# Helpers for Unicode.
#
# Mu has no characters, only code points and graphemes.
# Code points are the indivisible atoms of text streams.
# https://en.wikipedia.org/wiki/Code_point
# Graphemes are the smallest self-contained unit of text.
# Graphemes may consist of multiple code points.
#
# Mu graphemes are always represented in utf-8, and they are required to fit
# in 4 bytes.
#
# Mu doesn't currently support combining code points, or graphemes made of
# multiple code points. One day we will.
# We also don't currently support code points that translate into multiple
# or wide graphemes. (In particular, Tab will never be supported.)
# transliterated from tb_utf8_unicode_to_char in https://github.com/nsf/termbox
# https://wiki.tcl-lang.org/page/UTF%2D8+bit+by+bit explains the algorithm
#
# The day we want to support combining characters, this function will need to
# take multiple code points. Or something.
fn to-grapheme in: code-point -> _/eax: grapheme {
var c/eax: int <- copy in
var num-trailers/ecx: int <- copy 0
var first/edx: int <- copy 0
$to-grapheme:compute-length: {
# single byte: just return it
compare c, 0x7f
{
break-if->
var g/eax: grapheme <- copy c
return g
}
# 2 bytes
compare c, 0x7ff
{
break-if->
num-trailers <- copy 1
first <- copy 0xc0
break $to-grapheme:compute-length
}
# 3 bytes
compare c, 0xffff
{
break-if->
num-trailers <- copy 2
first <- copy 0xe0
break $to-grapheme:compute-length
}
# 4 bytes
compare c, 0x1fffff
{
break-if->
num-trailers <- copy 3
first <- copy 0xf0
break $to-grapheme:compute-length
}
# more than 4 bytes: unsupported
# TODO: print to stderr
compare c, 0x1fffff
{
break-if->
print-string-to-real-screen "unsupported code point "
print-int32-hex-to-real-screen c
print-string-to-real-screen "\n"
var exit-status/ebx: int <- copy 1
syscall_exit
}
}
# emit trailer bytes, 6 bits from 'in', first two bits '10'
var result/edi: grapheme <- copy 0
{
compare num-trailers, 0
break-if-<=
var tmp/esi: int <- copy c
tmp <- and 0x3f
tmp <- or 0x80
result <- shift-left 8
result <- or tmp
# update loop state
c <- shift-right 6
num-trailers <- decrement
loop
}
# emit engine
result <- shift-left 8
result <- or c
result <- or first
#
return result
}
# single-byte code point have identical graphemes
fn test-to-grapheme-single-byte {
var in-int/ecx: int <- copy 0
{
compare in-int, 0x7f
break-if->
var in/eax: code-point <- copy in-int
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, in-int, "F - test-to-grapheme-single-byte"
in-int <- increment
loop
}
}
# byte | byte | byte | byte
# smallest 2-byte utf-8
fn test-to-grapheme-two-bytes-min {
var in/eax: code-point <- copy 0x80 # 10 00-0000
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0x80c2, "F - to-grapheme/2a" # 110 0-0010 10 00-0000
}
# largest 2-byte utf-8
fn test-to-grapheme-two-bytes-max {
var in/eax: code-point <- copy 0x7ff # 1-1111 11-1111
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0xbfdf, "F - to-grapheme/2b" # 110 1-1111 10 11-1111
}
# smallest 3-byte utf-8
fn test-to-grapheme-three-bytes-min {
var in/eax: code-point <- copy 0x800 # 10-0000 00-0000
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0x80a0e0, "F - to-grapheme/3a" # 1110 0000 10 10-0000 10 00-0000
}
# largest 3-byte utf-8
fn test-to-grapheme-three-bytes-max {
var in/eax: code-point <- copy 0xffff # 1111 11-1111 11-1111
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0xbfbfef, "F - to-grapheme/3b" # 1110 1111 10 11-1111 10 11-1111
}
# smallest 4-byte utf-8
fn test-to-grapheme-four-bytes-min {
var in/eax: code-point <- copy 0x10000 # 1-0000 00-0000 00-0000
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0x808090f0, "F - to-grapheme/4a" # 1111-0 000 10 01-0000 10 00-0000 10 00-0000
}
# largest 4-byte utf-8
fn test-to-grapheme-four-bytes-max {
var in/eax: code-point <- copy 0x1fffff # 111 11-1111 11-1111 11-1111
var out/eax: grapheme <- to-grapheme in
var out-int/eax: int <- copy out
check-ints-equal out-int, 0xbfbfbff7, "F - to-grapheme/4b" # 1111-0 111 10 11-1111 10 11-1111 10 11-1111
}
# read the next grapheme from a stream of bytes
fn read-grapheme in: (addr stream byte) -> _/eax: grapheme {
# if at eof, return EOF
{
var eof?/eax: boolean <- stream-empty? in
compare eof?, 0/false
break-if-=
return 0xffffffff
}
var c/eax: byte <- read-byte in
var num-trailers/ecx: int <- copy 0
$read-grapheme:compute-length: {
# single byte: just return it
compare c, 0xc0
{
break-if->=
var g/eax: grapheme <- copy c
return g
}
compare c, 0xfe
{
break-if-<
var g/eax: grapheme <- copy c
return g
}
# 2 bytes
compare c, 0xe0
{
break-if->=
num-trailers <- copy 1
break $read-grapheme:compute-length
