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77 lines
2.3 KiB
77 lines
2.3 KiB
2 months ago
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Base64 and Base224 encodings
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============================
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These modules can be used to encode and decode data to and from
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base64 (described in RFC 3548) and base224 (not described in any
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standard, uses all non-control characters, briefly described in
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a comment at the beginning of `ucw/base224.c`).
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- <<base64,Base64>>
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- <<base224,Base224>>
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- <<usage,Usage>>
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- <<basecode,The basecode utility>>
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[[base64]]
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ucw/base64.h
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------------
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!!ucw/base64.h
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[[base224]]
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ucw/base224.h
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-------------
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!!ucw/base224.h
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[[usage]]
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Usage
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-----
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- You may want to encode small block of known size. Just allocate the
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output buffer and feed the data to the function.
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byte output[BASE64_ENC_LENGTH(input_size)];
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uint output_size = base64_encode(output, input, input_size);
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- Decoding can be done in similar way. It is enough to have output
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buffer of the same size as the input one.
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- Encoding of a stream of unknown or large size can be split into
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chunks. The input chunk size must be multiple of `BASE64_IN_CHUNK`.
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The output will be corresponding multiple of `BASE64_OUT_CHUNK`.
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uint input_size;
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byte input[BASE64_IN_CHUNK * 10];
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while(input_size = read_chunk(input, BASE64_IN_CHUNK * 10)) {
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byte output[BASE64_OUT_CHUNK * 10];
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uint output_size = base64_encode(output, input, input_size);
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use_chunk(output, output_size);
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}
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- Decoding of a stream is done in the same way, just swap
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`BASE64_IN_CHUNK` and `BASE64_OUT_CHUNK` (you feed the decode
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function with `BASE64_OUT_CHUNK` multiple and get `BASE64_IN_CHUNK`
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multiple).
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The base224 has similar interface, therefore you can use it the same
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way as base64.
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[[basecode]]
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The basecode utility
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--------------------
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You can use the encoding/decoding routines from command line, trough
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`ucw-basecode` command. You have to specify the operation by a command
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line argument and give it the data on standard input. The arguments
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are:
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- `-e`: Encode to base64.
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- `-d`: Decode from base64.
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- `-E`: Encode to base224.
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- `-D`: Decode from base224.
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Furthermore, you can provide `--prefix` argument. If you do, the
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output (when encoding) will be split to lines by default number of
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chunks and the value of prefix will be prepended to each of them.
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When decoding, it removes the prefix from the beginning of line.
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You can override the default number of blocks for line-splitting by
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`--blocks` argument.
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