ENCODE(2)                                               ENCODE(2)

          dec64, enc64, dec32, enc32, dec16, enc16, dec64chr,
          enc64chr, dec32chr, enc32chr, dec16chr, enc16chr, encodefmt
          - encoding byte arrays as strings

          #include <u.h>
          #include <libc.h>

          int  dec64(uchar *out, int lim, char *in, int n)

          int  enc64(char *out, int lim, uchar *in, int n)

          int  dec32(uchar *out, int lim, char *in, int n)

          int  enc32(char *out, int lim, uchar *in, int n)

          int  dec16(uchar *out, int lim, char *in, int n)

          int  enc16(char *out, int lim, uchar *in, int n)

          int  dec64chr(int c)

          int  enc64chr(int o)

          int  dec32chr(int c)

          int  enc32chr(int o)

          int  dec16chr(int c)

          int  enc16chr(int o)

          int  encodefmt(Fmt*)

          The functions described here handle encoding and decoding of
          bytes to printable ASCII strings as specified by RFC4648.

          Enc16, enc32 and enc64 create null terminated strings.  They
          return the size of the encoded string (without the null) or
          -1 if the encoding fails.  The encoding fails if lim, the
          length of the output buffer (including null), is too small.

          Dec16, dec32 and dec64 return the number of bytes decoded or
          -1 if the decoding fails.  The decoding fails if the output
          buffer is not large enough or, for base 32, if the input
          buffer length is not a multiple of 8.

          Dec16chr, dec32chr and dec64chr return the value for a

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     ENCODE(2)                                               ENCODE(2)

          symbol of the alphabet or -1 when the symbol is not in the

          Enc16chr, enc32chr and enc64chr encode a symbol of the
          alphabet given a value.  if the value is out of range then
          zero is returned.

          Encodefmt can be used with fmtinstall(2) and print(2) to
          print encoded representations of byte arrays.  The verbs are

          H    base 16 (i.e. hexadecimal). The default encoding is in
               upper case.  The l flag forces lower case.

          <    base 32. The default is upper case, same as H.

          [    base 64 (same as MIME)

          The length of the array is specified as f2. For example, to
          display a 15 byte array as hex:

              char x[15];

              fmtinstall('H', encodefmt);
              print("%.*H\n", sizeof x, x);


          In Jan 2018, base 32 encoding was changed from non-standard
          to standard RFC4648 alphabet.

          old: 23456789abcdefghijkmnpqrstuvwxyz


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