}
# 3 bytes
compare c, 0xf0
{
break-if->=
num-trailers <- copy 2
break $read-grapheme:compute-length
}
# 4 bytes
compare c, 0xf8
{
break-if->=
num-trailers <- copy 3
break $read-grapheme:compute-length
}
$read-grapheme:abort: {
# TODO: print to stderr
print-string-to-real-screen "utf-8 encodings larger than 4 bytes are not supported. First byte seen: "
var n/eax: int <- copy c
print-int32-hex-to-real-screen n
print-string-to-real-screen "\n"
var exit-status/ebx: int <- copy 1
syscall_exit
}
}
# prepend trailer bytes
var result/edi: grapheme <- copy c
var num-byte-shifts/edx: int <- copy 1
{
compare num-trailers, 0
break-if-<=
var tmp/eax: byte <- read-byte in
var tmp2/eax: int <- copy tmp
tmp2 <- shift-left-bytes tmp2, num-byte-shifts
result <- or tmp2
# update loop state
num-byte-shifts <- increment
num-trailers <- decrement
loop
}
return result
}
fn test-read-grapheme {
var s: (stream byte 0x30)
var s2/ecx: (addr stream byte) <- address s
write s2, "aΒc世d界e"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x61, "F - test grapheme/0"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x92ce/greek-capital-letter-beta, "F - test grapheme/1"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x63, "F - test grapheme/2"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x96b8e4, "F - test grapheme/3"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x64, "F - test grapheme/4"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x8c95e7, "F - test grapheme/5"
var c/eax: grapheme <- read-grapheme s2
var n/eax: int <- copy c
check-ints-equal n, 0x65, "F - test grapheme/6"
}
fn read-grapheme-buffered in: (addr buffered-file) -> _/eax: grapheme {
var c/eax: byte <- read-byte-buffered in
var num-trailers/ecx: int <- copy 0
$read-grapheme-buffered:compute-length: {
# single byte: just return it
compare c, 0xc0
{
break-if->=
var g/eax: grapheme <- copy c
return g
}
compare c, 0xfe
{
break-if-<
var g/eax: grapheme <- copy c
return g
}
# 2 bytes
compare c, 0xe0
{
break-if->=
num-trailers <- copy 1
break $read-grapheme-buffered:compute-length
}
# 3 bytes
compare c, 0xf0
{
break-if->=
num-trailers <- copy 2
break $read-grapheme-buffered:compute-length
}
# 4 bytes
compare c, 0xf8
{
break-if->=
num-trailers <- copy 3
break $read-grapheme-buffered:compute-length
}
$read-grapheme-buffered:abort: {
# TODO: print to stderr
print-string-to-real-screen "utf-8 encodings larger than 4 bytes are not supported. First byte seen: "
var n/eax: int <- copy c
print-int32-hex-to-real-screen n
print-string-to-real-screen "\n"
var exit-status/ebx: int <- copy 1
syscall_exit
}
}
# prepend trailer bytes
var result/edi: grapheme <- copy c
var num-byte-shifts/edx: int <- copy 1
{
compare num-trailers, 0
break-if-<=
var tmp/eax: byte <- read-byte-buffered in
var tmp2/eax: int <- copy tmp
tmp2 <- shift-left-bytes tmp2, num-byte-shifts
result <- or tmp2
# update loop state
num-byte-shifts <- increment
num-trailers <- decrement
loop
}
return result
}
# needed because available primitives only shift by a literal/constant number of bits
fn shift-left-bytes n: int, k: int -> _/eax: int {
var i/ecx: int <- copy 0
var result/eax: int <- copy n
{
compare i, k
break-if->=
compare i, 4 # only 4 bytes in 32 bits
break-if->=
result <- shift-left 8
i <- increment
loop
}
return result
}
fn test-shift-left-bytes-0 {
var result/eax: int <- shift-left-bytes 1, 0
check-ints-equal result, 1, "F - shift-left-bytes 0"
}
fn test-shift-left-bytes-1 {
var result/eax: int <- shift-left-bytes 1, 1
check-ints-equal result, 0x100, "F - shift-left-bytes 1"
}
fn test-shift-left-bytes-2 {
var result/eax: int <- shift-left-bytes 1, 2
check-ints-equal result, 0x10000, "F - shift-left-bytes 2"
}
fn test-shift-left-bytes-3 {
var result/eax: int <- shift-left-bytes 1, 3
check-ints-equal result, 0x1000000, "F - shift-left-bytes 3"
}
fn test-shift-left-bytes-4 {
var result/eax: int <- shift-left-bytes 1, 4
check-ints-equal result, 0, "F - shift-left-bytes 4"
}
fn test-shift-left-bytes-5 {
var result/eax: int <- shift-left-bytes 1, 5
check-ints-equal result, 0, "F - shift-left-bytes >4"
}
# write a grapheme to a stream of bytes
# this is like write-to-stream, except we skip leading 0 bytes
fn write-grapheme out: (addr stream byte), g: grapheme {
$write-grapheme:body: {
var c/eax: int <- copy g
append-byte out, c # first byte is always written
c <- shift-right 8
compare c, 0
break-if-= $write-grapheme:body
append-byte out, c
c <- shift-right 8
compare c, 0
break-if-= $write-grapheme:body
append-byte out, c
c <- shift-right 8
compare c, 0
break-if-= $write-grapheme:body
append-byte out, c
}
}