feat: add simple baidu query api support

lua/Trans/util/base64.lua

@@ -0,0 +1,39 @@
+local ffi = require('ffi')
+local base64 = {}
+
+local b64 = ffi.new('unsigned const char[65]',
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
+
+function base64.encode(str)
+    local band, bor, lsh, rsh = bit.band, bit.bor, bit.lshift, bit.rshift
+    local len = #str
+    local enc_len = 4 * math.ceil(len / 3) -- (len + 2) // 3 * 4 after Lua 5.3
+
+    local src = ffi.new('unsigned const char[?]', len+1, str)
+    local enc = ffi.new('unsigned char[?]', enc_len+1)
+
+    local i, j = 0, 0
+    while i < len-2 do
+        enc[j] = b64[band(rsh(src[i], 2), 0x3F)]
+        enc[j+1] = b64[bor(lsh(band(src[i], 0x3), 4), rsh(band(src[i+1], 0xF0), 4))]
+        enc[j+2] = b64[bor(lsh(band(src[i+1], 0xF), 2), rsh(band(src[i+2], 0xC0), 6))]
+        enc[j+3] = b64[band(src[i+2], 0x3F)]
+        i, j = i+3, j+4
+    end
+
+    if i < len then
+        enc[j] = b64[band(rsh(src[i], 2), 0x3F)]
+        if i == len-1 then
+            enc[j+1] = b64[lsh(band(src[i], 0x3), 4)]
+            enc[j+2] = 0x3D
+        else
+            enc[j+1] = b64[bor(lsh(band(src[i], 0x3), 4), rsh(band(src[i+1], 0xF0), 4))]
+            enc[j+2] = b64[lsh(band(src[i+1], 0xF), 2)]
+        end
+        enc[j+3] = 0x3D
+    end
+
+    return ffi.string(enc, enc_len)
+end
+
+return base64