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156 changes: 113 additions & 43 deletions
156
crates/polars-ops/src/chunked_array/strings/substring.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,51 +1,121 @@ | ||
| use arrow::array::Utf8Array; | ||
| use polars_core::prelude::arity::{binary_elementwise, ternary_elementwise, unary_elementwise}; | ||
| use polars_core::prelude::{Int64Chunked, StringChunked, UInt64Chunked}; | ||
|
|
||
| /// Returns a Utf8Array<O> with a substring starting from `start` and with optional length `length` of each of the elements in `array`. | ||
| /// `start` can be negative, in which case the start counts from the end of the string. | ||
| pub(super) fn utf8_substring( | ||
| array: &Utf8Array<i64>, | ||
| start: i64, | ||
| length: &Option<u64>, | ||
| ) -> Utf8Array<i64> { | ||
| let length = length.map(|v| v as usize); | ||
| fn substring_ternary( | ||
| opt_str_val: Option<&str>, | ||
| opt_start: Option<i64>, | ||
| opt_length: Option<u64>, | ||
| ) -> Option<&str> { | ||
| match (opt_str_val, opt_start) { | ||
| (Some(str_val), Some(start)) => { | ||
| // if `offset` is negative, it counts from the end of the string | ||
| let offset = if start >= 0 { | ||
| start as usize | ||
| } else { | ||
| let offset = (0i64 - start) as usize; | ||
| str_val | ||
| .char_indices() | ||
| .rev() | ||
| .nth(offset) | ||
| .map(|(idx, _)| idx + 1) | ||
| .unwrap_or(0) | ||
| }; | ||
|
|
||
| let iter = array.values_iter().map(|str_val| { | ||
| // compute where we should start slicing this entry. | ||
| let start = if start >= 0 { | ||
| start as usize | ||
| } else { | ||
| let start = (0i64 - start) as usize; | ||
| str_val | ||
| .char_indices() | ||
| .rev() | ||
| .nth(start) | ||
| .map(|(idx, _)| idx + 1) | ||
| .unwrap_or(0) | ||
| }; | ||
| let mut iter_chars = str_val.char_indices(); | ||
| if let Some((offset_idx, _)) = iter_chars.nth(offset) { | ||
| let len_end = str_val.len() - offset_idx; | ||
|
|
||
| let mut iter_chars = str_val.char_indices(); | ||
| if let Some((start_idx, _)) = iter_chars.nth(start) { | ||
| // length of the str | ||
| let len_end = str_val.len() - start_idx; | ||
| // slice to end of str if no length given | ||
| let length = if let Some(length) = opt_length { | ||
| length as usize | ||
| } else { | ||
| len_end | ||
| }; | ||
|
|
||
| // length to slice | ||
| let length = length.unwrap_or(len_end); | ||
| if length == 0 { | ||
| return Some(""); | ||
| } | ||
|
|
||
| if length == 0 { | ||
| return ""; | ||
| } | ||
| // compute | ||
| let end_idx = iter_chars | ||
| .nth(length.saturating_sub(1)) | ||
| .map(|(idx, _)| idx) | ||
| .unwrap_or(str_val.len()); | ||
| let end_idx = iter_chars | ||
| .nth(length.saturating_sub(1)) | ||
| .map(|(idx, _)| idx) | ||
| .unwrap_or(str_val.len()); | ||
|
|
||
| &str_val[start_idx..end_idx] | ||
| } else { | ||
| "" | ||
| } | ||
| }); | ||
| Some(&str_val[offset_idx..end_idx]) | ||
| } else { | ||
| Some("") | ||
| } | ||
| }, | ||
| _ => None, | ||
| } | ||
| } | ||
|
|
||
| let new = Utf8Array::<i64>::from_trusted_len_values_iter(iter); | ||
| new.with_validity(array.validity().cloned()) | ||
| pub(super) fn substring( | ||
| ca: &StringChunked, | ||
| start: &Int64Chunked, | ||
| length: &UInt64Chunked, | ||
| ) -> StringChunked { | ||
| match (ca.len(), start.len(), length.len()) { | ||
| (1, 1, _) => { | ||
| // SAFETY: index `0` is in bound. | ||
| let str_val = unsafe { ca.get_unchecked(0) }; | ||
| // SAFETY: index `0` is in bound. | ||
| let start = unsafe { start.get_unchecked(0) }; | ||
| unary_elementwise(length, |length| substring_ternary(str_val, start, length)) | ||
| .with_name(ca.name()) | ||
| }, | ||
| (_, 1, 1) => { | ||
| // SAFETY: index `0` is in bound. | ||
| let start = unsafe { start.get_unchecked(0) }; | ||
| // SAFETY: index `0` is in bound. | ||
| let length = unsafe { length.get_unchecked(0) }; | ||
| unary_elementwise(ca, |str_val| substring_ternary(str_val, start, length)) | ||
| }, | ||
| (1, _, 1) => { | ||
| // SAFETY: index `0` is in bound. | ||
| let str_val = unsafe { ca.get_unchecked(0) }; | ||
| // SAFETY: index `0` is in bound. | ||
| let length = unsafe { length.get_unchecked(0) }; | ||
| unary_elementwise(start, |start| substring_ternary(str_val, start, length)) | ||
| .with_name(ca.name()) | ||
| }, | ||
| (1, len_b, len_c) if len_b == len_c => { | ||
| // fn infer<F: for<'a> FnMut(Option<i64>, Option<u64>) -> Option<&'a str>>(f: F) -> F where | ||
| // { | ||
| // f | ||
| // } | ||
| // SAFETY: index `0` is in bound. | ||
| let str_val = unsafe { ca.get_unchecked(0) }; | ||
| binary_elementwise(start, length, |start, length| { | ||
| substring_ternary(str_val, start, length) | ||
| }) | ||
| }, | ||
| (len_a, 1, len_c) if len_a == len_c => { | ||
| fn infer<F: for<'a> FnMut(Option<&'a str>, Option<u64>) -> Option<&'a str>>(f: F) -> F where | ||
| { | ||
| f | ||
| } | ||
| // SAFETY: index `0` is in bound. | ||
| let start = unsafe { start.get_unchecked(0) }; | ||
| binary_elementwise( | ||
| ca, | ||
| length, | ||
| infer(|str_val, length| substring_ternary(str_val, start, length)), | ||
| ) | ||
| }, | ||
| (len_a, len_b, 1) if len_a == len_b => { | ||
| fn infer<F: for<'a> FnMut(Option<&'a str>, Option<i64>) -> Option<&'a str>>(f: F) -> F where | ||
| { | ||
| f | ||
| } | ||
| // SAFETY: index `0` is in bound. | ||
| let length = unsafe { length.get_unchecked(0) }; | ||
| binary_elementwise( | ||
| ca, | ||
| start, | ||
| infer(|str_val, start| substring_ternary(str_val, start, length)), | ||
| ) | ||
| }, | ||
| _ => ternary_elementwise(ca, start, length, substring_ternary), | ||
| } | ||
| } |
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