From 56253bf3895e258729130a7ec22acff74e5b4212 Mon Sep 17 00:00:00 2001
From: Max Wipfli <mail@maxwipfli.ch>
Date: Thu, 1 Jul 2021 14:58:37 +0200
Subject: [PATCH] AK: Reimplement StringView::find methods in StringUtils

This patch reimplements the StringView::find methods in StringUtils, so
they can also be used by String. The methods now also take an optional
start parameter, which moves their API in line with String's respective
methods.

This also implements a StringView::find_ast(char) method, which is
currently functionally equivalent to find_last_of(char). This is because
find_last_of(char) will be removed in a further commit.
---
 AK/String.cpp      |  5 +----
 AK/StringUtils.cpp | 29 ++++++++++++++++++++++++++---
 AK/StringUtils.h   |  7 ++++++-
 AK/StringView.cpp  | 10 ----------
 AK/StringView.h    |  6 ++++--
 5 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/AK/String.cpp b/AK/String.cpp
index 44fd77fb70..bf423b0c8a 100644
--- a/AK/String.cpp
+++ b/AK/String.cpp
@@ -483,10 +483,7 @@ Optional<size_t> String::find(char c, size_t start) const
 
 Optional<size_t> String::find(StringView const& view, size_t start) const
 {
-    auto index = StringUtils::find(substring_view(start), view);
-    if (!index.has_value())
-        return {};
-    return index.value() + start;
+    return StringUtils::find(*this, view, start);
 }
 
 }
diff --git a/AK/StringUtils.cpp b/AK/StringUtils.cpp
index 5c5d5db10c..fdc4830120 100644
--- a/AK/StringUtils.cpp
+++ b/AK/StringUtils.cpp
@@ -332,11 +332,34 @@ StringView trim_whitespace(const StringView& str, TrimMode mode)
     return trim(str, " \n\t\v\f\r", mode);
 }
 
-Optional<size_t> find(const StringView& haystack, const StringView& needle)
+Optional<size_t> find(StringView const& haystack, char needle, size_t start)
 {
-    return AK::memmem_optional(
-        haystack.characters_without_null_termination(), haystack.length(),
+    if (start >= haystack.length())
+        return {};
+    for (size_t i = start; i < haystack.length(); ++i) {
+        if (haystack[i] == needle)
+            return i;
+    }
+    return {};
+}
+
+Optional<size_t> find(StringView const& haystack, StringView const& needle, size_t start)
+{
+    if (start > haystack.length())
+        return {};
+    auto index = AK::memmem_optional(
+        haystack.characters_without_null_termination() + start, haystack.length() - start,
         needle.characters_without_null_termination(), needle.length());
+    return index.has_value() ? (*index + start) : index;
+}
+
+Optional<size_t> find_last(StringView const& haystack, char needle)
+{
+    for (size_t i = haystack.length(); i > 0; --i) {
+        if (haystack[i - 1] == needle)
+            return i - 1;
+    }
+    return {};
 }
 
 String to_snakecase(const StringView& str)
diff --git a/AK/StringUtils.h b/AK/StringUtils.h
index fa7ae1902d..f7211b0561 100644
--- a/AK/StringUtils.h
+++ b/AK/StringUtils.h
@@ -57,7 +57,12 @@ bool contains(const StringView&, const StringView&, CaseSensitivity);
 bool is_whitespace(const StringView&);
 StringView trim(const StringView& string, const StringView& characters, TrimMode mode);
 StringView trim_whitespace(const StringView& string, TrimMode mode);
-Optional<size_t> find(const StringView& haystack, const StringView& needle);
+
+Optional<size_t> find(StringView const& haystack, char needle, size_t start = 0);
+Optional<size_t> find(StringView const& haystack, StringView const& needle, size_t start = 0);
+Optional<size_t> find_last(StringView const& haystack, char needle);
+Vector<size_t> find_all(StringView const& haystack, StringView const& needle);
+
 String to_snakecase(const StringView&);
 
 }
diff --git a/AK/StringView.cpp b/AK/StringView.cpp
index 9053a6d131..9960d66707 100644
--- a/AK/StringView.cpp
+++ b/AK/StringView.cpp
@@ -282,16 +282,6 @@ Optional<size_t> StringView::find_last_of(const StringView& view) const
     return {};
 }
 
-Optional<size_t> StringView::find(char c) const
-{
-    return find(StringView { &c, 1 });
-}
-
-Optional<size_t> StringView::find(const StringView& view) const
-{
-    return StringUtils::find(*this, view);
-}
-
 String StringView::to_string() const { return String { *this }; }
 
 }
diff --git a/AK/StringView.h b/AK/StringView.h
index 356f65f8f2..1c4da71248 100644
--- a/AK/StringView.h
+++ b/AK/StringView.h
@@ -92,8 +92,10 @@ public:
     Optional<size_t> find_last_of(char) const;
     Optional<size_t> find_last_of(const StringView&) const;
 
-    Optional<size_t> find(const StringView&) const;
-    Optional<size_t> find(char c) const;
+    [[nodiscard]] Optional<size_t> find(char needle, size_t start = 0) const { return StringUtils::find(*this, needle, start); }
+    [[nodiscard]] Optional<size_t> find(StringView const& needle, size_t start = 0) const { return StringUtils::find(*this, needle, start); }
+    [[nodiscard]] Optional<size_t> find_last(char needle) const { return StringUtils::find_last(*this, needle); }
+    // FIXME: Implement find_last(StringView const&) for API symmetry.
 
     [[nodiscard]] constexpr StringView substring_view(size_t start, size_t length) const
     {