Module nom::consumer

Data consumers

The goal of data producers is to parse data depending on the previous result. It can be used to selectively seek in a file.

Example

This consumer will take 4 samples from the input, print them, then stop

 use nom::{IResult,Needed,MemProducer,Consumer,ConsumerState};
 use std::str;

 struct TestPrintConsumer {
   counter: usize
 }

 impl TestPrintConsumer {
   fn new() -> TestPrintConsumer {
     TestPrintConsumer { counter: 0 }
   }
 }

 fn take4(i:&[u8]) -> IResult<&[u8], &[u8]>{
   if i.len() < 4 {
     IResult::Incomplete(Needed::Size(4))
   } else {
     IResult::Done(&i[4..],&i[0..4])
   }
 }

 // Return ConsumerState::Await if it needs more data, or ConsumerDone when it ends
 impl Consumer for TestPrintConsumer {
   fn consume(&mut self, input: &[u8]) -> ConsumerState {
     match take4(input) {
       IResult::Error(a)      => ConsumerState::ConsumerError(0),
       IResult::Incomplete(a) => ConsumerState::Await(0, 4),
       IResult::Done(i, o)    => {
         println!("{} -> {}", self.counter, str::from_utf8(o).unwrap());
         self.counter = self.counter + 1;
         if self.counter <= 4 {
           ConsumerState::Await(4, 4)
         } else {
           ConsumerState::ConsumerDone
         }
       }
     }
   }

   fn end(&mut self) {
     println!("finished");
   }
 }

 // It can consume data directly from a producer
 let mut p = MemProducer::new(b"abcdefghijklmnopqrstuvwx", 4);
 let mut c = TestPrintConsumer::new();
 c.run(&mut p);

Enums

ConsumerState

Holds the current state of the consumer

Traits

Consumer

Implement the consume method, taking a byte array as input and returning a consumer state