength = stack[stack.length - 2]
+  var memStartDec = (new ethutil.BN(memoryStart.replace('0x', ''), 16)).toString(10)
+  memoryStart = parseInt(memStartDec) * 2
+  var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
+  memoryLength = parseInt(memLengthDec) * 2
+  var memoryHex = memory.join('')
+  var sha3Input = memoryHex.substr(memoryStart, memoryLength)
+  return sha3Input
+}
+
 TraceAnalyser.prototype.buildStorage = function (index, step, context) {
   if (traceHelper.newContextStorage(step) && !traceHelper.isCallToPrecompiledContract(index, this.trace)) {
     var calledAddress = traceHelper.resolveCalledAddress(index, this.trace)
@@ -80,6 +93,9 @@ TraceAnalyser.prototype.buildStorage = function (index, step, context) {
       console.log('unable to build storage changes. ' + index + ' does not match with a CALL. storage changes will be corrupted')
     }
     this.traceCache.pushStoreChanges(index + 1, context.storageContext[context.storageContext.length - 1])
+  } else if (traceHelper.isSHA3Instruction(step)) {
+    var sha3Input = getSha3Input(step.stack, step.memory)
+    this.traceCache.pushSha3Preimage(sha3Input, context.storageContext[context.storageContext.length - 1])
   } else if (traceHelper.isSSTOREInstruction(step)) {
     this.traceCache.pushStoreChanges(index + 1, context.storageContext[context.storageContext.length - 1], step.stack[step.stack.length - 1], step.stack[step.stack.length - 2])
   } else if (traceHelper.isReturnInstruction(step)) {
diff --git a/src/trace/traceCache.js b/src/trace/traceCache.js
index 71f14be8e..edff2aa98 100644
--- a/src/trace/traceCache.js
+++ b/src/trace/traceCache.js
@@ -1,5 +1,6 @@
 'use strict'
 var helper = require('../helpers/util')
+var ethutil = require('ethereumjs-util')
 
 function TraceCache () {
   this.init()
@@ -20,6 +21,9 @@ TraceCache.prototype.init = function () {
   this.memoryChanges = []
   this.storageChanges = []
   this.sstore = {} // all sstore occurence in the trace
+  if (!this.sha3Preimages) { // need to accumulate the preimages over multiple tx's, so dont clear
+    this.sha3Preimages = {}
+  }
 }
 
 TraceCache.prototype.pushSteps = function (index, currentCallIndex) {
@@ -92,6 +96,16 @@ TraceCache.prototype.pushStoreChanges = function (index, address, key, value) {
   this.storageChanges.push(index)
 }
 
+TraceCache.prototype.pushSha3Preimage = function (sha3Input, address) {
+  console.log('pushSha3Preimage sha3Input:', sha3Input)
+  var preimage = sha3Input
+  var imageHash = ethutil.sha3('0x' + sha3Input).toString('hex')
+  this.sha3Preimages[imageHash] = {
+    'address': address,
+    'preimage': preimage
+  }
+}
+
 TraceCache.prototype.accumulateStorageChanges = function (index, address, storage) {
   var ret = Object.assign({}, storage)
   for (var k in this.storageChanges) {
diff --git a/src/ui/SolidityState.js b/src/ui/SolidityState.js
index ed684f1b0..691e91131 100644
--- a/src/ui/SolidityState.js
+++ b/src/ui/SolidityState.js
@@ -3,6 +3,8 @@ var DropdownPanel = require('./DropdownPanel')
 var stateDecoder = require('../solidity/stateDecoder')
 var solidityTypeFormatter = require('./SolidityTypeFormatter')
 var StorageViewer = require('../storage/storageViewer')
+var util = require('../solidity/types/util')
+var ethutil = require('ethereumjs-util')
 var yo = require('yo-yo')
 
 function SolidityState (_parent, _traceManager, _codeManager, _solidityProxy) {
@@ -64,9 +66,28 @@ SolidityState.prototype.init = function () {
               tx: self.parent.tx,
               address: address
             }, self.storageResolver, self.traceManager)
-            stateDecoder.decodeState(stateVars, storageViewer).then((result) => {
-              if (!result.error) {
-                self.basicPanel.update(result)
+
+            var storageJSON = {}
+            storageViewer.storageRange(function (error, result) {
+              if (!error) {
+                storageJSON = result
+                var sha3Preimages = self.traceManager.traceCache.sha3Preimages
+                var mappingPreimages = getMappingPreimages(stateVars, storageJSON, sha3Preimages)
+
+                for (var k in stateVars) {
+                  var stateVar = stateVars[k]
+                  if (stateVar.type.typeName.indexOf('mapping') === 0) {
+                    var mapSlot = util.toBN(stateVar.storagelocation.slot).toString(16)
+                    mapSlot = ethutil.setLengthLeft('0x' + mapSlot, 32).toString('hex')
+                    stateVar.type.setMappingElements(mappingPreimages[mapSlot])
+                  }
+                }
+
+                stateDecoder.decodeState(stateVars, storageViewer).then((result) => {
+                  if (!result.error) {
+                    self.basicPanel.update(result)
+                  }
+                })
               }
             })
           }
@@ -76,4 +97,45 @@ SolidityState.prototype.init = function () {
   })
 }
 
