为了一个gb2312下post中文参数到utf-8页面的程序，随闷的难受，查了一下午资料，大部分是讲Gb2312传到Gb2312页面的UrlEncode，没有提供到Utf-8页面的UrlEncode，后来找到Unicode转Utf-8码的资料，参考之下，终于写出了Utf-8的UrlEncode，这里整理下各种UrlEncode方法，供有需要的朋友参考。

详细Utf-8编码规则请百度一下。

Unicode 与 Utf-8码间的内码规则模板为：
原始码（16进制）　UTF－8编码（二进制）
--------------------------------------------
0000 - 007F 0xxxxxxx
0080 - 07FF 110xxxxx 10xxxxxx
0800 - FFFF 1110xxxx 10xxxxxx 10xxxxxx （中文字在此区间)
……
--------------------------------------------

例如：
百度中查询“中国人”，会将中文URL参数转为Gb2312码的16进制表示，一个中文字用2个字节
http://www.baidu.com/s?wd=%D6%D0%B9%FA%C8%CB
Google中查询“中国人”，会将中文URL参数转为Utf-8编码的16进制表示，一个中文字用3个字节
http://www.google.cn/search?client=opera&rls=en&q=%E4%B8%AD%E5%9B%BD%E4%BA%BA&sourceid=opera&ie=utf-8&oe=utf-8

'Url编码，Gb2312页面之间传递参数
Function URLEncode_Gb(ByVal str)
Dim i,s
Dim B,bCode,gb,Hight8b,Low8b
s = ""
For i = 1 To Len(str)
B = Mid(str,i,1)
bCode=Abs(Asc(B))
If (bCode>=48 And bCode<=57) Or (bCode>=65 And bCode<=90) Or (bCode>=97 And bCode<=122) Or bCode=42 Or bCode=45 Or bCode=46 Or bCode=64 Or bCode=95 Then
'48 to 57代表0~9;65 to 90代表A~Z;97 to 122代表a~z
'42代表*;46代表.;64代表@;45代表-;95代表_
s=s & B
ElseIf bCode=32 Then '空格转成+
s=s & "+"
ElseIf bCode<128 Then '低于128的Ascii转成1个字节
s=s & "%" & Right("00" & Hex(bCode),2)
Else
gb = Asc(B)
If gb < 0 Then
gb = gb + &H10000 'gb编码为负数，要加上65536
End If
Hight8b = (gb And &HFF00) / &H100 '二进制高8位
Low8b = gb And &HFF '二进制低8位
s = s & "%" & Hex(Hight8b) & "%" & Hex(Low8b)
End If
Next
URLEncode_Gb = s
End Function

'Url解码，Gb2312页面之间传递参数
Function URLDecode_Gb(ByVal str)
Dim i,s
Dim B,bCode,gb,Hight8b,Low8b
s = ""
For i = 1 To Len(str)
B = Mid(str,i,1)
Select Case B
Case "+"
s=s & " "
Case "%"
gb=Mid(str,i+1,2)
bCode=CInt("&H" & gb)
If bCode<128 Then
i=i+2
Else
bCode=CInt("&H" & gb & Mid(str,i+4,2))
i=i+5
End If
s=s & Chr(bCode)
Case Else
s=s & B
End Select
Next
URLDecode_Gb = s
End Function

'URL编码，Gb2312页面提交到Utf-8页面
Function UrlEncode_GBToUtf8(ByVal str)
Dim B '单个字符
Dim ub '中文字的Unicode码(2字节)
Dim High8b, Low8b 'Unicode码的高低位字节
Dim UtfB1, UtfB2, UtfB3 'Utf-8码的三个字节
Dim i, s
For i = 1 To Len(str)
B=Mid(str, i, 1)
ub = AscW(B)
If (ub>=48 And ub<=57) Or (ub>=65 And ub<=90) Or (ub>=97 And ub<=122) Or ub=42 Or ub=45 Or ub=46 Or ub=64 Or ub=95 Then
'48 to 57代表0~9;65 to 90代表A~Z;97 to 122代表a~z
'42代表*;46代表.;64代表@;45代表-;95代表_
s=s & B
ElseIf ub=32 Then '空格转成+
s=s & "+"
ElseIf ub<128 Then '低于128的Ascii转成1个字节
s=s & "%" & Right("00" & Hex(ub),2)
Else
High8b = (ub And &HFF00) / &H100 'Unicode码高位
Low8b = ub And &HFF 'Unicode码低位
UtfB1 = (High8b And &HF0) / &H10 Or &HE0 '取Unicode高位字节的二进制的前4位 + 11100000
UtfB2 = ((High8b And &HF) * &H4 + (Low8b And &HC0) / &H40) Or &H80 '取Unicode高位字节的后4位及低位字节的前2位 +10000000
UtfB3 = (Low8b And &H3F) Or &H80 '取Unicode低位字节的二进制后6位 + 10000000
s = s & "%" & Hex(UtfB1) & "%" & Hex(UtfB2) & "%" & Hex(UtfB3)
End If
Next
UrlEncode_GBToUtf8 = s
End Function

