Ascii85 encoder/decoder written in C.
There are many Ascii85 or Base85 implementations available. I needed something with three features:
- Complete and working implementation with unit tests
- Whitespace not ignored (so, non-standard)
- No memory allocation
The intended use is embedded microcontroller with limited memory and realtime constraints, for ASCII encoding binary data to be sent/received over serial interfaces. Whitespace is used for message framing, so cannot be ignored. Encoding/decoding is done from a complete input buffer to a complete output buffer.
There is a nice looking standard implementation at https://github.com/judsonx/base85 -- take a look at that one if you don't share my constraints. It supports a stateful stream processing approach as opposed to my complete input buffer to complete output buffer approach.
/*!
* @brief encode_ascii85: encode binary input into Ascii85
* @param[in] inp pointer to a buffer of unsigned bytes
* @param[in] in_length the number of bytes at inp to encode
* @param[in] outp pointer to a buffer for the encoded data
* @param[in] out_max_length available space at outp in bytes; must be >= 5 * ceiling(in_length/4)
* @return number of bytes in the encoded value at outp if non-negative; error code from
* ascii85_errs_e if negative
* @par Possible errors include: ascii85_err_in_buf_too_large, ascii85_err_out_buf_too_small
*/
int32_t encode_ascii85 (const uint8_t *inp, int32_t in_length, uint8_t *outp, int32_t out_max_length);
/*!
* @brief decode_ascii85: decode Ascii85 input to binary output
* @param[in] inp pointer to a buffer of Ascii85 encoded unsigned bytes
* @param[in] in_length the number of bytes at inp to decode
* @param[in] outp pointer to a buffer for the decoded data
* @param[in] out_max_length available space at outp in bytes; must be >= 4 * ceiling(in_length/5)
* @return number of bytes in the decoded value at outp if non-negative; error code from
* ascii85_errs_e if negative
* @par Possible errors include: ascii85_err_in_buf_too_large, ascii85_err_out_buf_too_small,
* ascii85_err_bad_decode_char, ascii85_err_decode_overflow
*/
int32_t decode_ascii85 (const uint8_t *inp, int32_t in_length, uint8_t *outp, int32_t out_max_length);
A Makefile is included that may work for you. But you really only need: ascii85.c and ascii85.h
The Makefile targets are: test and lint.
Run the unit tests with: ./test
The ./test program can be used to encode and decode data in a limited way.
Encode example:
$ ./test -i hello
<~BOu!rDZ~>
Decode example:
$ ./test -o 'BOu!rDZ'
~Decoded: 68656c6c6f
Quick test example:
$ ./test -i hello -o 'BOu!rDZ'
~Encode OK
MIT/X11