702 lines
22 KiB
Rust
702 lines
22 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Macro support for format strings
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//!
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//! These structures are used when parsing format strings for the compiler.
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//! Parsing does not happen at runtime: structures of `std::fmt::rt` are
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//! generated instead.
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#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
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html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
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html_root_url = "https://doc.rust-lang.org/nightly/",
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html_playground_url = "https://play.rust-lang.org/",
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test(attr(deny(warnings))))]
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#![deny(warnings)]
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pub use self::Piece::*;
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pub use self::Position::*;
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pub use self::Alignment::*;
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pub use self::Flag::*;
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pub use self::Count::*;
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use std::str;
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use std::string;
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use std::iter;
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/// A piece is a portion of the format string which represents the next part
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/// to emit. These are emitted as a stream by the `Parser` class.
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#[derive(Copy, Clone, PartialEq)]
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pub enum Piece<'a> {
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/// A literal string which should directly be emitted
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String(&'a str),
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/// This describes that formatting should process the next argument (as
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/// specified inside) for emission.
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NextArgument(Argument<'a>),
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}
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/// Representation of an argument specification.
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#[derive(Copy, Clone, PartialEq)]
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pub struct Argument<'a> {
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/// Where to find this argument
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pub position: Position<'a>,
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/// How to format the argument
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pub format: FormatSpec<'a>,
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}
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/// Specification for the formatting of an argument in the format string.
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#[derive(Copy, Clone, PartialEq)]
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pub struct FormatSpec<'a> {
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/// Optionally specified character to fill alignment with
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pub fill: Option<char>,
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/// Optionally specified alignment
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pub align: Alignment,
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/// Packed version of various flags provided
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pub flags: u32,
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/// The integer precision to use
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pub precision: Count<'a>,
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/// The string width requested for the resulting format
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pub width: Count<'a>,
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/// The descriptor string representing the name of the format desired for
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/// this argument, this can be empty or any number of characters, although
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/// it is required to be one word.
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pub ty: &'a str,
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}
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/// Enum describing where an argument for a format can be located.
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#[derive(Copy, Clone, PartialEq)]
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pub enum Position<'a> {
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/// The argument is located at a specific index.
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ArgumentIs(usize),
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/// The argument has a name.
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ArgumentNamed(&'a str),
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}
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/// Enum of alignments which are supported.
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#[derive(Copy, Clone, PartialEq)]
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pub enum Alignment {
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/// The value will be aligned to the left.
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AlignLeft,
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/// The value will be aligned to the right.
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AlignRight,
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/// The value will be aligned in the center.
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AlignCenter,
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/// The value will take on a default alignment.
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AlignUnknown,
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}
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/// Various flags which can be applied to format strings. The meaning of these
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/// flags is defined by the formatters themselves.
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#[derive(Copy, Clone, PartialEq)]
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pub enum Flag {
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/// A `+` will be used to denote positive numbers.
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FlagSignPlus,
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/// A `-` will be used to denote negative numbers. This is the default.
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FlagSignMinus,
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/// An alternate form will be used for the value. In the case of numbers,
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/// this means that the number will be prefixed with the supplied string.
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FlagAlternate,
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/// For numbers, this means that the number will be padded with zeroes,
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/// and the sign (`+` or `-`) will precede them.
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FlagSignAwareZeroPad,
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}
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/// A count is used for the precision and width parameters of an integer, and
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/// can reference either an argument or a literal integer.
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#[derive(Copy, Clone, PartialEq)]
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pub enum Count<'a> {
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/// The count is specified explicitly.
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CountIs(usize),
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/// The count is specified by the argument with the given name.
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CountIsName(&'a str),
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/// The count is specified by the argument at the given index.
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CountIsParam(usize),
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/// The count is implied and cannot be explicitly specified.
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CountImplied,
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}
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/// The parser structure for interpreting the input format string. This is
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/// modeled as an iterator over `Piece` structures to form a stream of tokens
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/// being output.
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///
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/// This is a recursive-descent parser for the sake of simplicity, and if
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/// necessary there's probably lots of room for improvement performance-wise.
