src/libgraphviz/lib.rs

   1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Generate files suitable for use with [Graphviz](http://www.graphviz.org/)
  12 //!
  13 //! The `render` function generates output (e.g. an `output.dot` file) for
  14 //! use with [Graphviz](http://www.graphviz.org/) by walking a labelled
  15 //! graph. (Graphviz can then automatically lay out the nodes and edges
  16 //! of the graph, and also optionally render the graph as an image or
  17 //! other [output formats](
  18 //! http://www.graphviz.org/content/output-formats), such as SVG.)
  19 //!
  20 //! Rather than impose some particular graph data structure on clients,
  21 //! this library exposes two traits that clients can implement on their
  22 //! own structs before handing them over to the rendering function.
  23 //!
  24 //! Note: This library does not yet provide access to the full
  25 //! expressiveness of the [DOT language](
  26 //! http://www.graphviz.org/doc/info/lang.html). For example, there are
  27 //! many [attributes](http://www.graphviz.org/content/attrs) related to
  28 //! providing layout hints (e.g. left-to-right versus top-down, which
  29 //! algorithm to use, etc). The current intention of this library is to
  30 //! emit a human-readable .dot file with very regular structure suitable
  31 //! for easy post-processing.
  32 //!
  33 //! # Examples
  34 //!
  35 //! The first example uses a very simple graph representation: a list of
  36 //! pairs of ints, representing the edges (the node set is implicit).
  37 //! Each node label is derived directly from the int representing the node,
  38 //! while the edge labels are all empty strings.
  39 //!
  40 //! This example also illustrates how to use `Cow<[T]>` to return
  41 //! an owned vector or a borrowed slice as appropriate: we construct the
  42 //! node vector from scratch, but borrow the edge list (rather than
  43 //! constructing a copy of all the edges from scratch).
  44 //!
  45 //! The output from this example renders five nodes, with the first four
  46 //! forming a diamond-shaped acyclic graph and then pointing to the fifth
  47 //! which is cyclic.
  48 //!
  49 //! ```rust
  50 //! #![feature(rustc_private, core, into_cow)]
  51 //!
  52 //! use std::borrow::IntoCow;
  53 //! use std::io::Write;
  54 //! use graphviz as dot;
  55 //!
  56 //! type Nd = isize;
  57 //! type Ed = (isize,isize);
  58 //! struct Edges(Vec<Ed>);
  59 //!
  60 //! pub fn render_to<W: Write>(output: &mut W) {
  61 //!     let edges = Edges(vec!((0,1), (0,2), (1,3), (2,3), (3,4), (4,4)));
  62 //!     dot::render(&edges, output).unwrap()
  63 //! }
  64 //!
  65 //! impl<'a> dot::Labeller<'a, Nd, Ed> for Edges {
  66 //!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example1").unwrap() }
  67 //!
  68 //!     fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
  69 //!         dot::Id::new(format!("N{}", *n)).unwrap()
  70 //!     }
  71 //! }
  72 //!
  73 //! impl<'a> dot::GraphWalk<'a, Nd, Ed> for Edges {
  74 //!     fn nodes(&self) -> dot::Nodes<'a,Nd> {
  75 //!         // (assumes that |N| \approxeq |E|)
  76 //!         let &Edges(ref v) = self;
  77 //!         let mut nodes = Vec::with_capacity(v.len());
  78 //!         for &(s,t) in v {
  79 //!             nodes.push(s); nodes.push(t);
  80 //!         }
  81 //!         nodes.sort();
  82 //!         nodes.dedup();
  83 //!         nodes.into_cow()
  84 //!     }
  85 //!
  86 //!     fn edges(&'a self) -> dot::Edges<'a,Ed> {
  87 //!         let &Edges(ref edges) = self;
  88 //!         (&edges[..]).into_cow()
  89 //!     }
  90 //!
  91 //!     fn source(&self, e: &Ed) -> Nd { let &(s,_) = e; s }
  92 //!
  93 //!     fn target(&self, e: &Ed) -> Nd { let &(_,t) = e; t }
  94 //! }
  95 //!
  96 //! # pub fn main() { render_to(&mut Vec::new()) }
  97 //! ```
  98 //!
  99 //! ```no_run
 100 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
 101 //! pub fn main() {
 102 //!     use std::fs::File;
 103 //!     let mut f = File::create("example1.dot").unwrap();
 104 //!     render_to(&mut f)
 105 //! }
 106 //! ```
 107 //!
 108 //! Output from first example (in `example1.dot`):
 109 //!
 110 //! ```ignore
 111 //! digraph example1 {
 112 //!     N0[label="N0"];
 113 //!     N1[label="N1"];
 114 //!     N2[label="N2"];
 115 //!     N3[label="N3"];
 116 //!     N4[label="N4"];
 117 //!     N0 -> N1[label=""];
 118 //!     N0 -> N2[label=""];
 119 //!     N1 -> N3[label=""];
 120 //!     N2 -> N3[label=""];
 121 //!     N3 -> N4[label=""];
 122 //!     N4 -> N4[label=""];
 123 //! }
 124 //! ```
 125 //!
