From 0cebf66a1816e5bf3c005dff6fb17bba55c1517f Mon Sep 17 00:00:00 2001
From: Jordan Gong <jordan.gong@protonmail.com>
Date: Wed, 12 Aug 2020 16:15:01 +0800
Subject: Understand owership

---
 owership/src/main.rs | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 owership/src/main.rs

(limited to 'owership/src/main.rs')

diff --git a/owership/src/main.rs b/owership/src/main.rs
new file mode 100644
index 0000000..d2bd765
--- /dev/null
+++ b/owership/src/main.rs
@@ -0,0 +1,139 @@
+fn main() {
+    /* heap data deep copy */
+    let s1 = String::from("Hello");
+    let s2 = s1.clone();
+
+    println!("s1 = {}, s2 = {}", s1, s2);
+
+    /* stack data copy */
+    let x = 5;
+    let y = x;
+
+    println!("x = {}, y = {}", x, y);
+    
+    /* functions */
+    let s = String::from("hello");
+
+    takes_owership(s);
+
+    let x = 5;
+
+    makes_copy(x);
+
+    /* return values and scope */
+    let s1 = gives_owership();
+
+    let s2 = String::from("hello");
+
+    let s3 = takes_and_gives_back(s2);
+
+    /* parameters */
+    let s1 = String::from("hello");
+
+    let (s2, len) = calculate_length(s1);
+
+    println!("The length of '{}' is {}.", s2, len);
+
+    /* reference(borrowing) */
+    let s1 = String::from("hello");
+
+    let len = calculate_length_ref(&s1);
+
+    println!("The length of '{}' is {}.", s1, len);
+
+    /* mutable reference */
+    let mut s = String::from("hello");
+
+    change(&mut s);
+
+    /* mutable and immutable */
+    let mut s = String::from("hello");
+
+    let r1 = &s;
+    let r2 = &s;
+    println!("{} and {}", r1, r2);
+
+    let r3 = &mut s;
+    println!("{}", r3);
+
+    /* slice */
+    let mut s = String::from("hello world");
+
+    let word = first_word_index(&s);
+
+    s.clear();
+
+    println!("the first word index: 0-{}", word);
+
+    /* string slice */
+    let s = String::from("hello world");
+
+    let hello = &s[0..5];
+    let world = &s[6..11];
+
+    println!("{} {}", hello, world);
+
+    /* slice first word */
+    let mut s = String::from("hello world");
+
+    let word = first_word(&s);
+
+    println!("the first word: {}", word);
+
+    s.clear();
+}
+
+fn takes_owership(some_string: String) {
+    println!("{}", some_string);
+}
+
+fn makes_copy(some_integer: i32) {
+    println!("{}", some_integer);
+}
+
+fn gives_owership() -> String {
+    let some_string = String::from("hello");
+    some_string
+}
+
+fn takes_and_gives_back(a_string: String) -> String {
+    a_string
+}
+
+fn calculate_length(s: String) -> (String, usize) {
+    let length = s.len();
+
+    (s, length)
+}
+
+fn calculate_length_ref(s: &String) -> usize {
+    s.len()
+}
+
+fn change(some_string: &mut String) {
+    some_string.push_str(", world!");
+}
+
+fn first_word_index(s: &String) -> usize {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return i;
+        }
+    }
+
+    s.len()
+}
+
+fn first_word(s: &String) -> &str {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[0..i];
+        }
+    }
+
+    &s[..]
+}
-- 
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