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pub struct Parser<'a> {
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input: &'a str,
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cur: iter::Peekable<str::CharIndices<'a>>,
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/// Error messages accumulated during parsing
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pub errors: Vec<(string::String, Option<string::String>)>,
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/// Current position of implicit positional argument pointer
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curarg: usize,
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}
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impl<'a> Iterator for Parser<'a> {
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type Item = Piece<'a>;
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fn next(&mut self) -> Option<Piece<'a>> {
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if let Some(&(pos, c)) = self.cur.peek() {
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match c {
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'{' => {
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self.cur.next();
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if self.consume('{') {
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Some(String(self.string(pos + 1)))
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} else {
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let ret = Some(NextArgument(self.argument()));
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self.must_consume('}');
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ret
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}
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}
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'}' => {
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self.cur.next();
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if self.consume('}') {
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Some(String(self.string(pos + 1)))
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} else {
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self.err_with_note("unmatched `}` found",
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"if you intended to print `}`, \
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you can escape it using `}}`");
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None
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}
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}
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_ => Some(String(self.string(pos))),
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}
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} else {
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None
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}
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}
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}
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impl<'a> Parser<'a> {
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/// Creates a new parser for the given format string
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pub fn new(s: &'a str) -> Parser<'a> {
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Parser {
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input: s,
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cur: s.char_indices().peekable(),
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errors: vec![],
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curarg: 0,
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}
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}
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/// Notifies of an error. The message doesn't actually need to be of type
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/// String, but I think it does when this eventually uses conditions so it
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/// might as well start using it now.
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fn err(&mut self, msg: &str) {
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self.errors.push((msg.to_owned(), None));
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}
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/// Notifies of an error. The message doesn't actually need to be of type
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/// String, but I think it does when this eventually uses conditions so it
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/// might as well start using it now.
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fn err_with_note(&mut self, msg: &str, note: &str) {
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self.errors.push((msg.to_owned(), Some(note.to_owned())));
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}
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/// Optionally consumes the specified character. If the character is not at
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/// the current position, then the current iterator isn't moved and false is
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/// returned, otherwise the character is consumed and true is returned.
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fn consume(&mut self, c: char) -> bool {
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if let Some(&(_, maybe)) = self.cur.peek() {
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if c == maybe {
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self.cur.next();
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true
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} else {
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false
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}
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} else {
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false
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}
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}
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/// Forces consumption of the specified character. If the character is not
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/// found, an error is emitted.
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fn must_consume(&mut self, c: char) {
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self.ws();
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if let Some(&(_, maybe)) = self.cur.peek() {
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if c == maybe {
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self.cur.next();
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} else {
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self.err(&format!("expected `{:?}`, found `{:?}`", c, maybe));
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}
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} else {
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let msg = &format!("expected `{:?}` but string was terminated", c);
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if c == '}' {
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self.err_with_note(msg,
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"if you intended to print `{`, you can escape it using `{{`");
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} else {
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self.err(msg);
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}
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}
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}
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/// Consumes all whitespace characters until the first non-whitespace
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/// character
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fn ws(&mut self) {
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while let Some(&(_, c)) = self.cur.peek() {
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if c.is_whitespace() {
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self.cur.next();
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} else {
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break;
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}
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}
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}
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/// Parses all of a string which is to be considered a "raw literal" in a
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/// format string. This is everything outside of the braces.
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fn string(&mut self, start: usize) -> &'a str {
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// we may not consume the character, peek the iterator
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while let Some(&(pos, c)) = self.cur.peek() {
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match c {
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'{' | '}' => {
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return &self.input[start..pos];
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}
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_ => {
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self.cur.next();
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}
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}
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}
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&self.input[start..self.input.len()]
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}
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/// Parses an Argument structure, or what's contained within braces inside
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/// the format string
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fn argument(&mut self) -> Argument<'a> {
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let pos = self.position();
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let format = self.format();
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// Resolve position after parsing format spec.
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let pos = match pos {
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Some(position) => position,
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None => {
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let i = self.curarg;
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self.curarg += 1;
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ArgumentIs(i)
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}
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};
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Argument {
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position: pos,
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format,
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}
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}
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/// Parses a positional argument for a format. This could either be an
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/// integer index of an argument, a named argument, or a blank string.
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/// Returns `Some(parsed_position)` if the position is not implicitly
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/// consuming a macro argument, `None` if it's the case.
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fn position(&mut self) -> Option<Position<'a>> {
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if let Some(i) = self.integer() {
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Some(ArgumentIs(i))
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} else {
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match self.cur.peek() {
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Some(&(_, c)) if c.is_alphabetic() => Some(ArgumentNamed(self.word())),
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// This is an `ArgumentNext`.