 126 //! The second example illustrates using `node_label` and `edge_label` to
 127 //! add labels to the nodes and edges in the rendered graph. The graph
 128 //! here carries both `nodes` (the label text to use for rendering a
 129 //! particular node), and `edges` (again a list of `(source,target)`
 130 //! indices).
 131 //!
 132 //! This example also illustrates how to use a type (in this case the edge
 133 //! type) that shares substructure with the graph: the edge type here is a
 134 //! direct reference to the `(source,target)` pair stored in the graph's
 135 //! internal vector (rather than passing around a copy of the pair
 136 //! itself). Note that this implies that `fn edges(&'a self)` must
 137 //! construct a fresh `Vec<&'a (usize,usize)>` from the `Vec<(usize,usize)>`
 138 //! edges stored in `self`.
 139 //!
 140 //! Since both the set of nodes and the set of edges are always
 141 //! constructed from scratch via iterators, we use the `collect()` method
 142 //! from the `Iterator` trait to collect the nodes and edges into freshly
 143 //! constructed growable `Vec` values (rather use the `into_cow`
 144 //! from the `IntoCow` trait as was used in the first example
 145 //! above).
 146 //!
 147 //! The output from this example renders four nodes that make up the
 148 //! Hasse-diagram for the subsets of the set `{x, y}`. Each edge is
 149 //! labelled with the &sube; character (specified using the HTML character
 150 //! entity `&sube`).
 151 //!
 152 //! ```rust
 153 //! #![feature(rustc_private, core, into_cow)]
 154 //!
 155 //! use std::borrow::IntoCow;
 156 //! use std::io::Write;
 157 //! use graphviz as dot;
 158 //!
 159 //! type Nd = usize;
 160 //! type Ed<'a> = &'a (usize, usize);
 161 //! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
 162 //!
 163 //! pub fn render_to<W: Write>(output: &mut W) {
 164 //!     let nodes = vec!("{x,y}","{x}","{y}","{}");
 165 //!     let edges = vec!((0,1), (0,2), (1,3), (2,3));
 166 //!     let graph = Graph { nodes: nodes, edges: edges };
 167 //!
 168 //!     dot::render(&graph, output).unwrap()
 169 //! }
 170 //!
 171 //! impl<'a> dot::Labeller<'a, Nd, Ed<'a>> for Graph {
 172 //!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example2").unwrap() }
 173 //!     fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
 174 //!         dot::Id::new(format!("N{}", n)).unwrap()
 175 //!     }
 176 //!     fn node_label<'b>(&'b self, n: &Nd) -> dot::LabelText<'b> {
 177 //!         dot::LabelText::LabelStr(self.nodes[*n].as_slice().into_cow())
 178 //!     }
 179 //!     fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> {
 180 //!         dot::LabelText::LabelStr("&sube;".into_cow())
 181 //!     }
 182 //! }
 183 //!
 184 //! impl<'a> dot::GraphWalk<'a, Nd, Ed<'a>> for Graph {
 185 //!     fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() }
 186 //!     fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() }
 187 //!     fn source(&self, e: &Ed) -> Nd { let & &(s,_) = e; s }
 188 //!     fn target(&self, e: &Ed) -> Nd { let & &(_,t) = e; t }
 189 //! }
 190 //!
 191 //! # pub fn main() { render_to(&mut Vec::new()) }
 192 //! ```
 193 //!
 194 //! ```no_run
 195 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
 196 //! pub fn main() {
 197 //!     use std::fs::File;
 198 //!     let mut f = File::create("example2.dot").unwrap();
 199 //!     render_to(&mut f)
 200 //! }
 201 //! ```
 202 //!
 203 //! The third example is similar to the second, except now each node and
 204 //! edge now carries a reference to the string label for each node as well
 205 //! as that node's index. (This is another illustration of how to share
 206 //! structure with the graph itself, and why one might want to do so.)
 207 //!
 208 //! The output from this example is the same as the second example: the
 209 //! Hasse-diagram for the subsets of the set `{x, y}`.
 210 //!
 211 //! ```rust
 212 //! #![feature(rustc_private, core, into_cow)]
 213 //!
 214 //! use std::borrow::IntoCow;
 215 //! use std::io::Write;
 216 //! use graphviz as dot;
 217 //!
 218 //! type Nd<'a> = (usize, &'a str);
 219 //! type Ed<'a> = (Nd<'a>, Nd<'a>);
 220 //! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
 221 //!
 222 //! pub fn render_to<W: Write>(output: &mut W) {
 223 //!     let nodes = vec!("{x,y}","{x}","{y}","{}");
 224 //!     let edges = vec!((0,1), (0,2), (1,3), (2,3));
 225 //!     let graph = Graph { nodes: nodes, edges: edges };
 226 //!
 227 //!     dot::render(&graph, output).unwrap()
 228 //! }
 229 //!
 230 //! impl<'a> dot::Labeller<'a, Nd<'a>, Ed<'a>> for Graph {
 231 //!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example3").unwrap() }
 232 //!     fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> {
 233 //!         dot::Id::new(format!("N{}", n.0)).unwrap()
 234 //!     }
 235 //!     fn node_label<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> {
 236 //!         let &(i, _) = n;
 237 //!         dot::LabelText::LabelStr(self.nodes[i].into_cow())
 238 //!     }
 239 //!     fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> {
 240 //!         dot::LabelText::LabelStr("&sube;".into_cow())
 241 //!     }
 242 //! }
 243 //!
