kc3-lang/libxkbcommon/src/utf8-decoding.c

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• Hash : 08d9a031
  Author :
  Date : 2025-04-08T06:31:33
  

  Unicode: Make surrogate handling more explicit
  

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• src/utf8-decoding.c

• /*
   * Copyright © 2024 Pierre Le Marre <dev@wismill.eu>
   * SPDX-License-Identifier: MIT
   */
  
  #include "config.h"
  
  #include "utils.h"
  #include "utf8-decoding.h"
  
  /* Array mapping the leading byte to the length of a UTF-8 sequence.
   * A value of zero indicates that the byte can not begin a UTF-8 sequence. */
  static const uint8_t utf8_sequence_length_by_leading_byte[256] = {
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x00-0x0F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x10-0x1F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x20-0x2F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x30-0x3F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x40-0x4F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x50-0x5F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x60-0x6F */
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x70-0x7F */
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0x80-0x8F */
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0x90-0x9F */
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0xA0-0xAF */
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0xB0-0xBF */
      0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, /* 0xC0-0xCF */
      2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, /* 0xD0-0xDF */
      3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, /* 0xE0-0xEF */
      4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0xF0-0xFF */
  };
  
  /* Length of next utf-8 sequence */
  uint8_t
  utf8_sequence_length(const char *s)
  {
      return utf8_sequence_length_by_leading_byte[(unsigned char)s[0]];
  }
  
  /* Reads the next UTF-8 sequence in a string */
  uint32_t
  utf8_next_code_point(const char *s, size_t max_size, size_t *size_out)
  {
      uint32_t cp = 0;
      uint8_t len = utf8_sequence_length(s);
      *size_out = 0;
  
      if (!max_size || len > max_size)
          return INVALID_UTF8_CODE_POINT;
  
      /* Handle leading byte */
      switch (len) {
      case 1:
          *size_out = 1;
          return (uint32_t)s[0];
      case 2:
          cp = (uint32_t)s[0] & 0x1f;
          break;
      case 3:
          cp = (uint32_t)s[0] & 0x0f;
          break;
      case 4:
          cp = (uint32_t)s[0] & 0x07;
          break;
      default:
          return INVALID_UTF8_CODE_POINT;
      }
  
      /* Process remaining bytes of the UTF-8 sequence */
      for (size_t k = 1; k < len; k++) {
          if (((uint32_t)s[k] & 0xc0) != 0x80)
              return INVALID_UTF8_CODE_POINT;
          cp <<= 6;
          cp |= (uint32_t)s[k] & 0x3f;
      }
  
      /* Check surrogates */
      if (is_surrogate(cp))
          return INVALID_UTF8_CODE_POINT;
  
      *size_out = len;
      return cp;
  }
  

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