postagger 0.0.3

NLTK-inspired parts-of-speech tagger
Documentation 
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mod perceptron_tagger;
pub use self::perceptron_tagger::PerceptronTagger;

mod c_binding {

    use std::ffi::{ CStr , c_char , c_float , CString } ;
    use crate::perceptron_tagger::PerceptronTagger; 

    #[repr(C)]
    pub struct CTag {
        word: *const u8 , 
        tag: *const u8 , 
        conf: c_float ,
    }

    #[repr(C)]
    pub struct TagResults {
        tags: *const CTag , 
        num_tags: usize
    } 

    unsafe fn get_str(
        c_char_buffer: *const c_char
    ) -> String {
        CStr::from_ptr( c_char_buffer )
              .to_str()
              .expect( "Could not convert weights_filepath to &str" )
              .to_owned()
    }

    #[no_mangle]
    pub extern "C" fn tagger_create( 
        weights_filepath: *const c_char , 
        classes_filepath: *const c_char , 
        tags_filepath: *const c_char 
    ) -> *mut PerceptronTagger  {
        unsafe {
            let fp_weights = get_str( weights_filepath )  ;
            let fp_tags = get_str( tags_filepath ) ; 
            let fp_classes = get_str( classes_filepath ) ;                
            Box::into_raw( 
                Box::new( 
                    PerceptronTagger::new( fp_weights.as_str() , fp_classes.as_str() , fp_tags.as_str() ) 
                ) 
            ) 
        }
    }

    #[no_mangle]
    pub extern "C" fn tagger_annotate(
        tagger_ptr: *mut PerceptronTagger , 
        sentence: *const c_char
    ) -> *const TagResults {
        unsafe {
            let tagger = &*tagger_ptr ; 
            let sentence = get_str( sentence ) ; 
            let tags: Vec<CTag> = tagger.tag( sentence.as_str() )
                .iter()
                .map( |x| {
                        let word = CString::new( x.word ).expect( "Could not create CString") ; 
                        let word_ptr = word.as_ptr() ; 
                        let tag = CString::new( x.tag.as_str() ).expect( "Could not create CString" ) ; 
                        let tag_ptr = tag.as_ptr() ; 
                        std::mem::forget( word ) ; 
                        std::mem::forget( tag ) ;
                        CTag{ 
                            word: word_ptr.cast::<u8>() , 
                            tag: tag_ptr.cast::<u8>() , 
                            conf: x.conf
                        } 
                    }
                ).collect() ; 
            let num_tags = tags.len() ; 
            let tags_ptr = tags.as_ptr() ; 
            std::mem::forget( tags ) ; 
            Box::into_raw( Box::new( TagResults {
                tags: tags_ptr, 
                num_tags
            } ) )
        }
    }

    #[no_mangle]
    pub extern "C" fn tagger_release(
        tagger_ptr: *mut PerceptronTagger
    )  {
        if tagger_ptr.is_null() {
            return;
        }
        unsafe {
            let _ptr = Box::from_raw( tagger_ptr ) ; 
        }
    }

}

#[cfg(feature="java")]
mod java_binding {

    extern crate jni ; 
    use jni::objects::{JClass, JString};
    use jni::sys::{jfloat,jlong, jstring};
    use jni::JNIEnv;
    use crate::perceptron_tagger::PerceptronTagger;
    use serde_json ; 

    #[no_mangle]
    pub extern "C" fn  Java_pos_tagger_POSTagger_create<'a>(
        mut env: JNIEnv<'a> , 
        _: JClass<'a> , 
        weights_filepath: JString<'a> , 
        classes_filepath: JString<'a>  , 
        tags_filepath: JString<'a> 
    ) -> jlong {
        let fp_weights: String = env.get_string( &weights_filepath )
                                    .expect( "Could not convert weights_filepath to Rust String" )
                                    .into() ; 
        let fp_classes: String = env.get_string( &classes_filepath )
                                .expect( "Could not convert classes_filepath to Rust String" )
                                .into() ; 
        let fp_tags: String = env.get_string( &tags_filepath )
                            .expect( "Could not convert tags_filepath to Rust String" )
                            .into() ; 
        Box::into_raw(
            Box::new( 
                PerceptronTagger::new( fp_weights.as_str() , fp_classes.as_str() , fp_tags.as_str() ) 
            )
        ) as jlong
    }

    #[no_mangle]
    pub extern "C" fn Java_pos_tagger_POSTagger_annotate<'a>(
        mut env: JNIEnv<'a>,
        _: JClass<'a>,
        instance_ptr: jlong,
        sentence: JString<'a>
    ) -> JString<'a> {
        let instance = unsafe { &mut *(instance_ptr as *mut PerceptronTagger) } ; 
        let sentence: String = env.get_string( &sentence )
                                  .expect( "Could not convert sentence to Rust String" )
                                  .into() ; 
        let tags = instance.tag( sentence.as_str() ) ;
        let tags_json_str = serde_json::to_string( &tags ).expect( "Could not convert tags to JSON" ) ; 
        env.new_string( tags_json_str ).expect( "Could not convert tags_json_str to jstring" )
    }

    #[no_mangle]
    pub extern "C" fn Java_pos_tagger_POSTagger_release(
        _: JNIEnv,
        _: JClass,
        instance_ptr: jlong,
    ) {
        let _ptr = unsafe { Box::from_raw( instance_ptr as *mut PerceptronTagger) };
    }

}