 244 //! impl<'a> dot::GraphWalk<'a, Nd<'a>, Ed<'a>> for Graph {
 245 //!     fn nodes(&'a self) -> dot::Nodes<'a,Nd<'a>> {
 246 //!         self.nodes.iter().map(|s| &s[..]).enumerate().collect()
 247 //!     }
 248 //!     fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> {
 249 //!         self.edges.iter()
 250 //!             .map(|&(i,j)|((i, &self.nodes[i][..]),
 251 //!                           (j, &self.nodes[j][..])))
 252 //!             .collect()
 253 //!     }
 254 //!     fn source(&self, e: &Ed<'a>) -> Nd<'a> { let &(s,_) = e; s }
 255 //!     fn target(&self, e: &Ed<'a>) -> Nd<'a> { let &(_,t) = e; t }
 256 //! }
 257 //!
 258 //! # pub fn main() { render_to(&mut Vec::new()) }
 259 //! ```
 260 //!
 261 //! ```no_run
 262 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
 263 //! pub fn main() {
 264 //!     use std::fs::File;
 265 //!     let mut f = File::create("example3.dot").unwrap();
 266 //!     render_to(&mut f)
 267 //! }
 268 //! ```
 269 //!
 270 //! # References
 271 //!
 272 //! * [Graphviz](http://www.graphviz.org/)
 273 //!
 274 //! * [DOT language](http://www.graphviz.org/doc/info/lang.html)
 275
 276 // Do not remove on snapshot creation. Needed for bootstrap. (Issue #22364)
 277 #![cfg_attr(stage0, feature(custom_attribute))]
 278 #![crate_name = "graphviz"]
 279 #![unstable(feature = "rustc_private")]
 280 #![feature(staged_api)]
 281 #![staged_api]
 282 #![crate_type = "rlib"]
 283 #![crate_type = "dylib"]
 284 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
 285        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
 286        html_root_url = "http://doc.rust-lang.org/nightly/")]
 287
 288 #![feature(into_cow)]
 289 #![feature(str_escape)]
 290
 291 use self::LabelText::*;
 292
 293 use std::borrow::{IntoCow, Cow};
 294 use std::io::prelude::*;
 295 use std::io;
 296
 297 /// The text for a graphviz label on a node or edge.
 298 pub enum LabelText<'a> {
 299     /// This kind of label preserves the text directly as is.
 300     ///
 301     /// Occurrences of backslashes (`\`) are escaped, and thus appear
 302     /// as backslashes in the rendered label.
 303     LabelStr(Cow<'a, str>),
 304
 305     /// This kind of label uses the graphviz label escString type:
 306     /// http://www.graphviz.org/content/attrs#kescString
 307     ///
 308     /// Occurrences of backslashes (`\`) are not escaped; instead they
 309     /// are interpreted as initiating an escString escape sequence.
 310     ///
 311     /// Escape sequences of particular interest: in addition to `\n`
 312     /// to break a line (centering the line preceding the `\n`), there
 313     /// are also the escape sequences `\l` which left-justifies the
 314     /// preceding line and `\r` which right-justifies it.
 315     EscStr(Cow<'a, str>),
 316 }
 317
 318 /// The style for a node or edge.
 319 /// See http://www.graphviz.org/doc/info/attrs.html#k:style for descriptions.
 320 /// Note that some of these are not valid for edges.
 321 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 322 pub enum Style {
 323     None,
 324     Solid,
 325     Dashed,
 326     Dotted,
 327     Bold,
 328     Rounded,
 329     Diagonals,
 330     Filled,
 331     Striped,
 332     Wedged,
 333 }
 334
 335 impl Style {
 336     pub fn as_slice(self) -> &'static str {
 337         match self {
 338             Style::None => "",
 339             Style::Solid => "solid",
 340             Style::Dashed => "dashed",
 341             Style::Dotted => "dotted",
 342             Style::Bold => "bold",
 343             Style::Rounded => "rounded",
 344             Style::Diagonals => "diagonals",
 345             Style::Filled => "filled",
 346             Style::Striped => "striped",
 347             Style::Wedged => "wedged",
 348         }
 349     }
 350 }
 351
 352 // There is a tension in the design of the labelling API.
 353 //
 354 // For example, I considered making a `Labeller<T>` trait that
 355 // provides labels for `T`, and then making the graph type `G`
 356 // implement `Labeller<Node>` and `Labeller<Edge>`. However, this is
 357 // not possible without functional dependencies. (One could work
 358 // around that, but I did not explore that avenue heavily.)
 359 //
 360 // Another approach that I actually used for a while was to make a
 361 // `Label<Context>` trait that is implemented by the client-specific
 362 // Node and Edge types (as well as an implementation on Graph itself
 363 // for the overall name for the graph). The main disadvantage of this
 364 // second approach (compared to having the `G` type parameter
 365 // implement a Labelling service) that I have encountered is that it
 366 // makes it impossible to use types outside of the current crate
 367 // directly as Nodes/Edges; you need to wrap them in newtype'd
 368 // structs. See e.g. the `No` and `Ed` structs in the examples. (In
 369 // practice clients using a graph in some other crate would need to
 370 // provide some sort of adapter shim over the graph anyway to
 371 // interface with this library).
