Token parsing modified to use a ReadableTrackingBuffer, removing the …

…need to track the position within the buffer within the token parsing.

This is a complex and wide ranging change, that significantly simplifies token parsing, and makes it easier to read and maintain.
Any attempt to read past the end of the available buffer results in an exception being thrown. This may have a small runtime overhead, but it's worth it because of the simplified code.

Functions added to ReadableTrackingBuffer for more data types.
Functions added to WritableTrackingBuffer for more data types.
Many unit tests converted to use WritableTrackingBuffer, to avoid them needing to track the position withing the buffer.

lib/token/colmetadata-token-parser.coffee

@@ -3,82 +3,52 @@
 TYPE = require('./data-type').TYPE
 sprintf = require('sprintf').sprintf
 
-parser = (buffer, position) ->
-  startPosition = position
-
-  if buffer.length - position < 2
-    return false
-  columnCount = buffer.readUInt16LE(position)
-  position += 2
+parser = (buffer) ->
+  columnCount = buffer.readUInt16LE()
 
   columns = []
   for c in [1..columnCount]
-    if buffer.length - position < 4 + 2 + 1
-      return false
-
-    userType = buffer.readUInt32LE(position)
-    position += 4
-
-    flags = buffer.readUInt16LE(position)
-    position +=2
-
-    typeNumber = buffer.readUInt8(position)
+    userType = buffer.readUInt32LE()
+    flags = buffer.readUInt16LE()
+    typeNumber = buffer.readUInt8()
     type = TYPE[typeNumber]
-    position++
-
+
     if !type
-      error = sprintf('Unrecognised data type 0x%02X at offset 0x%04X', typeNumber, (position - 1))
+      error = sprintf('Unrecognised data type 0x%02X at offset 0x%04X', typeNumber, (buffer.position - 1))
       break
 
     #console.log(type)
 
     if type.fixedLength
       dataLength = type.dataLength
     else if type.variableLength
-      if buffer.length - position < type.dataLengthLength
-        return false
-
       switch type.dataLengthLength
         when 1
-          dataLength = buffer.readUInt8(position)
+          dataLength = buffer.readUInt8()
         when 2
-          dataLength = buffer.readUInt16LE(position)
+          dataLength = buffer.readUInt16LE()
         when 4
-          dataLength = buffer.readUInt32LE(position)
+          dataLength = buffer.readUInt32LE()
         else
           error = "Unrecognised dataLengthLength for type #{type}"
           break
-      position += type.dataLengthLength
 
     if type.hasPrecision
-      precision = buffer.readUInt8(position)
-      position++
+      precision = buffer.readUInt8()
     else
       precision = undefined
 
     if type.hasScale
-      scale = buffer.readUInt8(position)
-      position++
+      scale = buffer.readUInt8()
     else
       scale = undefined
 
     if type.hasCollation
-      if buffer.length - position < 5
-        return false
-      collation = Array.prototype.slice.call(buffer, position, position + 5)
-      position += 5
+      collation = buffer.readBuffer(5)
     else
       collation = undefined
 
-    if buffer.length - position < 1
-      return false
-    colNameLength = buffer.readUInt8(position) * 2
-    position++
-
-    if buffer.length - position < colNameLength
-      return false
-    colName = buffer.toString('ucs-2', position, position + colNameLength)
-    position += colNameLength
+    colName = buffer.readBVarchar()
 
     columns.push(
       userType: userType
@@ -98,7 +68,6 @@ parser = (buffer, position) ->
   else
     token =
       name: 'COLMETADATA'
-      length: position - startPosition
       event: 'columnMetadata'
       columns: columns
 

lib/token/done-token-parser.coffee

@@ -10,11 +10,8 @@ STATUS =
   ATTN: 0x0020
   SRVERROR: 0x0100
 
-parser = (buffer, position) ->
-  if buffer.length - position < 2
-    return false
-  status = buffer.readUInt16LE(position)
-  position += 2
+parser = (buffer) ->
+  status = buffer.readUInt16LE()
 
   more = !!(status & STATUS.MORE)
   sqlError = !!(status & STATUS.ERROR)
@@ -23,25 +20,15 @@ parser = (buffer, position) ->
   attention = !!(status & STATUS.ATTN)
   serverError = !!(status & STATUS.SRVERROR)
 
-  if buffer.length - position < 2
-    return false
-  curCmd = buffer.readUInt16LE(position)
-  position += 2
+  curCmd = buffer.readUInt16LE()
 
