Unicode UTF Converter
Python - 1367 UTF-8 chars
Alright! This was an extremely difficult question because of the sheer amount of work it took to understand and implement all the specifications, but I think that I have a correct implementation.
O,P,Q,R=65536,128,b'\xff\xfe\x00\x00',63
def A(x,y):assert x;return y
def B(x):
o,c=[],0
for b in x:
if c:c,v=c-1,A(127<b<192,v<<6)|(b-P)
else:
c,v=(b>127)+(b>223)+(b>239),b
if b>127:v=A(191<b<248,b&(R>>c))
o+=[v][c:]
return o[o[0]in(65279,O-2):]
def C(k):
def o(x,s=None):
for a,b in zip(x[k::2],x[1-k::2]):
d=a|(b<<8)
if s!=None:yield(A(56319<d<57344,d-56320)|(s<<10))+O;s=None
elif 55295<d<57344:s=A(s<1024,d-55296)
else:yield d
return o
def D(x):n=(2,3,1)[[Q[:2],Q[1::-1],x[:2]].index(x[:2])];return C(n&1)(x[n&2:])
E=lambda a,b,c,d:lambda x:[L|(l<<8)|(m<<16) for L,l,m in zip(x[a::4],x[b::4],x[c::4])]
def F(x):n,m=((1,4),(-1,4),(-1,0))[[Q,Q[::-1],x[:4]].index(x[:4])];return E(*range(4)[::n])(x[m:])
S=lambda x,s=0,a=255:(x>>s)&a
G=lambda e:(e,)if e<P else(192|S(e,6),P|(e&R))if e<2048 else(224|S(e,12),P|S(e,6,R),P|(e&R))if e<O else(240|S(e,18),P|S(e,12,R),P|S(e,6,R),P|(e&R))
H=lambda e:(S(e,8),S(e))if e<O else(216|S(e-O,18),S(e-O,10),220+S((e-O)&1023,8),S(e-O))
I=lambda e:(S(e),S(e,8))if e<O else(S(e-O,10),216|S(e-O,18),S(e-O),220+S((e-O)&1023,8))
J=lambda e:(S(e,24),S(e,16),S(e,8),S(e))
K=lambda e:(S(e),S(e,8),S(e,16),S(e,24))
convert=lambda d,i,o:bytes(sum(map(L[o],N(list(M[i](d)))),()))if d else d
L,M=[G,H,H,I,J,J,K],[B,D,C(1),C(0),F,E(3,2,1,0),E(0,1,2,3)]
N=lambda d:[A(-1<x<1114112 and x&~2047!=55296,x)for x in d]
convert is the function that takes the data 'bytes' object, the input ID, and the output ID. It seems to work - although python seems to have a slightly broken usage of BOMs when unspecified in the encoding, so using python's builtin encoding to test modes 1 and 4 won't work.
Fun fact: The size is also 55516 or 101010101012.
773 chars for decoding, 452 for encoding, 59 for verification and 83 for miscellaneous parts.
Python 3, 1138 bytes (UTF-8)
So it turns out that 14 hours of international travel is a fantastic opportunity to finish off a golfing challenge...
The conversion function is C(). This calls u(), v(), and w() to decode, and U(), V(), and W() to encode, UTF-8, -16 and -32, respectively. None of the encoders will output a BOM, but all of the decoders will correctly handle one. Error conditions result in an exception (usually a ZeroDivisionError, courtesy of the "die-suddenly" function E()).
