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.. Copyright 2017 Vector Creations Limited
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..
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.. Licensed under the Apache License, Version 2.0 (the "License");
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.. you may not use this file except in compliance with the License.
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.. You may obtain a copy of the License at
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..
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.. http://www.apache.org/licenses/LICENSE-2.0
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..
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.. Unless required by applicable law or agreed to in writing, software
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.. distributed under the License is distributed on an "AS IS" BASIS,
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.. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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.. See the License for the specific language governing permissions and
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.. limitations under the License.
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Unpadded Base64
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---------------
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*Unpadded* Base64 refers to 'standard' Base64 encoding as defined in `RFC
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4648`_, without "=" padding. Specifically, where RFC 4648 requires that encoded
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data be padded to a multiple of four characters using ``=`` characters,
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unpadded Base64 omits this padding.
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For reference, RFC 4648 uses the following alphabet for Base 64::
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Value Encoding Value Encoding Value Encoding Value Encoding
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0 A 17 R 34 i 51 z
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1 B 18 S 35 j 52 0
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2 C 19 T 36 k 53 1
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3 D 20 U 37 l 54 2
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4 E 21 V 38 m 55 3
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5 F 22 W 39 n 56 4
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6 G 23 X 40 o 57 5
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7 H 24 Y 41 p 58 6
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8 I 25 Z 42 q 59 7
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9 J 26 a 43 r 60 8
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10 K 27 b 44 s 61 9
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11 L 28 c 45 t 62 +
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12 M 29 d 46 u 63 /
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13 N 30 e 47 v
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14 O 31 f 48 w
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15 P 32 g 49 x
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16 Q 33 h 50 y
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Examples of strings encoded using unpadded Base64::
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UNPADDED_BASE64("") = ""
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UNPADDED_BASE64("f") = "Zg"
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UNPADDED_BASE64("fo") = "Zm8"
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UNPADDED_BASE64("foo") = "Zm9v"
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UNPADDED_BASE64("foob") = "Zm9vYg"
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UNPADDED_BASE64("fooba") = "Zm9vYmE"
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UNPADDED_BASE64("foobar") = "Zm9vYmFy"
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When decoding Base64, implementations SHOULD accept input with or without
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padding characters wherever possible, to ensure maximum interoperability.
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.. _`RFC 4648`: https://tools.ietf.org/html/rfc4648
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