 372 //
 373 // Another approach would be to make a single `Labeller<N,E>` trait
 374 // that provides three methods (graph_label, node_label, edge_label),
 375 // and then make `G` implement `Labeller<N,E>`. At first this did not
 376 // appeal to me, since I had thought I would need separate methods on
 377 // each data variant for dot-internal identifiers versus user-visible
 378 // labels. However, the identifier/label distinction only arises for
 379 // nodes; graphs themselves only have identifiers, and edges only have
 380 // labels.
 381 //
 382 // So in the end I decided to use the third approach described above.
 383
 384 /// `Id` is a Graphviz `ID`.
 385 pub struct Id<'a> {
 386     name: Cow<'a, str>,
 387 }
 388
 389 impl<'a> Id<'a> {
 390     /// Creates an `Id` named `name`.
 391     ///
 392     /// The caller must ensure that the input conforms to an
 393     /// identifier format: it must be a non-empty string made up of
 394     /// alphanumeric or underscore characters, not beginning with a
 395     /// digit (i.e. the regular expression `[a-zA-Z_][a-zA-Z_0-9]*`).
 396     ///
 397     /// (Note: this format is a strict subset of the `ID` format
 398     /// defined by the DOT language.  This function may change in the
 399     /// future to accept a broader subset, or the entirety, of DOT's
 400     /// `ID` format.)
 401     ///
 402     /// Passing an invalid string (containing spaces, brackets,
 403     /// quotes, ...) will return an empty `Err` value.
 404     pub fn new<Name: IntoCow<'a, str>>(name: Name) -> Result<Id<'a>, ()> {
 405         let name = name.into_cow();
 406         {
 407             let mut chars = name.chars();
 408             match chars.next() {
 409                 Some(c) if is_letter_or_underscore(c) => { ; },
 410                 _ => return Err(())
 411             }
 412             if !chars.all(is_constituent) {
 413                 return Err(())
 414             }
 415         }
 416         return Ok(Id{ name: name });
 417
 418         fn is_letter_or_underscore(c: char) -> bool {
 419             in_range('a', c, 'z') || in_range('A', c, 'Z') || c == '_'
 420         }
 421         fn is_constituent(c: char) -> bool {
 422             is_letter_or_underscore(c) || in_range('0', c, '9')
 423         }
 424         fn in_range(low: char, c: char, high: char) -> bool {
 425             low as usize <= c as usize && c as usize <= high as usize
 426         }
 427     }
 428
 429     pub fn as_slice(&'a self) -> &'a str {
 430         &*self.name
 431     }
 432
 433     pub fn name(self) -> Cow<'a, str> {
 434         self.name
 435     }
 436 }
 437
 438 /// Each instance of a type that implements `Label<C>` maps to a
 439 /// unique identifier with respect to `C`, which is used to identify
 440 /// it in the generated .dot file. They can also provide more
 441 /// elaborate (and non-unique) label text that is used in the graphviz
 442 /// rendered output.
 443
 444 /// The graph instance is responsible for providing the DOT compatible
 445 /// identifiers for the nodes and (optionally) rendered labels for the nodes and
 446 /// edges, as well as an identifier for the graph itself.
 447 pub trait Labeller<'a,N,E> {
 448     /// Must return a DOT compatible identifier naming the graph.
 449     fn graph_id(&'a self) -> Id<'a>;
 450
 451     /// Maps `n` to a unique identifier with respect to `self`. The
 452     /// implementer is responsible for ensuring that the returned name
 453     /// is a valid DOT identifier.
 454     fn node_id(&'a self, n: &N) -> Id<'a>;
 455
 456     /// Maps `n` to a label that will be used in the rendered output.
 457     /// The label need not be unique, and may be the empty string; the
 458     /// default is just the output from `node_id`.
 459     fn node_label(&'a self, n: &N) -> LabelText<'a> {
 460         LabelStr(self.node_id(n).name)
 461     }
 462
 463     /// Maps `e` to a label that will be used in the rendered output.
 464     /// The label need not be unique, and may be the empty string; the
 465     /// default is in fact the empty string.
 466     fn edge_label(&'a self, e: &E) -> LabelText<'a> {
 467         let _ignored = e;
 468         LabelStr("".into_cow())
 469     }
 470
 471     /// Maps `n` to a style that will be used in the rendered output.
 472     fn node_style(&'a self, _n: &N) -> Style {
 473         Style::None
 474     }
 475
 476     /// Maps `e` to a style that will be used in the rendered output.
 477     fn edge_style(&'a self, _e: &E) -> Style {
 478         Style::None
 479     }
 480 }
 481
 482 impl<'a> LabelText<'a> {
 483     pub fn label<S:IntoCow<'a, str>>(s: S) -> LabelText<'a> {
 484         LabelStr(s.into_cow())
 485     }
 486
 487     pub fn escaped<S:IntoCow<'a, str>>(s: S) -> LabelText<'a> {
 488         EscStr(s.into_cow())
 489     }
 490
 491     fn escape_char<F>(c: char, mut f: F) where F: FnMut(char) {
 492         match c {
 493             // not escaping \\, since Graphviz escString needs to
 494             // interpret backslashes; see EscStr above.