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// Record the fact and do the resolution after parsing the
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// format spec, to make things like `{:.*}` work.
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_ => None,
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}
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}
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}
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/// Parses a format specifier at the current position, returning all of the
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/// relevant information in the FormatSpec struct.
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fn format(&mut self) -> FormatSpec<'a> {
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let mut spec = FormatSpec {
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fill: None,
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align: AlignUnknown,
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flags: 0,
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precision: CountImplied,
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width: CountImplied,
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ty: &self.input[..0],
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};
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if !self.consume(':') {
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return spec;
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}
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// fill character
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if let Some(&(_, c)) = self.cur.peek() {
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match self.cur.clone().skip(1).next() {
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Some((_, '>')) | Some((_, '<')) | Some((_, '^')) => {
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spec.fill = Some(c);
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self.cur.next();
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}
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_ => {}
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}
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}
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// Alignment
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if self.consume('<') {
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spec.align = AlignLeft;
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} else if self.consume('>') {
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spec.align = AlignRight;
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} else if self.consume('^') {
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spec.align = AlignCenter;
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}
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// Sign flags
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if self.consume('+') {
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spec.flags |= 1 << (FlagSignPlus as u32);
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} else if self.consume('-') {
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spec.flags |= 1 << (FlagSignMinus as u32);
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}
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// Alternate marker
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if self.consume('#') {
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spec.flags |= 1 << (FlagAlternate as u32);
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}
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// Width and precision
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let mut havewidth = false;
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if self.consume('0') {
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// small ambiguity with '0$' as a format string. In theory this is a
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// '0' flag and then an ill-formatted format string with just a '$'
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// and no count, but this is better if we instead interpret this as
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// no '0' flag and '0$' as the width instead.
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if self.consume('$') {
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spec.width = CountIsParam(0);
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havewidth = true;
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} else {
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spec.flags |= 1 << (FlagSignAwareZeroPad as u32);
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}
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}
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if !havewidth {
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spec.width = self.count();
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}
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if self.consume('.') {
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if self.consume('*') {
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// Resolve `CountIsNextParam`.
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// We can do this immediately as `position` is resolved later.
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let i = self.curarg;
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self.curarg += 1;
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spec.precision = CountIsParam(i);
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} else {
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spec.precision = self.count();
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}
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}
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// Finally the actual format specifier
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if self.consume('?') {
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spec.ty = "?";
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} else {
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spec.ty = self.word();
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}
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spec
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}
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/// Parses a Count parameter at the current position. This does not check
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/// for 'CountIsNextParam' because that is only used in precision, not
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/// width.
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fn count(&mut self) -> Count<'a> {
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if let Some(i) = self.integer() {
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if self.consume('$') {
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CountIsParam(i)
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} else {
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CountIs(i)
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}
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} else {
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let tmp = self.cur.clone();
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let word = self.word();
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if word.is_empty() {
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self.cur = tmp;
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CountImplied
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} else {
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if self.consume('$') {
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CountIsName(word)
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} else {
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self.cur = tmp;
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CountImplied
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}
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}
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}
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}
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/// Parses a word starting at the current position. A word is considered to
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/// be an alphabetic character followed by any number of alphanumeric
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/// characters.
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fn word(&mut self) -> &'a str {
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let start = match self.cur.peek() {
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Some(&(pos, c)) if c.is_xid_start() => {
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self.cur.next();
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pos
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}
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_ => {
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return &self.input[..0];
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}
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};
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while let Some(&(pos, c)) = self.cur.peek() {
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if c.is_xid_continue() {
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self.cur.next();
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} else {
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return &self.input[start..pos];
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}
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}
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&self.input[start..self.input.len()]
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}
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/// Optionally parses an integer at the current position. This doesn't deal
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/// with overflow at all, it's just accumulating digits.