from struct import*
l=len
j=''.join
b=lambda c:[*bin(c)[2:]]
P,Q,i,o,z,Z='HI10><'
B=65279
O,F,H,L,X=1024,65536,55296,56320,57344
E=lambda:1/0
R=lambda y,e,c,n:unpack(([[z,Z][y[:n]==pack(Z+c,B)],e][l(e)])+c*(l(y)//n),y)
S=lambda d,e:B!=d[0]and d or e and E()or d[1:]
def u(y,d=(),p=0):
while p<l(y):
q=b(y[p])
if l(q)>7:
x=q.index(o);C=1<x<5and q[x+1:]or E();X=x+p;X>l(y)>E();p+=1
while p<X:q=b(y[p]);C=l(q)>7and(i,o==q[:2])and(*C,*q[2:])or E();p+=1
d=*d,int(j(C),2)
else:d=*d,y[p];p+=1
return S(d,0)
def T(p):
q=b(p);C=()
while l(q)not in(7,11,16,21):q=o,*q
while l(q)>6:C=int(i+o+j(q[-6:]),2),*C;q=q[:-6]
return bytes(p<128and[p]or[int(i*(7-l(q))+o+j(q),2),*C])
U=lambda c:b''.join(map(T,c))
def v(y,e=''):
c=R(y,e,P,2);d=[];n=0
while n<l(c)-1:h,a=c[n:n+2];D=[(h,a),(F+(h-H)*O+a-L,)][H<=h<L<=a<X];M=3-l(D);n+=M;d+=D[:M]
if n<l(c):d=*d,c[n]
return S(d,e)
V=lambda c,e=z:W(sum(map(lambda p:([H+(p-F)//O,L+(p-F)%O],[p])[p<F],c),[]),e,P)
w=lambda y,e='':S(R(y,e,Q,4),e)
W=lambda c,e=z,C=Q:pack(e+C*l(c),*c)
K=(u,U),(v,V),(v,V,z),(v,V,Z),(w,W),(w,W,z),(w,W,Z)
def C(y,f,t):f,_,*a=K[f];_,t,*b=K[t];return t(f(y,*a),*b)
C++, (UTF-8) 971 bytes
#include<cstdint>
using u=uint8_t;using U=uint32_t;U i,o,x,b,m;U R(u*&p){x=*p++;if(!i){m=0;while(128>>m&x)++m;if(m>1)for(x&=127>>m;--m;)x=x<<6|((*p&192)-128?~0:*p++&63);return m?x=~0:x;}else if(i<3){x<<=8;x+=*p++;}else if(i<4){x+=*p++<<8;}else if(i<6){x<<=24;x+=*p++<<16;x+=*p++<<8;x+=*p++;}else{x+=*p++<<8;x+=*p++<<16;x+=*p++<<24;}return x;}U r(u*&p){U x0=R(p);if(i&&i<4&&x>>10==54)x=R(p)>>10==55?(x0<<10)+x-56613888:~0;if(!b++){if(x==65279)if(!i||i%3==1)r(p);else x=~0;else if(x==65534&&i==1)i=3,r(p);else if(x==4294836224&&i==4)i=6,r(p);}return x>1114111||x>>11==27?x=~0:x;}void w(U x,u*&p){if(!o){if(x<128)*p++=x;else{for(m=0;~63<<m&x;m+=6);for(*p++=~127>>m/6|x>>m;m;)*p++=128|x>>(m-=6)&63;}}else if(o<4&&x>65535)x-=65536,w(55296|x>>10,p),w(56320|x&1023,p);else if(o<3)*p++=x>>8,*p++=x;else if(o<4)*p++=x,*p++=x>>8;else if(o<6)*p++=x>>24,*p++=x>>16,*p++=x>>8,*p++=x;else*p++=x,*p++=x>>8,*p++=x>>16,*p++=x>>24;}int t(u*&p,u*&q){for(b=0,x=1;U(x+x);)w(r(p),q);return x;}
The readable program below can be condensed to the above form by filtering it through the following Perl command:
perl -p0 -e 's!//.*!!g;s/\s+/ /g;s/ \B|\B //g;s/0x[\da-f]+/hex($&)/ige;s/#include<[^<>]+>/\n$&\n/g;s/^\n+//mg'
The above command
- removes comments
- removes unnecessary whitespace
- converts hexadecimal literals to decimal
- reinstates newlines around
#includelines
Readable code
#include <cstdint>
using u = uint8_t;
using U = uint32_t;
U i, // input encoding
o, // output encoding
x, // last read value
b, // char count(BOM only valid when b==0)
m; // temporary variable for measuring UTF-8
// Encodings:
// 0 UTF-8
// 1 UTF-16
// 2 UTF-16BE
// 3 UTF-16LE
// 4 UTF-32
// 5 UTF-32BE
// 6 UTF-32LE
// Read a character or UTF-16 surrogate
U R(u*& p) {
x = *p++;
if (!i) { // UTF-8
m=0; while (128>>m&x) ++m; // how many bytes?
if (m>1) for (x&=127>>m; --m; ) x = x<<6 | ((*p&192)-128?~0:*p++&63);
return m ? x=~0 : x;
} else if (i<3) { // UTF-16, UTF-16BE
x<<=8; x+=*p++;
} else if (i<4) { // UTF-16LE
x+=*p++<<8;
} else if (i<6) { // UTF-32, UTF-32BE
x<<=24; x+=*p++<<16; x+=*p++<<8; x+=*p++;
} else { // UTF-32LE
x+=*p++<<8; x+=*p++<<16; x+=*p++<<24;
}
return x;
}
// Read a character, combining surrogates, processing BOM, and checking range
U r(u*& p) {
U x0 = R(p);
if (i && i<4 && x>>10==54)
x = R(p)>>10==55 ? (x0<<10)+x-56613888: ~0; // 56613888 == 0xd800<<10 + 0xdc00 - 0x10000
if (!b++) { // first char - is it BOM?