 495             '\\' => f(c),
 496             _ => for c in c.escape_default() { f(c) }
 497         }
 498     }
 499     fn escape_str(s: &str) -> String {
 500         let mut out = String::with_capacity(s.len());
 501         for c in s.chars() {
 502             LabelText::escape_char(c, |c| out.push(c));
 503         }
 504         out
 505     }
 506
 507     /// Renders text as string suitable for a label in a .dot file.
 508     pub fn escape(&self) -> String {
 509         match self {
 510             &LabelStr(ref s) => s.escape_default(),
 511             &EscStr(ref s) => LabelText::escape_str(&s[..]),
 512         }
 513     }
 514
 515     /// Decomposes content into string suitable for making EscStr that
 516     /// yields same content as self.  The result obeys the law
 517     /// render(`lt`) == render(`EscStr(lt.pre_escaped_content())`) for
 518     /// all `lt: LabelText`.
 519     fn pre_escaped_content(self) -> Cow<'a, str> {
 520         match self {
 521             EscStr(s) => s,
 522             LabelStr(s) => if s.contains('\\') {
 523                 (&*s).escape_default().into_cow()
 524             } else {
 525                 s
 526             },
 527         }
 528     }
 529
 530     /// Puts `prefix` on a line above this label, with a blank line separator.
 531     pub fn prefix_line(self, prefix: LabelText) -> LabelText<'static> {
 532         prefix.suffix_line(self)
 533     }
 534
 535     /// Puts `suffix` on a line below this label, with a blank line separator.
 536     pub fn suffix_line(self, suffix: LabelText) -> LabelText<'static> {
 537         let mut prefix = self.pre_escaped_content().into_owned();
 538         let suffix = suffix.pre_escaped_content();
 539         prefix.push_str(r"\n\n");
 540         prefix.push_str(&suffix[..]);
 541         EscStr(prefix.into_cow())
 542     }
 543 }
 544
 545 pub type Nodes<'a,N> = Cow<'a,[N]>;
 546 pub type Edges<'a,E> = Cow<'a,[E]>;
 547
 548 // (The type parameters in GraphWalk should be associated items,
 549 // when/if Rust supports such.)
 550
 551 /// GraphWalk is an abstraction over a directed graph = (nodes,edges)
 552 /// made up of node handles `N` and edge handles `E`, where each `E`
 553 /// can be mapped to its source and target nodes.
 554 ///
 555 /// The lifetime parameter `'a` is exposed in this trait (rather than
 556 /// introduced as a generic parameter on each method declaration) so
 557 /// that a client impl can choose `N` and `E` that have substructure
 558 /// that is bound by the self lifetime `'a`.
 559 ///
 560 /// The `nodes` and `edges` method each return instantiations of
 561 /// `Cow<[T]>` to leave implementers the freedom to create
 562 /// entirely new vectors or to pass back slices into internally owned
 563 /// vectors.
 564 pub trait GraphWalk<'a, N, E> {
 565     /// Returns all the nodes in this graph.
 566     fn nodes(&'a self) -> Nodes<'a, N>;
 567     /// Returns all of the edges in this graph.
 568     fn edges(&'a self) -> Edges<'a, E>;
 569     /// The source node for `edge`.
 570     fn source(&'a self, edge: &E) -> N;
 571     /// The target node for `edge`.
 572     fn target(&'a self, edge: &E) -> N;
 573 }
 574
 575 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 576 pub enum RenderOption {
 577     NoEdgeLabels,
 578     NoNodeLabels,
 579     NoEdgeStyles,
 580     NoNodeStyles,
 581 }
 582
 583 /// Returns vec holding all the default render options.
 584 pub fn default_options() -> Vec<RenderOption> { vec![] }
 585
 586 /// Renders directed graph `g` into the writer `w` in DOT syntax.
 587 /// (Simple wrapper around `render_opts` that passes a default set of options.)
 588 pub fn render<'a, N:Clone+'a, E:Clone+'a, G:Labeller<'a,N,E>+GraphWalk<'a,N,E>, W:Write>(
 589               g: &'a G,
 590               w: &mut W) -> io::Result<()> {
 591     render_opts(g, w, &[])
 592 }
 593
 594 /// Renders directed graph `g` into the writer `w` in DOT syntax.
 595 /// (Main entry point for the library.)