+function getMappingPreimages (stateVars, storage, preimages) {
+  // loop over stateVars and get the locations of all the mappings
+  // then on each mapping, pass its specific preimage keys
+
+  // first filter out all non-mapping storage slots
+
+  var ignoreSlots = []
+  for (var k in stateVars) {
+    var stateVar = stateVars[k]
+    if (stateVar.type.typeName.indexOf('mapping') !== 0) {
+      ignoreSlots.push(stateVar.storagelocation.slot.toString())
+    }
+  }
+
+  var possibleMappings = []
+  for (var hashedLoc in storage) {
+    var slotNum = util.toBN(storage[hashedLoc].key).toString(10)
+    if (ignoreSlots.indexOf(slotNum) === -1) {
+      possibleMappings.push(storage[hashedLoc].key)
+    }
+  }
+
+  var storageMappings = {}
+  for (var pk in possibleMappings) {
+    var possMapKey = possibleMappings[pk].replace('0x', '')
+    if (preimages[possMapKey]) {
+      // got preimage!
+      var preimage = preimages[possMapKey].preimage
+      // get mapping position (i.e. storage slot), its the last 32 bytes
+      var slotByteOffset = preimage.length - 64
+      var mappingSlot = preimage.substr(slotByteOffset)
+      var mappingKey = preimage.substr(0, slotByteOffset)
+      if (!storageMappings[mappingSlot]) {
+        storageMappings[mappingSlot] = []
+      }
+      storageMappings[mappingSlot].push(mappingKey)
+    }
+  }
+  return storageMappings
+}
+
 module.exports = SolidityState
diff --git a/src/ui/SolidityTypeFormatter.js b/src/ui/SolidityTypeFormatter.js
index cfb03d99d..1d4b60af0 100644
--- a/src/ui/SolidityTypeFormatter.js
+++ b/src/ui/SolidityTypeFormatter.js
@@ -41,6 +41,12 @@ function extractData (item, parent, key) {
     })
     ret.self = item.type
     ret.isStruct = true
+  } else if (item.type.indexOf('mapping') === 0) {
+    ret.children = Object.keys((item.value || {})).map(function (key) {
+      return {key: key, value: item.value[key]}
+    })
+    ret.isMapping = true
+    ret.self = item.type
   } else {
     ret.children = []
     ret.self = item.value
@@ -51,7 +57,7 @@ function extractData (item, parent, key) {
 
 function fontColor (data) {
   var color = '#124B46'
-  if (data.isArray || data.isStruct) {
+  if (data.isArray || data.isStruct || data.isMapping) {
     color = '#847979'
   } else if (data.type.indexOf('uint') === 0 ||
               data.type.indexOf('int') === 0 ||
@@ -63,4 +69,3 @@ function fontColor (data) {
   }
   return 'color:' + color
 }
-

From aef34c6dd334f2d67ca11741a0e5cd4bb8961c52 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Thu, 18 May 2017 16:46:20 +0200
Subject: [PATCH 02/11] move sha3 mapping from traceChache to web3VMProvider -
 add we3.debug.preimage - move mapping resolver from soliditystate to
 storageViewer

---
 src/solidity/decodeInfo.js         |  4 +-
 src/solidity/types/Mapping.js      | 25 ++++++-----
 src/solidity/types/StringType.js   |  2 +-
 src/storage/mappingPreimages.js    | 58 +++++++++++++++++++++++++
 src/storage/storageViewer.js       | 12 ++++++
 src/trace/traceAnalyser.js         | 16 -------
 src/trace/traceCache.js            | 14 ------
 src/ui/SolidityState.js            | 68 ++----------------------------
 src/util/web3Admin.js              |  9 ++++
 src/web3Provider/web3VmProvider.js | 32 ++++++++++++++
 10 files changed, 132 insertions(+), 108 deletions(-)
 create mode 100644 src/storage/mappingPreimages.js

diff --git a/src/solidity/decodeInfo.js b/src/solidity/decodeInfo.js
index 4dbd1d341..a31e4e175 100644
--- a/src/solidity/decodeInfo.js
+++ b/src/solidity/decodeInfo.js
@@ -190,7 +190,7 @@ function struct (type, stateDefinitions, contractName, location) {
     if (!location) {
       location = match[2].trim()
     }
-    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName) // type is used to extract the ast struct definition
+    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName, location) // type is used to extract the ast struct definition
     if (!memberDetails) return null
     return new StructType(memberDetails, location, match[1])
   } else {
@@ -233,7 +233,7 @@ function getEnum (type, stateDefinitions, contractName) {
   * @param {String} location - location of the data (storage ref| storage pointer| memory| calldata)
   * @return {Array} containing all members of the current struct type
   */
-function getStructMembers (type, stateDefinitions, contractName) {
+function getStructMembers (type, stateDefinitions, contractName, location) {
   var split = type.split('.')
   if (!split.length) {
     type = contractName + '.' + type
diff --git a/src/solidity/types/Mapping.js b/src/solidity/types/Mapping.js
index 0e62012af..ae21c774c 100644
--- a/src/solidity/types/Mapping.js
+++ b/src/solidity/types/Mapping.js
@@ -1,5 +1,6 @@
 'use strict'
 var RefType = require('./RefType')
+var util = require('./util')
 var ethutil = require('ethereumjs-util')
 
 class Mapping extends RefType {
@@ -9,22 +10,26 @@ class Mapping extends RefType {
     this.valueType = underlyingTypes.valueType
   }
 
-  setMappingElements (mappingKeyPreimages) {
-    this.preimages = mappingKeyPreimages
-  }
-
   async decodeFromStorage (location, storageResolver) {
-    // location.offset should always be 0 for a mapping (?? double check)
-
+    try {
+      var mappingsPreimages = await storageResolver.mappingPreimages()
+    } catch (e) {
+      return {
+        value: '<error> ' + e.message,
+        type: this.type
+      }
+    }
+    var mapSlot = util.toBN(location.slot).toString(16)
+    mapSlot = ethutil.setLengthLeft('0x' + mapSlot, 32).toString('hex')
+    var mappingPreimages = mappingsPreimages[mapSlot]
     var ret = {}
-    for (var i in this.preimages) {
-      var preimage = this.preimages[i]
-      var mapLocation = getMappingLocation(preimage, location.slot)
+    for (var i in mappingPreimages) {
+      var mapLocation = getMappingLocation(i, location.slot)
       var globalLocation = {
         offset: location.offset,
         slot: mapLocation
       }
-      ret[preimage] = await this.valueType.decodeFromStorage(globalLocation, storageResolver)
+      ret[i] = await this.valueType.decodeFromStorage(globalLocation, storageResolver)
     }
 
