diff --git a/src/platform/src/lib.rs b/src/platform/src/lib.rs
index 09bd48bcd9..07be95a337 100644
--- a/src/platform/src/lib.rs
+++ b/src/platform/src/lib.rs
@@ -60,3 +60,52 @@ impl fmt::Write for FileWriter {
         Ok(())
     }
 }
+
+pub struct StringWriter(pub *mut u8, pub usize);
+
+impl StringWriter {
+    pub unsafe fn write(&mut self, buf: &[u8]) {
+        for &b in buf.iter() {
+            if self.1 == 0 {
+                break;
+            } else if self.1 == 1 {
+                *self.0 = b'\0';
+            } else {
+                *self.0 = b;
+            }
+
+            self.0 = self.0.offset(1);
+            self.1 -= 1;
+
+            if self.1 > 0 {
+                *self.0 = b'\0';
+            }
+        }
+    }
+}
+
+impl fmt::Write for StringWriter {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        unsafe { self.write(s.as_bytes()) };
+        Ok(())
+    }
+}
+
+pub struct UnsafeStringWriter(pub *mut u8);
+
+impl UnsafeStringWriter {
+    pub unsafe fn write(&mut self, buf: &[u8]) {
+        for &b in buf.iter() {
+            *self.0 = b;
+            self.0 = self.0.offset(1);
+            *self.0 = b'\0';
+        }
+    }
+}
+
+impl fmt::Write for UnsafeStringWriter {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        unsafe { self.write(s.as_bytes()) };
+        Ok(())
+    }
+}
diff --git a/src/stdio/src/lib.rs b/src/stdio/src/lib.rs
index c25858a7a4..8875f66aa9 100644
--- a/src/stdio/src/lib.rs
+++ b/src/stdio/src/lib.rs
@@ -5,6 +5,8 @@
 extern crate platform;
 extern crate va_list as vl;
 
+use core::slice;
+
 use platform::types::*;
 use vl::VaList as va_list;
 
@@ -210,12 +212,12 @@ pub extern "C" fn popen(command: *const c_char, mode: *const c_char) -> *mut FIL
 
 #[no_mangle]
 pub extern "C" fn putc(c: c_int, stream: *mut FILE) -> c_int {
-    unimplemented!();
+    fputc(c, stream)
 }
 
 #[no_mangle]
-pub extern "C" fn putchar(c: c_int) -> c_int {
-    unimplemented!();
+pub unsafe extern "C" fn putchar(c: c_int) -> c_int {
+    putc(c, stdout)
 }
 
 #[no_mangle]
@@ -224,8 +226,8 @@ pub extern "C" fn putc_unlocked(c: c_int, stream: *mut FILE) -> c_int {
 }
 
 #[no_mangle]
-pub extern "C" fn putchar_unlocked(c: c_int) -> c_int {
-    unimplemented!();
+pub unsafe extern "C" fn putchar_unlocked(c: c_int) -> c_int {
+    putc_unlocked(c, stdout)
 }
 
 #[no_mangle]
@@ -294,13 +296,13 @@ pub unsafe extern "C" fn vprintf(format: *const c_char, ap: va_list) -> c_int {
 }
 
 #[no_mangle]
-pub extern "C" fn vsnprintf(s: *mut c_char, n: usize, format: *const c_char, ap: va_list) -> c_int {
-    unimplemented!();
+pub unsafe extern "C" fn vsnprintf(s: *mut c_char, n: usize, format: *const c_char, ap: va_list) -> c_int {
+    printf::printf(platform::StringWriter(s as *mut u8, n as usize), format, ap)
 }
 
 #[no_mangle]
-pub extern "C" fn vsprintf(s: *mut c_char, format: *const c_char, ap: va_list) -> c_int {
-    unimplemented!();
+pub unsafe extern "C" fn vsprintf(s: *mut c_char, format: *const c_char, ap: va_list) -> c_int {
+    printf::printf(platform::UnsafeStringWriter(s as *mut u8), format, ap)
 }
 
 /*