alamb commented on code in PR #6231:
URL: https://github.com/apache/arrow-rs/pull/6231#discussion_r1721832656
##########
arrow-array/src/array/byte_view_array.rs:
##########
@@ -667,6 +699,58 @@ impl StringViewArray {
None => true,
})
}
+
+ /// Returns an iterator over the prefix bytes of this array with respect
to the prefix length.
+ /// If the prefix length is larger than the string length, it will return
the empty string.
+ pub fn prefix_iter(&self, prefix_len: usize) -> impl Iterator<Item = &str>
{
+ self.views().into_iter().map(move |v| {
+ let len = (*v as u32) as usize;
+
+ if len < prefix_len {
+ return "";
+ }
+
+ let b = if prefix_len <= 4 || len <= 12 {
+ unsafe { StringViewArray::inline_value(v, prefix_len) }
+ } else {
+ let view = ByteView::from(*v);
+ let data = unsafe {
+ self.data_buffers()
+ .get_unchecked(view.buffer_index as usize)
+ };
+ let offset = view.offset as usize;
+ unsafe { data.get_unchecked(offset..offset + prefix_len) }
+ };
+
+ unsafe { str::from_utf8_unchecked(b) }
+ })
+ }
+
+ /// Returns an iterator over the suffix bytes of this array with respect
to the suffix length.
+ /// If the suffix length is larger than the string length, it will return
the empty string.
+ pub fn suffix_iter(&self, suffix_len: usize) -> impl Iterator<Item = &str>
{
+ self.views().into_iter().map(move |v| {
+ let len = (*v as u32) as usize;
+
+ if len < suffix_len {
+ return "";
+ }
+
+ let b = if len <= 12 {
+ unsafe { &StringViewArray::inline_value(v, len)[len -
suffix_len..] }
+ } else {
+ let view = ByteView::from(*v);
+ let data = unsafe {
+ self.data_buffers()
+ .get_unchecked(view.buffer_index as usize)
+ };
+ let offset = view.offset as usize;
+ unsafe { data.get_unchecked(offset + len - suffix_len..offset
+ len) }
Review Comment:
How do we know this byte sequence is valid utf8?
For example, what if the last character of the array is a multi-byte UTF8
character and we call `suffix_iter()` -- that would return a 1 byte "str" that
wasn't valid utf8
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