string: Add sub_str command

src/cmd/string.rs

@@ -12,6 +12,7 @@ pub enum StringCommand {
     Append(String, Bytes),
     Get(String),
     GetDel(String),
+    GetRange(String, i64, i64),
     GetSet(String, Bytes),
     Set(String, Bytes),
     StrLen(String),
@@ -37,6 +38,12 @@ impl StringCommand {
                 let key = parser.next_string()?;
                 Self::GetDel(key)
             }
+            "getrange" => {
+                let key = parser.next_string()?;
+                let start = parser.next_i64()?;
+                let end = parser.next_i64()?;
+                Self::GetRange(key, start, end)
+            }
             "getset" => {
                 let key = parser.next_string()?;
                 let value = parser.next_bytes()?;

src/mem/string/get_range.rs

@@ -0,0 +1,13 @@
+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by GNU Affero General Public License
+// that can be found in the LICENSE file.
+
+use crate::cmd::frame::Frame;
+use crate::mem::db::Db;
+use crate::mem::string::sub_str::sub_str;
+
+#[must_use]
+#[inline]
+pub fn get_range(db: &Db, key: &str, start: i64, end: i64) -> Frame {
+    sub_str(db, key, start, end)
+}

src/mem/string/mod.rs

@@ -16,6 +16,7 @@ mod append;
 mod get_del;
 mod get_set;
 mod sub_str;
+mod get_range;
 
 #[derive(Debug, Clone)]
 pub enum StrObject {
@@ -73,6 +74,7 @@ impl Mem {
             StringCommand::Append(key, value) => append::append(&mut self.db, key, value),
             StringCommand::Get(key) => get::get(&self.db, &key),
             StringCommand::GetDel(key) => get_del::get_del(&mut self.db, &key),
+            StringCommand::GetRange(key, start, end) => get_range::get_range(&self.db, &key, start, end),
             StringCommand::GetSet(key, value) => get_set::get_set(&mut self.db, key, value),
             StringCommand::Set(key, value) => set::set(&mut self.db, key, value),
             StringCommand::StrLen(key) => strlen::strlen(&self.db, &key),

src/mem/string/sub_str.rs

@@ -2,10 +2,12 @@
 // Use of this source is governed by GNU Affero General Public License
 // that can be found in the LICENSE file.
 
+use bytes::Bytes;
+
 use crate::cmd::frame::Frame;
 use crate::mem::db::{Db, MemObject};
 use crate::mem::string::StrObject;
-use crate::util::prune_range::slice_range_to_bytes;
+use crate::util::prune_range::prune_range;
 
 /// Returns the substring of the string value stored at key,
 /// determined by the offsets start and end (both are inclusive).
@@ -19,7 +21,11 @@ pub fn sub_str(db: &Db, key: &str, start: i64, end: i64) -> Frame {
         Some(MemObject::Str(value)) => match value {
             StrObject::Integer(_) => todo!(),
             StrObject::Vec(vec) => {
-                let bytes = slice_range_to_bytes(vec, start, end);
+                let bytes = if let Some((start, end)) = prune_range(vec.len(), start, end) {
+                    Bytes::copy_from_slice(&vec[start..=end])
+                } else {
+                    Bytes::new()
+                };
                 Frame::Bulk(bytes)
             }
         }

src/util/prune_range.rs

@@ -2,20 +2,14 @@
 // Use of this source is governed by GNU Affero General Public License
 // that can be found in the LICENSE file.
 
-use bytes::Bytes;
-
-pub fn slice_range_to_bytes(slice: &[u8], start: i64, end: i64) -> Bytes {
-    if let Some((start, end)) = prune_range(slice.len(), start, end) {
-        Bytes::copy_from_slice(&slice[start..=end])
-    } else {
-        Bytes::new()
-    }
-}
-
+#[allow(clippy::cast_possible_truncation)]
+#[allow(clippy::cast_possible_wrap)]
+#[allow(clippy::cast_sign_loss)]
 pub fn prune_range(len: usize, mut start: i64, mut end: i64) -> Option<(usize, usize)> {
+    // TODO(Shaohua): Handle cast error
     let len_i64 = len as i64;
     if start < 0 {
-        start += len_i64 + start
+        start += len_i64;
     }
     if end < 0 {
         end += len_i64;