/*
punycode.c from RFC 3492
http://www.nicemice.net/idn/
Adam M. Costello
http://www.nicemice.net/amc/
This is ANSI C code (C89) implementing Punycode (RFC 3492).
*/
#include <string.h>
/*** Bootstring parameters for Punycode ***/
enum { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700,
initial_bias = 72, initial_n = 0x80, delimiter = 0x2D };
/* basic(cp) tests whether cp is a basic code point: */
#define basic(cp) ((punycode_uint)(cp) < 0x80)
/* delim(cp) tests whether cp is a delimiter: */
#define delim(cp) ((cp) == delimiter)
/* decode_digit(cp) returns the numeric value of a basic code */
/* point (for use in representing integers) in the range 0 to */
/* base-1, or base if cp is does not represent a value. */
static punycode_uint decode_digit(punycode_uint cp)
{
return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 :
cp - 97 < 26 ? cp - 97 : (punycode_uint) base;
}
/* encode_digit(d,flag) returns the basic code point whose value */
/* (when used for representing integers) is d, which needs to be in */
/* the range 0 to base-1. The lowercase form is used unless flag is */
/* nonzero, in which case the uppercase form is used. The behavior */
/* is undefined if flag is nonzero and digit d has no uppercase form. */
static char encode_digit(punycode_uint d, int flag)
{
return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
/* 0..25 map to ASCII a..z or A..Z */
/* 26..35 map to ASCII 0..9 */
}
/* flagged(bcp) tests whether a basic code point is flagged */
/* (uppercase). The behavior is undefined if bcp is not a */
/* basic code point. */
#define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26)
/* encode_basic(bcp,flag) forces a basic code point to lowercase */
/* if flag is zero, uppercase if flag is nonzero, and returns */
/* the resulting code point. The code point is unchanged if it */
/* is caseless. The behavior is undefined if bcp is not a basic */
/* code point. */
static char encode_basic(punycode_uint bcp, int flag)
{
bcp -= (bcp - 97 < 26) << 5;
return bcp + ((!flag && (bcp - 65 < 26)) << 5);
}
/*** Platform-specific constants ***/
/* maxint is the maximum value of a punycode_uint variable: */
static const punycode_uint maxint = -1U;
/* Because maxint is unsigned, -1 becomes the maximum value. */
/*** Bias adaptation function ***/
static punycode_uint adapt(
punycode_uint delta, punycode_uint numpoints, int firsttime )
{
punycode_uint k;
delta = firsttime ? delta / damp : delta >> 1;
/* delta >> 1 is a faster way of doing delta / 2 */
delta += delta / numpoints;
for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) {
delta /= base - tmin;
}
return k + (base - tmin + 1) * delta / (delta + skew);
}
/*** Main encode function ***/
enum punycode_status punycode_encode(
punycode_uint input_length,
const punycode_uint input[],
const unsigned char case_flags[],
punycode_uint *output_length,
char output[] )
{
punycode_uint n, delta, h, b, out, max_out, bias, j, m, q, k, t;
/* Initialize the state: */
n = initial_n;
delta = out = 0;
max_out = *output_length;
bias = initial_bias;
/* Handle the basic code points: */
for (j = 0; j < input_length; ++j) {
if (basic(input[j])) {
if (max_out - out < 2) return punycode_big_output;
output[out++] =
case_flags ? encode_basic(input[j], case_flags[j]) : input[j];
}
/* else if (input[j] < n) return punycode_bad_input; */
/* (not needed for Punycode with unsigned code points) */
}
h = b = out;
/* h is the number of code points that have been handled, b is the */
/* number of basic code points, and out is the number of characters */
/* that have been output. */
if (b > 0) output[out++] = delimiter;
/* Main encoding loop: */
while (h < input_length) {
/* All non-basic code points < n have been */
/* handled already. Find the next larger one: */
for (m = maxint, j = 0; j < input_length; ++j) {
