From b390b3113a7494060ec3ee7ec646c38c0d802fa6 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <jolesen@mozilla.com>
Date: Fri, 29 Apr 2016 13:30:07 -0700
Subject: [PATCH] Add a write.rs module.

Convert a function to text.
---
 cranelift/src/libcretonne/lib.rs   |   1 +
 cranelift/src/libcretonne/repr.rs  |   5 ++
 cranelift/src/libcretonne/write.rs | 113 +++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)
 create mode 100644 cranelift/src/libcretonne/write.rs

diff --git a/cranelift/src/libcretonne/lib.rs b/cranelift/src/libcretonne/lib.rs
index b67ca5df10..f47b049156 100644
--- a/cranelift/src/libcretonne/lib.rs
+++ b/cranelift/src/libcretonne/lib.rs
@@ -8,3 +8,4 @@
 pub mod types;
 pub mod immediates;
 pub mod repr;
+pub mod write;
diff --git a/cranelift/src/libcretonne/repr.rs b/cranelift/src/libcretonne/repr.rs
index 702a371609..3917fa8f48 100644
--- a/cranelift/src/libcretonne/repr.rs
+++ b/cranelift/src/libcretonne/repr.rs
@@ -382,6 +382,11 @@ impl Function {
         Self::with_name_signature(FunctionName::new(), Signature::new())
     }
 
+    /// Get the signature of this function.
+    pub fn own_signature(&self) -> &Signature {
+        &self.signature
+    }
+
     /// Allocate a new stack slot.
     pub fn make_stack_slot(&mut self, data: StackSlotData) -> StackSlot {
         let ss = StackSlot::new(self.stack_slots.len());
diff --git a/cranelift/src/libcretonne/write.rs b/cranelift/src/libcretonne/write.rs
new file mode 100644
index 0000000000..7281294fe6
--- /dev/null
+++ b/cranelift/src/libcretonne/write.rs
@@ -0,0 +1,113 @@
+//! Converting Cretonne IL to text.
+//!
+//! The `write` module provides the `write_function` function which converts an IL `Function` to an
+//! equivalent textual representation. This textual representation can be read back by the
+//! `ctonfile` crate.
+
+use std::io::{self, Write};
+use repr::Function;
+
+pub type Result = io::Result<()>;
+
+/// Write `func` to `w` as equivalent text.
+pub fn write_function(w: &mut Write, func: &Function) -> Result {
+    try!(write_spec(w, func));
+    try!(writeln!(w, " {{"));
+    try!(write_preamble(w, func));
+    writeln!(w, "}}")
+}
+
+/// Convert `func` to a string.
+pub fn function_to_string(func: &Function) -> String {
+    let mut buffer: Vec<u8> = Vec::new();
+    // Any errors here would be out-of-memory, which should not happen with normal functions.
+    write_function(&mut buffer, func).unwrap();
+    // A UTF-8 conversion error is a real bug.
+    String::from_utf8(buffer).unwrap()
+}
+
+// ====--------------------------------------------------------------------------------------====//
+//
+// Function spec.
+//
+// ====--------------------------------------------------------------------------------------====//
+
+// The function name may need quotes if it doesn't parse as an identifier.
+fn needs_quotes(name: &str) -> bool {
+    let mut iter = name.chars();
+    if let Some(ch) = iter.next() {
+        !ch.is_alphabetic() || !iter.all(char::is_alphanumeric)
+    } else {
+        // A blank function name needs quotes.
+        true
+    }
+}
+
+// Use Rust's escape_default which provides a few simple \t \r \n \' \" \\ escapes and uses
+// \u{xxxx} for anything else outside the ASCII printable range.
+fn escaped(name: &str) -> String {
+    name.chars().flat_map(char::escape_default).collect()
+}
+
+fn write_spec(w: &mut Write, func: &Function) -> Result {
+    let sig = func.own_signature();
+    if !needs_quotes(&func.name) {
+        write!(w, "function {}{}", func.name, sig)
+    } else {
+        write!(w, "function \"{}\" {}", escaped(&func.name), sig)
+    }
+}
+
+fn write_preamble(w: &mut Write, func: &Function) -> Result {
+    let mut any = false;
+
+    for ss in func.stack_slot_iter() {
+        any = true;
+        try!(writeln!(w, "    {} = {}", ss, func[ss]));
+    }
+
+    // Put a blank line after the preamble unless it was empty.
+    if any {
+        writeln!(w, "")
+    } else {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use super::{needs_quotes, escaped};
+    use repr::{Function, StackSlotData};
+
+    #[test]
+    fn quoting() {
+        assert_eq!(needs_quotes(""), true);
+        assert_eq!(needs_quotes("x"), false);
+        assert_eq!(needs_quotes(" "), true);
+        assert_eq!(needs_quotes("0"), true);
+        assert_eq!(needs_quotes("x0"), false);
+    }
+
+    #[test]
+    fn escaping() {
+        assert_eq!(escaped(""), "");
+        assert_eq!(escaped("x"), "x");
+        assert_eq!(escaped(" "), " ");
+        assert_eq!(escaped(" \n"), " \\n");
+        assert_eq!(escaped("a\u{1000}v"), "a\\u{1000}v");
+    }
+
+    #[test]
+    fn basic() {
+        let mut f = Function::new();
+        assert_eq!(function_to_string(&f), "function \"\" () {\n}\n");
+
+        f.name.push_str("foo");
+        assert_eq!(function_to_string(&f), "function foo() {\n}\n");
+
+        f.make_stack_slot(StackSlotData::new(4));
+        assert_eq!(function_to_string(&f),
+                   "function foo() {\n    ss0 = stack_slot 4\n\n}\n");
+    }
+}