added comments

src/core/index.rs

@@ -114,6 +114,7 @@ impl Index {
         Index::create_from_metas(directory, &metas)
     }
 
+    /// Reads the index meta file from the directory.
     pub fn load_metas(&self) -> Result<IndexMeta> {
         load_metas(self.directory())
     }

src/schema/text_options.rs

@@ -42,6 +42,11 @@ impl Default for TextOptions {
     }
 }
 
+/// Configuration defining indexing for a text field.
+/// It wraps:
+/// 
+/// * record (See [`IndexRecordOption`](./enum.IndexRecordOption.html))
+/// * tokenizer
 #[derive(Clone, PartialEq, Eq, Debug, Serialize, Deserialize)]
 pub struct TextFieldIndexing {
     record: IndexRecordOption,

src/tokenizer/stemmer.rs

@@ -3,6 +3,7 @@ use super::{Token, TokenFilter, TokenStream};
 use rust_stemmers::{self, Algorithm};
 
 /// `Stemmer` token filter. Currently only English is supported.
+/// Tokens are expected to be lowercased beforehands.
 #[derive(Clone)]
 pub struct Stemmer {
     stemmer_algorithm: Arc<Algorithm>,

src/tokenizer/tokenizer.rs

@@ -253,7 +253,10 @@ where
     }
 }
 
+
+/// Trait for the pluggable components of `Tokenizer`s.
 pub trait TokenFilter<TailTokenStream: TokenStream>: Clone {
+    /// The resulting `TokenStream` type.
     type ResultTokenStream: TokenStream;
 
     /// Wraps a token stream and returns the modified one.

src/tokenizer/tokenizer_manager.rs

@@ -28,6 +28,7 @@ pub struct TokenizerManager {
 }
 
 impl TokenizerManager {
+    /// Registers a new tokenizer associated with a given name.
     pub fn register<A>(&self, tokenizer_name: &str, tokenizer: A)
     where
         A: 'static + Send + Sync + for<'a> Tokenizer<'a>,
@@ -39,6 +40,7 @@ impl TokenizerManager {
             .insert(tokenizer_name.to_string(), boxed_tokenizer);
     }
 
+    /// Accessing a tokenizer given its name.
     pub fn get(&self, tokenizer_name: &str) -> Option<Box<BoxedTokenizer>> {
         self.tokenizers
             .read()