add platform_set_snprintf
diff --git a/include/polarssl/check_config.h b/include/polarssl/check_config.h
index 51b124d..be7aefe 100644
--- a/include/polarssl/check_config.h
+++ b/include/polarssl/check_config.h
@@ -198,6 +198,11 @@
 #error "POLARSSL_PKCS11_C defined, but not all prerequisites"
 #endif
 
+#if defined(POLARSSL_PLATFORM_SNPRINTF_ALT) && ( defined(_WIN32)\
+    && !defined(EFIX64) && !defined(EFI32) )
+#error "POLARSSL_PLATFORM_SNPRINTF_ALT defined but not available on Windows"
+#endif
+
 #if defined(POLARSSL_RSA_C) && ( !defined(POLARSSL_BIGNUM_C) ||         \
     !defined(POLARSSL_OID_C) )
 #error "POLARSSL_RSA_C defined, but not all prerequisites"
diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index 02e8985..75cf677 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -159,9 +159,13 @@
  *
  * All these define require POLARSSL_PLATFORM_C to be defined!
  *
+ * WARNING: POLARSSL_PLATFORM_SNPRINTF_ALT is not available on Windows
+ * for compatibility reasons.
+ *
  * Uncomment a macro to enable alternate implementation of specific base
  * platform function
  */
+//#define POLARSSL_PLATFORM_SNPRINTF_ALT
 //#define POLARSSL_PLATFORM_PRINTF_ALT
 //#define POLARSSL_PLATFORM_FPRINTF_ALT
 /* \} name SECTION: System support */
@@ -1890,7 +1894,7 @@
  * \def POLARSSL_PLATFORM_C
  *
  * Enable the platform abstraction layer that allows you to re-assign
- * functions like malloc(), free(), printf(), fprintf()
+ * functions like malloc(), free(), snprintf(), printf(), fprintf()
  *
  * Module:  library/platform.c
  * Caller:  Most other .c files
@@ -2238,6 +2242,7 @@
 //#define POLARSSL_PLATFORM_STD_MEM_HDR <stdlib.h> /**< Header to include if POLARSSL_PLATFORM_NO_STD_FUNCTIONS is defined. Don't define if no header is needed. */
 //#define POLARSSL_PLATFORM_STD_MALLOC   malloc /**< Default allocator to use, can be undefined */
 //#define POLARSSL_PLATFORM_STD_FREE       free /**< Default free to use, can be undefined */
+//#define POLARSSL_PLATFORM_STD_SNPRINTF 	snprintf /**< Default snprintf to use, can be undefined */
 //#define POLARSSL_PLATFORM_STD_PRINTF   printf /**< Default printf to use, can be undefined */
 //#define POLARSSL_PLATFORM_STD_FPRINTF fprintf /**< Default fprintf to use, can be undefined */
 
diff --git a/include/polarssl/platform.h b/include/polarssl/platform.h
index 127b7fe..4844d2d 100644
--- a/include/polarssl/platform.h
+++ b/include/polarssl/platform.h
@@ -50,6 +50,9 @@
 #if !defined(POLARSSL_PLATFORM_NO_STD_FUNCTIONS)
 #include <stdio.h>
 #include <stdlib.h>
+#if !defined(POLARSSL_PLATFORM_STD_SNPRINTF)
+#define POLARSSL_PLATFORM_STD_SNPRINTF   snprintf /**< Default snprintf to use  */
+#endif
 #if !defined(POLARSSL_PLATFORM_STD_PRINTF)
 #define POLARSSL_PLATFORM_STD_PRINTF   printf /**< Default printf to use  */
 #endif
@@ -93,6 +96,25 @@
 #endif /* POLARSSL_PLATFORM_MEMORY */
 
 /*
+ * The function pointers for snprintf
+ */
+#if defined(POLARSSL_PLATFORM_SNPRINTF_ALT)
+extern int (*polarssl_snprintf)( char * s, size_t n, const char * format, ... );
+
+/**
+ * \brief   Set your own snprintf function pointer
+ *
+ * \param snprintf_func   the snprintf function implementation
+ *
+ * \return              0
+ */
+int platform_set_snprintf( int (*snprintf_func)( char * s, size_t n,
+                                                 const char * format, ... ) );
+#else /* POLARSSL_PLATFORM_SNPRINTF_ALT */
+#define polarssl_snprintf   snprintf
+#endif /* POLARSSL_PLATFORM_SNPRINTF_ALT */
+
+/*
  * The function pointers for printf
  */
 #if defined(POLARSSL_PLATFORM_PRINTF_ALT)