diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,14 @@
+2021-08-19
+        * Version bump (3.5). (#247)
+        * Update travis domain in README. (#222)
+        * Remove second element of pair FunEnv. (#170)
+        * Allow customizing name of step function. (#64)
+        * Update official maintainer. (#236)
+        * Deprecate internal modules. (#237, #242)
+        * Update source repo location. (#241)
+        * Fix out-of-bounds array access. (#238)
+        * Add I. Perez to author list. (#243)
+
 2021-07-07
         * Version bump (3.4). (#231)
         * Remove broken test. (#232)
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/Copilot-Language/copilot-c99.svg?branch=master)](https://travis-ci.org/Copilot-Language/copilot-core)
+[![Build Status](https://travis-ci.com/Copilot-Language/copilot-c99.svg?branch=master)](https://travis-ci.com/Copilot-Language/copilot-core)
 
 # Copilot: a stream DSL
 Copilot-c99 implements a C99 backend for Copilot, producing high quality code
diff --git a/copilot-c99.cabal b/copilot-c99.cabal
--- a/copilot-c99.cabal
+++ b/copilot-c99.cabal
@@ -1,6 +1,6 @@
 cabal-version             : >= 1.10
 name                      : copilot-c99
-version                   : 3.4
+version                   : 3.5
 synopsis                  : A compiler for Copilot targeting C99.
 description               :
   This package is a back-end from Copilot to C.
@@ -14,7 +14,7 @@
 
 license                   : BSD3
 license-file              : LICENSE
-maintainer                : Frank Dedden <dev@dedden.net>
+maintainer                : Ivan Perez <ivan.perezdominguez@nasa.gov>
 homepage                  : https://copilot-language.github.io
 bug-reports               : https://github.com/Copilot-Language/copilot/issues
 stability                 : Experimental
@@ -25,15 +25,22 @@
 
 author                    : Frank Dedden
                           , Alwyn Goodloe
+                          , Ivan Perez
 
 source-repository head
     type:       git
-    location:   git://github.com/Copilot-Language/copilot-c99.git
+    location:   git://github.com/Copilot-Language/copilot.git
+    subdir:     lib/copilot-c99
 
 library
   default-language        : Haskell2010
   hs-source-dirs          : src
-  ghc-options             : -Wall -fwarn-tabs
+
+  -- The following -Wno-deprecations is temprary and related to issue
+  -- https://github.com/Copilot-Language/copilot/issues/237
+  -- It should be removed in a future version, when this library hides
+  -- internal modules.
+  ghc-options             : -Wall -fwarn-tabs -Wno-deprecations
   build-depends           : base                >= 4.9 && < 5
                           , containers          >= 0.4 && < 0.7
                           , directory           >= 1.3 && < 1.4
@@ -41,7 +48,7 @@
                           , mtl                 >= 2.2 && < 2.3
                           , pretty              >= 1.1 && < 1.2
 
-                          , copilot-core        >= 3.4   && < 3.5
+                          , copilot-core        >= 3.5   && < 3.6
                           , language-c99        >= 0.1.1 && < 0.2
                           , language-c99-util   >= 0.1.1 && < 0.2
                           , language-c99-simple >= 0.1.1 && < 0.2
@@ -52,3 +59,7 @@
                           , Copilot.Compile.C99.CodeGen
                           , Copilot.Compile.C99.External
                           , Copilot.Compile.C99.Compile
+                          , Copilot.Compile.C99.Settings
+
+  other-modules          : Copilot.Compile.C99.Compile.Internal
+                         , Copilot.Compile.C99.Settings.Internal
diff --git a/src/Copilot/Compile/C99.hs b/src/Copilot/Compile/C99.hs
--- a/src/Copilot/Compile/C99.hs
+++ b/src/Copilot/Compile/C99.hs
@@ -1,6 +1,10 @@
 -- | Compile Copilot specifications to C99 code.
 module Copilot.Compile.C99
   ( compile
+  , compileWith
+  , CSettings(..)
+  , mkDefaultCSettings
   ) where
 