-  if rowCountValid
-    if buffer.length - position < 8
-      return false
-
-    # If rowCount > 53 bits then rowCount will be incorrect (because Javascript uses IEEE_754 for number representation).
-    rowCountLow = buffer.readUInt32LE(position)
-    position += 4
-    rowCountHigh = buffer.readUInt32LE(position)
-    position += 4
-    rowCount = rowCountLow + (0x100000000 * rowCountHigh)
+  # If rowCount > 53 bits then rowCount will be incorrect (because Javascript uses IEEE_754 for number representation).
+  rowCount = buffer.readUInt64LE()
+  if !rowCountValid
+    rowCount = undefined
 
   token =
     name: 'DONE'
-    length: 2 + 2 + 8
     event: 'done'
     more: more
     sqlError: sqlError
@@ -50,22 +37,22 @@ parser = (buffer, position) ->
     rowCount: rowCount
     curCmd: curCmd
 
-doneParser = (buffer, position) ->
-  token = parser(buffer, position)
+doneParser = (buffer) ->
+  token = parser(buffer)
   token.name = 'DONE'
   token.event = 'done'
 
   token
 
-doneInProcParser = (buffer, position) ->
-  token = parser(buffer, position)
+doneInProcParser = (buffer) ->
+  token = parser(buffer)
   token.name = 'DONEINPROC'
   token.event = 'doneInProc'
 
   token
 
-doneProcParser = (buffer, position) ->
-  token = parser(buffer, position)
+doneProcParser = (buffer) ->
+  token = parser(buffer)
   token.name = 'DONEPROC'
   token.event = 'doneProc'
 

lib/token/env-change-token-parser.coffee

@@ -27,51 +27,30 @@ types =
   17:
     name: 'TXN_ENDED'
 
-module.exports = (buffer, position) ->
-  if buffer.length - position < 3
-    # Not long enough to contain length and type bytes.
-    return false
-
-  length = buffer.readUInt16LE(position)
-  position += 2
-  if (buffer.length - position < length)
-    # Not long enough for the extracted length
-    return false
-
-  typeNumber = buffer.readUInt8(position)
-  position++
+module.exports = (buffer) ->
+  length = buffer.readUInt16LE()
+  typeNumber = buffer.readUInt8()
   type = types[typeNumber]
 
   if type
     switch type.name
       when 'DATABASE', 'LANGUAGE', 'CHARSET', 'PACKET_SIZE'
-        valueLength = buffer.readUInt8(position) * 2
-        position++
-        newValue = buffer.toString('ucs-2', position, position + valueLength)
-        position += valueLength
-
-        valueLength = buffer.readUInt8(position) * 2
-        position++
-        oldValue = buffer.toString('ucs-2', position, position + valueLength)
-        position += valueLength
+        newValue = buffer.readBVarchar()
+        oldValue = buffer.readBVarchar()
       when 'SQL_COLLATION'
-        valueLength = buffer.readUInt8(position)
-        position++
-        newValue = buffer.slice(position, position + valueLength)
-        position += valueLength
+        valueLength = buffer.readUInt8()
+        newValue = buffer.readBuffer(valueLength)
 
-        valueLength = buffer.readUInt8(position)
-        position++
-        oldValue = buffer.slice(position, position + valueLength)
-        position += valueLength
+        valueLength = buffer.readUInt8()
+        oldValue = buffer.readBuffer(valueLength)
       else
-        error = "Unsupported ENVCHANGE type #{typeNumber} #{type.name} at offset #{position}"
+        error = "Unsupported ENVCHANGE type #{typeNumber} #{type.name} at offset #{buffer.position - 1}"
 
     if type.name == 'PACKET_SIZE'
       newValue = parseInt(newValue)
       oldValue = parseInt(oldValue)
   else
-    error = "Unsupported ENVCHANGE type #{typeNumber}"
+    error = "Unsupported ENVCHANGE type #{typeNumber} at offset #{buffer.position - 1}"
 
   if error
     token =
@@ -80,7 +59,6 @@ module.exports = (buffer, position) ->
   else
     token =
       name: 'ENVCHANGE'
-      length: length + 2
       type: type.name
       event: type.event
       oldValue: oldValue

