Coverage Report

Created: 2025-03-06 07:58

/src/libidn2/lib/punycode.c
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/* punycode.c - punycode encoding/decoding
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   Copyright (C) 2011-2024 Simon Josefsson
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   Libidn2 is free software: you can redistribute it and/or modify it
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   under the terms of either:
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     * the GNU Lesser General Public License as published by the Free
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       Software Foundation; either version 3 of the License, or (at
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       your option) any later version.
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   or
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     * the GNU General Public License as published by the Free
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       Software Foundation; either version 2 of the License, or (at
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       your option) any later version.
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   or both in parallel, as here.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   GNU General Public License for more details.
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   You should have received copies of the GNU General Public License and
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   the GNU Lesser General Public License along with this program.  If
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   not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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  Code copied from http://www.nicemice.net/idn/punycode-spec.gz on
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  2011-01-04 with SHA-1 a966a8017f6be579d74a50a226accc7607c40133
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  labeled punycode-spec 1.0.3 (2006-Mar-23-Thu).  It is modified for
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  Libidn2 by Simon Josefsson and others.  Original code license:
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  punycode-spec 1.0.3 (2006-Mar-23-Thu)
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  http://www.nicemice.net/idn/
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  Adam M. Costello
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  http://www.nicemice.net/amc/
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  B. Disclaimer and license
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    Regarding this entire document or any portion of it (including
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    the pseudocode and C code), the author makes no guarantees and
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    is not responsible for any damage resulting from its use.  The
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    author grants irrevocable permission to anyone to use, modify,
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    and distribute it in any way that does not diminish the rights
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    of anyone else to use, modify, and distribute it, provided that
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    redistributed derivative works do not contain misleading author or
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    version information.  Derivative works need not be licensed under
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    similar terms.
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  C. Punycode sample implementation
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  punycode-sample.c 2.0.0 (2004-Mar-21-Sun)
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  http://www.nicemice.net/idn/
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  Adam M. Costello
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  http://www.nicemice.net/amc/
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  This is ANSI C code (C89) implementing Punycode 1.0.x.
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*/
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#include <config.h>
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#include "idn2.h"   /* IDN2_OK, ... */
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#include <string.h>
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/*** Bootstring parameters for Punycode ***/
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enum
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{ base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700,
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  initial_bias = 72, initial_n = 0x80, delimiter = 0x2D
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};
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/* basic(cp) tests whether cp is a basic code point: */
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0
#define encode_basic(cp) ((uint32_t)(cp) < 0x80)
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/* encode_digit(d,flag) returns the basic code point whose value      */
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/* (when used for representing integers) is d, which needs to be in   */
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/* the range 0 to base-1.  The lowercase form is used unless flag is  */
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/* nonzero, in which case the uppercase form is used.  The behavior   */
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/* is undefined if flag is nonzero and digit d has no uppercase form. */
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static char
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encode_digit (uint32_t d, int flag)
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0
{
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0
  return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
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  /*  0..25 map to ASCII a..z or A..Z */
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  /* 26..35 map to ASCII 0..9         */
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0
}
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/* basic(cp) tests whether cp is a basic code point: */
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#define decode_basic(cp)             \
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  ((cp >= 'a' && cp <= 'z') || (cp >= '0' && cp <='9')   \
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   || (cp >= 'A' && cp <='Z') || cp == '-' || cp == '_')
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/* decode_digit(cp) returns the numeric value of a basic code */
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/* point (for use in representing integers) in the range 0 to */
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/* base-1, or base if cp does not represent a value.          */
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static unsigned
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decode_digit (int cp)
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0
{
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0
  if (cp >= 'a' && cp <= 'z')
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0
    return cp - 'a';
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0
  if (cp >= '0' && cp <= '9')
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    return cp - '0' + 26;
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  if (cp >= 'A' && cp <= 'Z')
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    return cp - 'A';
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  return 0;
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0
}
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/*** Bias adaptation function ***/
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static uint32_t
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adapt (uint32_t delta, uint32_t numpoints, int firsttime)
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  _GL_ATTRIBUTE_CONST;
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     static uint32_t adapt (uint32_t delta, uint32_t numpoints, int firsttime)
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0
{
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  uint32_t k;
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0
  delta = firsttime ? delta / damp : delta >> 1;
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  /* delta >> 1 is a faster way of doing delta / 2 */
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  delta += delta / numpoints;
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  for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base)
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    {
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      delta /= base - tmin;
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    }
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  return k + (base - tmin + 1) * delta / (delta + skew);
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0
}
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/**
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 * idn2_punycode_encode:
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 * @input: array of input Unicode (UCS-4) code points
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 * @input_length: number of code points in the @input array.
