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+/*
+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).
+
+
+C. Disclaimer and license
+
+ Regarding this entire document or any portion of it (including
+ the pseudocode and C code), the author makes no guarantees and
+ is not responsible for any damage resulting from its use. The
+ author grants irrevocable permission to anyone to use, modify,
+ and distribute it in any way that does not diminish the rights
+ of anyone else to use, modify, and distribute it, provided that
+ redistributed derivative works do not contain misleading author or
+ version information. Derivative works need not be licensed under
+ similar terms.
+*/
+
+#include "punycode.h"
+
+/**********************************************************/
+/* Implementation (would normally go in its own .c file): */
+
+#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
+ : 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 = (punycode_uint)-1;
+/* 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]) : (char)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 */ ? tmin : /* +tmin not needed */
+ k >= bias + tmax ? tmax
+ : k - 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;
+
+ if (!input_length) {
+ return punycode_bad_input;
+ }
+
+ /* 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 = 0, j = input_length - 1; j > 0; --j) {
+ if (delim(input[j])) {
+ b = j;
+ break;
+ }
+ }
+ 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 <= bias /* + tmin */ ? tmin : /* +tmin not needed */
+ k >= bias + tmax ? tmax
+ : k - 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;
+}
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