Add 'EXISTS' query

README.md

@@ -26,6 +26,7 @@ TerrabaseDB (or TDB for short) is an effort to provide the best of key/value sto
 * `GET` - Get a key
 * `SET` - Set a key
 * `UPDATE` - Update the value of a key which has already been created with `SET`
+* `EXISTS` - Check if a key exists
 * `DEL` - Delete a key
 
 And, a lot more actions are coming soon!

corelib/src/builders/response.rs

@@ -50,7 +50,7 @@ impl SResp {
         self.dataframe.extend(&cmd);
         self.dataframe.push(b'\n');
     }
-    pub fn prepare_query(mut self) -> (Vec<u8>, Vec<u8>, Vec<u8>) {
+    pub fn prepare_response(mut self) -> (Vec<u8>, Vec<u8>, Vec<u8>) {
         self.metaline
             .extend(self.dataframe.len().to_string().as_bytes());
         self.metaline.push(b'!');

server/src/coredb/mod.rs

@@ -105,6 +105,12 @@ impl CoreDB {
             Err(RespCodes::NotFound)
         }
     }
+
+    /// Check if a `key` exists
+    pub fn exists(&self, key: &str) -> bool {
+        self.acquire_read().contains_key(&key.to_owned())
+    }
+
     #[cfg(Debug)]
     /// Flush the coretable entries when in debug mode
     pub fn print_debug_table(&self) {

server/src/queryengine/mod.rs

@@ -24,7 +24,7 @@
 use crate::coredb::CoreDB;
 use corelib::builders::response::*;
 use corelib::terrapipe::{RespBytes, RespCodes};
-pub mod tags {
+mod tags {
     //! This module is a collection of tags/strings used for evaluating queries
     //! and responses
     /// `GET` command tag
@@ -37,6 +37,8 @@ pub mod tags {
     pub const TAG_DEL: &'static str = "DEL";
     /// `HEYA` command tag
     pub const TAG_HEYA: &'static str = "HEYA";
+    /// `EXISTS` command tag
+    pub const TAG_EXISTS: &'static str = "EXISTS";
 }
 
 /// Execute a simple(*) query
@@ -54,7 +56,7 @@ pub fn execute_simple(db: &CoreDB, buf: Vec<String>) -> Vec<u8> {
                         };
                         let mut resp = SResp::new(RespCodes::Okay.into());
                         resp.add(res.to_vec());
-                        return cat(resp.prepare_query());
+                        return cat(resp.prepare_response());
                     }
                 }
             }
@@ -112,11 +114,23 @@ pub fn execute_simple(db: &CoreDB, buf: Vec<String>) -> Vec<u8> {
                     }
                 }
             }
+            tags::TAG_EXISTS => {
+                // This is an `EXISTS` query
+                if let Some(key) = buf.next() {
+                    if buf.next().is_none() {
+                        let ex = db.exists(&key) as u8;
+                        let mut resp = SResp::new(RespCodes::Okay.into());
+                        resp.add(ex.to_string());
+                        return cat(resp.prepare_response());
+                    }
+                }
+            }
             tags::TAG_HEYA => {
+                // This is a `HEYA` query
                 if buf.next().is_none() {
                     let mut resp = SResp::new(RespCodes::Okay.into());
                     resp.add("HEY!");
-                    return cat(resp.prepare_query());
+                    return cat(resp.prepare_response());
                 }
             }
             _ => return RespCodes::OtherError(Some("Unknown command".to_owned())).into_response(),