if (x==0xFEFF)
if (!i || i%3==1)
r(p); // BOM in UTF-8 or UTF-16 or UTF-32 - ignore, and read next char
else
x = ~0; // not allowed in these modes
else if (x==0xFFFE && i==1)
i=3,r(p); // reversed BOM in UTF-16 - change to little-endian, and read next char
else if (x==0xFFFE0000 && i==4)
i=6,r(p); // reversed BOM in UTF-32 - change to little-endian, and read next char
}
return x>0x10ffff || x>>11==27 ? x=~0 : x;
}
// Write character(assumed in-range)
void w(U x, u*& p) {
if (!o) { // UTF-8
if (x<128) *p++=x; // ASCII
else {
for (m=0; ~63<<m&x; m+=6); // how many bits?
for (*p++=~127>>m/6|x>>m; m; ) *p++ = 128|x>>(m-=6)&63;
}
} else if (o<4 && x>65535) // UTF-16 surrogate
x-=65536, w(0xD800|x>>10,p), w(0xDC00|x&0x3FF,p);
else if (o<3) // UTF-16, UTF-16BE
*p++=x>>8, *p++=x;
else if (o<4) // UTF-16LE
*p++=x, *p++=x>>8;
else if (o<6) // UTF-32, UTF-32BE
*p++=x>>24, *p++=x>>16, *p++=x>>8, *p++=x;
else // UTF-32LE
*p++=x, *p++=x>>8, *p++=x>>16, *p++=x>>24;
}
// Transcode
int t(u*& p, u*& q) // input, output
{
for (b=0,x=1;U(x+x);) // exit condition is true only for x==-x, i.e. 0 and ~0
w(r(p),q);
return x;
}
The function to be called is t(), with input and output encodings passed in the global variables i and o respectively, and p pointing at the bytes of input, which must be null-terminated. q points to the output buffer, which will be overwritten, and must be big enough for the result - there is no attempt to avoid buffer overrun.
I hope the code comments are sufficiently explanatory - ask below if one of them is too cryptic (but do make an effort first!).
I compiled a substantial test suite whilst developing this answer; I include it below for the benefit of other entrants, and to document my interpretation of requirements:
Test functions
#include <vector>
#include <iostream>
std::ostream& operator<<(std::ostream& out, const std::vector<u>& v)
{
out << "{ ";
for (int i: v) out << i << " ";
out << "}";
return out;
}
int test_read(int encoding, std::vector<u> input, U expected)
{
b = 0;
i = encoding;
auto d = input.data();
U actual = r(d);
if (actual == expected) return 0;
std::cerr << std::hex << "Decoding " << encoding << "; " << input << " gave " << actual
<< " instead of " << expected << std::endl;
return 1;
}
int test_write(int encoding, U input, std::vector<u> expected)
{
o = encoding;
u buf[20], *p = buf;
w(input, p);
std::vector<u> actual(buf,p);
if (expected == actual) return 0;
std::cerr << std::hex << "Encoding " << encoding << "; " << input << " gave " << actual
<< " instead of " << expected << std::endl;
return 1;
}
int test_transcode(int ienc, std::vector<u> input, int oenc, std::vector<u> expected)
{
b = 0;
i = ienc; o = oenc;
u buf[200], *p = buf, *d = input.data();
int result = t(d, p);
std::vector<u> actual(buf,p);
if (result ? expected.empty() : expected == actual) return 0;
std::cerr << std::hex << "Encoding " << ienc << " to " << oenc << "; " << input << " gave " << actual
<< " instead of " << expected << std::endl;
return 1;
}
Test suite
static const U FAIL = ~0;
int main() {
int e = 0; // error count
// UTF-8
e += test_read(0, { 128 }, FAIL); // unexpected continuation
e += test_read(0, { 128, 1 }, FAIL);
e += test_read(0, { 128, 128 }, FAIL);
e += test_read(0, { 192, 192 }, FAIL); // start without continuation