-import Copilot.Compile.C99.Compile
+import Copilot.Compile.C99.Compile.Internal
+import Copilot.Compile.C99.Settings.Internal
diff --git a/src/Copilot/Compile/C99/CodeGen.hs b/src/Copilot/Compile/C99/CodeGen.hs
--- a/src/Copilot/Compile/C99/CodeGen.hs
+++ b/src/Copilot/Compile/C99/CodeGen.hs
@@ -2,7 +2,9 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 
 -- | High-level translation of Copilot Core into C99.
-module Copilot.Compile.C99.CodeGen where
+module Copilot.Compile.C99.CodeGen
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
+  where
 
 import Control.Monad.State  (runState)
 import Data.List            (union, unzip4)
@@ -13,6 +15,7 @@
 import Copilot.Core
 import Copilot.Compile.C99.Util
 import Copilot.Compile.C99.External
+import Copilot.Compile.C99.Settings
 import Copilot.Compile.C99.Translate
 
 -- | Write a declaration for a generator function.
@@ -24,7 +27,7 @@
 genfun :: String -> Expr a -> Type a -> C.FunDef
 genfun name expr ty = C.FunDef cty name [] cvars [C.Return $ Just cexpr] where
   cty = C.decay $ transtype ty
-  (cexpr, (cvars, _)) = runState (transexpr expr) mempty
+  (cexpr, cvars) = runState (transexpr expr) mempty
 
 -- | Make a extern declaration of a variable.
 mkextdecln :: External -> C.Decln
@@ -53,9 +56,22 @@
   cty     = C.TypeSpec $ C.TypedefName "size_t"
   initval = Just $ C.InitExpr $ C.LitInt 0
 
+-- | Define an accessor functions for the ring buffer associated with a stream
+mkaccessdecln :: Id -> Type a -> [a] -> C.FunDef
+mkaccessdecln sid ty xs = C.FunDef cty name params [] [C.Return (Just expr)]
+  where
+    cty        = C.decay $ transtype ty
+    name       = streamaccessorname sid
+    bufflength = C.LitInt $ fromIntegral $ length xs
+    params     = [C.Param (C.TypeSpec $ C.TypedefName "size_t") "x"]
+    index      = (C.Ident (indexname sid) C..+ C.Ident "x") C..% bufflength
+    expr       = C.Index (C.Ident (streamname sid)) index
+
 -- | Writes the step function, that updates all streams.
-mkstep :: [Stream] -> [Trigger] -> [External] -> C.FunDef
-mkstep streams triggers exts = C.FunDef void "step" [] declns stmts where
+mkstep :: CSettings -> [Stream] -> [Trigger] -> [External] -> C.FunDef
+mkstep cSettings streams triggers exts =
+  C.FunDef void (cSettingsStepFunctionName cSettings) [] declns stmts where
+
   void = C.TypeSpec C.Void
   stmts  =  map mkexcopy exts
          ++ map mktriggercheck triggers
diff --git a/src/Copilot/Compile/C99/Compile.hs b/src/Copilot/Compile/C99/Compile.hs
--- a/src/Copilot/Compile/C99/Compile.hs
+++ b/src/Copilot/Compile/C99/Compile.hs
@@ -1,130 +1,11 @@
 -- | Compile Copilot specifications to C99 code.
 module Copilot.Compile.C99.Compile
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
   ( compile
+  , compileWith
+  , CSettings(..)
+  , mkDefaultCSettings
   ) where
 