 596 pub fn render_opts<'a, N:Clone+'a, E:Clone+'a, G:Labeller<'a,N,E>+GraphWalk<'a,N,E>, W:Write>(
 597               g: &'a G,
 598               w: &mut W,
 599               options: &[RenderOption]) -> io::Result<()>
 600 {
 601     fn writeln<W:Write>(w: &mut W, arg: &[&str]) -> io::Result<()> {
 602         for &s in arg { try!(w.write_all(s.as_bytes())); }
 603         write!(w, "\n")
 604     }
 605
 606     fn indent<W:Write>(w: &mut W) -> io::Result<()> {
 607         w.write_all(b"    ")
 608     }
 609
 610     try!(writeln(w, &["digraph ", g.graph_id().as_slice(), " {"]));
 611     for n in g.nodes().iter() {
 612         try!(indent(w));
 613         let id = g.node_id(n);
 614
 615         let escaped = &g.node_label(n).escape();
 616
 617         let mut text = vec![id.as_slice()];
 618
 619         if !options.contains(&RenderOption::NoNodeLabels) {
 620             text.push("[label=\"");
 621             text.push(escaped);
 622             text.push("\"]");
 623         }
 624
 625         let style = g.node_style(n);
 626         if !options.contains(&RenderOption::NoNodeStyles) && style != Style::None {
 627             text.push("[style=\"");
 628             text.push(style.as_slice());
 629             text.push("\"]");
 630         }
 631
 632         text.push(";");
 633         try!(writeln(w, &text));
 634     }
 635
 636     for e in g.edges().iter() {
 637         let escaped_label = &g.edge_label(e).escape();
 638         try!(indent(w));
 639         let source = g.source(e);
 640         let target = g.target(e);
 641         let source_id = g.node_id(&source);
 642         let target_id = g.node_id(&target);
 643
 644         let mut text = vec![source_id.as_slice(), " -> ", target_id.as_slice()];
 645
 646         if !options.contains(&RenderOption::NoEdgeLabels) {
 647             text.push("[label=\"");
 648             text.push(escaped_label);
 649             text.push("\"]");
 650         }
 651
 652         let style = g.edge_style(e);
 653         if !options.contains(&RenderOption::NoEdgeStyles) && style != Style::None {
 654             text.push("[style=\"");
 655             text.push(style.as_slice());
 656             text.push("\"]");
 657         }
 658
 659         text.push(";");
 660         try!(writeln(w, &text));
 661     }
 662
 663     writeln(w, &["}"])
 664 }
 665
 666 #[cfg(test)]
 667 mod tests {
 668     use self::NodeLabels::*;
 669     use super::{Id, Labeller, Nodes, Edges, GraphWalk, render, Style};
 670     use super::LabelText::{self, LabelStr, EscStr};
 671     use std::io;
 672     use std::io::prelude::*;
 673     use std::borrow::IntoCow;
 674
 675     /// each node is an index in a vector in the graph.
 676     type Node = usize;
 677     struct Edge {
 678         from: usize,
 679         to: usize,
 680         label: &'static str,
 681         style: Style,
 682     }
 683
 684     fn edge(from: usize, to: usize, label: &'static str, style: Style) -> Edge {
 685         Edge { from: from, to: to, label: label, style: style }
 686     }
 687
 688     struct LabelledGraph {
 689         /// The name for this graph. Used for labelling generated `digraph`.
 690         name: &'static str,
 691
 692         /// Each node is an index into `node_labels`; these labels are
 693         /// used as the label text for each node. (The node *names*,
 694         /// which are unique identifiers, are derived from their index
 695         /// in this array.)
 696         ///
 697         /// If a node maps to None here, then just use its name as its
 698         /// text.
 699         node_labels: Vec<Option<&'static str>>,
 700
 701         node_styles: Vec<Style>,
 702
 703         /// Each edge relates a from-index to a to-index along with a
 704         /// label; `edges` collects them.
 705         edges: Vec<Edge>,
 706     }
 707
 708     // A simple wrapper around LabelledGraph that forces the labels to
 709     // be emitted as EscStr.
 710     struct LabelledGraphWithEscStrs {
 711         graph: LabelledGraph
 712     }
 713
 714     enum NodeLabels<L> {
 715         AllNodesLabelled(Vec<L>),
 716         UnlabelledNodes(usize),
 717         SomeNodesLabelled(Vec<Option<L>>),
 718     }
 719
 720     type Trivial = NodeLabels<&'static str>;
 721
 722     impl NodeLabels<&'static str> {
 723         fn to_opt_strs(self) -> Vec<Option<&'static str>> {
 724             match self {
 725                 UnlabelledNodes(len)
 726                     => vec![None; len],
 727                 AllNodesLabelled(lbls)
 728                     => lbls.into_iter().map(
 729                         |l|Some(l)).collect(),
 730                 SomeNodesLabelled(lbls)
 731                     => lbls.into_iter().collect(),