e += test_read(0, { 192, 0 }, FAIL);
e += test_read(0, { 224, 0 }, FAIL);
e += test_read(0, { 224, 192 }, FAIL);
e += test_read(0, { 0xf4, 0x90, 128, 128 }, FAIL); // Unicode maximum+1
e += test_read(0, { 127 }, 127);
e += test_read(0, { 192, 129 }, 1); // We accept overlong UTF-8
e += test_read(0, { 0xc2, 128 }, 128);
e += test_read(0, { 224, 128, 129 }, 1);
e += test_read(0, { 0xef, 128, 128 }, 0xF000);
e += test_read(0, { 0xef, 191, 191 }, 0xFFFF);
e += test_read(0, { 0xf4, 128, 128, 128 }, 0x100000);
e += test_read(0, { 0xf4, 0x8f, 191, 191 }, 0x10FFFF); // Unicode maximum
e += test_read(0, { 0xEF, 0xBB, 0xBF, 127 }, 127); // byte-order mark
e += test_write(0, 0, { 0 });
e += test_write(0, 127, { 127 });
e += test_write(0, 128, { 0xc2, 128 });
e += test_write(0, 255, { 0xc3, 191 });
e += test_write(0, 0xFFFF, { 0xef, 191, 191 });
e += test_write(0, 0x10FFFF, { 0xf4, 0x8f, 191, 191 });
// UTF-16
e += test_read(1, { 0, 1 }, 1);
e += test_read(1, { 0xd8, 0, 0xdc, 1 }, 0x10001);
e += test_read(1, { 0xdb, 0xff, 0xdf, 0xff }, 0x10ffff);
e += test_read(1, { 0xd8, 0, 0xd8, 1 }, FAIL); // mismatched surrogate
e += test_read(1, { 0xd8, 0, 0, 1 }, FAIL); // mismatched surrogate
e += test_read(1, { 0xdc, 0 }, FAIL);
e += test_write(1, 1, { 0, 1 });
e += test_write(1, 256, { 1, 0 });
e += test_write(1, 0xffff, { 255, 255 });
e += test_write(1, 0x10001, { 0xd8, 0, 0xdc, 1 });
e += test_write(1, 0x10ffff, { 0xdb, 0xff, 0xdf, 0xff });
// UTF-16LE
e += test_write(3, 1, { 1, 0 });
e += test_write(3, 256, { 0, 1 });
e += test_write(3, 0x10001, { 0, 0xd8, 1, 0xdc });
e += test_write(3, 0x10fffe, { 0xff, 0xdb, 0xfe, 0xdf });
// UTF-16 byte-order mark
e += test_read(1, { 0xFE, 0xFF, 0x0, 1 }, 1); // byte-order mark
e += test_read(1, { 0xFF, 0xFE, 1, 0x0 }, 1); // reversed byte-order mark
// disallowed byte-order marks
e += test_read(2, { 0xFE, 0xFF }, FAIL);
e += test_read(3, { 0xFF, 0xFE }, FAIL);
// reversed byte-order mark is an unassigned character - to be treated like regular character, according to question
e += test_read(2, { 0xFF, 0xFE }, 0xfffe);
e += test_read(3, { 0xFE, 0xFF }, 0xfffe);
// UTF-32
e += test_read(4, { 0, 0, 0, 1 }, 1);
e += test_read(4, { 1, 0, 0, 0 }, FAIL);
e += test_write(4, 1, { 0, 0, 0, 1 });
e += test_write(4, 0x10203, { 0, 1, 2, 3 });
// UTF-32LE
e += test_read(6, { 0, 0, 0, 1 }, FAIL);
e += test_read(6, { 1, 0, 0, 0 }, 1);
// UTF-32 byte-order mark
e += test_read(4, { 0, 0, 0xFE, 0xFF, 0, 0, 0, 1 }, 1); // byte-order mark
e += test_read(4, { 0xFF, 0xFE, 0, 0, 1, 0, 0, 0 }, 1); // reversed byte-order mark
// disallowed byte-order marks
e += test_read(5, { 0, 0, 0xFE, 0xFF }, FAIL);
e += test_read(5, { 0xFF, 0xFE, 0, 0 }, FAIL);
e += test_read(6, { 0, 0, 0xFE, 0xFF }, FAIL);
e += test_read(6, { 0xFF, 0xFE, 0, 0 }, FAIL);
e += test_transcode(1, { 1, 2, 0xFE, 0xFF, 0, 0 }, // That's not a BOM; it's a zwnj when not the first char
1, { 1, 2, 0xFE, 0xFF, 0, 0 });
e += test_transcode(1, { 0xFF, 0xFE, 1, 2, 0, 0 }, // reversed byte-order mark implies little-endian
1, { 2, 1, 0, 0 });
e += test_transcode(4, { 0xFF, 0xFE, 0, 0, 1, 2, 0, 0, 0, 0 }, // reversed BOM means little-endian
4, { 0, 0, 2, 1, 0, 0, 0, 0 });
e += test_transcode(1, { 0xdb, 0xff, 0xdf, 0xff, 0, 0 }, // U+10ffff UTF-16 to UTF-8
0, { 0xf4, 0x8f, 191, 191, 0 });
return e;
}