-import Text.PrettyPrint     (render)
-import Data.List            (nub)
-import Data.Maybe           (catMaybes)
-
-import Language.C99.Pretty  (pretty)
-import qualified Language.C99.Simple as C
-
-import Copilot.Core
-import Copilot.Compile.C99.Util
-import Copilot.Compile.C99.External
-import Copilot.Compile.C99.Translate
-import Copilot.Compile.C99.CodeGen
-
--- | Compile a specification to a .h and a .c file.
---
--- The first argument is used as prefix for the .h and .c files generated.
-compile :: String -> Spec -> IO ()
-compile prefix spec = do
-  let cfile = render $ pretty $ C.translate $ compilec spec
-      hfile = render $ pretty $ C.translate $ compileh spec
-
-      -- TODO: find a nicer solution using annotated AST's
-      -- Should figure out exactly which headers are needed, based on what
-      -- is used.
-      cmacros = unlines [ "#include <stdint.h>"
-                        , "#include <stdbool.h>"
-                        , "#include <string.h>"
-                        , "#include <stdlib.h>"
-                        , "#include <math.h>"
-                        , ""
-                        , "#include \"" ++ prefix ++ ".h\""
-                        , ""
-                        ]
-
-  writeFile (prefix ++ ".c") $ cmacros ++ cfile
-  writeFile (prefix ++ ".h") hfile
-
--- | Generate the .c file from a 'Spec'.
---
--- The generated C file has the following structure:
---
--- * Include .h file.
--- * Declarations of global buffers and indices.
--- * Generator functions for streams, guards and trigger arguments.
--- * Declaration of the @step()@ function.
-compilec :: Spec -> C.TransUnit
-compilec spec = C.TransUnit declns funs where
-  streams  = specStreams spec
-  triggers = specTriggers spec
-  exts     = gatherexts streams triggers
-  exprs    = gatherexprs streams triggers
-
-  declns = mkstructdeclns exprs ++ mkexts exts ++ mkglobals streams
-  funs   = genfuns streams triggers ++ [mkstep streams triggers exts]
-
-  -- Write struct datatypes
-  mkstructdeclns :: [UExpr] -> [C.Decln]
-  mkstructdeclns es = catMaybes $ map mkdecln utypes where
-    mkdecln (UType ty) = case ty of
-      Struct x -> Just $ mkstructdecln ty
-      _        -> Nothing
-
-    utypes = nub $ concatMap (\(UExpr _ e) -> exprtypes e) es
-
-  -- Make declarations for copies of external variables.
-  mkexts :: [External] -> [C.Decln]
-  mkexts exts = map mkextcpydecln exts
-
-  -- Make buffer and index declarations for streams.
-  mkglobals :: [Stream] -> [C.Decln]
-  mkglobals streams = map buffdecln streams ++ map indexdecln streams where
-    buffdecln  (Stream sid buff _ ty) = mkbuffdecln  sid ty buff
-    indexdecln (Stream sid _    _ _ ) = mkindexdecln sid
-
-  -- Make generator functions, including trigger arguments.
-  genfuns :: [Stream] -> [Trigger] -> [C.FunDef]
-  genfuns streams triggers =  map streamgen streams
-                           ++ concatMap triggergen triggers where
-    streamgen :: Stream -> C.FunDef
-    streamgen (Stream sid _ expr ty) = genfun (generatorname sid) expr ty
-
-    triggergen :: Trigger -> [C.FunDef]
-    triggergen (Trigger name guard args) = guarddef : argdefs where
-      guarddef = genfun (guardname name) guard Bool
-      argdefs  = map arggen (zip (argnames name) args)
-
-      arggen :: (String, UExpr) -> C.FunDef
-      arggen (argname, UExpr ty expr) = genfun argname expr ty
-
--- | Generate the .h file from a 'Spec'.
-compileh :: Spec -> C.TransUnit
-compileh spec = C.TransUnit declns [] where
-  streams  = specStreams spec
