accessibility_helper.cc 2.0 KB

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  1. // Copyright 2020 The Chromium Authors. All rights reserved.
  2. // Use of this source code is governed by a BSD-style license that can be
  3. // found in the LICENSE file.
  4. #include "pdf/accessibility_helper.h"
  5. #include <stdint.h>
  6. #include <vector>
  7. #include "base/numerics/safe_math.h"
  8. #include "pdf/accessibility_structs.h"
  9. #include "third_party/abseil-cpp/absl/types/optional.h"
  10. namespace chrome_pdf {
  11. bool IsCharWithinTextRun(const AccessibilityTextRunInfo& text_run,
  12. uint32_t text_run_start_char_index,
  13. uint32_t char_index) {
  14. return char_index >= text_run_start_char_index &&
  15. char_index - text_run_start_char_index < text_run.len;
  16. }
  17. // If a valid text run range is not found for the char range then return the
  18. // fallback value.
  19. AccessibilityTextRunRangeInfo GetEnclosingTextRunRangeForCharRange(
  20. const std::vector<AccessibilityTextRunInfo>& text_runs,
  21. int start_char_index,
  22. int char_count) {
  23. // Initialize with fallback value.
  24. AccessibilityTextRunRangeInfo text_range = {text_runs.size(), 0};
  25. if (start_char_index < 0 || char_count <= 0)
  26. return text_range;
  27. base::CheckedNumeric<uint32_t> checked_end_char_index = char_count - 1;
  28. checked_end_char_index += start_char_index;
  29. if (!checked_end_char_index.IsValid())
  30. return text_range;
  31. uint32_t end_char_index = checked_end_char_index.ValueOrDie();
  32. uint32_t current_char_index = 0;
  33. absl::optional<size_t> start_text_run;
  34. for (size_t i = 0; i < text_runs.size(); ++i) {
  35. if (!start_text_run.has_value() &&
  36. IsCharWithinTextRun(text_runs[i], current_char_index,
  37. start_char_index)) {
  38. start_text_run = i;
  39. }
  40. if (start_text_run.has_value() &&
  41. IsCharWithinTextRun(text_runs[i], current_char_index, end_char_index)) {
  42. text_range.index = start_text_run.value();
  43. text_range.count = i - text_range.index + 1;
  44. break;
  45. }
  46. current_char_index += text_runs[i].len;
  47. }
  48. return text_range;
  49. }
  50. } // namespace chrome_pdf