TLV 格式及编解码

几乎所有的需要在卡片和终端之间传送的数据都是TLV格式的.

我给你举个例子方便快速理吵隐如解：

TLV 是 tag , length 和 value 的缩写.一个基本的数据元就包括上面三个域. Tag 唯一标识该数据元, length 是 value 域的长度. Value就是数据本身了. 举升启个例子, 下面是一个tlv格式的AID（应用标识符）字节串” 9F0607A0000000031010 ”, 其中 9F06 是tag, 07 是长度, A0000000031010 就是AID本身的值了.

对于程序编写人员来说，如果有类似上面这样的一串TLV编码的字节串从卡片传过来, 怎么样从中提取我们想要的数据. 这就牵扯出TLV解码的问题了

TLV一种可变格式，TLV的意思就是：Type类型， Lenght长度，携困Value值；

Type和Length的长度固定，一般那是2、4个字节；

Value的长度有Length指定；

解析方法：

1.读取type 转换为ntohl、ntohs转换为主机字节序得到类型；指针偏移+2或4

2.读取lenght，转换为ntohl、ntohs转换为主机字节序得到长度；指针偏移+2或4

3.根据得到的长度读取value，指针偏移+Length；

TLV编码就是指先对Tag编码，再对Length编码，最后对Value编码。

有点长，慢慢看吧

Begin VB.Form frmMain

Caption = "Form1"

ClientHeight= 3090

ClientLeft = 60

ClientTop = 450

ClientWidth = 4680

LinkTopic = "Form1"

ScaleHeight = 3090

ScaleWidth = 4680

StartUpPosition = 3 '窗口缺省

Begin VB.CommandButton Command1

Caption = "Command1"

Height = 975

Left= 1320

TabIndex= 0

Top = 1080

Width = 2415

End

End

Attribute VB_Name = "frmMain"

Attribute VB_GlobalNameSpace = False

Attribute VB_Creatable = False

Attribute VB_PredeclaredId = True

Attribute VB_Exposed = False

Option Explicit

Private Const MEM_RELEASE = &H8000

Private Const LVM_FIRST = &H1000

Private Const LVM_GETHEADER = LVM_FIRST + 31

Private Const LVM_GETITEMCOUNT = (LVM_FIRST + 4)

Private Const LVM_GETITEM = (LVM_FIRST + 5)

Private Const LVM_GETSTRINGWIDTH = (LVM_FIRST + 17)

Private Const LVM_GETCOLUMN = (LVM_FIRST + 25)

Private Const LVM_GETITEMTEXT = (LVM_FIRST + 45)

Private Const HDM_FIRST = &H1200

Private Const HDM_GETITEMCOUNT = (HDM_FIRST + 0)

Private Const HDM_ORDERTOINDEX = (HDM_FIRST + 15)

Private Const PROCESS_QUERY_INFORMATION = 1024

Private Const PROCESS_VM_OPERATION = &H8

Private Const PROCESS_VM_READ = &H10

Private Const PROCESS_VM_WRITE = &H20

Private Const STANDARD_RIGHTS_REQUIRED = &HF0000

Private Const MAX_LVMSTRING As Long = 255

Private Const MEM_COMMIT = &H1000

Private Const PAGE_READWRITE = &H4

Private Const LVIF_TEXT As Long = &H1

Private Const LVM_GETCOLUMNCOUNT = &HF11B

Private Type LV_ITEMA

mask As Long

iItemAs Long

iSubItem As Long

stateAs Long

stateMaskAs Long

pszText As Long

cchTextMax As Long

iImage As Long

lParam As Long

iIndent As Long

End Type

Private Declare Function OpenProcess Lib "kernel32" (ByVal dwDesiredAccess As Long, ByVal bInheritHandle As Long, ByVal dwProcId As Long) As Long

Private Declare Function VirtualAllocEx Lib "kernel32" (ByVal hProcess As Long, ByVal lpAddress As Long, ByVal dwSize As Long, ByVal flAllocationType As Long, ByVal flProtect As Long) As Long

Private Declare Function VirtualFreeEx Lib "kernel32" (ByVal hProcess As Long, ByVal lpAddress As Long, ByVal dwSize As Long, ByVal dwFreeType As Long) As Long

Private Declare Function WriteProcessMemory Lib "kernel32" (ByVal hProcess As Long, ByVal lpBaseAddress As Any, ByRef lpBuffer As Any, ByVal nSize As Long, lpNumberOfBytesWritten As Long) As Long

Private Declare Function ReadProcessMemory Lib "kernel32" (ByVal hProcess As Long, ByVal lpBaseAddress As Any, ByRef lpBuffer As Any, ByVal nSize As Long, lpNumberOfBytesWritten As Long) As Long

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As Long

Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long

Private Declare Function GetCurrentProcessId Lib "kernel32" () As Long

Private Function GetListViewTextArray(ByVal hWindow As Long, ByVal ProcessID As Long) As String()

