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nesC 1.2

nesC 1.2 David Gay Intel Research Berkeley Introduction nesC 1.2 is a major revision to the nesC language “external” types (with Kevin Chang, UCLA) generic components binary components attributes Goals simplify TinyOS programming make it easier to define new abstractions and services

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nesC 1.2

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  1. nesC 1.2 David Gay Intel Research Berkeley

  2. Introduction • nesC 1.2 is a major revision to the nesC language • “external” types (with Kevin Chang, UCLA) • generic components • binary components • attributes • Goals • simplify TinyOS programming • make it easier to define new abstractions and services

  3. External Types: Why? • Current message formats defined as C structures • machine-dependent representation • different padding • different endianness • Until recently, not a problem: • homogeneous networks, with platform-specific radios • mig tool decodes structures for PCs • Now: 802.15.4 on telos, micaz, imote2 • want interoperability!

  4. Standard Solutions • Marshalling/unmarshalling: • needs extra RAM • protocol stack built by wiring components, so no obvious central place to do marshalling/unmarshalling • Unix-style htons, htonl, etc calls • programmer-unfriendly • only addresses endiannness • gcc’s “packed” attribute • only addresses padding

  5. External Types • nesC 1.2 introduces “external types”, which have a platform-independent representation: OLDNEW struct TOSMsg { nx_struct TOSMsg { uint16_t addr; nx_uint16_t addr; uint8_t group; nx_uint8_t group; … … • nx_structs have no padding • nx_uint16_t, etc are big-endian on all platforms • these types can be used like any C types (some minor restrictions) • Very easy to convert TinyOS code to use external types

  6. Generic Components • Components with numeric and type arguments, that can be instantiated at compile-time • Interfaces can also have type arguments • Uses: • utility components: filters, adapters, queues, buffers, etc • wiring patterns: see OSKI generic module QueueC(typedef t, int n) { provides interface Queue<t>; } implementation { t q[n]; … } configuration App { } implementation { components AppM, new QueueC(TOSMsg, 10) as MyQ; AppM.MsgQ -> MyQ; }

  7. Other Changes (in brief) • Attributes (inspired by Java 1.5) • programmers can add custom annotations to nesC programs • external tools can extract program information • uses: wiring checks, network management attributes, etc • Binary components • compile nesC “app” to .o file with specified entry, exit points • uses: • build, use, distribute components in binary form • encapsulate set of components as C library

  8. Status • All features implemented • Alpha release at http://sf.net/projects/nescc • Being used for TinyOS 2.x development work • Will be released with TinyOS 2.0

  9. Backup

  10. Generic Configurations generic configuration SomeAssembly() { provides interface X; } implementation { components new SomeAssemblyM() as SA, new QueueC(TOSMsg, 10) as SomeQ; X = SA.X; SA.Queue -> SomeQ; } • Every instantiation of SomeAssembly will create new instances of SomeAssemblyM and IntQueueC

  11. Generic Interfaces • Many interfaces similar, except for result, argument types • Generic interfaces support this by allowing interfaces to take type parameters • Two generic interfaces are connectable iff they have the same type arguments • Generic components with type arguments can use generic interfaces to: • Provide functionality dependent on that type • Express requirements of operations on that type

  12. configuration MyApp { } implementation { components MyCode, new QueueC(int, 10) as MyQ; MyCode.Queue -> MyQ; } interface Queue<t> { command void push(t x); command t pop(); } generic module QueueC (typedef t, int n) { provides interface Queue<t> as Q; } implementation { t q[n]; int p1, p2; command void Q.push(t x) { q[p1++] = x; if (p1 == n) p1 = 0; } … }

  13. Another example interface Compare<t> { command bool lessthan(t x1, t x2); } generic module Sort(typedef t) { uses interface Compare<t> as C; } implementation { void f() { t x1, x2; … if (call C.lessthan(x1, x2)) …

  14. Binary Components component ExternalInterface { provides interface StdControl; uses interface Timer; } • entry points (of program including ExternalInterface): • ExternalInterface.Timer.fired • exit points: • ExternalInterface.StdControl.{init, start, stop} • ExternalInterface.Timer.{start, stop}

  15. Attributes struct @atmostonce { }; struct @snms { int key; }; … provides interface Timer @atmostonce(); … provides interface SNMSAttribute @snms(KEY_PARENT); • Information on attributes, etc output in XML • Java-based parser for this XML schema • Sample “wiring check” demo app

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