NAME

byte2char, char2byte − convert between bytes and characters

SYNOPSIS

include "sys.m";
sys := load Sys Sys->PATH;
 byte2char: fn(buf: array of byte, n: int): (int, int, int);
char2byte: fn(c: int, buf: array of byte, n: int): int;

DESCRIPTION

­Byte2char converts a byte sequence to one Unicode character.  ­Buf is an array of bytes and ­n is the index of the first byte to examine in the array.  The returned tuple, say (c, length, status), specifies the result of the translation: ­c is the resulting Unicode character, ­status is non-zero if the bytes are a valid UTF sequence and zero otherwise, and ­length is set to the number of bytes consumed by the translation.  If the input sequence is not long enough to determine its validity, ­byte2char consumes zero bytes; if the input sequence is otherwise invalid, ­byte2char consumes one input byte and generates an error character (Sys->UTFerror, 16r80), which prints in most fonts as a boxed question mark. 

­Char2byte performs the inverse of byte2char.  It translates a Unicode character, c, to a UTF byte sequence, which is placed in successive bytes starting at buf[ n]. The longest UTF sequence for a single Unicode character is ­Sys->UTFmax (3) bytes.  If the translation succeeds, ­char2byte returns the number of bytes placed in the buffer.  If the buffer is too small to hold the result, ­char2byte returns zero and leaves the array unchanged. 

SOURCE

­/interp/runt.c

SEE ALSO

sys-intro(2), sys-utfbytes(2), utf(6)

DIAGNOSTICS

A run-time error occurs if ­n exceeds the bounds of the array. 

Plan 9  —  June 29, 2000