     return {
diff --git a/src/solidity/types/StringType.js b/src/solidity/types/StringType.js
index a74b6745a..f21eac4a5 100644
--- a/src/solidity/types/StringType.js
+++ b/src/solidity/types/StringType.js
@@ -40,7 +40,7 @@ function format (decoded) {
   var value = decoded.value
   value = value.replace('0x', '').replace(/(..)/g, '%$1')
   var ret = {
-    // length: decoded.length, // unneeded, only dynamicBytes uses length
+    length: decoded.length,
     raw: decoded.value,
     type: 'string'
   }
diff --git a/src/storage/mappingPreimages.js b/src/storage/mappingPreimages.js
new file mode 100644
index 000000000..b85901e8e
--- /dev/null
+++ b/src/storage/mappingPreimages.js
@@ -0,0 +1,58 @@
+var global = require('../helpers/global')
+
+module.exports = {
+  extractMappingPreimages: extractMappingPreimages
+}
+
+async function extractMappingPreimages (storageViewer) {
+  return new Promise((resolve, reject) => {
+    storageViewer.storageRange(function (error, storage) {
+      if (!error) {
+        decodeMappingsKeys(storage, (error, mappings) => {
+          if (error) {
+            reject(error)
+          } else {
+            resolve(mappings)
+          }
+        })
+      } else {
+        reject(error)
+      }
+    })
+  })
+}
+
+async function decodeMappingsKeys (storage, callback) {
+  var ret = {}
+  for (var hashedLoc in storage) {
+    var preimage
+    try {
+      preimage = await getPreimage(storage[hashedLoc].key)
+    } catch (e) {
+    }
+    if (preimage) {
+      // got preimage!
+      // get mapping position (i.e. storage slot), its the last 32 bytes
+      var slotByteOffset = preimage.length - 64
+      var mappingSlot = preimage.substr(slotByteOffset)
+      var mappingKey = preimage.substr(0, slotByteOffset)
+      if (!ret[mappingSlot]) {
+        ret[mappingSlot] = {}
+      }
+      ret[mappingSlot][mappingKey] = preimage
+    }
+  }
+  callback(null, ret)
+}
+
+function getPreimage (key) {
+  return new Promise((resolve, reject) => {
+    global.web3.debug.preimage(key, function (error, preimage) {
+      if (error) {
+        reject(error)
+      } else {
+        resolve(preimage)
+      }
+    })
+  })
+}
diff --git a/src/storage/storageViewer.js b/src/storage/storageViewer.js
index ca117f5b6..289805e89 100644
--- a/src/storage/storageViewer.js
+++ b/src/storage/storageViewer.js
@@ -1,10 +1,15 @@
 'use strict'
 var helper = require('../helpers/util')
+var mappingPreimagesExtractor = require('./mappingPreimages')
 
 class StorageViewer {
   constructor (_context, _storageResolver, _traceManager) {
     this.context = _context
     this.storageResolver = _storageResolver
+    // contains [mappingSlot][mappingkey] = preimage
+    // this map is renewed for each execution step
+    // this map is shared among all the mapping types
+    this.mappingsPreimages = null
     _traceManager.accumulateStorageChanges(this.context.stepIndex, this.context.address, {}, (error, storageChanges) => {
       if (!error) {
         this.storageChanges = storageChanges
@@ -58,6 +63,13 @@ class StorageViewer {
   isComplete (address) {
     return this.storageResolver.isComplete(address)
   }
+
+  async mappingPreimages () {
+    if (!this.mappingsPreimages) {
+      this.mappingsPreimages = await mappingPreimagesExtractor.extractMappingPreimages(this)
+    }
+    return this.mappingsPreimages
+  }
 }
 
 module.exports = StorageViewer
diff --git a/src/trace/traceAnalyser.js b/src/trace/traceAnalyser.js
index 2dd60fbad..66aefa2c5 100644
--- a/src/trace/traceAnalyser.js
+++ b/src/trace/traceAnalyser.js
@@ -1,6 +1,5 @@
 'use strict'
 var traceHelper = require('../helpers/traceHelper')
-var ethutil = require('ethereumjs-util')
 
 function TraceAnalyser (_cache) {
   this.traceCache = _cache
@@ -72,18 +71,6 @@ TraceAnalyser.prototype.buildMemory = function (index, step) {
   }
 }
 
-function getSha3Input (stack, memory) {
-  var memoryStart = stack[stack.length - 1]
-  var memoryLength = stack[stack.length - 2]
-  var memStartDec = (new ethutil.BN(memoryStart.replace('0x', ''), 16)).toString(10)
-  memoryStart = parseInt(memStartDec) * 2
-  var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
-  memoryLength = parseInt(memLengthDec) * 2
-  var memoryHex = memory.join('')
-  var sha3Input = memoryHex.substr(memoryStart, memoryLength)
-  return sha3Input
-}
-
 TraceAnalyser.prototype.buildStorage = function (index, step, context) {
   if (traceHelper.newContextStorage(step) && !traceHelper.isCallToPrecompiledContract(index, this.trace)) {
     var calledAddress = traceHelper.resolveCalledAddress(index, this.trace)
@@ -93,9 +80,6 @@ TraceAnalyser.prototype.buildStorage = function (index, step, context) {
       console.log('unable to build storage changes. ' + index + ' does not match with a CALL. storage changes will be corrupted')
     }
     this.traceCache.pushStoreChanges(index + 1, context.storageContext[context.storageContext.length - 1])
-  } else if (traceHelper.isSHA3Instruction(step)) {
-    var sha3Input = getSha3Input(step.stack, step.memory)
-    this.traceCache.pushSha3Preimage(sha3Input, context.storageContext[context.storageContext.length - 1])
   } else if (traceHelper.isSSTOREInstruction(step)) {
     this.traceCache.pushStoreChanges(index + 1, context.storageContext[context.storageContext.length - 1], step.stack[step.stack.length - 1], step.stack[step.stack.length - 2])
   } else if (traceHelper.isReturnInstruction(step)) {
diff --git a/src/trace/traceCache.js b/src/trace/traceCache.js
index edff2aa98..71f14be8e 100644
--- a/src/trace/traceCache.js
+++ b/src/trace/traceCache.js
@@ -1,6 +1,5 @@
 'use strict'
 var helper = require('../helpers/util')
-var ethutil = require('ethereumjs-util')
 
 function TraceCache () {
   this.init()
@@ -21,9 +20,6 @@ TraceCache.prototype.init = function () {
   this.memoryChanges = []
   this.storageChanges = []
   this.sstore = {} // all sstore occurence in the trace
-  if (!this.sha3Preimages) { // need to accumulate the preimages over multiple tx's, so dont clear
-    this.sha3Preimages = {}
-  }
 }
 
 TraceCache.prototype.pushSteps = function (index, currentCallIndex) {
@@ -96,16 +92,6 @@ TraceCache.prototype.pushStoreChanges = function (index, address, key, value) {
   this.storageChanges.push(index)
 }
 
