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glibc/libidn/punycode.c

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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, see <http://www.gnu.org/licenses/>.
*/
/*
* 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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