Document a few undocumented modules in libstd

Hopefull this will make our libstd docs appear a little more "full".

Author: alexcrichton

src/libstd/c_str.rs

@@ -8,6 +8,58 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+/*!
+
+C-string manipulation and management
+
+This modules provides the basic methods for creating and manipulating
+null-terminated strings for use with FFI calls (back to C). Most C APIs require
+that the string being passed to them is null-terminated, and by default rust's
+string types are *not* null terminated.
+
+The other problem with translating Rust strings to C strings is that Rust
+strings can validly contain a null-byte in the middle of the string (0 is a
+valid unicode codepoint). This means that not all Rust strings can actually be
+translated to C strings.
+
+# Creation of a C string
+
+A C string is managed through the `CString` type defined in this module. It
+"owns" the internal buffer of characters and will automatically deallocate the
+buffer when the string is dropped. The `ToCStr` trait is implemented for `&str`
+and `&[u8]`, but the conversions can fail due to some of the limitations
+explained above.
+
+This also means that currently whenever a C string is created, an allocation
+must be performed to place the data elsewhere (the lifetime of the C string is
+not tied to the lifetime of the original string/data buffer). If C strings are
+heavily used in applications, then caching may be advisable to prevent
+unnecessary amounts of allocations.
+
+An example of creating and using a C string would be:
+
+~~~{.rust}
+use std::libc;
+externfn!(fn puts(s: *libc::c_char))
+
+let my_string = "Hello, world!";
+
+// Allocate the C string with an explicit local that owns the string. The
+// `c_buffer` pointer will be deallocated when `my_c_string` goes out of scope.
+let my_c_string = my_string.to_c_str();
+do my_c_string.with_ref |c_buffer| {
+    unsafe { puts(c_buffer); }
+}
+
+// Don't save off the allocation of the C string, the `c_buffer` will be
+// deallocated when this block returns!
+do my_string.with_c_str |c_buffer| {
+    unsafe { puts(c_buffer); }
+}
+~~~
+
+*/
+
 use cast;
 use iter::{Iterator, range};
 use libc;

src/libstd/condition.rs

@@ -8,71 +8,179 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-/*! Condition handling */
+/*!
 
-#[allow(missing_doc)];
+Condition handling
+
+Conditions are a utility used to deal with handling error conditions. The syntax
+of a condition handler strikes a resemblance to try/catch blocks in other
+languages, but condition handlers are *not* a form of exception handling in the
+same manner.
+
+A condition is declared through the `condition!` macro provided by the compiler:
+
+~~~{.rust}
+condition! {
+    pub my_error: int -> ~str;
+}
+~~~
+
+This macro declares an inner module called `my_error` with one static variable,
+`cond` that is a static `Condition` instance. To help understand what the other
+parameters are used for, an example usage of this condition would be:
+
+~~~{.rust}
+do my_error::cond.trap(|raised_int| {
+
+    // the condition `my_error` was raised on, and the value it raised is stored
+    // in `raised_int`. This closure must return a `~str` type (as specified in
+    // the declaration of the condition
+    if raised_int == 3 { ~"three" } else { ~"oh well" }
+
+}).inside {
+
+    // The condition handler above is installed for the duration of this block.
+    // That handler will override any previous handler, but the previous handler
+    // is restored when this block returns (handlers nest)
+    //
+    // If any code from this block (or code from another block) raises on the
+    // condition, then the above handler will be invoked (so long as there's no
+    // other nested handler).
+
+    println(my_error::cond.raise(3)); // prints "three"
+    println(my_error::cond.raise(4)); // prints "oh well"
+
+}
+~~~
+
+Condition handling is useful in cases where propagating errors is either to
+cumbersome or just not necessary in the first place. It should also be noted,
+though, that if there is not handler installed when a condition is raised, then
+the task invokes `fail!()` and will terminate.
+
+## More Info
+
+Condition handlers as an error strategy is well explained in the [conditions
+tutorial](http://static.rust-lang.org/doc/master/tutorial-conditions.html),
+along with comparing and contrasting it with other error handling strategies.
+
+*/
 
 use local_data;
 use prelude::*;
+use unstable::raw::Closure;
 