-TraceCache.prototype.pushSha3Preimage = function (sha3Input, address) {
-  console.log('pushSha3Preimage sha3Input:', sha3Input)
-  var preimage = sha3Input
-  var imageHash = ethutil.sha3('0x' + sha3Input).toString('hex')
-  this.sha3Preimages[imageHash] = {
-    'address': address,
-    'preimage': preimage
-  }
-}
-
 TraceCache.prototype.accumulateStorageChanges = function (index, address, storage) {
   var ret = Object.assign({}, storage)
   for (var k in this.storageChanges) {
diff --git a/src/ui/SolidityState.js b/src/ui/SolidityState.js
index 691e91131..ed684f1b0 100644
--- a/src/ui/SolidityState.js
+++ b/src/ui/SolidityState.js
@@ -3,8 +3,6 @@ var DropdownPanel = require('./DropdownPanel')
 var stateDecoder = require('../solidity/stateDecoder')
 var solidityTypeFormatter = require('./SolidityTypeFormatter')
 var StorageViewer = require('../storage/storageViewer')
-var util = require('../solidity/types/util')
-var ethutil = require('ethereumjs-util')
 var yo = require('yo-yo')
 
 function SolidityState (_parent, _traceManager, _codeManager, _solidityProxy) {
@@ -66,28 +64,9 @@ SolidityState.prototype.init = function () {
               tx: self.parent.tx,
               address: address
             }, self.storageResolver, self.traceManager)
-
-            var storageJSON = {}
-            storageViewer.storageRange(function (error, result) {
-              if (!error) {
-                storageJSON = result
-                var sha3Preimages = self.traceManager.traceCache.sha3Preimages
-                var mappingPreimages = getMappingPreimages(stateVars, storageJSON, sha3Preimages)
-
-                for (var k in stateVars) {
-                  var stateVar = stateVars[k]
-                  if (stateVar.type.typeName.indexOf('mapping') === 0) {
-                    var mapSlot = util.toBN(stateVar.storagelocation.slot).toString(16)
-                    mapSlot = ethutil.setLengthLeft('0x' + mapSlot, 32).toString('hex')
-                    stateVar.type.setMappingElements(mappingPreimages[mapSlot])
-                  }
-                }
-
-                stateDecoder.decodeState(stateVars, storageViewer).then((result) => {
-                  if (!result.error) {
-                    self.basicPanel.update(result)
-                  }
-                })
+            stateDecoder.decodeState(stateVars, storageViewer).then((result) => {
+              if (!result.error) {
+                self.basicPanel.update(result)
               }
             })
           }
@@ -97,45 +76,4 @@ SolidityState.prototype.init = function () {
   })
 }
 
-function getMappingPreimages (stateVars, storage, preimages) {
-  // loop over stateVars and get the locations of all the mappings
-  // then on each mapping, pass its specific preimage keys
-
-  // first filter out all non-mapping storage slots
-
-  var ignoreSlots = []
-  for (var k in stateVars) {
-    var stateVar = stateVars[k]
-    if (stateVar.type.typeName.indexOf('mapping') !== 0) {
-      ignoreSlots.push(stateVar.storagelocation.slot.toString())
-    }
-  }
-
-  var possibleMappings = []
-  for (var hashedLoc in storage) {
-    var slotNum = util.toBN(storage[hashedLoc].key).toString(10)
-    if (ignoreSlots.indexOf(slotNum) === -1) {
-      possibleMappings.push(storage[hashedLoc].key)
-    }
-  }
-
-  var storageMappings = {}
-  for (var pk in possibleMappings) {
-    var possMapKey = possibleMappings[pk].replace('0x', '')
-    if (preimages[possMapKey]) {
-      // got preimage!
-      var preimage = preimages[possMapKey].preimage
-      // get mapping position (i.e. storage slot), its the last 32 bytes
-      var slotByteOffset = preimage.length - 64
-      var mappingSlot = preimage.substr(slotByteOffset)
-      var mappingKey = preimage.substr(0, slotByteOffset)
-      if (!storageMappings[mappingSlot]) {
-        storageMappings[mappingSlot] = []
-      }
-      storageMappings[mappingSlot].push(mappingKey)
-    }
-  }
-  return storageMappings
-}
-
 module.exports = SolidityState
diff --git a/src/util/web3Admin.js b/src/util/web3Admin.js
index fa9350f6a..4ebb9c910 100644
--- a/src/util/web3Admin.js
+++ b/src/util/web3Admin.js
@@ -6,6 +6,15 @@ module.exports = {
     }
     // DEBUG
     var methods = []
+    if (!(web3.debug && web3.debug.preimage)) {
+      methods.push(new web3._extend.Method({
+        name: 'preimage',
+        call: 'debug_preimage',
+        inputFormatter: [null],
+        params: 1
+      }))
+    }
+
     if (!(web3.debug && web3.debug.traceTransaction)) {
       methods.push(new web3._extend.Method({
         name: 'traceTransaction',
diff --git a/src/web3Provider/web3VmProvider.js b/src/web3Provider/web3VmProvider.js
index e53d6a0b5..741022f20 100644
--- a/src/web3Provider/web3VmProvider.js
+++ b/src/web3Provider/web3VmProvider.js
@@ -1,6 +1,7 @@
 var util = require('../helpers/util')
 var uiutil = require('../helpers/ui')
 var traceHelper = require('../helpers/traceHelper')
+var ethutil = require('ethereumjs-util')
 var Web3 = require('web3')
 
 function web3VmProvider () {
@@ -22,9 +23,11 @@ function web3VmProvider () {
   this.eth.getBlockNumber = function (cb) { return self.getBlockNumber(cb) }
   this.debug.traceTransaction = function (hash, options, cb) { return self.traceTransaction(hash, options, cb) }
   this.debug.storageRangeAt = function (blockNumber, txIndex, address, start, end, maxLength, cb) { return self.storageRangeAt(blockNumber, txIndex, address, start, end, maxLength, cb) }
+  this.debug.preimage = function (hashedKey, cb) { return self.preimage(hashedKey, cb) }
   this.providers = { 'HttpProvider': function (url) {} }
   this.currentProvider = {'host': 'vm provider'}
   this.storageCache = {}
+  this.sha3Preimages = {}
 }
 
 web3VmProvider.prototype.setVM = function (vm) {
@@ -128,6 +131,10 @@ web3VmProvider.prototype.pushTrace = function (self, data) {
       }
     }
   }
+  if (traceHelper.isSHA3Instruction(step)) {
+    var sha3Input = getSha3Input(step.stack, step.memory)
+    pushSha3Preimage(this, sha3Input)
+  }
   this.processingIndex++
   this.previousDepth = depth
 }
@@ -189,4 +196,29 @@ web3VmProvider.prototype.getTransactionFromBlock = function (blockNumber, txInde
   }
 }
 
