diff --git a/adler32.c b/adler32.c
index eed4ec8..9a831b8 100644
--- a/adler32.c
+++ b/adler32.c
@@ -73,22 +73,30 @@ AARU_EXPORT int AARU_CALL adler32_update(adler32_ctx* ctx, const uint8_t* data,
     }
 #endif
 
-    uint32_t sum1 = ctx->sum1;
-    uint32_t sum2 = ctx->sum2;
+    adler32_slicing(&ctx->sum1, &ctx->sum2, data, len);
+
+    return 0;
+}
+
+void adler32_slicing(uint16_t* sum1, uint16_t* sum2, const unsigned char* data, long len)
+{
+    uint32_t s1 = *sum1;
+    uint32_t s2 = *sum2;
 
     unsigned n;
 
     /* in case user likes doing a byte at a time, keep it fast */
     if(len == 1)
     {
-        sum1 += data[0];
-        if(sum1 >= ADLER_MODULE) sum1 -= ADLER_MODULE;
-        sum2 += sum1;
-        if(sum2 >= ADLER_MODULE) sum2 -= ADLER_MODULE;
+        s1 += data[0];
+        if(s1 >= ADLER_MODULE) s1 -= ADLER_MODULE;
+        s2 += s1;
+        if(s2 >= ADLER_MODULE) s2 -= ADLER_MODULE;
 
-        ctx->sum1 = sum1 & 0xFFFF;
-        ctx->sum2 = sum2 & 0xFFFF;
-        return 0;
+        *sum1 = s1 & 0xFFFF;
+        *sum2 = s2 & 0xFFFF;
+
+        return;
     }
 
     /* in case short lengths are provided, keep it somewhat fast */
@@ -96,14 +104,15 @@ AARU_EXPORT int AARU_CALL adler32_update(adler32_ctx* ctx, const uint8_t* data,
     {
         while(len--)
         {
-            sum1 += *data++;
-            sum2 += sum1;
+            s1 += *data++;
+            s2 += s1;
         }
-        if(sum1 >= ADLER_MODULE) sum1 -= ADLER_MODULE;
-        sum2 %= ADLER_MODULE; /* only added so many ADLER_MODULE's */
-        ctx->sum1 = sum1 & 0xFFFF;
-        ctx->sum2 = sum2 & 0xFFFF;
-        return 0;
+        if(s1 >= ADLER_MODULE) s1 -= ADLER_MODULE;
+        s2 %= ADLER_MODULE; /* only added so many ADLER_MODULE's */
+        *sum1 = s1 & 0xFFFF;
+        *sum2 = s2 & 0xFFFF;
+
+        return;
     }
 
     /* do length NMAX blocks -- requires just one modulo operation */
@@ -112,44 +121,44 @@ AARU_EXPORT int AARU_CALL adler32_update(adler32_ctx* ctx, const uint8_t* data,
         len -= NMAX;
         n = NMAX / 16; /* NMAX is divisible by 16 */
         do {
-            sum1 += (data)[0];
-            sum2 += sum1;
-            sum1 += (data)[0 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 2];
-            sum2 += sum1;
-            sum1 += (data)[0 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 2];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8];
-            sum2 += sum1;
-            sum1 += (data)[8 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 2];
-            sum2 += sum1;
-            sum1 += (data)[8 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 2];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 2 + 1];
-            sum2 += sum1;
+            s1 += (data)[0];
+            s2 += s1;
+            s1 += (data)[0 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 2];
+            s2 += s1;
+            s1 += (data)[0 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 4];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 2];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[8];
+            s2 += s1;
+            s1 += (data)[8 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 2];
+            s2 += s1;
+            s1 += (data)[8 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 4];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 2];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 2 + 1];
+            s2 += s1;
 
             /* 16 sums unrolled */
             data += 16;
         } while(--n);
-        sum1 %= ADLER_MODULE;
-        sum2 %= ADLER_MODULE;
+        s1 %= ADLER_MODULE;
+        s2 %= ADLER_MODULE;
     }
 
     /* do remaining bytes (less than NMAX, still just one modulo) */
@@ -158,53 +167,52 @@ AARU_EXPORT int AARU_CALL adler32_update(adler32_ctx* ctx, const uint8_t* data,
         while(len >= 16)
         {
             len -= 16;
-            sum1 += (data)[0];
-            sum2 += sum1;
-            sum1 += (data)[0 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 2];
-            sum2 += sum1;
-            sum1 += (data)[0 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 1];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 2];
-            sum2 += sum1;
-            sum1 += (data)[0 + 4 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8];
-            sum2 += sum1;
-            sum1 += (data)[8 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 2];
-            sum2 += sum1;
-            sum1 += (data)[8 + 2 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 1];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 2];
-            sum2 += sum1;
-            sum1 += (data)[8 + 4 + 2 + 1];
-            sum2 += sum1;
+            s1 += (data)[0];
+            s2 += s1;
+            s1 += (data)[0 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 2];
+            s2 += s1;
+            s1 += (data)[0 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 4];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 1];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 2];
+            s2 += s1;
+            s1 += (data)[0 + 4 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[8];
+            s2 += s1;
+            s1 += (data)[8 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 2];
+            s2 += s1;
+            s1 += (data)[8 + 2 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 4];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 1];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 2];
+            s2 += s1;
+            s1 += (data)[8 + 4 + 2 + 1];
+            s2 += s1;
 
             data += 16;
         }
         while(len--)
         {
-            sum1 += *data++;
-            sum2 += sum1;
+            s1 += *data++;
+            s2 += s1;
         }
-        sum1 %= ADLER_MODULE;
-        sum2 %= ADLER_MODULE;
+        s1 %= ADLER_MODULE;
+        s2 %= ADLER_MODULE;
     }
 
