Format tuple-like structs

src/string.rs

@@ -0,0 +1,103 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Format string literals.
+
+use utils::{make_indent, next_char, prev_char, round_up_to_power_of_two};
+
+use MIN_STRING;
+
+pub struct StringFormat<'a> {
+    pub opener: &'a str,
+    pub closer: &'a str,
+    pub line_start: &'a str,
+    pub line_end: &'a str,
+    pub width: usize,
+    pub offset: usize,
+    pub trim_end: bool,
+}
+
+// TODO: simplify this!
+pub fn rewrite_string<'a>(s: &str, fmt: &StringFormat<'a>) -> String {
+    // FIXME I bet this stomps unicode escapes in the source string
+    // TODO if lo.col > IDEAL - 10, start a new line (need cur indent for that)
+
+    let indent = make_indent(fmt.offset);
+    let indent = &indent;
+
+    let mut cur_start = 0;
+    let mut result = String::with_capacity(round_up_to_power_of_two(s.len()));
+    result.push_str(fmt.opener);
+
+    let ender_length = fmt.line_end.len();
+    let max_chars = fmt.width.checked_sub(fmt.opener.len()).unwrap_or(0)
+                             .checked_sub(ender_length).unwrap_or(1);
+
+    loop {
+        let mut cur_end = cur_start + max_chars;
+
+        if cur_end >= s.len() {
+            result.push_str(&s[cur_start..]);
+            break;
+        }
+
+        // Make sure we're on a char boundary.
+        cur_end = next_char(&s, cur_end);
+
+        // Push cur_end left until we reach whitespace.
+        while !s.char_at(cur_end - 1).is_whitespace() {
+            cur_end = prev_char(&s, cur_end);
+
+            if cur_end - cur_start < MIN_STRING {
+                // We can't break at whitespace, fall back to splitting
+                // anywhere that doesn't break an escape sequence.
+                cur_end = next_char(&s, cur_start + max_chars);
+                while s.char_at(prev_char(&s, cur_end)) == '\\' {
+                    cur_end = prev_char(&s, cur_end);
+                }
+                break;
+            }
+        }
+        // Make sure there is no whitespace to the right of the break.
+        while cur_end < s.len() && s.char_at(cur_end).is_whitespace() {
+            cur_end = next_char(&s, cur_end + 1);
+        }
+
+        let line: &str = if fmt.trim_end {
+            &s[cur_start..cur_end].trim_right_matches(char::is_whitespace)
+        } else {
+            &s[cur_start..cur_end]
+        };
+
+        result.push_str(line);
+        result.push_str(fmt.line_end);
+        result.push('\n');
+        result.push_str(indent);
+        result.push_str(fmt.line_start);
+
+        cur_start = cur_end;
+    }
+    result.push_str(fmt.closer);
+
+    result
+}
+
+#[inline]
+// Checks if a appears before b in given string and, if so, returns the index of
+// a.
+// FIXME: could be more generic
+pub fn before<'x>(s: &'x str, a: &str, b: &str) -> Option<usize> {
+    s.find(a).and_then(|i| {
+        match s.find(b) {
+            Some(j) if j <= i => None,
+            _ => Some(i)
+        }
+    })
+}