Create a simple wrapper around liblex and libds.

src/lex/lexer.cr

@@ -0,0 +1,50 @@
+require "./lib.cr"
+
+module Lex
+    class Lexer
+        def initialize
+            @config = LibLex::EvalConfig.new
+            LibLex.eval_config_init(pointerof(@config))
+        end
+
+        def add_pattern(pattern : String, id : Int32)
+            LibLex.eval_config_add(pointerof(@config), pattern, id)
+        end
+
+        def lex(string)
+            # Initialize variables
+            tokens = [] of Tuple(String, Int32)
+            list = LibDs::Ll.new
+
+            # Initialize the list the list
+            LibDs.ll_init(pointerof(list))
+            # Perform the lexing operation
+            result = LibLex.eval_all(string, 0, 
+                                     pointerof(@config), 
+                                     pointerof(list))
+
+            # Transform void* matches into actual tuples.
+            if result == LibLex::Result::Success
+                node = list.head
+                while node
+                    match = node.value.data.as(LibLex::Match*)
+                    str = string[match.value.from...match.value.to]
+                    tokens << { str, match.value.pattern }
+                    node = node.value.next
+                end
+            end
+
+            # Clean up.
+            LibDs.ll_foreach(pointerof(list), nil,
+                             ->LibDs.compare_always,
+                             ->LibLex.eval_foreach_match_free)
+            LibDs.ll_free(pointerof(list))
+
+            return tokens
+        end
+
+        def finalize
+            LibLex.eval_config_free(pointerof(@config))
+        end
+    end
+end

src/lex/lib.cr

@@ -0,0 +1,55 @@
+@[Link(ldflags: "#{__DIR__}/../../external/liblex/build/external/libds/libds.a")]
+lib LibDs
+    struct LlNode
+        next: LlNode*
+        prev: LlNode*
+        data: Void*
+    end
+
+    struct Ll
+        head: LlNode*
+        tail: LlNode*
+    end
+
+    enum Result
+        Success,
+        Malloc
+    end
+
+    fun compare_always(a: Void*, b: Void*): Int32
+
+    fun ll_init(list: Ll*)
+    fun ll_foreach(list: Ll*, compare_to: Void*,
+                   compare: Void*, Void* -> Int32,
+                   foreach: Void*, LibC::VaList-> Int32, ...): Int32
+    fun ll_free(list: Ll*)
+end
+
+@[Link(ldflags: "#{__DIR__}/../../external/liblex/build/liblex.a #{__DIR__}/../../external/liblex/build/external/libds/libds.a")]
+lib LibLex
+    struct EvalConfig
+        stats: LibDs::Ll
+    end
+
+    struct Match
+        from: LibC::SizeT
+        to: LibC::SizeT
+        pattern: Int32
+    end
+
+    enum Result
+        Success,
+        Malloc,
+        Invalid,
+        Unrecognized
+    end
+
+    fun eval_config_init(config: EvalConfig*)
+    fun eval_config_add(config: EvalConfig*, string: UInt8*, id: Int32): Result
+    fun eval_all(string: UInt8*, index: LibC::SizeT, config: EvalConfig*,
+                 matches: LibDs::Ll*): Result
+    fun eval_config_remove(config: EvalConfig*, string: UInt8*,
+                           id: Int32): Result
+    fun eval_config_free(config: EvalConfig*): Result
+    fun eval_foreach_match_free(match: Void*, args: LibC::VaList): Int32
+end