reader: add # for "swap" command

README.md

@@ -31,7 +31,8 @@ values (when appropriate).  The REPL will always print the value
 returned by the last command.
 
 The `@` command duplicates the value at the top of the stack and
-pushes the duplicate.  The `$` command will push a `nil`.
+pushes the duplicate.  The `$` command will push a `nil`.  The
+`#` command swaps the two elements at the top of the stack.
 
 To push an element onto the stack, use the `push` command.  To
 pop the top element, one may use the `pop` command.  Note also
@@ -95,6 +96,8 @@ equivalent to:
 rz | @inflate | mount | load /platform/oxide/kernel/amd64/unix | call
 ```
 
+## Commands
+
 The reader supports a handful of "reader commands":
 
 * `clear` clears the terminal window
@@ -126,6 +129,10 @@ Supported commands include:
   entry point.
 * `loadmem <addr>,<len>` to load an ELF object from the given
   region of memory.
+* `call <location> [<up to 6 args>]` calls the System V ABI
+  compliant function at `<location>`, passing up to six
+  arguments taken from the environment stack argument list
+  terminated by nil.
 * `rdmsr <u32>` to read the numbered MSR (note some MSRs can be
   specified by name, such as `IA32_APIC_BASE`).
 * `wrmsr <u32> <u64>` to write the given value to the given MSR.

src/repl/mod.rs

@@ -250,7 +250,7 @@ fn evalcmd(
         "outw" => pio::outw(config, env),
         "peek" => memory::read(config, env),
         "poke" => memory::write(config, env),
-        "pop" => Ok(popenv(env)),
+        "pop" => Ok(pop2(env)),
         "push" => Ok(Value::Nil),
         "rdmsr" => msr::read(config, env),
         "rdsmn" => smn::read(config, env),
@@ -276,24 +276,43 @@ fn dup(env: &mut Vec<Value>) -> Value {
     }
 }
 
+fn swaptop(env: &mut [Value]) -> Value {
+    let len = env.len();
+    if len > 1 {
+        env.swap(len - 1, len - 2);
+        env[len - 1].clone()
+    } else {
+        Value::Nil
+    }
+}
+
 fn popenv(env: &mut Vec<Value>) -> Value {
     if let Some(v) = env.pop() { v } else { Value::Nil }
 }
 
+fn pop2(env: &mut Vec<Value>) -> Value {
+    popenv(env);
+    popenv(env)
+}
+
 fn eval(
     config: &mut bldb::Config,
     cmd: &reader::Command,
     env: &mut Vec<Value>,
 ) -> Result<Value> {
     match cmd {
         reader::Command::Push => Ok(dup(env)),
+        reader::Command::Swap => Ok(swaptop(env)),
         reader::Command::Cmd(_, tokens) => {
             let mut tokens = tokens.clone();
             while let Some(token) = tokens.pop() {
                 match token {
                     reader::Token::Push => {
                         dup(env);
                     }
+                    reader::Token::Swap => {
+                        swaptop(env);
+                    }
                     reader::Token::Term => env.push(Value::Nil),
                     reader::Token::Value(v) => env.push(v),
                 }
@@ -304,9 +323,7 @@ fn eval(
             match evalcmd(config, &cmd, env)? {
                 Value::Nil => Ok(Value::Nil),
                 v => {
-                    if &cmd != "pop" {
-                        env.push(v.clone());
-                    }
+                    env.push(v.clone());
                     Ok(v)
                 }
             }

src/repl/reader.rs

@@ -15,13 +15,15 @@ use core::fmt;
 #[derive(Clone, Debug)]
 pub enum Token {
     Push,
+    Swap,
     Term,
     Value(Value),
 }
 
 #[derive(Clone)]
 pub enum Command {
     Push,
+    Swap,
     Cmd(String, Vec<Token>),
 }
 
@@ -32,6 +34,7 @@ impl fmt::Debug for Command {
     ) -> core::result::Result<(), fmt::Error> {
         match self {
             Self::Push => write!(f, "Push"),
+            Self::Swap => write!(f, "Swap"),
             Self::Cmd(cmd, _) => write!(f, "{cmd}"),
         }
     }
@@ -159,21 +162,35 @@ pub fn read(
     for cmd in cs {
         let mut cmd = cmd.trim();
         let cmdline = String::from(cmd);
-        while let Some(rest) = cmd.strip_prefix("@") {
-            cmds.push(Command::Push);
-            cmd = rest.trim();
+        while !cmd.is_empty() {
+            if let Some(rest) = cmd.strip_prefix("@") {
+                cmds.push(Command::Push);
+                cmd = rest.trim();
+                continue;
+            }
+            if let Some(rest) = cmd.strip_prefix("#") {
+                cmds.push(Command::Swap);
+                cmd = rest.trim();
+                continue;
+            }
+            break;
         }
         let mut tokens = Vec::<Token>::new();
         for mut tok in cmd.split_ascii_whitespace() {
             while !tok.is_empty() {
                 if let Some(rest) = tok.strip_prefix("@") {
                     tokens.push(Token::Push);
-                    tok = rest;
+                    tok = rest.trim();
+                    continue;
+                }
+                if let Some(rest) = tok.strip_prefix("#") {
+                    tokens.push(Token::Swap);
+                    tok = rest.trim();
                     continue;
                 }
                 if let Some(rest) = tok.strip_prefix("$") {
                     tokens.push(Token::Term);
-                    tok = rest;
+                    tok = rest.trim();
                     continue;
                 }
                 tokens.push(Token::Value(parse_value(tok)?));
@@ -225,7 +242,8 @@ values (when appropriate).  The REPL will always print the value
 returned by the last command.
 
 The `@` command duplicates the value at the top of the stack and
-pushes the duplicate.  The `$` command will push a `nil`.
+pushes the duplicate.  The `$` command will push a `nil`.  The
+`#` command swaps the two elements at the top of the stack.
 
 To push an element onto the stack, use the `push` command.  To
 pop the top element, one may use the `pop` command.  Note also
@@ -265,6 +283,8 @@ equivalent to:
 rz | @inflate | mount | load /platform/oxide/kernel/amd64/unix | call
 ```
 
+## Commands
+
 The reader supports a handful of "reader commands":
 
 * `clear` clears the terminal window
@@ -296,6 +316,10 @@ Supported commands include:
   entry point
 * `loadmem <addr>,<len>` to load an ELF object from the given
   region of memory.
+* `call <location> [<up to 6 args>]` calls the System V ABI
+  compliant function at `<location>`, passing up to six
+  arguments taken from the environment stack argument list
+  terminated by nil.
 * `rdmsr <u32>` to read the numbered MSR (note some MSRs can be
   specified by name, such as `IA32_APIC_BASE`)
 * `wrmsr <u32> <u64>` to write the given value to the given MSR