/* if (basic(input[j])) continue; */
/* (not needed for Punycode) */
if (input[j] >= n && input[j] < m) m = input[j];
}
/* Increase delta enough to advance the decoder's */
/* <n,i> state to <m,0>, but guard against overflow: */
if (m - n > (maxint - delta) / (h + 1)) return punycode_overflow;
delta += (m - n) * (h + 1);
n = m;
for (j = 0; j < input_length; ++j) {
/* Punycode does not need to check whether input[j] is basic: */
if (input[j] < n /* || basic(input[j]) */ ) {
if (++delta == 0) return punycode_overflow;
}
if (input[j] == n) {
/* Represent delta as a generalized variable-length integer: */
for (q = delta, k = base; ; k += base) {
if (out >= max_out) return punycode_big_output;
t = k <= bias /* + tmin */ ? (punycode_uint) tmin : /* +tmin not needed */
k >= (punycode_uint) bias + (punycode_uint) tmax ? (punycode_uint) tmax : k - (punycode_uint) bias;
if (q < t) break;
output[out++] = encode_digit(t + (q - t) % (base - t), 0);
q = (q - t) / (base - t);
}
output[out++] = encode_digit(q, case_flags && case_flags[j]);
bias = adapt(delta, h + 1, h == b);
delta = 0;
++h;
}
}
++delta, ++n;
}
*output_length = out;
return punycode_success;
}
/*** Main decode function ***/
enum punycode_status punycode_decode(
punycode_uint input_length,
const char input[],
punycode_uint *output_length,
punycode_uint output[],
unsigned char case_flags[] )
{
punycode_uint n, out, i, max_out, bias,
b, j, in, oldi, w, k, digit, t;
/* Initialize the state: */
n = initial_n;
out = i = 0;
max_out = *output_length;
bias = initial_bias;
/* Handle the basic code points: Let b be the number of input code */
/* points before the last delimiter, or 0 if there is none, then */
/* copy the first b code points to the output. */
for (b = j = 0; j < input_length; ++j) if (delim(input[j])) b = j;
if (b > max_out) return punycode_big_output;
for (j = 0; j < b; ++j) {
if (case_flags) case_flags[out] = flagged(input[j]);
if (!basic(input[j])) return punycode_bad_input;
output[out++] = input[j];
}
/* Main decoding loop: Start just after the last delimiter if any */
/* basic code points were copied; start at the beginning otherwise. */
for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) {
/* in is the index of the next character to be consumed, and */
/* out is the number of code points in the output array. */
/* Decode a generalized variable-length integer into delta, */
/* which gets added to i. The overflow checking is easier */
/* if we increase i as we go, then subtract off its starting */
/* value at the end to obtain delta. */
for (oldi = i, w = 1, k = base; ; k += base) {
if (in >= input_length) return punycode_bad_input;
digit = decode_digit(input[in++]);
if (digit >= base) return punycode_bad_input;
if (digit > (maxint - i) / w) return punycode_overflow;
i += digit * w;
t = k <= (punycode_uint) bias /* + tmin */ ? (punycode_uint) tmin : /* +tmin not needed */
k >= (punycode_uint) bias + (punycode_uint) tmax ? (punycode_uint) tmax : k - (punycode_uint) bias;
if (digit < t) break;
if (w > maxint / (base - t)) return punycode_overflow;
w *= (base - t);
}
bias = adapt(i - oldi, out + 1, oldi == 0);
/* i was supposed to wrap around from out+1 to 0, */
/* incrementing n each time, so we'll fix that now: */
if (i / (out + 1) > maxint - n) return punycode_overflow;
n += i / (out + 1);
i %= (out + 1);
/* Insert n at position i of the output: */
/* not needed for Punycode: */
/* if (decode_digit(n) <= base) return punycode_invalid_input; */
if (out >= max_out) return punycode_big_output;
if (case_flags) {
memmove(case_flags + i + 1, case_flags + i, out - i);
/* Case of last character determines uppercase flag: */
case_flags[i] = flagged(input[in - 1]);
}
memmove(output + i + 1, output + i, (out - i) * sizeof *output);
output[i++] = n;
}
*output_length = out;
return punycode_success;
}