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 * @output: output character array with ASCII code points.
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 * @output_length: size of @output array
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 *
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 * Converts a sequence of code points to Punycode.
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 *
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 * Warning: Be aware that is rare for applications to need to perform
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 *   Punycode operations, and you should consider idn2_to_ascii_8z(),
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 *   idn2_to_ascii_lz(), idn2_to_ascii_4z() etc.
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 *
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 * Returns: On successful encoding %IDN2_OK is returned, or an error
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 *   codes like %IDN2_PUNYCODE_BAD_INPUT, %IDN2_PUNYCODE_BIG_OUTPUT,
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 *   or %IDN2_PUNYCODE_OVERFLOW.
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 *
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 * Since: 2.3.5
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 **/
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int
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idn2_punycode_encode (const uint32_t *input,
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          size_t input_length,
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          char *output, size_t *output_length)
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0
{
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  uint32_t our_input_length, n, delta, h, b, bias, j, m, q, k, t;
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  size_t out, max_out;
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  /* The Punycode spec assumes that the input length is the same type */
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  /* of integer as a code point, so we need to convert the size_t to  */
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  /* a uint32_t, which could overflow.                           */
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  if (input_length > UINT32_MAX)
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    return IDN2_PUNYCODE_OVERFLOW;
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  our_input_length = (uint32_t) input_length;
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  /* Initialize the state: */
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  n = initial_n;
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  delta = 0;
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  out = 0;
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  max_out = *output_length;
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  bias = initial_bias;
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  /* Handle the basic code points: */
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  for (j = 0; j < our_input_length; ++j)
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    {
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      if (encode_basic (input[j]))
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  {
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    if (max_out - out < 2)
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      return IDN2_PUNYCODE_BIG_OUTPUT;
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    output[out++] = (char) input[j];
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  }
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      else if (input[j] > 0x10FFFF
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         || (input[j] >= 0xD800 && input[j] <= 0xDBFF))
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  return IDN2_PUNYCODE_BAD_INPUT;
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    }
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  h = b = (uint32_t) out;
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  /* cannot overflow because out <= our_input_length <= UINT32_MAX */
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  /* h is the number of code points that have been handled, b is the  */
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  /* number of basic code points, and out is the number of ASCII code */
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  /* points that have been output.                                    */
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  if (b > 0)
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    output[out++] = delimiter;
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  /* Main encoding loop: */
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  while (h < our_input_length)
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    {
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      /* All non-basic code points < n have been     */
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      /* handled already.  Find the next larger one: */
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      for (m = UINT32_MAX, j = 0; j < our_input_length; ++j)
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  {
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    /* if (basic(input[j])) continue; */
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    /* (not needed for Punycode) */
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    if (input[j] >= n && input[j] < m)
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      m = input[j];
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  }
