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byte2char, char2byte - convert between bytes and characters


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;


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[.IRn]. 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.




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


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

SYS-BYTE2CHAR(2 ) Rev:  Thu Feb 15 14:43:27 GMT 2007