-// helper for transmutation, shown below.
-type RustClosure = (int, int);
-
+#[doc(hidden)]
 pub struct Handler<T, U> {
-    handle: RustClosure,
-    prev: Option<@Handler<T, U>>,
+    priv handle: Closure,
+    priv prev: Option<@Handler<T, U>>,
 }
 
+/// This struct represents the state of a condition handler. It contains a key
+/// into TLS which holds the currently install handler, along with the name of
+/// the condition (useful for debugging).
+///
+/// This struct should never be created directly, but rather only through the
+/// `condition!` macro provided to all libraries using libstd.
 pub struct Condition<T, U> {
+    /// Name of the condition handler
     name: &'static str,
+    /// TLS key used to insert/remove values in TLS.
     key: local_data::Key<@Handler<T, U>>
 }
 
 impl<T, U> Condition<T, U> {
+    /// Creates an object which binds the specified handler. This will also save
+    /// the current handler *on creation* such that when the `Trap` is consumed,
+    /// it knows which handler to restore.
+    ///
+    /// # Example
+    ///
+    /// ~~~{.rust}
+    /// condition! { my_error: int -> int; }
+    ///
+    /// let trap = my_error::cond.trap(|error| error + 3);
+    ///
+    /// // use `trap`'s inside method to register the handler and then run a
+    /// // block of code with the handler registered
+    /// ~~~
     pub fn trap<'a>(&'a self, h: &'a fn(T) -> U) -> Trap<'a, T, U> {
-        unsafe {
-            let p : *RustClosure = ::cast::transmute(&h);
-            let prev = local_data::get(self.key, |k| k.map(|&x| *x));
-            let h = @Handler { handle: *p, prev: prev };
-            Trap { cond: self, handler: h }
-        }
+        let h: Closure = unsafe { ::cast::transmute(h) };
+        let prev = local_data::get(self.key, |k| k.map(|&x| *x));
+        let h = @Handler { handle: h, prev: prev };
+        Trap { cond: self, handler: h }
     }
 
+    /// Raises on this condition, invoking any handler if one has been
+    /// registered, or failing the current task otherwise.
+    ///
+    /// While a condition handler is being run, the condition will have no
+    /// handler listed, so a task failure will occur if the condition is
+    /// re-raised during the handler.
+    ///
+    /// # Arguments
+    ///
+    /// * t - The argument to pass along to the condition handler.
+    ///
+    /// # Return value
+    ///
+    /// If a handler is found, its return value is returned, otherwise this
+    /// function will not return.
     pub fn raise(&self, t: T) -> U {
         let msg = fmt!("Unhandled condition: %s: %?", self.name, t);
         self.raise_default(t, || fail!(msg.clone()))
     }
 
+    /// Performs the same functionality as `raise`, except that when no handler
+    /// is found the `default` argument is called instead of failing the task.
     pub fn raise_default(&self, t: T, default: &fn() -> U) -> U {
-        unsafe {
-            match local_data::pop(self.key) {
-                None => {
-                    debug!("Condition.raise: found no handler");
-                    default()
-                }
-                Some(handler) => {
-                    debug!("Condition.raise: found handler");
-                    match handler.prev {
-                        None => {}
-                        Some(hp) => local_data::set(self.key, hp)
-                    }
-                    let handle : &fn(T) -> U =
-                        ::cast::transmute(handler.handle);
-                    let u = handle(t);
-                    local_data::set(self.key, handler);
-                    u
+        match local_data::pop(self.key) {
+            None => {
+                debug!("Condition.raise: found no handler");
+                default()
+            }
+            Some(handler) => {
+                debug!("Condition.raise: found handler");
+                match handler.prev {
+                    None => {}
+                    Some(hp) => local_data::set(self.key, hp)
                 }
+                let handle : &fn(T) -> U = unsafe {
+                    ::cast::transmute(handler.handle)
+                };
+                let u = handle(t);
+                local_data::set(self.key, handler);
+                u
             }
         }
     }
 }
 
