add read_term_from_chars/3 (#637)

src/lib/charsio.pl

@@ -12,6 +12,7 @@ read and write chars.
                     get_n_chars/3,
                     get_line_to_chars/3,
                     read_from_chars/2,
+                    read_term_from_chars/3,
                     write_term_to_chars/3,
                     chars_base64/3]).
 
@@ -194,7 +195,22 @@ get_single_char(C) :-
 read_from_chars(Chars, Term) :-
     must_be(chars, Chars),
     must_be(var, Term),
-    '$read_term_from_chars'(Chars, Term).
+    '$read_from_chars'(Chars, Term).
+
+%% read_term_from_chars(+Chars, -Term, +Options).
+%
+% Like `read_from_chars`, except the reader is configured according to
+% `Options` which are those of `read_term`.
+%
+% ```
+% ?- read_term_from_chars("f(X,y).", T, [variable_names(['X'=X])]).
+%    T = f(X,y).
+% ```
+read_term_from_chars(Chars, Term, Options) :-
+    must_be(chars, Chars),
+    must_be(var, Term),
+    builtins:parse_read_term_options(Options, [Singletons, VariableNames, Variables], read_term_from_chars/3),
+    '$read_term_from_chars'(Chars, Term, Singletons, Variables, VariableNames).
 
 %% write_term_to_chars(+Term, +Options, -Chars).
 %

src/machine/dispatch.rs

@@ -4270,6 +4270,14 @@ impl Machine {
                     self.quoted_token();
                     step_or_fail!(self, self.machine_st.p = self.machine_st.cp);
                 }
+                &Instruction::CallReadFromChars => {
+                    try_or_throw!(self.machine_st, self.read_from_chars());
+                    step_or_fail!(self, self.machine_st.p += 1);
+                }
+                &Instruction::ExecuteReadFromChars => {
+                    try_or_throw!(self.machine_st, self.read_from_chars());
+                    step_or_fail!(self, self.machine_st.p = self.machine_st.cp);
+                }
                 &Instruction::CallReadTermFromChars => {
                     try_or_throw!(self.machine_st, self.read_term_from_chars());
                     step_or_fail!(self, self.machine_st.p += 1);

src/machine/system_calls.rs

@@ -5792,7 +5792,7 @@ impl Machine {
     }
 
     #[inline(always)]
-    pub(crate) fn read_term_from_chars(&mut self) -> CallResult {
+    pub(crate) fn read_from_chars(&mut self) -> CallResult {
         if let Some(atom_or_string) = self.machine_st.value_to_str_like(self.machine_st.registers[1]) {
             let chars = CharReader::new(ByteStream::from_string(atom_or_string.to_string()));
             let mut parser = Parser::new(chars, &mut self.machine_st);
@@ -5829,6 +5829,16 @@ impl Machine {
         Ok(())
     }
 
+    #[inline(always)]
+    pub(crate) fn read_term_from_chars(&mut self) -> CallResult {
+        if let Some(atom_or_string) = self.machine_st.value_to_str_like(self.machine_st.registers[1]) {
+            let stream = Stream::from_owned_string(atom_or_string.to_string(), &mut self.machine_st.arena);
+            self.machine_st.read_term(stream, &mut self.indices)
+        } else {
+            unreachable!()
+        }
+    }
+
     #[inline(always)]
     pub(crate) fn reset_block(&mut self) {
         let addr = self.deref_register(1);