+web3VmProvider.prototype.preimage = function (hashedKey, cb) {
+  hashedKey = hashedKey.replace('0x', '')
+  cb(null, this.sha3Preimages[hashedKey] !== undefined ? this.sha3Preimages[hashedKey].preimage : null)
+}
+
+function pushSha3Preimage (self, sha3Input) {
+  var preimage = sha3Input
+  var imageHash = ethutil.sha3('0x' + sha3Input).toString('hex')
+  self.sha3Preimages[imageHash] = {
+    'preimage': preimage
+  }
+}
+
+function getSha3Input (stack, memory) {
+  var memoryStart = stack[stack.length - 1]
+  var memoryLength = stack[stack.length - 2]
+  var memStartDec = (new ethutil.BN(memoryStart.replace('0x', ''), 16)).toString(10)
+  memoryStart = parseInt(memStartDec) * 2
+  var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
+  memoryLength = parseInt(memLengthDec) * 2
+  var memoryHex = memory.join('')
+  var sha3Input = memoryHex.substr(memoryStart, memoryLength)
+  return sha3Input
+}
+
 module.exports = web3VmProvider

From 3ff34f1f3aa3410f398393166c673c987bc04b91 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Fri, 19 May 2017 13:51:59 +0200
Subject: [PATCH 03/11] remove location from getStructMembers

---
 src/solidity/decodeInfo.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/solidity/decodeInfo.js b/src/solidity/decodeInfo.js
index a31e4e175..c0d9238a4 100644
--- a/src/solidity/decodeInfo.js
+++ b/src/solidity/decodeInfo.js
@@ -190,7 +190,7 @@ function struct (type, stateDefinitions, contractName, location) {
     if (!location) {
       location = match[2].trim()
     }
-    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName, location) // type is used to extract the ast struct definition
+    var memberDetails = getStructMembers(match[1], stateDefinitions, contractName) // type is used to extract the ast struct definition
     if (!memberDetails) return null
     return new StructType(memberDetails, location, match[1])
   } else {
@@ -230,10 +230,9 @@ function getEnum (type, stateDefinitions, contractName) {
   * @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) for all contracts
   * @param {String} contractName - contract the @args typeName belongs to
-  * @param {String} location - location of the data (storage ref| storage pointer| memory| calldata)
   * @return {Array} containing all members of the current struct type
   */
-function getStructMembers (type, stateDefinitions, contractName, location) {
+function getStructMembers (type, stateDefinitions, contractName) {
   var split = type.split('.')
   if (!split.length) {
     type = contractName + '.' + type

From ce16924682542c5b410dc1baee49e61bca436465 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Mon, 22 May 2017 15:31:09 +0200
Subject: [PATCH 04/11] use helper

---
 src/solidity/types/Mapping.js | 4 ++--
 src/solidity/types/util.js    | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/solidity/types/Mapping.js b/src/solidity/types/Mapping.js
index ae21c774c..e540a6c6a 100644
--- a/src/solidity/types/Mapping.js
+++ b/src/solidity/types/Mapping.js
@@ -19,8 +19,8 @@ class Mapping extends RefType {
         type: this.type
       }
     }
-    var mapSlot = util.toBN(location.slot).toString(16)
-    mapSlot = ethutil.setLengthLeft('0x' + mapSlot, 32).toString('hex')
+    var mapSlot = util.normalizeHex(ethutil.bufferToHex(location.slot))
+    console.log(mapSlot, mappingsPreimages)
     var mappingPreimages = mappingsPreimages[mapSlot]
     var ret = {}
     for (var i in mappingPreimages) {
diff --git a/src/solidity/types/util.js b/src/solidity/types/util.js
index 3bf63f03d..35918aedb 100644
--- a/src/solidity/types/util.js
+++ b/src/solidity/types/util.js
@@ -10,7 +10,8 @@ module.exports = {
   toBN: toBN,
   add: add,
   extractLocation: extractLocation,
-  removeLocation: removeLocation
+  removeLocation: removeLocation,
+  normalizeHex: normalizeHex
 }
 
 function decodeIntFromHex (value, byteLength, signed) {

From 0958b7eb290ff0696a69df8041d19a95e00c1c12 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Mon, 22 May 2017 16:00:48 +0200
Subject: [PATCH 05/11] add doc

---
 src/storage/mappingPreimages.js | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/storage/mappingPreimages.js b/src/storage/mappingPreimages.js
index b85901e8e..5156f0191 100644
--- a/src/storage/mappingPreimages.js
+++ b/src/storage/mappingPreimages.js
@@ -4,6 +4,13 @@ module.exports = {
   extractMappingPreimages: extractMappingPreimages
 }
 
+/**
+ * Uses the storageViewer to retrieve the storage and returns a mapping containing possible solidity mappping type location.
+ * like { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... }
+ *
+ * @param {Object} address  - storageViewer
+ * @return {Map} - solidity mapping location
+ */
 async function extractMappingPreimages (storageViewer) {
   return new Promise((resolve, reject) => {
     storageViewer.storageRange(function (error, storage) {
@@ -22,6 +29,14 @@ async function extractMappingPreimages (storageViewer) {
   })
 }
 
+/**
+ * Uses the storageViewer to retrieve the storage and returns a mapping containing possible solidity mappping type location.
+ * like { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... }
+ *
+ * @param {Object} storage  - storage given by storage Viewer (basically a mapping hashedkey : {key, value})
+ * @param {Function} callback  - calback
+ * @return {Map} - solidity mapping location (e.g { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... })
+ */
 async function decodeMappingsKeys (storage, callback) {
   var ret = {}
   for (var hashedLoc in storage) {
@@ -45,6 +60,12 @@ async function decodeMappingsKeys (storage, callback) {
   callback(null, ret)
 }
 
+/**
+ * Uses web3 to return preimage of a key
+ *
+ * @param {String} key  - key to retrieve the preimage of
+ * @return {String} - preimage of the given key
+ */
 function getPreimage (key) {
   return new Promise((resolve, reject) => {
     global.web3.debug.preimage(key, function (error, preimage) {

From 72e1b875ab377643091547679a3837e99fd5a2da Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Mon, 22 May 2017 16:06:48 +0200
Subject: [PATCH 06/11] remove uneeded function