lib/token/infoerror-token-parser.coffee

@@ -1,45 +1,16 @@
 # s2.2.7.9, s2.2.7.10
 
-parser = (buffer, position) ->
-  if buffer.length - position < 3
-    # Not long enough to contain length and type bytes.
-    return false
-
-  length = buffer.readUInt16LE(position)
-  position += 2
-  if (buffer.length - position < length)
-    # Not long enough for the extracted length
-    return false
-
-  number = buffer.readUInt32LE(position)
-  position += 4
-
-  state = buffer.readUInt8(position)
-  position++
-
-  class_ = buffer.readUInt8(position)
-  position++
-
-  valueLength = buffer.readUInt16LE(position) * 2
-  position += 2
-  message = buffer.toString('ucs-2', position, position + valueLength)
-  position += valueLength
-
-  valueLength = buffer.readUInt8(position) * 2
-  position++
-  serverName = buffer.toString('ucs-2', position, position + valueLength)
-  position += valueLength
-
-  valueLength = buffer.readUInt8(position) * 2
-  position++
-  procName = buffer.toString('ucs-2', position, position + valueLength)
-  position += valueLength
-
-  lineNumber = buffer.readUInt32LE(position)
-  position += 4
+parser = (buffer) ->
+  length = buffer.readUInt16LE()
+  number = buffer.readUInt32LE()
+  state = buffer.readUInt8()
+  class_ = buffer.readUInt8()
+  message = buffer.readUsVarchar()
+  serverName = buffer.readBVarchar()
+  procName = buffer.readBVarchar()
+  lineNumber = buffer.readUInt32LE()
 
   token =
-    length: length + 2
     number: number
     state: state
     class: class_
@@ -48,15 +19,15 @@ parser = (buffer, position) ->
     procName: procName
     lineNumber: lineNumber
 
-infoParser = (buffer, position) ->
-  token = parser(buffer, position)
+infoParser = (buffer) ->
+  token = parser(buffer)
   token.name = 'INFO'
   token.event = 'infoMessage'
 
   token
 
-errorParser = (buffer, position) ->
-  token = parser(buffer, position)
+errorParser = (buffer) ->
+  token = parser(buffer)
   token.name = 'ERROR'
   token.event = 'errorMessage'
 

lib/token/loginack-token-parser.coffee

@@ -6,39 +6,26 @@ interfaces =
   0: 'SQL_DFLT'
   1: 'SQL_TSQL'
 
-parser = (buffer, position) ->
-  if buffer.length - position < 3
-    # Not long enough to contain length and type bytes.
-    return false
-
-  length = buffer.readUInt16LE(position)
-  position += 2
-  if (buffer.length - position < length)
-    # Not long enough for the extracted length
-    return false
-
-  interfaceNumber = buffer.readUInt8(position)
+parser = (buffer) ->
+  length = buffer.readUInt16LE()
+
+  interfaceNumber = buffer.readUInt8()
   interface = interfaces[interfaceNumber]
   if !interface
-    error = "Unknown LOGINACK Interface #{interfaceNumber} at offset #{position}"
-  position++
+    error = "Unknown LOGINACK Interface #{interfaceNumber} at offset #{buffer.position}"
 
-  tdsVersionNumber = buffer.readUInt32BE(position)
+  tdsVersionNumber = buffer.readUInt32BE()
   tdsVersion = versions[tdsVersionNumber]
   if !tdsVersion
-    error = "Unknown LOGINACK TDSVersion #{tdsVersionNumber} at offset #{position}"
-  position += 4
-
-  valueLength = buffer.readUInt8(position) * 2
-  position++
-  progName = buffer.toString('ucs-2', position, position + valueLength)
-  position += valueLength
-
+    error = "Unknown LOGINACK TDSVersion #{tdsVersionNumber} at offset #{buffer.position}"
+
+  progName = buffer.readBVarchar()
+
   progVersion =
-    major: buffer.readUInt8(position++)
-    minor: buffer.readUInt8(position++)
-    buildNumHi: buffer.readUInt8(position++)
-    buildNumLow: buffer.readUInt8(position++)
+    major: buffer.readUInt8()
+    minor: buffer.readUInt8()
+    buildNumHi: buffer.readUInt8()
+    buildNumLow: buffer.readUInt8()
 
   if error
     token =
@@ -47,7 +34,6 @@ parser = (buffer, position) ->
   else
     token =
       name: 'LOGINACK'
-      length: length + 2
       event: 'loginack'
       interface: interface
       tdsVersion: tdsVersion