'“汉”－AscW("汉")=27721(十进制) 01101100 01001001(二进制) 6C49(十六进制)
'将Gb2312码转成Utf-8码（十六进制表示）的方法为，先用AscW将Gb2312转为Unicode码(2字节),再'将Unicode码的二进制中的位按utf-8(3字节）模板规则填充 x 位：

'URL解码，Gb2312页面提交到Utf-8页面
Function UrlDecode_GBToUtf8(ByVal str)
Dim B,ub '中文字的Unicode码(2字节)
Dim UtfB 'Utf-8单个字节
Dim UtfB1, UtfB2, UtfB3 'Utf-8码的三个字节
Dim i, n, s
n=0
ub=0
For i = 1 To Len(str)
B=Mid(str, i, 1)
Select Case B
Case "+"
s=s & " "
Case "%"
ub=Mid(str, i + 1, 2)
UtfB = CInt("&H" & ub)
If UtfB<128 Then
i=i+2
s=s & ChrW(UtfB)
Else
UtfB1=(UtfB And &H0F) * &H1000 '取第1个Utf-8字节的二进制后4位
UtfB2=(CInt("&H" & Mid(str, i + 4, 2)) And &H3F) * &H40 '取第2个Utf-8字节的二进制后6位
UtfB3=CInt("&H" & Mid(str, i + 7, 2)) And &H3F '取第3个Utf-8字节的二进制后6位
s=s & ChrW(UtfB1 Or UtfB2 Or UtfB3)
i=i+8
End If
Case Else 'Ascii码
s=s & B
End Select
Next
UrlDecode_GBToUtf8 = s
End Function

'URL编码，Gb2312页面提交到Utf-8页面，另一种位计算方法
Private Function UrlEncode_GBToUtf8_V2(szInput)
Dim wch, uch, szRet
Dim x
Dim nAsc, nAsc2, nAsc3
If szInput = "" Then
UrlEncode_GBToUtf8_V2= szInput
Exit Function
End If
For x = 1 To Len(szInput)
wch = Mid(szInput, x, 1)
nAsc = AscW(wch)
If nAsc < 0 Then nAsc = nAsc + 65536
If (nAsc And &HFF80) = 0 Then
szRet = szRet & wch
Else
If (nAsc And &HF000) = 0 Then
uch = "%" & Hex(((nAsc 2 ^ 6)) Or &HC0) & Hex(nAsc And &H3F Or &H80)
szRet = szRet & uch
Else
uch = "%" & Hex((nAsc 2 ^ 12) Or &HE0) & "%" & _
Hex((nAsc 2 ^ 6) And &H3F Or &H80) & "%" & _
Hex(nAsc And &H3F Or &H80)
szRet = szRet & uch
End If
End If
Next
UrlEncode_GBToUtf8_V2= szRet
End Function

'VB下用API方法的Unicode转Utf-8方法：
Private Declare Function WideCharToMultiByte Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long, ByRef lpMultiByteStr As Any, ByVal cchMultiByte As Long, ByVal lpDefaultChar As String, ByVal lpUsedDefaultChar As Long) As Long
Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpMultiByteStr As Long, ByVal cchMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long) As Long
Private Const CP_UTF8 = 65001

Function Utf8ToUnicode(ByRef Utf() As Byte) As String
Dim lRet As Long
Dim lLength As Long
Dim lBufferSize As Long
lLength = UBound(Utf) - LBound(Utf) + 1
If lLength <= 0 Then Exit Function
lBufferSize = lLength * 2
Utf8ToUnicode = String$(lBufferSize, Chr(0))
lRet = MultiByteToWideChar(CP_UTF8, 0, VarPtr(Utf(0)), lLength, StrPtr(Utf8ToUnicode), lBufferSize)
If lRet <> 0 Then
Utf8ToUnicode = Left(Utf8ToUnicode, lRet)
End If
End Function

Function UnicodeToUtf8(ByVal UCS As String) As Byte()
Dim lLength As Long
Dim lBufferSize As Long
Dim lResult As Long
Dim abUTF8() As Byte
lLength = Len(UCS)
If lLength = 0 Then Exit Function
lBufferSize = lLength * 3 + 1
ReDim abUTF8(lBufferSize - 1)
lResult = WideCharToMultiByte(CP_UTF8, 0, StrPtr(UCS), lLength, abUTF8(0), lBufferSize, vbNullString, 0)
If lResult <> 0 Then
lResult = lResult - 1
ReDim Preserve abUTF8(lResult)
UnicodeToUtf8 = abUTF8
End If
End Function