---
 src/web3Provider/web3VmProvider.js | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/src/web3Provider/web3VmProvider.js b/src/web3Provider/web3VmProvider.js
index 741022f20..0aef043d6 100644
--- a/src/web3Provider/web3VmProvider.js
+++ b/src/web3Provider/web3VmProvider.js
@@ -133,7 +133,11 @@ web3VmProvider.prototype.pushTrace = function (self, data) {
   }
   if (traceHelper.isSHA3Instruction(step)) {
     var sha3Input = getSha3Input(step.stack, step.memory)
-    pushSha3Preimage(this, sha3Input)
+    var preimage = sha3Input
+    var imageHash = ethutil.sha3('0x' + sha3Input).toString('hex')
+    self.sha3Preimages[imageHash] = {
+      'preimage': preimage
+    }
   }
   this.processingIndex++
   this.previousDepth = depth
@@ -201,14 +205,6 @@ web3VmProvider.prototype.preimage = function (hashedKey, cb) {
   cb(null, this.sha3Preimages[hashedKey] !== undefined ? this.sha3Preimages[hashedKey].preimage : null)
 }
 
-function pushSha3Preimage (self, sha3Input) {
-  var preimage = sha3Input
-  var imageHash = ethutil.sha3('0x' + sha3Input).toString('hex')
-  self.sha3Preimages[imageHash] = {
-    'preimage': preimage
-  }
-}
-
 function getSha3Input (stack, memory) {
   var memoryStart = stack[stack.length - 1]
   var memoryLength = stack[stack.length - 2]

From e59e5644d3248d282cb27a13499fbd20c167aa35 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Tue, 23 May 2017 09:45:02 +0200
Subject: [PATCH 07/11] extract sha3 input

---
 src/web3Provider/web3VmProvider.js | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/web3Provider/web3VmProvider.js b/src/web3Provider/web3VmProvider.js
index 0aef043d6..e1f23d4a8 100644
--- a/src/web3Provider/web3VmProvider.js
+++ b/src/web3Provider/web3VmProvider.js
@@ -212,8 +212,13 @@ function getSha3Input (stack, memory) {
   memoryStart = parseInt(memStartDec) * 2
   var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
   memoryLength = parseInt(memLengthDec) * 2
-  var memoryHex = memory.join('')
-  var sha3Input = memoryHex.substr(memoryStart, memoryLength)
+
+  var subMemoryIndex = Math.floor(memoryStart / 32)
+  var sha3Input = ''
+  while (sha3Input.length < memoryLength) {
+    sha3Input += memory[subMemoryIndex]
+    subMemoryIndex++
+  }
   return sha3Input
 }
 

From ce3caa69916931f1291d85dff0043db8cd6683cf Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Tue, 23 May 2017 12:57:40 +0200
Subject: [PATCH 08/11] cache the preimages for a debug session (using the
 initial state)

---
 src/solidity/types/Mapping.js   |  7 +--
 src/storage/mappingPreimages.js | 51 ++++++----------------
 src/storage/storageResolver.js  | 43 ++++++++++++++++---
 src/storage/storageViewer.js    | 75 +++++++++++++++++++++++++++------
 4 files changed, 116 insertions(+), 60 deletions(-)

diff --git a/src/solidity/types/Mapping.js b/src/solidity/types/Mapping.js
index e540a6c6a..17ddd3373 100644
--- a/src/solidity/types/Mapping.js
+++ b/src/solidity/types/Mapping.js
@@ -11,12 +11,13 @@ class Mapping extends RefType {
   }
 
   async decodeFromStorage (location, storageResolver) {
+    var mappingsPreimages
     try {
-      var mappingsPreimages = await storageResolver.mappingPreimages()
+      mappingsPreimages = await storageResolver.mappingsLocation()
     } catch (e) {
       return {
-        value: '<error> ' + e.message,
-        type: this.type
+        value: e.message,
+        type: this.typeName
       }
     }
     var mapSlot = util.normalizeHex(ethutil.bufferToHex(location.slot))
diff --git a/src/storage/mappingPreimages.js b/src/storage/mappingPreimages.js
index 5156f0191..5a70a92ec 100644
--- a/src/storage/mappingPreimages.js
+++ b/src/storage/mappingPreimages.js
@@ -1,42 +1,17 @@
 var global = require('../helpers/global')
 
 module.exports = {
-  extractMappingPreimages: extractMappingPreimages
+  decodeMappingsKeys: decodeMappingsKeys
 }
 
 /**
- * Uses the storageViewer to retrieve the storage and returns a mapping containing possible solidity mappping type location.
- * like { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... }
- *
- * @param {Object} address  - storageViewer
- * @return {Map} - solidity mapping location
- */
-async function extractMappingPreimages (storageViewer) {
-  return new Promise((resolve, reject) => {
-    storageViewer.storageRange(function (error, storage) {
-      if (!error) {
-        decodeMappingsKeys(storage, (error, mappings) => {
-          if (error) {
-            reject(error)
-          } else {
-            resolve(mappings)
-          }
-        })
-      } else {
-        reject(error)
-      }
-    })
-  })
-}
-
-/**
- * Uses the storageViewer to retrieve the storage and returns a mapping containing possible solidity mappping type location.
- * like { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... }
- *
- * @param {Object} storage  - storage given by storage Viewer (basically a mapping hashedkey : {key, value})
- * @param {Function} callback  - calback
- * @return {Map} - solidity mapping location (e.g { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... })
- */
+  * extract the mappings location from the storage
+  * like { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... }
+  *
+  * @param {Object} storage  - storage given by storage Viewer (basically a mapping hashedkey : {key, value})
+  * @param {Function} callback  - calback
+  * @return {Map} - solidity mapping location (e.g { "<mapping_slot>" : { "<mapping-key1>": preimageOf1 }, { "<mapping-key2>": preimageOf2 }, ... })
+  */
 async function decodeMappingsKeys (storage, callback) {
   var ret = {}
   for (var hashedLoc in storage) {
@@ -61,11 +36,11 @@ async function decodeMappingsKeys (storage, callback) {
 }
 