+/// A `Trap` is created when the `trap` method is invoked on a `Condition`, and
+/// it is used to actually bind a handler into the TLS slot reserved for this
+/// condition.
+///
+/// Normally this object is not dealt with directly, but rather it's directly
+/// used after being returned from `trap`
 struct Trap<'self, T, U> {
-    cond: &'self Condition<T, U>,
-    handler: @Handler<T, U>
+    priv cond: &'self Condition<T, U>,
+    priv handler: @Handler<T, U>
 }
 
 impl<'self, T, U> Trap<'self, T, U> {
+    /// Execute a block of code with this trap handler's exception handler
+    /// registered.
+    ///
+    /// # Example
+    ///
+    /// ~~~{.rust}
+    /// condition! { my_error: int -> int; }
+    ///
+    /// let result = do my_error::cond.trap(|error| error + 3).inside {
+    ///     my_error::cond.raise(4)
+    /// };
+    /// assert_eq!(result, 7);
+    /// ~~~
     pub fn inside<V>(&self, inner: &'self fn() -> V) -> V {
         let _g = Guard { cond: self.cond };
         debug!("Trap: pushing handler to TLS");
@@ -81,8 +189,9 @@ impl<'self, T, U> Trap<'self, T, U> {
     }
 }
 
+#[doc(hidden)]
 struct Guard<'self, T, U> {
-    cond: &'self Condition<T, U>
+    priv cond: &'self Condition<T, U>
 }
 
 #[unsafe_destructor]

src/libstd/fmt/mod.rs

@@ -10,17 +10,18 @@
 
 /*!
 
-# The Formatting Module
+The Formatting Module
 
-This module contains the runtime support for the `format!` syntax extension. This
-macro is implemented in the compiler to emit calls to this module in order to
-format arguments at runtime into strings and streams.
+This module contains the runtime support for the `format!` syntax extension.
+This macro is implemented in the compiler to emit calls to this module in order
+to format arguments at runtime into strings and streams.
 
 The functions contained in this module should not normally be used in everyday
-use cases of `format!`. The assumptions made by these functions are unsafe for all
-inputs, and the compiler performs a large amount of validation on the arguments
-to `format!` in order to ensure safety at runtime. While it is possible to call
-these functions directly, it is not recommended to do so in the general case.
+use cases of `format!`. The assumptions made by these functions are unsafe for
+all inputs, and the compiler performs a large amount of validation on the
+arguments to `format!` in order to ensure safety at runtime. While it is
+possible to call these functions directly, it is not recommended to do so in the
+general case.
 
 ## Usage
 

src/libstd/iter.rs

@@ -8,12 +8,59 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-/*! Composable external iterators
+/*!
 
-The `Iterator` trait defines an interface for objects which implement iteration as a state machine.
+Composable external iterators
 
-Algorithms like `zip` are provided as `Iterator` implementations which wrap other objects
-implementing the `Iterator` trait.
+# The `Iterator` trait
+
+This module defines Rust's core iteration trait. The `Iterator` trait has one
+un-implemented method, `next`. All other methods are derived through default
+methods to perform operations such as `zip`, `chain`, `enumerate`, and `fold`.
+
+The goal of this module is to unify iteration across all containers in Rust.
+An iterator can be considered as a state machine which is used to track which
+element will be yielded next.
+
+There are various extensions also defined in this module to assist with various
+types of iteration, such as the `DoubleEndedIterator` for iterating in reverse,
+the `FromIterator` trait for creating a container from an iterator, and much
+more.
+
+## Rust's `for` loop
+
+The special syntax used by rust's `for` loop is based around the `Iterator`
+trait defined in this module. For loops can be viewed as a syntactical expansion
+into a `loop`, for example, the `for` loop in this example is essentially
+translated to the `loop` below.
+
+~~~{.rust}
+let values = ~[1, 2, 3];
+
+// "Syntactical sugar" taking advantage of an iterator
+for &x in values.iter() {
+    println!("{}", x);
+}
+
+// Rough translation of the iteration without a `for` iterator.
+let mut it = values.iter();
+loop {
+    match it.next() {
+        Some(&x) => {
+            println!("{}", x);
+        }
+        None => { break }
+    }
+}
+~~~
+
+This `for` loop syntax can be applied to any iterator over any type.
+
+## Iteration protocol and more
+
+More detailed information about iterators can be found in the [container
+tutorial](http://static.rust-lang.org/doc/master/tutorial-container.html) with
+the rest of the rust manuals.
 
 */