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fn integer(&mut self) -> Option<usize> {
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let mut cur = 0;
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let mut found = false;
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while let Some(&(_, c)) = self.cur.peek() {
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if let Some(i) = c.to_digit(10) {
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cur = cur * 10 + i as usize;
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found = true;
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self.cur.next();
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} else {
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break;
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}
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}
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if found {
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Some(cur)
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} else {
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None
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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fn same(fmt: &'static str, p: &[Piece<'static>]) {
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let parser = Parser::new(fmt);
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assert!(parser.collect::<Vec<Piece<'static>>>() == p);
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}
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fn fmtdflt() -> FormatSpec<'static> {
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return FormatSpec {
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fill: None,
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align: AlignUnknown,
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flags: 0,
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precision: CountImplied,
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width: CountImplied,
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ty: "",
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};
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}
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fn musterr(s: &str) {
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let mut p = Parser::new(s);
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p.next();
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assert!(!p.errors.is_empty());
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}
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#[test]
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fn simple() {
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same("asdf", &[String("asdf")]);
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same("a{{b", &[String("a"), String("{b")]);
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same("a}}b", &[String("a"), String("}b")]);
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same("a}}", &[String("a"), String("}")]);
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same("}}", &[String("}")]);
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same("\\}}", &[String("\\"), String("}")]);
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}
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#[test]
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fn invalid01() {
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musterr("{")
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}
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#[test]
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fn invalid02() {
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musterr("}")
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}
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#[test]
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fn invalid04() {
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musterr("{3a}")
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}
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#[test]
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fn invalid05() {
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musterr("{:|}")
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}
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#[test]
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fn invalid06() {
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musterr("{:>>>}")
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}
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#[test]
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fn format_nothing() {
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same("{}",
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&[NextArgument(Argument {
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position: ArgumentIs(0),
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format: fmtdflt(),
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})]);
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}
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#[test]
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fn format_position() {
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same("{3}",
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&[NextArgument(Argument {
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position: ArgumentIs(3),
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format: fmtdflt(),
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})]);
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}
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#[test]
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fn format_position_nothing_else() {
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same("{3:}",
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&[NextArgument(Argument {
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position: ArgumentIs(3),
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format: fmtdflt(),
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})]);
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}
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#[test]
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fn format_type() {
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same("{3:a}",
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&[NextArgument(Argument {
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position: ArgumentIs(3),
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format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "a",
|
|
},
|
|
})]);
|
|
}
|
|
#[test]
|
|
fn format_align_fill() {
|
|
same("{3:>}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(3),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignRight,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "",
|
|
},
|
|
})]);
|
|
same("{3:0<}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(3),
|
|
format: FormatSpec {
|
|
fill: Some('0'),
|
|
align: AlignLeft,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "",
|
|
},
|
|
})]);
|
|
same("{3:*<abcd}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(3),
|
|
format: FormatSpec {
|
|
fill: Some('*'),
|
|
align: AlignLeft,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "abcd",
|
|
},
|
|
})]);
|
|
}
|
|
#[test]
|
|
fn format_counts() {
|
|
same("{:10s}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountIs(10),
|
|
ty: "s",
|
|
},
|
|
})]);
|
|
same("{:10$.10s}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountIs(10),
|
|
width: CountIsParam(10),
|
|
ty: "s",
|
|
},
|
|
})]);
|
|
same("{:.*s}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(1),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountIsParam(0),
|
|
width: CountImplied,
|
|
ty: "s",
|
|
},
|
|
})]);
|
|
same("{:.10$s}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountIsParam(10),
|
|
width: CountImplied,
|
|
ty: "s",
|
|
},
|
|
})]);
|
|
same("{:a$.b$s}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountIsName("b"),
|
|
width: CountIsName("a"),
|
|
ty: "s",
|
|
},
|
|
})]);
|
|
}
|
|
#[test]
|
|
fn format_flags() {
|
|
same("{:-}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: (1 << FlagSignMinus as u32),
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "",
|
|
},
|
|
})]);
|
|
same("{:+#}",
|
|
&[NextArgument(Argument {
|
|
position: ArgumentIs(0),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: (1 << FlagSignPlus as u32) | (1 << FlagAlternate as u32),
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "",
|
|
},
|
|
})]);
|
|
}
|
|
#[test]
|
|
fn format_mixture() {
|
|
same("abcd {3:a} efg",
|
|
&[String("abcd "),
|
|
NextArgument(Argument {
|
|
position: ArgumentIs(3),
|
|
format: FormatSpec {
|
|
fill: None,
|
|
align: AlignUnknown,
|
|
flags: 0,
|
|
precision: CountImplied,
|
|
width: CountImplied,
|
|
ty: "a",
|
|
},
|
|
}),
|
|
String(" efg")]);
|
|
}
|
|
}
|