kc3-lang/libxkbcommon/src/utf8.c

Branch : - branch - android master - tag -

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  Commit

• Author : Pierre Le Marre
  Date : 2025-04-08 06:31:33
  Hash : 08d9a031
  Message : Unicode: Make surrogate handling more explicit

• src/utf8.c

• /*
   * Copyright © 2012 Intel Corporation
   * Copyright © 2014 Ran Benita <ran234@gmail.com>
   * SPDX-License-Identifier: MIT
   *
   * Author: Rob Bradford <rob@linux.intel.com>
   */
  
  #include "config.h"
  
  #include "utils.h"
  #include "utf8.h"
  
  /* Conformant encoding form conversion from UTF-32 to UTF-8.
   *
   * See https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G28875
   * for further details.
  */
  int
  utf32_to_utf8(uint32_t unichar, char *buffer)
  {
      int count, shift, length;
      uint8_t head;
  
      /* NOLINTBEGIN(bugprone-branch-clone) */
      if (unichar <= 0x007f) {
          buffer[0] = (char) unichar;
          buffer[1] = '\0';
          return 2;
      }
      else if (unichar <= 0x07FF) {
          length = 2;
          head = 0xc0;
      }
      /* Handle surrogates */
      else if (is_surrogate(unichar)) {
          goto ill_formed_code_unit_subsequence;
      }
      else if (unichar <= 0xffff) {
          length = 3;
          head = 0xe0;
      }
      else if (unichar <= 0x10ffff) {
          length = 4;
          head = 0xf0;
      }
      else {
          goto ill_formed_code_unit_subsequence;
      }
      /* NOLINTEND(bugprone-branch-clone) */
  
      for (count = length - 1, shift = 0; count > 0; count--, shift += 6)
          buffer[count] = (char)(0x80 | ((unichar >> shift) & 0x3f));
  
      buffer[0] = (char)(head | ((unichar >> shift) & 0x3f));
      buffer[length] = '\0';
  
      return length + 1;
  
  ill_formed_code_unit_subsequence:
      buffer[0] = '\0';
      return 0;
  }
  
  bool
  is_valid_utf8(const char *ss, size_t len)
  {
      size_t i = 0;
      size_t tail_bytes = 0;
      const uint8_t *s = (const uint8_t *) ss;
  
      /* This beauty is from:
       *  The Unicode Standard Version 6.2 - Core Specification, Table 3.7
       *  https://www.unicode.org/versions/Unicode6.2.0/ch03.pdf#G7404
       * We can optimize if needed. */
      while (i < len)
      {
          /* NOLINTBEGIN(bugprone-branch-clone) */
          if (s[i] <= 0x7F) {
              tail_bytes = 0;
          }
          else if (s[i] >= 0xC2 && s[i] <= 0xDF) {
              tail_bytes = 1;
          }
          else if (s[i] == 0xE0) {
              i++;
              if (i >= len || !(s[i] >= 0xA0 && s[i] <= 0xBF))
                  return false;
              tail_bytes = 1;
          }
          else if (s[i] >= 0xE1 && s[i] <= 0xEC) {
              tail_bytes = 2;
          }
          else if (s[i] == 0xED) {
              i++;
              if (i >= len || !(s[i] >= 0x80 && s[i] <= 0x9F))
                  return false;
              tail_bytes = 1;
          }
          else if (s[i] >= 0xEE && s[i] <= 0xEF) {
              tail_bytes = 2;
          }
          else if (s[i] == 0xF0) {
              i++;
              if (i >= len || !(s[i] >= 0x90 && s[i] <= 0xBF))
                  return false;
              tail_bytes = 2;
          }
          else if (s[i] >= 0xF1 && s[i] <= 0xF3) {
              tail_bytes = 3;
          }
          else if (s[i] == 0xF4) {
              i++;
              if (i >= len || !(s[i] >= 0x80 && s[i] <= 0x8F))
                  return false;
              tail_bytes = 2;
          }
          else {
              return false;
          }
          /* NOLINTEND(bugprone-branch-clone) */
  
          i++;
  
          while (i < len && tail_bytes > 0 && s[i] >= 0x80 && s[i] <= 0xBF) {
              i++;
              tail_bytes--;
          }
  
          if (tail_bytes != 0)
              return false;
      }
  
      return true;
  }