-  triggers = specTriggers spec
-  exts     = gatherexts streams triggers
-  exprs    = gatherexprs streams triggers
-
-  declns =  mkstructforwdeclns exprs
-         ++ mkexts exts
-         ++ extfundeclns triggers
-         ++ [stepdecln]
-
-  mkstructforwdeclns :: [UExpr] -> [C.Decln]
-  mkstructforwdeclns es = catMaybes $ map mkdecln utypes where
-    mkdecln (UType ty) = case ty of
-      Struct x -> Just $ mkstructforwdecln ty
-      _        -> Nothing
-
-    utypes = nub $ concatMap (\(UExpr _ e) -> exprtypes e) es
-
-  -- Make declarations for external variables.
-  mkexts :: [External] -> [C.Decln]
-  mkexts = map mkextdecln
-
-  extfundeclns :: [Trigger] -> [C.Decln]
-  extfundeclns triggers = map extfundecln triggers where
-    extfundecln :: Trigger -> C.Decln
-    extfundecln (Trigger name _ args) = C.FunDecln Nothing cty name params where
-        cty    = C.TypeSpec C.Void
-        params = map mkparam $ zip (argnames name) args
-        mkparam (name, UExpr ty _) = C.Param (transtype ty) name
-
-  -- Declaration for the step function.
-  stepdecln :: C.Decln
-  stepdecln = C.FunDecln Nothing (C.TypeSpec C.Void) "step" []
+import Copilot.Compile.C99.Compile.Internal
+import Copilot.Compile.C99.Settings.Internal
diff --git a/src/Copilot/Compile/C99/Compile/Internal.hs b/src/Copilot/Compile/C99/Compile/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src/Copilot/Compile/C99/Compile/Internal.hs
@@ -0,0 +1,146 @@
+-- | Compile Copilot specifications to C99 code.
+module Copilot.Compile.C99.Compile.Internal
+  ( compile
+  , compileWith
+  ) where
+
+import Text.PrettyPrint     (render)
+import Data.List            (nub)
+import Data.Maybe           (catMaybes)
+
+import Language.C99.Pretty  (pretty)
+import qualified Language.C99.Simple as C
+
+import Copilot.Core
+import Copilot.Compile.C99.Util
+import Copilot.Compile.C99.External
+import Copilot.Compile.C99.Settings.Internal
+import Copilot.Compile.C99.Translate
+import Copilot.Compile.C99.CodeGen
+
+-- | Compile a specification to a .h and a .c file.
+--
+-- The first argument is the settings for the C code generated.
+--
+-- The second argument is used as prefix for the .h and .c files generated.
+compileWith :: CSettings -> String -> Spec -> IO ()
+compileWith cSettings prefix spec = do
+  let cfile = render $ pretty $ C.translate $ compilec cSettings spec
+      hfile = render $ pretty $ C.translate $ compileh cSettings spec
+
+      -- TODO: find a nicer solution using annotated AST's
+      -- Should figure out exactly which headers are needed, based on what
+      -- is used.
+      cmacros = unlines [ "#include <stdint.h>"
+                        , "#include <stdbool.h>"
+                        , "#include <string.h>"
+                        , "#include <stdlib.h>"
+                        , "#include <math.h>"
+                        , ""
+                        , "#include \"" ++ prefix ++ ".h\""
+                        , ""
+                        ]
+
+  writeFile (prefix ++ ".c") $ cmacros ++ cfile
+  writeFile (prefix ++ ".h") hfile
+
+-- | Compile a specification to a .h and a .c file.
+--
+-- The first argument is used as prefix for the .h and .c files generated.
+compile :: String -> Spec -> IO ()
+compile = compileWith mkDefaultCSettings
+
+-- | Generate the .c file from a 'Spec'.
+--
+-- The generated C file has the following structure:
+--
+-- * Include .h file.
+-- * Declarations of global buffers and indices.
+-- * Generator functions for streams, guards and trigger arguments.
+-- * Declaration of the @step()@ function.