Dim result As Long

Dim myItem() As LV_ITEMA

Dim pHandle As Long

Dim pStrBufferMemoryAs Long

Dim pMyItemMemory As Long

Dim strBuffer() As Byte

Dim index As Long

Dim tmpString As String

Dim strLength As Long

Dim i As Integer, sum As Integer, j As Integer, hCount As Long

Dim strArr() As String, itemString As String

hCount = SendMessage(hWindow, LVM_GETHEADER, 0, 0)

If hCount >0 Then

hCount = SendMessage(hCount, HDM_GETITEMCOUNT, 0, 0)

Else

hCount = 0

End If

ReDim strBuffer(MAX_LVMSTRING)

pHandle = OpenProcess(PROCESS_VM_OPERATION Or PROCESS_VM_READ Or PROCESS_VM_WRITE, False, ProcessID)

ReDim myItem(hCount)

For j = 0 To SendMessage(hWindow, LVM_GETITEMCOUNT, 0, 0) - 1

For i = 0 To hCount

pStrBufferMemory = VirtualAllocEx(pHandle, 0, MAX_LVMSTRING, MEM_COMMIT, PAGE_READWRITE)

myItem(i).mask = LVIF_TEXT

myItem(i).iSubItem = i

myItem(i).pszText = pStrBufferMemory

myItem(i).cchTextMax = MAX_LVMSTRING

pMyItemMemory = VirtualAllocEx(pHandle, 0, Len(myItem(i)), MEM_COMMIT, PAGE_READWRITE)

result = WriteProcessMemory(pHandle, pMyItemMemory, myItem(i), Len(myItem(i)), 0)

result = SendMessage(hWindow, LVM_GETITEMTEXT, j, ByVal pMyItemMemory)

If result = 0 Then

result = VirtualFreeEx(pHandle, pStrBufferMemory, 0, MEM_RELEASE)

result = VirtualFreeEx(pHandle, pMyItemMemory, 0, MEM_RELEASE)

Exit For

End If

result = ReadProcessMemory(pHandle, pStrBufferMemory, strBuffer(0), MAX_LVMSTRING, 0)

result = ReadProcessMemory(pHandle, pMyItemMemory, myItem(i), Len(myItem(i)), 0)

tmpString = StrConv(strBuffer, vbUnicode)

tmpString = Left(tmpString, InStr(tmpString, vbNullChar) - 1)

itemString = itemString &tmpString &","

result = VirtualFreeEx(pHandle, pStrBufferMemory, 0, MEM_RELEASE)

result = VirtualFreeEx(pHandle, pMyItemMemory, 0, MEM_RELEASE)

Next

ReDim Preserve strArr(0 To sum)

strArr(j) = Left(itemString, Len(itemString) - 1)

sum = sum + 1

itemString = ""

Next

result = CloseHandle(pHandle)

GetListViewTextArray = strArr

End Function

Private Sub Command1_Click()

Dim itemStr() As String, i As Integer

itemStr = GetListViewTextArray(frmListView.lvTest.hwnd, GetCurrentProcessId)

For i = 0 To UBound(itemStr)

MsgBox itemStr(i)

Next

End Sub

Private Sub Form_Load()

frmListView.Show

End Sub

VERSION 5.00

Object = "{831FDD16-0C5C-11D2-A9FC-0000F8754DA1}#2.0#0""MSCOMCTL.OCX"

Begin VB.Form frmListView

Caption = "测试窗体"

ClientHeight= 5730

ClientLeft = 60

ClientTop = 450

ClientWidth = 7425

LinkTopic = "Form2"

ScaleHeight = 5730

ScaleWidth = 7425

StartUpPosition = 3 '窗口缺省

Begin MSComctlLib.ListView lvTest

Height = 4695

Left= 360

TabIndex= 0

Top = 480

Width = 6495

_ExtentX= 11456

_ExtentY= 8281

View= 3

LabelWrap = -1 'True

HideSelection = -1 'True

_Version= 393217

ForeColor = -2147483640

BackColor = -2147483643

BorderStyle = 1

Appearance = 1

NumItems= 0

End

End

Attribute VB_Name = "frmListView"

Attribute VB_GlobalNameSpace = False

Attribute VB_Creatable = False

Attribute VB_PredeclaredId = True

Attribute VB_Exposed = False

Private Sub Form_Load()

With lvTest

.ColumnHeaders.Add , , "序号"

.ColumnHeaders.Add , , "名称"

.ColumnHeaders.Add , , "性别"

.ColumnHeaders.Add , , "年龄"

End With

AddToListview "陈辉", "男", "24"

AddToListview "张三", "男", "22"

AddToListview "李四", "女", "20"

AddToListview "王二", "男", "31"

AddToListview "麻子", "女", "18"

End Sub

Private Sub AddToListview(ByVal sName As String, sSex As String, ByVal sAge As String)

Dim item As ListItem

Set item = lvTest.ListItems.Add(, , CStr(lvTest.ListItems.Count + 1))

item.SubItems(1) = sName

item.SubItems(2) = sSex

item.SubItems(3) = sAge

End Sub

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