-    ctx->sum1 = sum1 & 0xFFFF;
-    ctx->sum2 = sum2 & 0xFFFF;
-    return 0;
+    *sum1 = s1 & 0xFFFF;
+    *sum2 = s2 & 0xFFFF;
 }
 
 AARU_EXPORT int AARU_CALL adler32_final(adler32_ctx* ctx, uint32_t* checksum)
diff --git a/adler32.h b/adler32.h
index 1097b07..49094b3 100644
--- a/adler32.h
+++ b/adler32.h
@@ -33,18 +33,19 @@ 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);
+AARU_EXPORT void AARU_CALL         adler32_slicing(uint16_t* sum1, uint16_t* sum2, const unsigned char* data, long len);
 
 #if defined(__x86_64__) || defined(__amd64) || defined(_M_AMD64) || defined(_M_X64) || defined(__I386__) ||            \
     defined(__i386__) || defined(__THW_INTEL) || defined(_M_IX86)
 
-void adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, size_t len);
-void adler32_avx2(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, size_t len);
+AARU_EXPORT void AARU_CALL adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, long len);
+AARU_EXPORT void AARU_CALL adler32_avx2(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, long len);
 
 #endif
 
 #if defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)
 
-void adler32_neon(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, uint32_t len);
+AARU_EXPORT void AARU_CALL adler32_neon(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, uint32_t len);
 
 #endif
 
diff --git a/adler32_avx2.c b/adler32_avx2.c
index 735d535..f3f3536 100644
--- a/adler32_avx2.c
+++ b/adler32_avx2.c
@@ -12,7 +12,7 @@
 #include "adler32.h"
 #include "simd.h"
 
-AVX2 void adler32_avx2(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, size_t len)
+AVX2 void adler32_avx2(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, long len)
 {
     uint32_t s1 = *sum1;
     uint32_t s2 = *sum2;
@@ -21,7 +21,7 @@ AVX2 void adler32_avx2(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf,
      * Process the data in blocks.
      */
     const unsigned BLOCK_SIZE = 1 << 5;
-    size_t         blocks     = len / BLOCK_SIZE;
+    long           blocks     = len / BLOCK_SIZE;
     len -= blocks * BLOCK_SIZE;
 
     while(blocks)
diff --git a/adler32_ssse3.c b/adler32_ssse3.c
index 107c03f..93b1d7f 100644
--- a/adler32_ssse3.c
+++ b/adler32_ssse3.c
@@ -51,7 +51,7 @@
 #include "library.h"
 #include "adler32.h"
 
-SSSE3 void adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, size_t len)
+SSSE3 void adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, long len)
 {
     uint32_t s1 = *sum1;
     uint32_t s2 = *sum2;
@@ -60,7 +60,7 @@ SSSE3 void adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* bu
      * Process the data in blocks.
      */
     const unsigned BLOCK_SIZE = 1 << 5;
-    size_t         blocks     = len / BLOCK_SIZE;
+    long           blocks     = len / BLOCK_SIZE;
     len -= blocks * BLOCK_SIZE;
     while(blocks)
     {
diff --git a/simd.c b/simd.c
index fab4b8e..c32b74c 100644
--- a/simd.c
+++ b/simd.c
@@ -1,3 +1,4 @@
+#include "library.h"
 #include "simd.h"
 
 #if defined(__x86_64__) || defined(__amd64) || defined(_M_AMD64) || defined(_M_X64) || defined(__I386__) ||            \
diff --git a/simd.h b/simd.h
index dfbc6ef..639dd02 100644
--- a/simd.h
+++ b/simd.h
@@ -16,9 +16,9 @@
 #define CLMUL __attribute__((target("pclmul,sse4.1")))
 #endif
 
-int have_clmul(void);
-int have_ssse3(void);
-int have_avx2(void);
+AARU_EXPORT int have_clmul(void);
+AARU_EXPORT int have_ssse3(void);
+AARU_EXPORT int have_avx2(void);
 #endif
 
 #if defined(__arm__) || defined(_M_ARM)
@@ -34,9 +34,9 @@ int have_avx2(void);
 #endif
 
 #if defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)
-int have_neon(void);
-int have_arm_crc32(void);
-int have_arm_crypto(void);
+AARU_EXPORT int have_neon(void);
+AARU_EXPORT int have_arm_crc32(void);
+AARU_EXPORT int have_arm_crypto(void);
 #endif
 
