debian-packages/vibe-core
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

Let empty block to make sure the following consumeOne succeeds.

Browse source 
This change ensures that a return value of false guarantees the next call to consumeOne to succeed, meaning that the combination of empty/consumeOne is sound in a single-consumer scenario. This also updates the documentation to stress that tryConsumeOne is still the preferred API.
This commit is contained in:
Sönke Ludwig 2019-06-16 22:33:15 +02:00
parent 19ea38fc72
commit 37ad77c701
1 changed files with 13 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
source/vibe/core/channel.d
View file

@ -41,7 +41,7 @@ struct Channel(T, size_t buffer_size = 100) {
private shared ChannelImpl!(T, buffer_size) m_impl; private shared ChannelImpl!(T, buffer_size) m_impl;
/** Determines whether there is more data to read. /** Determines whether there is more data to read in a single-reader scenario.
This property is empty $(I iff) no more elements are in the internal This property is empty $(I iff) no more elements are in the internal
buffer and `close()` has been called. Once the channel is empty, buffer and `close()` has been called. Once the channel is empty,
@ -49,8 +49,8 @@ struct Channel(T, size_t buffer_size = 100) {
exception. exception.
Note that relying on the return value to determine whether another Note that relying on the return value to determine whether another
element can be read is only safe in a single-reader scenario. Use element can be read is only safe in a single-reader scenario. It is
`tryConsumeOne` in a multiple-reader scenario instead. generally recommended to use `tryConsumeOne` instead.
*/ */
@property bool empty() { return m_impl.empty; } @property bool empty() { return m_impl.empty; }
/// ditto /// ditto
@ -78,6 +78,10 @@ struct Channel(T, size_t buffer_size = 100) {
This function will block if no elements are available. If the `empty` This function will block if no elements are available. If the `empty`
property is `true`, an exception will be thrown. property is `true`, an exception will be thrown.
Note that it is recommended to use `tryConsumeOne` instead of a
combination of `empty` and `consumeOne` due to being more efficient and
also being reliable in a multiple-reader scenario.
*/ */
T consumeOne() { return m_impl.consumeOne(); } T consumeOne() { return m_impl.consumeOne(); }
/// ditto /// ditto
@ -143,6 +147,12 @@ private final class ChannelImpl(T, size_t buffer_size) {
scope (exit) m_mutex.unlock_nothrow(); scope (exit) m_mutex.unlock_nothrow();
auto thisus = () @trusted { return cast(ChannelImpl)this; } (); auto thisus = () @trusted { return cast(ChannelImpl)this; } ();
// ensure that in a single-reader scenario !empty guarantees a
// successful call to consumeOne
while (!thisus.m_closed && thisus.m_items.empty)
thisus.m_condition.wait();
return thisus.m_closed && thisus.m_items.empty; return thisus.m_closed && thisus.m_items.empty;
} }
} }