AK: Add StringView::to_int()

This is a shameless copy-paste of String::to_int(). We should find some
way to share this code between String and StringView instead of having
two duplicate copies like this.

AK/AKString.h

@@ -92,6 +92,7 @@ public:
     static String repeated(char, int count);
     bool matches(const StringView& pattern, CaseSensitivity = CaseSensitivity::CaseInsensitive) const;
 
+    // FIXME: These should be shared between String and StringView somehow!
     int to_int(bool& ok) const;
     unsigned to_uint(bool& ok) const;
 

AK/StringView.cpp

@@ -66,6 +66,34 @@ StringView StringView::substring_view_starting_after_substring(const StringView&
     return { remaining_characters, remaining_length };
 }
 
+int StringView::to_int(bool& ok) const
+{
+    bool negative = false;
+    int value = 0;
+    int i = 0;
+
+    if (is_empty()) {
+        ok = false;
+        return 0;
+    }
+
+    if (characters_without_null_termination()[0] == '-') {
+        i++;
+        negative = true;
+    }
+    for (; i < length(); i++) {
+        if (characters_without_null_termination()[i] < '0' || characters_without_null_termination()[i] > '9') {
+            ok = false;
+            return 0;
+        }
+        value = value * 10;
+        value += characters_without_null_termination()[i] - '0';
+    }
+    ok = true;
+
+    return negative ? -value : value;
+}
+
 unsigned StringView::to_uint(bool& ok) const
 {
     unsigned value = 0;

AK/StringView.h

@@ -41,7 +41,10 @@ public:
 
     StringView substring_view(int start, int length) const;
     Vector<StringView> split_view(char) const;
+
+    // FIXME: These should be shared between String and StringView somehow!
     unsigned to_uint(bool& ok) const;
+    int to_int(bool& ok) const;
 
     // Create a new substring view of this string view, starting either at the beginning of
     // the given substring view, or after its end, and continuing until the end of this string