 #if defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d8bc8f3..cdccb9a 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -10,5 +10,5 @@ file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/data/random
 
 # 'Google_Tests_run' is the target name
 # 'test1.cpp tests2.cpp' are source files with tests
-add_executable(tests_run crc32.cpp)
+add_executable(tests_run adler32.cpp crc32.cpp)
 target_link_libraries(tests_run gtest gtest_main "Aaru.Checksums.Native")
\ No newline at end of file
diff --git a/tests/adler32.cpp b/tests/adler32.cpp
new file mode 100644
index 0000000..2362294
--- /dev/null
+++ b/tests/adler32.cpp
@@ -0,0 +1,130 @@
+//
+// Created by claunia on 5/10/21.
+//
+
+#include <cstdint>
+
+#include "../library.h"
+#include "../adler32.h"
+#include "gtest/gtest.h"
+
+#define EXPECTED_ADLER32 0x3728d186
+
+static const uint8_t* buffer;
+
+class adler32Fixture : public ::testing::Test
+{
+  public:
+    adler32Fixture()
+    {
+        // initialization;
+        // can also be done in SetUp()
+    }
+
+  protected:
+    void SetUp()
+    {
+        FILE* file = fopen("/home/claunia/random", "rb");
+        buffer     = (const uint8_t*)malloc(1048576);
+        fread((void*)buffer, 1, 1048576, file);
+        fclose(file);
+    }
+
+    void TearDown() { free((void*)buffer); }
+
+    ~adler32Fixture()
+    {
+        // resources cleanup, no exceptions allowed
+    }
+
+    // shared user data
+};
+
+TEST_F(adler32Fixture, adler32_auto)
+{
+    adler32_ctx* ctx = adler32_init();
+    uint32_t     adler32;
+
+    EXPECT_NE(ctx, nullptr);
+
+    adler32_update(ctx, buffer, 1048576);
+    adler32_final(ctx, &adler32);
+
+    EXPECT_EQ(adler32, EXPECTED_ADLER32);
+}
+
+TEST_F(adler32Fixture, adler32_slicing)
+{
+    uint16_t sum1;
+    uint16_t sum2;
+    uint32_t adler32;
+
+    sum1 = 1;
+    sum2 = 0;
+
+    adler32_slicing(&sum1, &sum2, buffer, 1048576);
+
+    adler32 = (sum2 << 16) | sum1;
+
+    EXPECT_EQ(adler32, EXPECTED_ADLER32);
+}
+
+#if defined(__aarch64__) || defined(_M_ARM64) || defined(__arm__) || defined(_M_ARM)
+TEST_F(adler32Fixture, adler32_neon)
+{
+    if(!have_neon()) return;
+
+    uint16_t sum1;
+    uint16_t sum2;
+    uint32_t adler32;
+
+    sum1 = 1;
+    sum2 = 0;
+
+    adler32_neon(&sum1, &sum2, buffer, 1048576);
+
+    adler32 = (sum2 << 16) | sum1;
+
+    EXPECT_EQ(adler32, EXPECTED_ADLER32);
+}
+#endif
+
+#if defined(__x86_64__) || defined(__amd64) || defined(_M_AMD64) || defined(_M_X64) || defined(__I386__) ||            \
+    defined(__i386__) || defined(__THW_INTEL) || defined(_M_IX86)
+
+TEST_F(adler32Fixture, adler32_avx2)
+{
+    if(!have_avx2()) return;
+
+    uint16_t sum1;
+    uint16_t sum2;
+    uint32_t adler32;
+
+    sum1 = 1;
+    sum2 = 0;
+
+    adler32_avx2(&sum1, &sum2, buffer, 1048576);
+
+    adler32 = (sum2 << 16) | sum1;
+
+    EXPECT_EQ(adler32, EXPECTED_ADLER32);
+}
+
+TEST_F(adler32Fixture, adler32_ssse3)
+{
+    if(!have_ssse3()) return;
+
+    uint16_t sum1;
+    uint16_t sum2;
+    uint32_t adler32;
+
+    sum1 = 1;
+    sum2 = 0;
+
+    adler32_ssse3(&sum1, &sum2, buffer, 1048576);
+
+    adler32 = (sum2 << 16) | sum1;
+
+    EXPECT_EQ(adler32, EXPECTED_ADLER32);
+}
+#endif
diff --git a/tests/crc32.cpp b/tests/crc32.cpp
index 061a302..85950a3 100644
--- a/tests/crc32.cpp
+++ b/tests/crc32.cpp
@@ -2,7 +2,7 @@
 // Created by claunia on 5/10/21.
 //
 
-#include <stdint.h>
+#include <cstdint>
 
 #include "../library.h"
 #include "../crc32.h"
@@ -10,7 +10,7 @@
 
 #define EXPECTED_CRC32 0x2B6E6854
 
-const uint8_t* buffer;
+static const uint8_t* buffer;
 
 class crc32Fixture : public ::testing::Test
 {