Lightweight, Stackless Threads in C (original) (raw)
Protothreads are extremely lightweight stackless threads designed for severely memory constrained systems, such as small embedded systems or wireless sensor network nodes. Protothreads provide linear code execution for event-driven systems implemented in C. Protothreads can be used with or without an underlying operating system to provide blocking event-handlers. Protothreads provide sequential flow of control without complex state machines or full multi-threading.
#include "pt.h"
struct pt pt; struct timer timer;
PT_THREAD(example(struct pt *pt)) { PT_BEGIN(pt);
while(1) { if(initiate_io()) { timer_start(&timer); PT_WAIT_UNTIL(pt, io_completed() || timer_expired(&timer)); read_data(); } } PT_END(pt); }
Example protothreads code.
While protothreads originally were created for memory-constrained embedded systems, it has found many uses as a general purpose library too. Examples include multimedia streaming server software, grid computing research software, and MPEG decoding software for Internet TVs.
Main features:
- Very small RAM overhead - only two bytes per protothread and no extra stacks
- Highly portable - the protothreads library is 100% pure C and no architecture specific assembly code
- Can be used with or without an OS
- Provides blocking wait without full multi-threading or stack-switching
- Freely available under a BSD-like open source license
Example applications:
- Memory constrained systems
- Event-driven protocol stacks
- Small embedded systems
- Sensor network nodes
- Portable C applications
For example usages, see the Examples page.
The protothreads library is released under an open sourceBSD-style license that freely allows for both non-commercial and commercial usage. The only requirement is that credit is given. Download the full source code here.
Protothreads were invented by Adam Dunkels with support from Oliver Schmidt ol.sc@web.de.