bkietz commented on a change in pull request #8470:
URL: https://github.com/apache/arrow/pull/8470#discussion_r505708835
##########
File path: cpp/src/arrow/util/utf8.h
##########
@@ -154,13 +156,52 @@ inline bool ValidateUTF8(const uint8_t* data, int64_t
size) {
return false;
}
- // Validate string tail one byte at a time
+ // Check if string tail is full ASCII (common case, fast)
+ if (size >= 4) {
+ uint32_t mask1, mask2;
+ memcpy(&mask2, data + size - 4, 4);
+ memcpy(&mask1, data, 4);
+ if (ARROW_PREDICT_TRUE(((mask1 | mask2) & high_bits_32) == 0)) {
+ return true;
+ }
Review comment:
```suggestion
uint32_t head_mask = internal::SafeLoadAs<uint32_t>(data);
uint32_t tail_mask = internal::SafeLoadAs<uint32_t>(data + size - 4);
if (ARROW_PREDICT_TRUE(((head_mask | tail_mask) & high_bits_32) == 0)) {
return true;
}
```
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