ENCODE(2) ENCODE(2)
NAME
dec64, enc64, dec32, enc32, dec16, enc16, dec64x, enc64x,
dec32x, enc32x, dec64chr, enc64chr, dec32chr, enc32chr,
dec16chr, enc16chr, encodefmt - encoding byte arrays as
strings
SYNOPSIS
#include <u.h>
#include <libc.h>
int dec64(uchar *out, int lim, char *in, int n)
int dec64x(uchar *out, int lim, char *in, int n, int
(*map)(int))
int enc64(char *out, int lim, uchar *in, int n)
int enc64x(char *out, int lim, uchar *in, int n, int
(*map)(int))
int dec32(uchar *out, int lim, char *in, int n)
int dec32x(uchar *out, int lim, char *in, int n, int
(*map)(int))
int enc32(char *out, int lim, uchar *in, int n)
int enc32x(char *out, int lim, uchar *in, int n, int
(*map)(int))
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*)
DESCRIPTION
The functions described here handle encoding and decoding of
Page 1 Plan 9 (printed 11/18/24)
ENCODE(2) ENCODE(2)
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 sym-
bol of the alphabet or -1 when the symbol is not in the
alphabet.
Enc16chr, enc32chr and enc64chr encode a symbol of the
alphabet given a value. if the value is out of range then
zero is returned.
The enc64x and enc32x variants are identical to the above,
except that they take a function mapping from an arbitrary
index in the alphabet to the encoded character. For exam-
ple, in the following 32-character alphabet,
ABCDEFGHIJKLMNOPQRSTUVWXYZ234567
the chr function would map the value 3 to the character D.
The dec64x and dec32x variants are similar to the above,
however the function passed maps from a character within the
alphabet to the index within the alphabet.
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);
SOURCE
Page 2 Plan 9 (printed 11/18/24)
ENCODE(2) ENCODE(2)
/sys/src/libc/port/u16.c
/sys/src/libc/port/u32.c
/sys/src/libc/port/u64.c
/sys/src/libc/port/encodefmt.c
HISTORY
In Jan 2018, base 32 encoding was changed from non-standard
to standard RFC4648 alphabet.
old: 23456789abcdefghijkmnpqrstuvwxyz
new: ABCDEFGHIJKLMNOPQRSTUVWXYZ234567
Page 3 Plan 9 (printed 11/18/24)