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+/* punycode.c Implementation of punycode used to ASCII encode IDN's.
+ * Copyright (C) 2002, 2003 Simon Josefsson
+ *
+ * This file is part of GNU Libidn.
+ *
+ * GNU Libidn is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * GNU Libidn is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with GNU Libidn; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+/*
+ * This file is derived from RFC 3492bis written by Adam M. Costello.
+ *
+ * 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.
+ *
+ * Copyright (C) The Internet Society (2003). All Rights Reserved.
+ *
+ * This document and translations of it may be copied and furnished to
+ * others, and derivative works that comment on or otherwise explain it
+ * or assist in its implementation may be prepared, copied, published
+ * and distributed, in whole or in part, without restriction of any
+ * kind, provided that the above copyright notice and this paragraph are
+ * included on all such copies and derivative works. However, this
+ * document itself may not be modified in any way, such as by removing
+ * the copyright notice or references to the Internet Society or other
+ * Internet organizations, except as needed for the purpose of
+ * developing Internet standards in which case the procedures for
+ * copyrights defined in the Internet Standards process must be
+ * followed, or as required to translate it into languages other than
+ * English.
+ *
+ * The limited permissions granted above are perpetual and will not be
+ * revoked by the Internet Society or its successors or assigns.
+ *
+ * This document and the information contained herein is provided on an
+ * "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ * TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ * BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ * HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <string.h>
+
+#include "punycode.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 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 = -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 ***/
+
+/**
+ * punycode_encode:
+ * @input_length: The number of code points in the @input array and
+ * the number of flags in the @case_flags array.
+ * @input: An array of code points. They are presumed to be Unicode
+ * code points, but that is not strictly REQUIRED. The array
+ * contains code points, not code units. UTF-16 uses code units
+ * D800 through DFFF to refer to code points 10000..10FFFF. The
+ * code points D800..DFFF do not occur in any valid Unicode string.
+ * The code points that can occur in Unicode strings (0..D7FF and
+ * E000..10FFFF) are also called Unicode scalar values.
+ * @case_flags: A %NULL pointer or an array of boolean values parallel
+ * to the @input array. Nonzero (true, flagged) suggests that the
+ * corresponding Unicode character be forced to uppercase after
+ * being decoded (if possible), and zero (false, unflagged) suggests
+ * that it be forced to lowercase (if possible). ASCII code points
+ * (0..7F) are encoded literally, except that ASCII letters are
+ * forced to uppercase or lowercase according to the corresponding
+ * case flags. If @case_flags is a %NULL pointer then ASCII letters
+ * are left as they are, and other code points are treated as
+ * unflagged.
+ * @output_length: The caller passes in the maximum number of ASCII
+ * code points that it can receive. On successful return it will
+ * contain the number of ASCII code points actually output.
+ * @output: An array of ASCII code points. It is *not*
+ * null-terminated; it will contain zeros if and only if the @input
+ * contains zeros. (Of course the caller can leave room for a
+ * terminator and add one if needed.)
+ *
+ * Converts a sequence of code points (presumed to be Unicode code
+ * points) to Punycode.
+ *
+ * Return value: The return value can be any of the punycode_status
+ * values defined above except %punycode_bad_input. If not
+ * %punycode_success, then @output_size and @output might contain
+ * garbage.