+compilec :: CSettings -> Spec -> C.TransUnit
+compilec cSettings spec = C.TransUnit declns funs where
+  streams  = specStreams spec
+  triggers = specTriggers spec
+  exts     = gatherexts streams triggers
+  exprs    = gatherexprs streams triggers
+
+  declns = mkstructdeclns exprs ++ mkexts exts ++ mkglobals streams
+  funs   = genfuns streams triggers ++ [mkstep cSettings streams triggers exts]
+
+  -- Write struct datatypes
+  mkstructdeclns :: [UExpr] -> [C.Decln]
+  mkstructdeclns es = catMaybes $ map mkdecln utypes where
+    mkdecln (UType ty) = case ty of
+      Struct x -> Just $ mkstructdecln ty
+      _        -> Nothing
+
+    utypes = nub $ concatMap (\(UExpr _ e) -> exprtypes e) es
+
+  -- Make declarations for copies of external variables.
+  mkexts :: [External] -> [C.Decln]
+  mkexts exts = map mkextcpydecln exts
+
+  -- Make buffer and index declarations for streams.
+  mkglobals :: [Stream] -> [C.Decln]
+  mkglobals streams = map buffdecln streams ++ map indexdecln streams where
+    buffdecln  (Stream sid buff _ ty) = mkbuffdecln  sid ty buff
+    indexdecln (Stream sid _    _ _ ) = mkindexdecln sid
+
+  -- Make generator functions, including trigger arguments.
+  genfuns :: [Stream] -> [Trigger] -> [C.FunDef]
+  genfuns streams triggers =  map accessdecln streams
+                           ++ map streamgen streams
+                           ++ concatMap triggergen triggers where
+
+    accessdecln :: Stream -> C.FunDef
+    accessdecln (Stream sid buff _ ty) = mkaccessdecln sid ty buff
+
+    streamgen :: Stream -> C.FunDef
+    streamgen (Stream sid _ expr ty) = genfun (generatorname sid) expr ty
+
+    triggergen :: Trigger -> [C.FunDef]
+    triggergen (Trigger name guard args) = guarddef : argdefs where
+      guarddef = genfun (guardname name) guard Bool
+      argdefs  = map arggen (zip (argnames name) args)
+
+      arggen :: (String, UExpr) -> C.FunDef
+      arggen (argname, UExpr ty expr) = genfun argname expr ty
+
+-- | Generate the .h file from a 'Spec'.
+compileh :: CSettings -> Spec -> C.TransUnit
+compileh cSettings spec = C.TransUnit declns [] where
+  streams  = specStreams spec
+  triggers = specTriggers spec
+  exts     = gatherexts streams triggers
+  exprs    = gatherexprs streams triggers
+
+  declns =  mkstructforwdeclns exprs
+         ++ mkexts exts
+         ++ extfundeclns triggers
+         ++ [stepdecln]
+
+  mkstructforwdeclns :: [UExpr] -> [C.Decln]
+  mkstructforwdeclns es = catMaybes $ map mkdecln utypes where
+    mkdecln (UType ty) = case ty of
+      Struct x -> Just $ mkstructforwdecln ty
+      _        -> Nothing
+
+    utypes = nub $ concatMap (\(UExpr _ e) -> exprtypes e) es
+
+  -- Make declarations for external variables.
+  mkexts :: [External] -> [C.Decln]
+  mkexts = map mkextdecln
+
+  extfundeclns :: [Trigger] -> [C.Decln]
+  extfundeclns triggers = map extfundecln triggers where
+    extfundecln :: Trigger -> C.Decln
+    extfundecln (Trigger name _ args) = C.FunDecln Nothing cty name params where
+        cty    = C.TypeSpec C.Void
+        params = map mkparam $ zip (argnames name) args
+        mkparam (name, UExpr ty _) = C.Param (transtype ty) name
+
+  -- Declaration for the step function.
+  stepdecln :: C.Decln
+  stepdecln = C.FunDecln Nothing (C.TypeSpec C.Void)
+                  (cSettingsStepFunctionName cSettings) []
diff --git a/src/Copilot/Compile/C99/External.hs b/src/Copilot/Compile/C99/External.hs
--- a/src/Copilot/Compile/C99/External.hs
+++ b/src/Copilot/Compile/C99/External.hs
@@ -2,7 +2,9 @@
 