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      /* Increase delta enough to advance the decoder's    */
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      /* <n,i> state to <m,0>, but guard against overflow: */
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      if (m - n > (UINT32_MAX - delta) / (h + 1))
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  return IDN2_PUNYCODE_OVERFLOW;
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      delta += (m - n) * (h + 1);
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      n = m;
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      for (j = 0; j < our_input_length; ++j)
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  {
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    /* Punycode does not need to check whether input[j] is basic: */
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    if (input[j] < n /* || basic(input[j]) */ )
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      {
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        if (++delta == 0)
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    return IDN2_PUNYCODE_OVERFLOW;
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      }
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    if (input[j] == n)
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      {
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        /* Represent delta as a generalized variable-length integer: */
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        for (q = delta, k = base;; k += base)
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    {
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      if (out >= max_out)
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        return IDN2_PUNYCODE_BIG_OUTPUT;
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      t = k <= bias /* + tmin */ ? tmin :  /* +tmin not needed */
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        k >= bias + tmax ? tmax : k - bias;
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      if (q < t)
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        break;
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      output[out++] = encode_digit (t + (q - t) % (base - t), 0);
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      q = (q - t) / (base - t);
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    }
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        output[out++] = encode_digit (q, 0);
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        bias = adapt (delta, h + 1, h == b);
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        delta = 0;
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        ++h;
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      }
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  }
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      ++delta, ++n;
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    }
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  *output_length = out;
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  return IDN2_OK;
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0
}
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/**
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 * idn2_punycode_decode:
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 * @input: array of ASCII characters (0..7F)
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 * @input_length: Number of ASCII characters in the @input array.
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 * @output: output character array with ASCII code points.
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 * @output_length: on input, guarantee that @output has room
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 *   for this many code points; on output, *@output_length
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 *   holds number of code points in @output.
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 *
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 * Converts Punycode to a sequence of code points.
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 *
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 * The decoder will never need to output more code points than the
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 * number of ASCII code points in the input, because of the way the
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 * encoding is defined.
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 *
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 * The number of code points output cannot exceed the maximum possible
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 * value of a uint32_t, even if the supplied @output_length is greater
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 * than that.
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 *
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 * Warning: Be aware that is rare for applications to need to perform
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 *   Punycode operations, and you should consider
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 *   idn2_to_unicode_8z8z(), idn2_to_unicode_lzlz() etc.
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 *
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 * Returns: On successful encoding %IDN2_OK is returned, or an error
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 *   codes like %IDN2_PUNYCODE_BAD_INPUT, %IDN2_PUNYCODE_BIG_OUTPUT,
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 *   or %IDN2_PUNYCODE_OVERFLOW.
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 *