 732             }
 733         }
 734
 735         fn len(&self) -> usize {
 736             match self {
 737                 &UnlabelledNodes(len) => len,
 738                 &AllNodesLabelled(ref lbls) => lbls.len(),
 739                 &SomeNodesLabelled(ref lbls) => lbls.len(),
 740             }
 741         }
 742     }
 743
 744     impl LabelledGraph {
 745         fn new(name: &'static str,
 746                node_labels: Trivial,
 747                edges: Vec<Edge>,
 748                node_styles: Option<Vec<Style>>) -> LabelledGraph {
 749             let count = node_labels.len();
 750             LabelledGraph {
 751                 name: name,
 752                 node_labels: node_labels.to_opt_strs(),
 753                 edges: edges,
 754                 node_styles: match node_styles {
 755                     Some(nodes) => nodes,
 756                     None => vec![Style::None; count],
 757                 }
 758             }
 759         }
 760     }
 761
 762     impl LabelledGraphWithEscStrs {
 763         fn new(name: &'static str,
 764                node_labels: Trivial,
 765                edges: Vec<Edge>) -> LabelledGraphWithEscStrs {
 766             LabelledGraphWithEscStrs {
 767                 graph: LabelledGraph::new(name,
 768                                           node_labels,
 769                                           edges,
 770                                           None)
 771             }
 772         }
 773     }
 774
 775     fn id_name<'a>(n: &Node) -> Id<'a> {
 776         Id::new(format!("N{}", *n)).unwrap()
 777     }
 778
 779     impl<'a> Labeller<'a, Node, &'a Edge> for LabelledGraph {
 780         fn graph_id(&'a self) -> Id<'a> {
 781             Id::new(&self.name[..]).unwrap()
 782         }
 783         fn node_id(&'a self, n: &Node) -> Id<'a> {
 784             id_name(n)
 785         }
 786         fn node_label(&'a self, n: &Node) -> LabelText<'a> {
 787             match self.node_labels[*n] {
 788                 Some(ref l) => LabelStr(l.into_cow()),
 789                 None        => LabelStr(id_name(n).name()),
 790             }
 791         }
 792         fn edge_label(&'a self, e: & &'a Edge) -> LabelText<'a> {
 793             LabelStr(e.label.into_cow())
 794         }
 795         fn node_style(&'a self, n: &Node) -> Style {
 796             self.node_styles[*n]
 797         }
 798         fn edge_style(&'a self, e: & &'a Edge) -> Style {
 799             e.style
 800         }
 801     }
 802
 803     impl<'a> Labeller<'a, Node, &'a Edge> for LabelledGraphWithEscStrs {
 804         fn graph_id(&'a self) -> Id<'a> { self.graph.graph_id() }
 805         fn node_id(&'a self, n: &Node) -> Id<'a> { self.graph.node_id(n) }
 806         fn node_label(&'a self, n: &Node) -> LabelText<'a> {
 807             match self.graph.node_label(n) {
 808                 LabelStr(s) | EscStr(s) => EscStr(s),
 809             }
 810         }
 811         fn edge_label(&'a self, e: & &'a Edge) -> LabelText<'a> {
 812             match self.graph.edge_label(e) {
 813                 LabelStr(s) | EscStr(s) => EscStr(s),
 814             }
 815         }
 816     }
 817
 818     impl<'a> GraphWalk<'a, Node, &'a Edge> for LabelledGraph {
 819         fn nodes(&'a self) -> Nodes<'a,Node> {
 820             (0..self.node_labels.len()).collect()
 821         }
 822         fn edges(&'a self) -> Edges<'a,&'a Edge> {
 823             self.edges.iter().collect()
 824         }
 825         fn source(&'a self, edge: & &'a Edge) -> Node {
 826             edge.from
 827         }
 828         fn target(&'a self, edge: & &'a Edge) -> Node {
 829             edge.to
 830         }
 831     }
 832
 833     impl<'a> GraphWalk<'a, Node, &'a Edge> for LabelledGraphWithEscStrs {
 834         fn nodes(&'a self) -> Nodes<'a,Node> {
 835             self.graph.nodes()
 836         }
 837         fn edges(&'a self) -> Edges<'a,&'a Edge> {
 838             self.graph.edges()
 839         }
 840         fn source(&'a self, edge: & &'a Edge) -> Node {
 841             edge.from
 842         }
 843         fn target(&'a self, edge: & &'a Edge) -> Node {
 844             edge.to
 845         }
 846     }
 847
 848     fn test_input(g: LabelledGraph) -> io::Result<String> {
 849         let mut writer = Vec::new();
 850         render(&g, &mut writer).unwrap();
 851         let mut s = String::new();
 852         try!(Read::read_to_string(&mut &*writer, &mut s));
 853         Ok(s)
 854     }
 855
 856     // All of the tests use raw-strings as the format for the expected outputs,
 857     // so that you can cut-and-paste the content into a .dot file yourself to
 858     // see what the graphviz visualizer would produce.
