Polyphonic C

1
Polyphonic C
MSR CambridgeProgramming Principles Tools
Here's how to provide methods for obtaining and
releasing either exclusive (for writing), or
shared (for reading), access to a resource
delegate async IntCB(int v) class Service
public async request(String arg, IntCB cllbck)
// do some work cllbck(result)

• class ReaderWriter
• public void Exclusive() async Idle()
• public void ReleaseExclusive() Idle()
• public void Shared() async Idle() S(1)
• public void Shared() async S(int n)
  S(n1)
• public void ReleaseShared() async S(int n)
• if (n 1) Idle() else S(n-1)
• public ReaderWriter() Idle()

class Join2 void wait(out int i, out int j)
async first(int r1) async second(int r2)
i r1 j r2 return // client
code int i,j Join2 x new Join2() service1.req
uest(arg1, new IntCB(x.first)) service2.request(a
rg2, new IntCB(x.second)) // do something
useful // now wait until both results have come
back x.wait(i,j) // do something with i and j
Notes
State is kept in a single private message none
?? Idle() ?? S(1) ?? S(2) ?? S(3) If, for
example, a thread has called Exclusive() on a new
ReaderWriter(), subsequent calls of Shared() from
other threads will block until ReleaseExclusive()
is called. A second call to Exclusive() will then
block until a matching number of ReleaseShared()
messages have been received.
Chords
http//research.microsoft.com/nick/polyphony