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 * Since: 2.3.5
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 **/
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int
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idn2_punycode_decode (const char *input,
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          size_t input_length,
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          uint32_t *output, size_t *output_length)
299
0
{
300
0
  uint32_t n, out = 0, i, max_out, bias, oldi, w, k, digit, t;
301
0
  size_t b = 0, j, in;
302
303
0
  if (!input_length)
304
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    return IDN2_PUNYCODE_BAD_INPUT;
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  /* Check that all chars are basic */
307
0
  for (j = 0; j < input_length; ++j)
308
0
    {
309
0
      if (!decode_basic (input[j]))
310
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  return IDN2_PUNYCODE_BAD_INPUT;
311
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      if (input[j] == delimiter)
312
0
  b = j;
313
0
    }
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0
  max_out =
316
0
    *output_length > UINT32_MAX ? UINT32_MAX : (uint32_t) * output_length;
317
318
0
  if (input[b] == delimiter)
319
0
    {
320
      /* do not accept leading or trailing delimiter
321
       *   - leading delim must be omitted if there is no ASCII char in u-label
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       *   - trailing delim means there where no non-ASCII chars in u-label
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       */
324
0
      if (!b || b == input_length - 1)
325
0
  return IDN2_PUNYCODE_BAD_INPUT;
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327
0
      if (b >= max_out)
328
0
  return IDN2_PUNYCODE_BIG_OUTPUT;
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      /* Check that all chars before last delimiter are basic chars */
331
      /* and copy the first b code points to the output. */
332
0
      for (j = 0; j < b; j++)
333
0
  output[out++] = input[j];
334
335
0
      b += 1;     /* advance to non-basic char encoding */
336
0
    }
337
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  /* Initialize the state: */
339
0
  n = initial_n;
340
0
  i = 0;
341
0
  bias = initial_bias;
342
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  /* Main decoding loop:  Start just after the last delimiter if any  */
344
  /* basic code points were copied; start at the beginning otherwise. */
345
0
  for (in = b; in < input_length; ++out)
346
0
    {
347
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      /* in is the index of the next ASCII code point to be consumed, */
349
      /* and out is the number of code points in the output array.    */
350
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      /* Decode a generalized variable-length integer into delta,  */
352
      /* which gets added to i.  The overflow checking is easier   */
353
      /* if we increase i as we go, then subtract off its starting */
354
      /* value at the end to obtain delta.                         */
355
0
      for (oldi = i, w = 1, k = base;; k += base)
356
0
  {
357
0
    if (in >= input_length)
358
0
      return IDN2_PUNYCODE_BAD_INPUT;
359
0
    digit = decode_digit (input[in++]);
360
0
    if (digit >= base)
361
0
      return IDN2_PUNYCODE_BAD_INPUT;
362
0
    if (digit > (UINT32_MAX - i) / w)
363
0
      return IDN2_PUNYCODE_OVERFLOW;
364
0
    i += digit * w;
365
0
    t = k <= bias /* + tmin */ ? tmin :  /* +tmin not needed */
366
0
      k >= bias + tmax ? tmax : k - bias;
367
0
    if (digit < t)
368
0
      break;
369
0
    if (w > UINT32_MAX / (base - t))
370
0
      return IDN2_PUNYCODE_OVERFLOW;
371
0
    w *= (base - t);
372
0
  }
373
374
0
      bias = adapt (i - oldi, out + 1, oldi == 0);
375
376
      /* i was supposed to wrap around from out+1 to 0,   */
377
      /* incrementing n each time, so we'll fix that now: */
378
0
      if (i / (out + 1) > UINT32_MAX - n)
379
0
  return IDN2_PUNYCODE_OVERFLOW;
380
0
      n += i / (out + 1);
381
0
      if (n > 0x10FFFF || (n >= 0xD800 && n <= 0xDBFF))
382
0
  return IDN2_PUNYCODE_BAD_INPUT;
383
0
      i %= (out + 1);
384
385
      /* Insert n at position i of the output: */
386
387
      /* not needed for Punycode: */
388
      /* if (basic(n)) return IDN2_PUNYCODE_BAD_INPUT; */
389
0
      if (out >= max_out)
390
0
  return IDN2_PUNYCODE_BIG_OUTPUT;
391
392
0
      memmove (output + i + 1, output + i, (out - i) * sizeof *output);
393
0
      output[i++] = n;
394
0
    }
395
396
0
  *output_length = (size_t) out;
397
  /* cannot overflow because out <= old value of *output_length */
398
0
  return IDN2_OK;
399
0
}
400
401
/* We are stuck exporting these old internal interfaces because old
402
   versions of GNUTLS used them, and maybe other software. */
403
404
extern int _IDN2_API _idn2_punycode_decode (size_t input_length,
405
              const char input[],
406
              size_t *output_length,
407
              uint32_t output[]);
408
extern int _IDN2_API _idn2_punycode_encode (size_t input_length,
409
              const uint32_t input[],
410
              size_t *output_length,
411
              char output[]);
412
413
int
414
_idn2_punycode_decode (size_t input_length,
415
           const char input[],
416
           size_t *output_length, uint32_t output[])
417
0
{
418
0
  return idn2_punycode_decode (input, input_length, output, output_length);
419
420
0
}
421
422
int
423
_idn2_punycode_encode (size_t input_length,
424
           const uint32_t input[],
425
           size_t *output_length, char output[])
426
0
{
427
0
  return idn2_punycode_encode (input, input_length, output, output_length);
428
0
}