 859
 860     #[test]
 861     fn empty_graph() {
 862         let labels : Trivial = UnlabelledNodes(0);
 863         let r = test_input(LabelledGraph::new("empty_graph", labels, vec![], None));
 864         assert_eq!(r.unwrap(),
 865 r#"digraph empty_graph {
 866 }
 867 "#);
 868     }
 869
 870     #[test]
 871     fn single_node() {
 872         let labels : Trivial = UnlabelledNodes(1);
 873         let r = test_input(LabelledGraph::new("single_node", labels, vec![], None));
 874         assert_eq!(r.unwrap(),
 875 r#"digraph single_node {
 876     N0[label="N0"];
 877 }
 878 "#);
 879     }
 880
 881     #[test]
 882     fn single_node_with_style() {
 883         let labels : Trivial = UnlabelledNodes(1);
 884         let styles = Some(vec![Style::Dashed]);
 885         let r = test_input(LabelledGraph::new("single_node", labels, vec![], styles));
 886         assert_eq!(r.unwrap(),
 887 r#"digraph single_node {
 888     N0[label="N0"][style="dashed"];
 889 }
 890 "#);
 891     }
 892
 893     #[test]
 894     fn single_edge() {
 895         let labels : Trivial = UnlabelledNodes(2);
 896         let result = test_input(LabelledGraph::new("single_edge", labels,
 897                                                    vec![edge(0, 1, "E", Style::None)], None));
 898         assert_eq!(result.unwrap(),
 899 r#"digraph single_edge {
 900     N0[label="N0"];
 901     N1[label="N1"];
 902     N0 -> N1[label="E"];
 903 }
 904 "#);
 905     }
 906
 907     #[test]
 908     fn single_edge_with_style() {
 909         let labels : Trivial = UnlabelledNodes(2);
 910         let result = test_input(LabelledGraph::new("single_edge", labels,
 911                                                    vec![edge(0, 1, "E", Style::Bold)], None));
 912         assert_eq!(result.unwrap(),
 913 r#"digraph single_edge {
 914     N0[label="N0"];
 915     N1[label="N1"];
 916     N0 -> N1[label="E"][style="bold"];
 917 }
 918 "#);
 919     }
 920
 921     #[test]
 922     fn test_some_labelled() {
 923         let labels : Trivial = SomeNodesLabelled(vec![Some("A"), None]);
 924         let styles = Some(vec![Style::None, Style::Dotted]);
 925         let result = test_input(LabelledGraph::new("test_some_labelled", labels,
 926                                                    vec![edge(0, 1, "A-1", Style::None)], styles));
 927         assert_eq!(result.unwrap(),
 928 r#"digraph test_some_labelled {
 929     N0[label="A"];
 930     N1[label="N1"][style="dotted"];
 931     N0 -> N1[label="A-1"];
 932 }
 933 "#);
 934     }
 935
 936     #[test]
 937     fn single_cyclic_node() {
 938         let labels : Trivial = UnlabelledNodes(1);
 939         let r = test_input(LabelledGraph::new("single_cyclic_node", labels,
 940                                               vec![edge(0, 0, "E", Style::None)], None));
 941         assert_eq!(r.unwrap(),
 942 r#"digraph single_cyclic_node {
 943     N0[label="N0"];
 944     N0 -> N0[label="E"];
 945 }
 946 "#);
 947     }
 948
 949     #[test]
 950     fn hasse_diagram() {
 951         let labels = AllNodesLabelled(vec!("{x,y}", "{x}", "{y}", "{}"));
 952         let r = test_input(LabelledGraph::new(
 953             "hasse_diagram", labels,
 954             vec![edge(0, 1, "", Style::None), edge(0, 2, "", Style::None),
 955                  edge(1, 3, "", Style::None), edge(2, 3, "", Style::None)],
 956             None));
 957         assert_eq!(r.unwrap(),
 958 r#"digraph hasse_diagram {
 959     N0[label="{x,y}"];
 960     N1[label="{x}"];
 961     N2[label="{y}"];
 962     N3[label="{}"];
 963     N0 -> N1[label=""];
 964     N0 -> N2[label=""];
 965     N1 -> N3[label=""];
 966     N2 -> N3[label=""];
 967 }
 968 "#);
 969     }
 970
 971     #[test]
 972     fn left_aligned_text() {
 973         let labels = AllNodesLabelled(vec!(
 974             "if test {\
 975            \\l    branch1\
 976            \\l} else {\
 977            \\l    branch2\
 978            \\l}\
 979            \\lafterward\
 980            \\l",
 981             "branch1",
 982             "branch2",
 983             "afterward"));
 984
 985         let mut writer = Vec::new();
 986
 987         let g = LabelledGraphWithEscStrs::new(
 988             "syntax_tree", labels,
 989             vec![edge(0, 1, "then", Style::None), edge(0, 2, "else", Style::None),
 990                  edge(1, 3, ";", Style::None),    edge(2, 3, ";", Style::None)]);
 991
 992         render(&g, &mut writer).unwrap();
 993         let mut r = String::new();
 994         Read::read_to_string(&mut &*writer, &mut r).unwrap();
 995
 996         assert_eq!(r,
 997 r#"digraph syntax_tree {
 998     N0[label="if test {\l    branch1\l} else {\l    branch2\l}\lafterward\l"];
 999     N1[label="branch1"];
1000     N2[label="branch2"];
1001     N3[label="afterward"];
1002     N0 -> N1[label="then"];
1003     N0 -> N2[label="else"];
1004     N1 -> N3[label=";"];
1005     N2 -> N3[label=";"];
1006 }
1007 "#);
1008     }
1009
1010     #[test]
1011     fn simple_id_construction() {
1012         let id1 = Id::new("hello");
1013         match id1 {
1014             Ok(_) => {;},
1015             Err(..) => panic!("'hello' is not a valid value for id anymore")
1016         }
1017     }
1018
1019     #[test]
1020     fn badly_formatted_id() {
1021         let id2 = Id::new("Weird { struct : ure } !!!");
1022         match id2 {
1023             Ok(_) => panic!("graphviz id suddenly allows spaces, brackets and stuff"),
1024             Err(..) => {;}
1025         }
1026     }
1027 }