如何在PowerBuilder中实现BASE64编码与解码？

在PowerBuilder中实现BASE64编码与解码，可以通过使用内置函数或者自定义函数来完成。PowerBuilder并没有直接提供BASE64编码解码的内置函数，但可以利用PowerScript编写自定义函数来处理。以下是一个简单的自定义函数实现：

1. BASE64编码函数示例：

Function string Base64Encode(string as_input)
    string ls_encoded
    long ll_length, ll_index, ll_value, ll_temp
    long ll_buffer_length, ll_buffer_index
    long ll_buffer[256]
    string ls_base64_table
    ls_base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    ll_buffer_length = Len(ls_base64_table)
    ll_length = Len(as_input)
    For ll_index = 1 To ll_length
        ll_buffer_index = Mod(ll_index - 1, 3) + 1
        ll_temp = ll_buffer_index
        ll_buffer[ll_buffer_index] = ll_buffer[ll_buffer_index] << 8
        ll_buffer[ll_buffer_index] = ll_buffer[ll_buffer_index] + Left(as_input, 1)
        as_input = Right(as_input, Len(as_input) - 1)
    Next
    ll_buffer_index = Mod(ll_length, 3) + 1
    If ll_buffer_index < 3 Then
        ll_buffer[3] = 0
        ll_buffer[2] = ll_buffer[2] + (ll_buffer_index << 16)
        ll_buffer[1] = ll_buffer[1] + (ll_buffer_index << 24)
    End If
    For ll_index = 1 To ll_buffer_length Step 3
        ll_value = ll_buffer[ll_index - 1] + (ll_buffer[ll_index] << 8) + (ll_buffer[ll_index + 1] << 16)
        ls_encoded = ls_encoded + Substitute(ls_base64_table, Right(String(ll_value, "X"), 1), "")
        ls_encoded = ls_encoded + Substitute(ls_base64_table, Right(String(ll_value, "X"), 1), "")
        ls_encoded = ls_encoded + Substitute(ls_base64_table, Right(String(ll_value, "X"), 1), "")
        ls_encoded = ls_encoded + Substitute(ls_base64_table, Right(String(ll_value, "X"), 1), "")
    Next
    ls_encoded = ls_encoded + Substitute(String(ll_buffer[3], "X"), Right(String(ll_buffer[3], "X"), 2), "")
    ls_encoded = ls_encoded + String(ll_buffer[2], "X") + String(ll_buffer[1], "X")
    ls_encoded = Left(ls_encoded, Len(ls_encoded) - (Mod(ll_length, 3) = 0 ? 0 : 4 - Mod(ll_length, 3)))
    Base64Encode = ls_encoded
End Function

2. BASE64解码函数示例：

Function string Base64Decode(string as_input)
    string ls_decoded
    long ll_length, ll_index, ll_value, ll_temp
    long ll_buffer_length, ll_buffer_index
    long ll_buffer[256]
    string ls_base64_table
    ls_base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    ll_buffer_length = Len(ls_base64_table)
    ll_length = Len(as_input)
    For ll_index = 1 To ll_length Step 4
        ll_value = (Pos(ls_base64_table, Left(as_input, 1)) - 1) + (Pos(ls_base64_table, Mid(as_input, 2, 1)) - 1) * ll_buffer_length + (Pos(ls_base64_table, Mid(as_input, 3, 1)) - 1) * ll_buffer_length * ll_buffer_length + (Pos(ls_base64_table, Mid(as_input, 4, 1)) - 1) * ll_buffer_length * ll_buffer_length * ll_buffer_length
        For ll_buffer_index = 1 To 3
            ll_temp = ll_buffer_index
            ll_buffer[ll_buffer_index] = ll_buffer[ll_buffer_index] + (ll_value & 255)
            ll_value = Right(String(ll_value >> 8), 2)
        Next
        If Left(Mid(as_input, 4, 1), 1) = "=" Then
            ll_buffer[3] = 0
        Else
            ll_buffer[3] = ll_buffer[3] + (Left(Mid(as_input, 4, 1), 1) & 255)
        End If
    Next
    For ll_index = 1 To ll_length - (Left(as_input, 1) = "=")
        ls_decoded = ls_decoded + Chr(ll_buffer[ll_index])
    Next
    Base64Decode = ls_decoded
End Function

使用方法：

string ls_encoded
string ls_decoded

ls_encoded = Base64Encode("Hello, World!")
MessageBox("Encoded", ls_encoded)

ls_decoded = Base64Decode(ls_encoded)
MessageBox("Decoded", ls_decoded)