+ **/
+int
+punycode_encode (size_t input_length,
+ const punycode_uint input[],
+ const unsigned char case_flags[],
+ size_t * output_length, char output[])
+{
+ punycode_uint input_len, n, delta, h, b, bias, j, m, q, k, t;
+ size_t out, max_out;
+
+ /* The Punycode spec assumes that the input length is the same type */
+ /* of integer as a code point, so we need to convert the size_t to */
+ /* a punycode_uint, which could overflow. */
+
+ if (input_length > maxint)
+ return punycode_overflow;
+ input_len = (punycode_uint) input_length;
+
+ /* Initialize the state: */
+
+ n = initial_n;
+ delta = 0;
+ out = 0;
+ max_out = *output_length;
+ bias = initial_bias;
+
+ /* Handle the basic code points: */
+
+ for (j = 0; j < input_len; ++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 = (punycode_uint) out;
+ /* cannot overflow because out <= input_len <= maxint */
+
+ /* 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 ASCII code */
+ /* points that have been output. */
+
+ if (b > 0)
+ output[out++] = delimiter;
+
+ /* Main encoding loop: */
+
+ while (h < input_len)
+ {
+ /* All non-basic code points < n have been */
+ /* handled already. Find the next larger one: */
+
+ for (m = maxint, j = 0; j < input_len; ++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_len; ++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 ***/
+
+/**
+ * punycode_decode:
+ * @input_length: The number of ASCII code points in the @input array.
+ * @input: An array of ASCII code points (0..7F).
+ * @output_length: The caller passes in the maximum number of code
+ * points that it can receive into the @output array (which is also
+ * the maximum number of flags that it can receive into the
+ * @case_flags array, if @case_flags is not a %NULL pointer). On
+ * successful return it will contain the number of code points
+ * actually output (which is also the number of flags actually
+ * output, if case_flags is not a null pointer). The decoder will
+ * never need to output more code points than the number of ASCII
+ * code points in the input, because of the way the encoding is
+ * defined. The number of code points output cannot exceed the
+ * maximum possible value of a punycode_uint, even if the supplied
+ * @output_length is greater than that.
+ * @output: An array of code points like the input argument of
+ * punycode_encode() (see above).
+ * @case_flags: A %NULL pointer (if the flags are not needed by the
+ * caller) or an array of boolean values parallel to the @output
+ * array. Nonzero (true, flagged) suggests that the corresponding
+ * Unicode character be forced to uppercase by the caller (if
+ * possible), and zero (false, unflagged) suggests that it be forced
+ * to lowercase (if possible). ASCII code points (0..7F) are output
+ * already in the proper case, but their flags will be set
+ * appropriately so that applying the flags would be harmless.
+ *
+ * Converts Punycode to a sequence of code points (presumed to be
+ * Unicode code points).
+ *
+ * Return value: The return value can be any of the punycode_status
+ * values defined above. If not %punycode_success, then
+ * @output_length, @output, and @case_flags might contain garbage.
+ *
+ **/
+int
+punycode_decode (size_t input_length,
+ const char input[],
+ size_t * output_length,
+ punycode_uint output[], unsigned char case_flags[])
+{
+ punycode_uint n, out, i, max_out, bias, oldi, w, k, digit, t;
+ size_t b, j, in;
+
+ /* Initialize the state: */
+
+ n = initial_n;
+ out = i = 0;
+ max_out = *output_length > maxint ? maxint
+ : (punycode_uint) * 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 ASCII code point 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 (basic(n)) 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 ASCII code point determines case flag: */
+ case_flags[i] = flagged (input[in - 1]);
+ }
+
+ memmove (output + i + 1, output + i, (out - i) * sizeof *output);
+ output[i++] = n;
+ }
+
+ *output_length = (size_t) out;
+ /* cannot overflow because out <= old value of *output_length */
+ return punycode_success;
+}
+
+/**
+ * punycode_uint
+ *
+ * Unicode code point data type, this is always a 32 bit unsigned
+ * integer.
+ */
+
+/**
+ * Punycode_status
+ * @PUNYCODE_SUCCESS: Successful operation. This value is guaranteed
+ * to always be zero, the remaining ones are only guaranteed to hold
+ * non-zero values, for logical comparison purposes.
+ * @PUNYCODE_BAD_INPUT: Input is invalid.
+ * @PUNYCODE_BIG_OUTPUT: Output would exceed the space provided.
+ * @PUNYCODE_OVERFLOW: Input needs wider integers to process.
+ *
+ * Enumerated return codes of punycode_encode() and punycode_decode().
+ * The value 0 is guaranteed to always correspond to success.
+ */
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