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fix #19500; remove find optimization [backport: 1.6] (#19714)

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* remove find optimization

close #19500

* save find to std

* add simple tests

* Apply suggestions from code review

Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>

Co-authored-by: sandytypical <43030857+xflywind@users.noreply.github.com>
Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>
This commit is contained in:
ringabout
2022-09-29 04:05:41 +08:00
committed by GitHub
parent 919a889ba8
commit 65c2518d5c
4 changed files with 49 additions and 20 deletions
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37
lib/std/private/strimpl.nim
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@@ -74,3 +74,40 @@ template endsWithImpl*[T: string | cstring](s, suffix: T) =
func cmpNimIdentifier*[T: string | cstring](a, b: T): int =
cmpIgnoreStyleImpl(a, b, true)
func c_memchr(cstr: pointer, c: char, n: csize_t): pointer {.
importc: "memchr", header: "<string.h>".}
func c_strstr(haystack, needle: cstring): cstring {.
importc: "strstr", header: "<string.h>".}
func find*(s: cstring, sub: char, start: Natural = 0, last = 0): int =
## Searches for `sub` in `s` inside the range `start..last` (both ends included).
## If `last` is unspecified, it defaults to `s.high` (the last element).
##
## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
## Otherwise the index returned is relative to `s[0]`, not `start`.
## Use `s[start..last].rfind` for a `start`-origin index.
let last = if last == 0: s.high else: last
let L = last-start+1
if L > 0:
let found = c_memchr(s[start].unsafeAddr, sub, cast[csize_t](L))
if not found.isNil:
return cast[ByteAddress](found) -% cast[ByteAddress](s)
return -1
func find*(s, sub: cstring, start: Natural = 0, last = 0): int =
## Searches for `sub` in `s` inside the range `start..last` (both ends included).
## If `last` is unspecified, it defaults to `s.high` (the last element).
##
## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
## Otherwise the index returned is relative to `s[0]`, not `start`.
## Use `s[start..last].find` for a `start`-origin index.
if sub.len > s.len - start: return -1
if sub.len == 1: return find(s, sub[0], start, last)
if last == 0 and s.len > start:
let found = c_strstr(s[start].unsafeAddr, sub)
if not found.isNil:
result = cast[ByteAddress](found) -% cast[ByteAddress](s)
else:
result = -1