 -- | Represent information about externs needed in the generation of C99 code
 -- for stream declarations and triggers.
-module Copilot.Compile.C99.External where
+module Copilot.Compile.C99.External
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
+  where
 
 import Data.List  (unionBy)
 
diff --git a/src/Copilot/Compile/C99/Settings.hs b/src/Copilot/Compile/C99/Settings.hs
new file mode 100644
--- /dev/null
+++ b/src/Copilot/Compile/C99/Settings.hs
@@ -0,0 +1,8 @@
+-- | Settings used by the code generator to customize the code.
+module Copilot.Compile.C99.Settings
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
+  (module Copilot.Compile.C99.Settings.Internal)
+ where
+
+import Copilot.Compile.C99.Settings.Internal
+
diff --git a/src/Copilot/Compile/C99/Settings/Internal.hs b/src/Copilot/Compile/C99/Settings/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src/Copilot/Compile/C99/Settings/Internal.hs
@@ -0,0 +1,11 @@
+-- | Settings used by the code generator to customize the code.
+module Copilot.Compile.C99.Settings.Internal where
+
+-- | Settings used to customize the code generated.
+data CSettings = CSettings
+  { cSettingsStepFunctionName :: String
+  }
+
+-- | Default settings with a step function called @step@.
+mkDefaultCSettings :: CSettings
+mkDefaultCSettings = CSettings "step"
diff --git a/src/Copilot/Compile/C99/Translate.hs b/src/Copilot/Compile/C99/Translate.hs
--- a/src/Copilot/Compile/C99/Translate.hs
+++ b/src/Copilot/Compile/C99/Translate.hs
@@ -1,7 +1,9 @@
 {-# LANGUAGE GADTs #-}
 
 -- | Translate Copilot Core expressions and operators to C99.
-module Copilot.Compile.C99.Translate where
+module Copilot.Compile.C99.Translate
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
+  where
 
 import Control.Monad.State
 
@@ -18,19 +20,16 @@
   e1' <- transexpr e1
   let cty1 = transtype ty1
       init = Just $ C.InitExpr e1'
-  statetell ([C.VarDecln Nothing cty1 name init], [])
+  statetell [C.VarDecln Nothing cty1 name init]
 
   transexpr e2
 
 transexpr (Var _ n) = return $ C.Ident n
 
 transexpr (Drop _ amount sid) = do
-  let var    = streamname sid
-      indexvar = indexname sid
-      index  = case amount of
-        0 -> C.Ident indexvar
-        n -> C.Ident indexvar C..+ C.LitInt (fromIntegral n)
-  return $ C.Index (C.Ident var) index
+  let accessvar = streamaccessorname sid
+      index     = C.LitInt (fromIntegral amount)
+  return $ funcall accessvar [index]
 
 transexpr (ExternVar _ name _) = return $ C.Ident (excpyname name)
 
diff --git a/src/Copilot/Compile/C99/Util.hs b/src/Copilot/Compile/C99/Util.hs
--- a/src/Copilot/Compile/C99/Util.hs
+++ b/src/Copilot/Compile/C99/Util.hs
@@ -1,5 +1,7 @@
 -- | Auxiliary helper functions to generate C99 code.
-module Copilot.Compile.C99.Util where
+module Copilot.Compile.C99.Util
+  {-# DEPRECATED "This module will be hidden in future versions." #-}
+  where
 
 import Control.Monad.State
 
@@ -9,7 +11,7 @@
 -- | Auxiliary type used to collect all the declarations of all the variables
 -- used in a function to be generated, since variable declarations are always
 -- listed first at the top of the function body.
-type FunEnv = ([C.Decln], [C.Ident])
+type FunEnv = [C.Decln]
 
 -- | `tell` equivalent for `State`.
 statetell :: Monoid m => m -> State m ()
@@ -32,6 +34,10 @@
 -- | Turn a stream id into the global varname for indices.
 indexname :: Id -> String
 indexname sid = streamname sid ++ "_idx"
+
+-- | Turn a stream id into the name of its accessor function
+streamaccessorname :: Id -> String
+streamaccessorname sid = streamname sid ++ "_get"
 
 -- | Add a postfix for copies of external variables the name.
 excpyname :: String -> String