diff --git a/CMakeLists.txt b/CMakeLists.txt
index 99a6841..5e8c8b5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,4 +3,4 @@ project("Aaru.Checksums.Native" C)
 
 set(CMAKE_C_STANDARD 90)
 
-add_library("Aaru.Checksums.Native" SHARED library.c)
+add_library("Aaru.Checksums.Native" SHARED adler32.h adler32.c library.h)
diff --git a/adler32.c b/adler32.c
new file mode 100644
index 0000000..78999f5
--- /dev/null
+++ b/adler32.c
@@ -0,0 +1,65 @@
+/*
+ * This file is part of the Aaru Data Preservation Suite.
+ * Copyright (c) 2019-2021 Natalia Portillo.
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "library.h"
+#include "adler32.h"
+
+adler32_ctx* adler32_init()
+{
+    adler32_ctx* ctx;
+
+    ctx = (adler32_ctx*)malloc(sizeof(adler32_ctx));
+
+    if(!ctx) return NULL;
+
+    ctx->sum1 = 1;
+    ctx->sum2 = 0;
+
+    return ctx;
+}
+
+int adler32_update(adler32_ctx* ctx, const uint8_t* data, uint32_t len)
+{
+    if(!ctx || !data) return -1;
+
+    for(uint32_t i = 0; i < len; i++)
+    {
+        ctx->sum1 = (ctx->sum1 + data[i]) % ADLER_MODULE;
+        ctx->sum2 = (ctx->sum2 + ctx->sum1) % ADLER_MODULE;
+    }
+
+    return 0;
+}
+
+int adler32_final(adler32_ctx* ctx, uint32_t* checksum)
+{
+    if(!ctx) return -1;
+
+    *checksum = (ctx->sum2 << 16) | ctx->sum1;
+    return 0;
+}
+
+void adler32_free(adler32_ctx* ctx)
+{
+    if(!ctx) return;
+
+    free(ctx);
+}
\ No newline at end of file
diff --git a/adler32.h b/adler32.h
new file mode 100644
index 0000000..07d5ed5
--- /dev/null
+++ b/adler32.h
@@ -0,0 +1,34 @@
+/*
+ * This file is part of the Aaru Data Preservation Suite.
+ * Copyright (c) 2019-2021 Natalia Portillo.
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef AARU_CHECKSUMS_NATIVE_ADLER32_H
+#define AARU_CHECKSUMS_NATIVE_ADLER32_H
+
+#define ADLER_MODULE 65521
+
+typedef struct {
+    uint16_t sum1;
+    uint16_t sum2;
+} adler32_ctx;
+
+AARU_EXPORT adler32_ctx* AARU_CALL adler32_init();
+AARU_EXPORT int AARU_CALL adler32_update(adler32_ctx* ctx, const uint8_t* data, uint32_t len);
+AARU_EXPORT int AARU_CALL adler32_final(adler32_ctx* ctx, uint32_t* checksum);
+AARU_EXPORT void AARU_CALL adler32_free(adler32_ctx* ctx);
+
+#endif//AARU_CHECKSUMS_NATIVE_LIBRARY_H
diff --git a/library.c b/library.c
deleted file mode 100644
index efc825f..0000000
--- a/library.c
+++ /dev/null
@@ -1,5 +0,0 @@
-#include <stdio.h>
-
-#include "library.h"
-
-void hello(void) { printf("Hello, World!\n"); }
diff --git a/library.h b/library.h
index 73835ce..5899c71 100644
--- a/library.h
+++ b/library.h
@@ -1,6 +1,30 @@
 #ifndef AARU_CHECKSUMS_NATIVE_LIBRARY_H
 #define AARU_CHECKSUMS_NATIVE_LIBRARY_H
 
-void hello(void);
+#ifdef __cplusplus
+#define EXTERNC         extern "C"
+#else
+#define EXTERNC
+#endif
+
+#if defined(_WIN32)                   
+#define AARU_CALL            __stdcall
+#define AARU_EXPORT          EXTERNC __declspec(dllexport)
+#define AARU_LOCAL
+#else                 
+#define AARU_CALL
+#if defined(__APPLE__)
+#define AARU_EXPORT          EXTERNC __attribute__((visibility("default")))
+#define AARU_LOCAL       __attribute__((visibility("hidden")))
+#else  
+#if __GNUC__ >= 4
+#define AARU_EXPORT          EXTERNC __attribute__ ((visibility("default")))
+#define AARU_LOCAL       __attribute__((visibility("hidden")))
+#else
+#define AARU_EXPORT          EXTERNC
+#define idaAARU_LOCAL_local
+#endif
+#endif
+#endif
 
 #endif//AARU_CHECKSUMS_NATIVE_LIBRARY_H