diff --git a/libmaxsi/c/hsrc/stdio.h b/libmaxsi/c/hsrc/stdio.h
index 5b95fc34..e6179e60 100644
--- a/libmaxsi/c/hsrc/stdio.h
+++ b/libmaxsi/c/hsrc/stdio.h
@@ -100,8 +100,12 @@ extern int putc(int c, FILE* stream);
 extern int putchar(int c);
 extern int remove(const char* path);
 extern void rewind(FILE* stream);
+extern int snprintf(char* restrict s, size_t n, const char* restrict format, ...);
+extern int sprintf(char* restrict s, const char* restrict format, ...);
 extern int vfprintf(FILE* restrict stream, const char* restrict format, va_list ap);
 extern int vprintf(const char* restrict format, va_list ap);
+extern int vsnprintf(char* restrict, size_t, const char* restrict, va_list);
+extern int vsprintf(char* restrict s, const char* restrict format, va_list ap);
 
 /* TODO: These are not implemented in libmaxsi/sortix yet. */
 #ifndef SORTIX_UNIMPLEMENTED
@@ -128,15 +132,11 @@ extern int rename(const char* oldname, const char* newname);
 extern int renameat(int oldfd, const char* oldname, int newfd, const char* newname);
 extern int scanf(const char* restrict format, ...);
 extern int setvbuf(FILE* restrict stream, char* restrict buf, int type, size_t size);
-extern int snprintf(char* restrict s, size_t n, const char* restrict format, ...);
-extern int sprintf(char* restrict s, const char* restrict format, ...);
 extern int sscanf(const char* restrict s, const char* restrict format, ...);
 extern int ungetc(int c, FILE* stream);
 extern int vdprintf(int fildes, const char* restrict format, va_list ap);
 extern int vfscanf(FILE* restrict stream, const char* restrict format, va_list arg);
 extern int vscanf(const char* restrict format, va_list arg);
-extern int vsnprintf(char* restrict, size_t, const char* restrict, va_list);
-extern int vsprintf(char* restrict s, const char* restrict format, va_list ap);
 extern int vsscanf(const char* restrict s, const char* restrict format, va_list arg);
 extern ssize_t getdelim(char** restrict lineptr, size_t* restrict n, int delimiter, FILE* restrict stream);
 extern ssize_t getline(char** restrict lineptr, size_t* restrict n, FILE* restrict stream);
diff --git a/libmaxsi/io.cpp b/libmaxsi/io.cpp
index 0dec9a8a..4963edef 100644
--- a/libmaxsi/io.cpp
+++ b/libmaxsi/io.cpp
@@ -27,6 +27,7 @@
 #include "io.h"
 #include "format.h"
 #include "string.h"
+#include "memory.h"
 #include <sys/readdirents.h>
 #include <unistd.h>
 #include <errno.h>
@@ -110,6 +111,63 @@ namespace Maxsi
 		return (int) result;
 	}
 
+	typedef struct vsnprintf_struct
+	{
+		char* str;
+		size_t size;
+		size_t produced;
+		size_t written;
+	} vsnprintf_t;
+
+	size_t StringPrintCallback(void* user, const char* string, size_t stringlen)
+	{
+		vsnprintf_t* info = (vsnprintf_t*) user;
+		if ( info->produced < info->size )
+		{
+			size_t available = info->size - info->produced;
+			size_t possible = (stringlen < available) ? stringlen : available;
+			Memory::Copy(info->str + info->produced, string, possible);
+			info->written += possible;
+		}
+		info->produced += stringlen;
+		return stringlen;
+	}
+
+	extern "C" int vsnprintf(char* restrict str, size_t size, const char* restrict format, va_list list)
+	{
+		vsnprintf_t info;
+		info.str = str;
+		info.size = (size) ? size-1 : 0;
+		info.produced = 0;
+		info.written = 0;
+		Maxsi::Format::Virtual(StringPrintCallback, &info, format, list);
+		if ( size ) { info.str[info.written] = '\0'; }
+		return (int) info.produced;
+	}
+
+	extern "C" int snprintf(char* restrict str, size_t size, const char* restrict format, ...)
+	{
+		va_list list;
+		va_start(list, format);
+		int result = vsnprintf(str, size, format, list);
+		va_end(list);
+		return result;
+	}
+
+	extern "C" int vsprintf(char* restrict str, const char* restrict format, va_list list)
+	{
+		return vsnprintf(str, SIZE_MAX, format, list);
+	}
+
+	extern "C" int sprintf(char* restrict str, const char* restrict format, ...)
+	{
+		va_list list;
+		va_start(list, format);
+		int result = vsprintf(str, format, list);
+		va_end(list);
+		return result;
+	}
+
 	extern "C" void error(int status, int errnum, const char *format, ...)
 	{
 		fprintf(stderr, "%s: ", program_invocation_name);