From cf8d3c6ff9589abb1961811e9114fb8c31c9acf5 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sun, 22 Jan 2023 11:27:54 +0100
Subject: [PATCH] OwnedStringView: Add a method to extract a substring

---
 luna/include/luna/OwnedStringView.h |  3 +++
 luna/src/OwnedStringView.cpp        | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/luna/include/luna/OwnedStringView.h b/luna/include/luna/OwnedStringView.h
index 876e9c60..09454b0f 100644
--- a/luna/include/luna/OwnedStringView.h
+++ b/luna/include/luna/OwnedStringView.h
@@ -5,6 +5,7 @@ class OwnedStringView
 {
   public:
     OwnedStringView(char* c_str);
+    OwnedStringView(char* c_str, usize length);
     OwnedStringView();
     OwnedStringView(OwnedStringView&&);
     OwnedStringView(const OwnedStringView&) = delete;
@@ -12,6 +13,8 @@ class OwnedStringView
 
     Result<OwnedStringView> clone() const;
 
+    Result<OwnedStringView> substring(usize begin, usize size) const;
+
     static Result<OwnedStringView> from_string_literal(const char* str);
 
     const char* chars() const
diff --git a/luna/src/OwnedStringView.cpp b/luna/src/OwnedStringView.cpp
index c53fc446..10637a23 100644
--- a/luna/src/OwnedStringView.cpp
+++ b/luna/src/OwnedStringView.cpp
@@ -21,6 +21,12 @@ OwnedStringView::OwnedStringView(char* c_str)
     if (m_string) { m_length = strlen(m_string); }
 }
 
+OwnedStringView::OwnedStringView(char* c_str, usize length)
+{
+    m_string = c_str;
+    m_length = length;
+}
+
 OwnedStringView::~OwnedStringView()
 {
     if (m_string) free_impl(m_string);
@@ -31,6 +37,14 @@ Result<OwnedStringView> OwnedStringView::clone() const
     return from_string_literal(m_string);
 }
 
+Result<OwnedStringView> OwnedStringView::substring(usize begin, usize size) const
+{
+    if (begin + size >= size) return err(EINVAL);
+    char* const dup = strndup(m_string + begin, size);
+    if (!dup) return err(ENOMEM);
+    return OwnedStringView { dup, size };
+}
+
 const char& OwnedStringView::operator[](usize index) const
 {
     expect(index < m_length, "index out of range");