diff --git a/lib/codec_avx2.c b/lib/codec_avx2.c
index ef931f66..934a7273 100644
--- a/lib/codec_avx2.c
+++ b/lib/codec_avx2.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stddef.h>
+#include <stdlib.h>
 
 #include "../include/libbase64.h"
 #include "codecs.h"
diff --git a/lib/codec_neon32.c b/lib/codec_neon32.c
index b70b91c6..41f0b1f1 100644
--- a/lib/codec_neon32.c
+++ b/lib/codec_neon32.c
@@ -4,6 +4,7 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include <stdlib.h>
 #ifdef __ARM_NEON__
 #include <arm_neon.h>
 #endif
diff --git a/lib/codec_neon64.c b/lib/codec_neon64.c
index 920ab222..aafa27f5 100644
--- a/lib/codec_neon64.c
+++ b/lib/codec_neon64.c
@@ -4,6 +4,7 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include <stdlib.h>
 #ifdef __ARM_NEON__
 #include <arm_neon.h>
 #endif
diff --git a/lib/codec_plain.c b/lib/codec_plain.c
index 02f5f369..1d987fae 100644
--- a/lib/codec_plain.c
+++ b/lib/codec_plain.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stddef.h>
+#include <stdlib.h>
 
 #include "../include/libbase64.h"
 #include "codecs.h"
@@ -7,9 +8,9 @@
 BASE64_ENC_FUNCTION(plain)
 {
 	#include "enc/head.c"
-#if __WORDSIZE == 32
+#if BASE64_WORDSIZE == 32
 	#include "enc/uint32.c"
-#elif __WORDSIZE == 64
+#elif BASE64_WORDSIZE == 64
 	#include "enc/uint64.c"
 #endif
 	#include "enc/tail.c"
@@ -18,9 +19,9 @@ BASE64_ENC_FUNCTION(plain)
 BASE64_DEC_FUNCTION(plain)
 {
 	#include "dec/head.c"
-#if __WORDSIZE == 32
+#if BASE64_WORDSIZE == 32
 	#include "dec/uint32.c"
-#elif __WORDSIZE == 64
+#elif BASE64_WORDSIZE == 64
 	#include "dec/uint64.c"
 #endif
 	#include "dec/tail.c"
diff --git a/lib/codec_ssse3.c b/lib/codec_ssse3.c
index d561521c..dbadf31c 100644
--- a/lib/codec_ssse3.c
+++ b/lib/codec_ssse3.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stddef.h>
+#include <stdlib.h>
 
 #include "../include/libbase64.h"
 #include "codecs.h"
diff --git a/lib/codecs.h b/lib/codecs.h
index 586db25c..c90b5cd1 100644
--- a/lib/codecs.h
+++ b/lib/codecs.h
@@ -58,31 +58,45 @@ struct codec
 
 // Define machine endianness. This is for GCC:
 #if (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
-	#define LITTLE_ENDIAN 1
+	#define BASE64_LITTLE_ENDIAN 1
 #else
-	#define LITTLE_ENDIAN 0
+	#define BASE64_LITTLE_ENDIAN 0
 #endif
 
 // This is for Clang:
 #ifdef __LITTLE_ENDIAN__
-	#define LITTLE_ENDIAN 1
+	#define BASE64_LITTLE_ENDIAN 1
 #endif
 
 #ifdef __BIG_ENDIAN__
-	#define LITTLE_ENDIAN 0
+	#define BASE64_LITTLE_ENDIAN 0
 #endif
 
 // Endian conversion functions
-#if LITTLE_ENDIAN
+#if BASE64_LITTLE_ENDIAN
+#ifdef _MSC_VER
+	#define cpu_to_be32(x)	_byteswap_ulong(x)
+	#define cpu_to_be64(x)	_byteswap_uint64(x)
+	#define be32_to_cpu(x)	_byteswap_ulong(x)
+	#define be64_to_cpu(x)	_byteswap_uint64(x)
+#else
 	#define cpu_to_be32(x)	__builtin_bswap32(x)
 	#define cpu_to_be64(x)	__builtin_bswap64(x)
 	#define be32_to_cpu(x)	__builtin_bswap32(x)
 	#define be64_to_cpu(x)	__builtin_bswap64(x)
+#endif
 #else
 	#define cpu_to_be32(x)	(x)
 	#define cpu_to_be64(x)	(x)
 	#define be32_to_cpu(x)	(x)
 	#define be64_to_cpu(x)	(x)
+#endif 
+
+// detect word size
+#ifdef _INTEGRAL_MAX_BITS
+#define BASE64_WORDSIZE _INTEGRAL_MAX_BITS
+#else
+#define BASE64_WORDSIZE __WORDSIZE
 #endif
 
 void codec_choose (struct codec *, int flags);
diff --git a/lib/lib_openmp.c b/lib/lib_openmp.c
index c61b0776..7369a725 100644
--- a/lib/lib_openmp.c
+++ b/lib/lib_openmp.c
@@ -24,7 +24,7 @@ base64_encode_openmp
 	size_t t;
 	size_t sum = 0, len, last_len;
 	struct base64_state state, initial_state;   
-	int num_threads;
+	int num_threads, i;
 
 	// Request a number of threads but not necessarily get them:
 	#pragma omp parallel
@@ -50,7 +50,7 @@ base64_encode_openmp
 		// Single has an implicit barrier for all threads to wait here
 		// for the above to complete:
 		#pragma omp for firstprivate(state) private(s) reduction(+:sum) schedule(static,1)
-		for (int i = 0; i < num_threads; i++)
+		for (i = 0; i < num_threads; i++)
 		{
 			// Feed each part of the string to the stream reader:
 			base64_stream_encode(&state, src + i * len, len, out + i * len * 4 / 3, &s);
@@ -82,7 +82,7 @@ base64_decode_openmp
 	, int		 flags
 	)
 {
-	int num_threads, result = 0;
+	int num_threads, result = 0, i;
 	size_t sum = 0, len, last_len, s;
 	struct base64_state state, initial_state;
 
@@ -111,7 +111,7 @@ base64_decode_openmp
 		// Single has an implicit barrier to wait here for the above to
 		// complete:
 		#pragma omp for firstprivate(state) private(s) reduction(+:sum, result) schedule(static,1)
-		for (int i = 0; i < num_threads; i++)
+		for (i = 0; i < num_threads; i++)
 		{
 			int this_result;