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ost::Buffer(3) Library Functions Manual ost::Buffer(3)

NAME

ost::Buffer - The buffer class represents an IPC service that is built upon a buffer of fixed capacity that can be used to transfer objects between one or more producer and consumer threads.

SYNOPSIS

#include <buffer.h>

Inherits ost::Conditional.

Inherited by ost::FixedBuffer.

Public Member Functions


Buffer (size_t capacity)
Create a buffer object of known capacity. virtual ~Buffer ()
In derived functions, may be used to free the actual memory used to hold buffered data. size_t getSize (void)
Return the capacity of the buffer as specified at creation. size_t getUsed (void)
Return the current capacity in use for the buffer. size_t wait (void *buf, timeout_t timeout=0)
Let one or more threads wait for an object to become available in the buffer. size_t post (void *buf, timeout_t timeout=0)
Post an object into the buffer and enable a waiting thread to receive it. size_t peek (void *buf)
Peek at the current content (first object) in the buffer. virtual bool isValid (void)
New virtual to test if buffer is a valid object.

Static Public Attributes


static const size_t timeout
value to return when a timed operation returned with a timeout.

Protected Member Functions


virtual size_t onPeek (void *buf)=0
Invoke derived class buffer peeking method. virtual size_t onWait (void *buf)=0
Invoke derived class object request from buffer. virtual size_t onPost (void *buf)=0
Invoke derived class posting of object to buffer.
(Note that these are not member functions.)
size_t get (Buffer &b, void *o, timeout_t t=0)
size_t put (Buffer &b, void *o, timeout_t t=0)
size_t peek (Buffer &b, void *o)

Detailed Description

The buffer class represents an IPC service that is built upon a buffer of fixed capacity that can be used to transfer objects between one or more producer and consumer threads.

Producer threads post objects into the buffer, and consumer threads wait for and receive objects from the buffer. Semaphores are used to to block the buffer from overflowing and indicate when there is data available, and mutexes are used to protect multiple consumers and producer threads from stepping over each other.

The buffer class is an abstract class in that the actual data being buffered is not directly specified within the buffer class itself. The buffer class should be used as a base class for a class that actually impliments buffering and which may be aware of the data types actually are being buffered. A template class could be created based on buffer for this purpose. Another possibility is to create a class derived from both Thread and Buffer which can be used to implement message passing threads.

Author

David Sugar dyfet@ostel.com

Producer/Consumer buffer for use between threads.

Constructor & Destructor Documentation

ost::Buffer::Buffer (size_t capacity)

Create a buffer object of known capacity.

Parameters

capacity is the integer capacity of the buffer.

virtual ost::Buffer::~Buffer () [virtual]

In derived functions, may be used to free the actual memory used to hold buffered data.

Member Function Documentation

size_t ost::Buffer::getSize (void) [inline]

Return the capacity of the buffer as specified at creation.

Returns

size of buffer.

size_t ost::Buffer::getUsed (void) [inline]

Return the current capacity in use for the buffer. Free space is technically getSize() - getUsed().

Returns

integer used capacity of the buffer.

See also

getSize

virtual bool ost::Buffer::isValid (void) [virtual]

New virtual to test if buffer is a valid object.

Returns

true if object is valid.

Reimplemented in ost::FixedBuffer.

virtual size_t ost::Buffer::onPeek (void * buf) [protected], [pure virtual]

Invoke derived class buffer peeking method.

Returns

size of object found.

Parameters

buf pointer to copy contents of head of buffer to.

Implemented in ost::FixedBuffer.

virtual size_t ost::Buffer::onPost (void * buf) [protected], [pure virtual]

Invoke derived class posting of object to buffer.

Returns

size of object posted.

Parameters

buf pointer to object being posted to the buffer.

Implemented in ost::FixedBuffer.

virtual size_t ost::Buffer::onWait (void * buf) [protected], [pure virtual]

Invoke derived class object request from buffer.

Returns

size of object returned.

Parameters

buf pointer to hold object returned from the buffer.

Implemented in ost::FixedBuffer.

size_t ost::Buffer::peek (void * buf)

Peek at the current content (first object) in the buffer.

Returns

size of object in the buffer.

Parameters

buf pointer to store object found in the buffer.

Referenced by peek().

size_t ost::Buffer::post (void * buf, timeout_t timeout = 0)

Post an object into the buffer and enable a waiting thread to receive it.

Returns

size of object posted in bytes.

Parameters

buf pointer to object to store in the buffer.
timeout time to wait.

Referenced by put().

size_t ost::Buffer::wait (void * buf, timeout_t timeout = 0)

Let one or more threads wait for an object to become available in the buffer. The waiting thread(s) will wait forever if no object is ever placed into the buffer.

Returns

size of object passed by buffer in bytes.

Parameters

buf pointer to store object retrieved from the buffer.
timeout time to wait.

Referenced by get().

Friends And Related Function Documentation

size_t get (Buffer & b, void * o, timeout_t t = 0) [related]

References wait().

size_t peek (Buffer & b, void * o) [related]

Examples
SampleSocketPort.cpp.

References peek().

size_t put (Buffer & b, void * o, timeout_t t = 0) [related]

References post().

Member Data Documentation

const size_t ost::Buffer::timeout [static]

value to return when a timed operation returned with a timeout.

Author

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Sat Dec 28 2019 GNU CommonC++