 /**
- * Uses web3 to return preimage of a key
- *
- * @param {String} key  - key to retrieve the preimage of
- * @return {String} - preimage of the given key
- */
+  * Uses web3 to return preimage of a key
+  *
+  * @param {String} key  - key to retrieve the preimage of
+  * @return {String} - preimage of the given key
+  */
 function getPreimage (key) {
   return new Promise((resolve, reject) => {
     global.web3.debug.preimage(key, function (error, preimage) {
diff --git a/src/storage/storageResolver.js b/src/storage/storageResolver.js
index 416538864..3ad236c0a 100644
--- a/src/storage/storageResolver.js
+++ b/src/storage/storageResolver.js
@@ -1,10 +1,16 @@
 'use strict'
 var traceHelper = require('../helpers/traceHelper')
 var util = require('../helpers/global')
+var mappingPreimages = require('./mappingPreimages')
 
+/**
+  * Basically one instance is created for one debugging session.
+  * (TODO: one instance need to be shared over all the components)
+  */
 class StorageResolver {
   constructor () {
     this.storageByAddress = {}
+    this.preimagesMappingByAddress = {}
     this.maxSize = 100
   }
 
@@ -21,6 +27,33 @@ class StorageResolver {
     storageRangeInternal(this, zeroSlot, tx, stepIndex, address, callback)
   }
 
+  /**
+    * compute the mappgings type locations for the current address (cached for a debugging session)
+    * note: that only retrieve the first 100 items.
+    *
+    * @param {String} address  - contract address
+    * @param {Object} address  - storage
+    * @return {Function} - callback
+    */
+  initialPreimagesMappings (tx, stepIndex, address, callback) {
+    if (this.preimagesMappingByAddress[address]) {
+      return callback(null, this.preimagesMappingByAddress[address])
+    }
+    this.storageRange(tx, stepIndex, address, (error, storage) => {
+      if (error) {
+        return callback(error)
+      }
+      mappingPreimages.decodeMappingsKeys(storage, (error, mappings) => {
+        if (error) {
+          callback(error)
+        } else {
+          this.preimagesMappingByAddress[address] = mappings
+          callback(null, mappings)
+        }
+      })
+    })
+  }
+
   /**
     * return a slot value for the given context (address and vm trace index)
     *
@@ -96,11 +129,11 @@ function fromCache (self, address) {
 }
 
 /**
- * store the result of `storageRangeAtInternal`
- *
- * @param {String} address  - contract address
- * @param {Object} storage  - result of `storageRangeAtInternal`, contains {key, hashedKey, value}
- */
+  * store the result of `storageRangeAtInternal`
+  *
+  * @param {String} address  - contract address
+  * @param {Object} storage  - result of `storageRangeAtInternal`, contains {key, hashedKey, value}
+  */
 function toCache (self, address, storage) {
   if (!self.storageByAddress[address]) {
     self.storageByAddress[address] = {}
diff --git a/src/storage/storageViewer.js b/src/storage/storageViewer.js
index 289805e89..fde0d56e1 100644
--- a/src/storage/storageViewer.js
+++ b/src/storage/storageViewer.js
@@ -1,15 +1,16 @@
 'use strict'
 var helper = require('../helpers/util')
-var mappingPreimagesExtractor = require('./mappingPreimages')
+var mappingPreimages = require('./mappingPreimages')
 
+ /**
+   * easier access to the storage resolver
+   * Basically one instance is created foreach execution step and foreach component that need it.
+   * (TODO: one instance need to be shared over all the components)
+   */
 class StorageViewer {
   constructor (_context, _storageResolver, _traceManager) {
     this.context = _context
     this.storageResolver = _storageResolver
-    // contains [mappingSlot][mappingkey] = preimage
-    // this map is renewed for each execution step
-    // this map is shared among all the mapping types
-    this.mappingsPreimages = null
     _traceManager.accumulateStorageChanges(this.context.stepIndex, this.context.address, {}, (error, storageChanges) => {
       if (!error) {
         this.storageChanges = storageChanges
@@ -20,11 +21,11 @@ class StorageViewer {
   }
 
   /**
-   * return the storage for the current context (address and vm trace index)
-   * by default now returns the range 0 => 1000
-   *
-   * @param {Function} - callback - contains a map: [hashedKey] = {key, hashedKey, value}
-   */
+    * return the storage for the current context (address and vm trace index)
+    * by default now returns the range 0 => 1000
+    *
+    * @param {Function} - callback - contains a map: [hashedKey] = {key, hashedKey, value}
+    */
   storageRange (callback) {
     this.storageResolver.storageRange(this.context.tx, this.context.stepIndex, this.context.address, (error, storage) => {
       if (error) {
@@ -64,12 +65,58 @@ class StorageViewer {
     return this.storageResolver.isComplete(address)
   }
 
-  async mappingPreimages () {
-    if (!this.mappingsPreimages) {
-      this.mappingsPreimages = await mappingPreimagesExtractor.extractMappingPreimages(this)
+  /**
+    * return all the possible mappings locations for the current context (cached)
+    *
+    * @param {Function} callback
+    */
+  async mappingsLocation () {
+    return new Promise((resolve, reject) => {
+      if (this.completeMappingsLocation) {
+        return resolve(this.completeMappingsLocation)
+      }
+      this.storageResolver.initialPreimagesMappings(this.context.tx, this.context.stepIndex, this.context.address, (error, initialMappingsLocation) => {
+        if (error) {
+          reject(error)
+        } else {
+          this.extractMappingsLocationChanges(this.storageChanges, (error, mappingsLocationChanges) => {
+            if (error) {
+              return reject(error)
+            }
+            this.completeMappingsLocation = Object.assign({}, initialMappingsLocation)
+            for (var key in mappingsLocationChanges) {
+              if (!initialMappingsLocation[key]) {
+                initialMappingsLocation[key] = {}
+              }
+              this.completeMappingsLocation[key] = Object.assign({}, initialMappingsLocation[key], mappingsLocationChanges[key])
+            }
+            resolve(this.completeMappingsLocation)
+          })
+        }
+      })
+    })
+  }
+
+  /**
+    * retrieve mapping location changes from the storage changes.
+    *
+    * @param {Function} callback
+    */
+  extractMappingsLocationChanges (storageChanges, callback) {
+    if (this.mappingsLocationChanges) {
+      return callback(null, this.mappingsLocationChanges)
     }
-    return this.mappingsPreimages
+    mappingPreimages.decodeMappingsKeys(storageChanges, (error, mappings) => {
+      if (!error) {
+        this.mappingsLocationChanges = mappings
+        return callback(null, this.mappingsLocationChanges)
+      } else {
+        callback(error)
+      }
+    })
   }
 }
 
+
+
 module.exports = StorageViewer

From 075fa4ee5987d0754df4cd48bf5402681b441aab Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Tue, 23 May 2017 15:00:51 +0200
Subject: [PATCH 09/11] fix sha3 input extract

---
 src/web3Provider/web3VmProvider.js | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/web3Provider/web3VmProvider.js b/src/web3Provider/web3VmProvider.js
index e1f23d4a8..079db3b62 100644
--- a/src/web3Provider/web3VmProvider.js
+++ b/src/web3Provider/web3VmProvider.js
@@ -213,11 +213,16 @@ function getSha3Input (stack, memory) {
   var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
   memoryLength = parseInt(memLengthDec) * 2
 
-  var subMemoryIndex = Math.floor(memoryStart / 32)
-  var sha3Input = ''
-  while (sha3Input.length < memoryLength) {
-    sha3Input += memory[subMemoryIndex]
-    subMemoryIndex++
+  var min = Math.floor(memoryStart / 32)
+  var fillLength = Math.floor(memoryLength / 32)
+  var sha3Input = memory[min].slice(memoryStart - 32 * min)
+  min++
+  while (min < fillLength) {
+    sha3Input += memory[min]
+    min++
+  }
+  if (sha3Input.length < memoryLength) {
+    sha3Input += memory[min].slice(0, memoryLength - sha3Input.length)
   }
   return sha3Input
 }

From 4013d3528d7eaa489607e3fd0db75c69b8570b00 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Wed, 24 May 2017 12:48:56 +0200
Subject: [PATCH 10/11] return a promise if mappings alrady requested

---
 src/storage/storageViewer.js | 48 +++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 22 deletions(-)

diff --git a/src/storage/storageViewer.js b/src/storage/storageViewer.js
index fde0d56e1..5aeeece5f 100644
--- a/src/storage/storageViewer.js
+++ b/src/storage/storageViewer.js
@@ -11,6 +11,7 @@ class StorageViewer {
   constructor (_context, _storageResolver, _traceManager) {
     this.context = _context
     this.storageResolver = _storageResolver
+    this.completeMapingsLocationPromise = null
     _traceManager.accumulateStorageChanges(this.context.stepIndex, this.context.address, {}, (error, storageChanges) => {
       if (!error) {
         this.storageChanges = storageChanges
@@ -71,30 +72,33 @@ class StorageViewer {
     * @param {Function} callback
     */
   async mappingsLocation () {
-    return new Promise((resolve, reject) => {
-      if (this.completeMappingsLocation) {
-        return resolve(this.completeMappingsLocation)
-      }
-      this.storageResolver.initialPreimagesMappings(this.context.tx, this.context.stepIndex, this.context.address, (error, initialMappingsLocation) => {
-        if (error) {
-          reject(error)
-        } else {
-          this.extractMappingsLocationChanges(this.storageChanges, (error, mappingsLocationChanges) => {
-            if (error) {
-              return reject(error)
-            }
-            this.completeMappingsLocation = Object.assign({}, initialMappingsLocation)
-            for (var key in mappingsLocationChanges) {
-              if (!initialMappingsLocation[key]) {
-                initialMappingsLocation[key] = {}
-              }
-              this.completeMappingsLocation[key] = Object.assign({}, initialMappingsLocation[key], mappingsLocationChanges[key])
-            }
-            resolve(this.completeMappingsLocation)
-          })
+    if (!this.completeMapingsLocationPromise) {
+      this.completeMapingsLocationPromise = new Promise((resolve, reject) => {
+        if (this.completeMappingsLocation) {
+          return this.completeMappingsLocation
         }
+        this.storageResolver.initialPreimagesMappings(this.context.tx, this.context.stepIndex, this.context.address, (error, initialMappingsLocation) => {
+          if (error) {
+            reject(error)
+          } else {
+            this.extractMappingsLocationChanges(this.storageChanges, (error, mappingsLocationChanges) => {
+              if (error) {
+                return reject(error)
+              }
+              this.completeMappingsLocation = Object.assign({}, initialMappingsLocation)
+              for (var key in mappingsLocationChanges) {
+                if (!initialMappingsLocation[key]) {
+                  initialMappingsLocation[key] = {}
+                }
+                this.completeMappingsLocation[key] = Object.assign({}, initialMappingsLocation[key], mappingsLocationChanges[key])
+              }
+              resolve(this.completeMappingsLocation)
+            })
+          }
+        })
       })
-    })
+    }
+    return this.completeMapingsLocationPromise
   }
 
   /**

From cbd30b86eca8d41eeeee7c166e995d237af9e2e7 Mon Sep 17 00:00:00 2001
From: yann300 <yann.levreau@gmail.com>
Date: Wed, 24 May 2017 12:59:13 +0200
Subject: [PATCH 11/11] typo + emptyFill if memory not yet filled

---
 src/web3Provider/web3VmProvider.js | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/web3Provider/web3VmProvider.js b/src/web3Provider/web3VmProvider.js
index 079db3b62..f3b68f79c 100644
--- a/src/web3Provider/web3VmProvider.js
+++ b/src/web3Provider/web3VmProvider.js
@@ -213,18 +213,26 @@ function getSha3Input (stack, memory) {
   var memLengthDec = (new ethutil.BN(memoryLength.replace('0x', ''), 16).toString(10))
   memoryLength = parseInt(memLengthDec) * 2
 
-  var min = Math.floor(memoryStart / 32)
-  var fillLength = Math.floor(memoryLength / 32)
-  var sha3Input = memory[min].slice(memoryStart - 32 * min)
-  min++
-  while (min < fillLength) {
-    sha3Input += memory[min]
-    min++
+  var i = Math.floor(memoryStart / 32)
+  var maxIndex = Math.floor(memoryLength / 32)
+  if (!memory[i]) {
+    return emptyFill(memoryLength)
+  }
+  var sha3Input = memory[i].slice(memoryStart - 32 * i)
+  i++
+  while (i < maxIndex) {
+    sha3Input += memory[i] ? memory[i] : emptyFill(32)
+    i++
   }
   if (sha3Input.length < memoryLength) {
-    sha3Input += memory[min].slice(0, memoryLength - sha3Input.length)
+    var leftSize = memoryLength - sha3Input.length
+    sha3Input += memory[i] ? memory[i].slice(0, leftSize) : emptyFill(leftSize)
   }
   return sha3Input
 }
 
+function emptyFill (size) {
+  return (new Array(size)).join('0')
+}
+
 module.exports = web3VmProvider