diff --git a/src/dc_strencode.rs b/src/dc_strencode.rs
index e445b653b..b6d6d4e22 100644
--- a/src/dc_strencode.rs
+++ b/src/dc_strencode.rs
@@ -245,23 +245,18 @@ unsafe fn quote_word(
     // col = (*mmapstr).len as libc::c_int;
     cur = word;
     while i < size {
-        let mut do_quote_char: libc::c_int = 0;
-        match *cur as libc::c_int {
-            44 | 58 | 33 | 34 | 35 | 36 | 64 | 91 | 92 | 93 | 94 | 96 | 123 | 124 | 125 | 126
-            | 61 | 63 | 95 => do_quote_char = 1i32,
+        let mut do_quote_char = false;
+        match *cur as u8 as char {
+            ',' | ':' | '!' | '"' | '#' | '$' | '@' | '[' | '\\' | ']' | '^' | '`' | '{' | '|'
+            | '}' | '~' | '=' | '?' | '_' => do_quote_char = true,
             _ => {
-                if *cur as libc::c_uchar as libc::c_int >= 128i32 {
-                    do_quote_char = 1i32
+                if *cur as u8 >= 128 {
+                    do_quote_char = true;
                 }
             }
         }
-        if 0 != do_quote_char {
-            snprintf(
-                hex.as_mut_ptr(),
-                4,
-                b"=%2.2X\x00" as *const u8 as *const libc::c_char,
-                *cur as libc::c_uchar as libc::c_int,
-            );
+        if do_quote_char {
+            print_hex(hex.as_mut_ptr(), cur);
             if mmap_string_append(mmapstr, hex.as_mut_ptr()).is_null() {
                 return false;
             }
@@ -716,6 +711,15 @@ pub unsafe fn dc_decode_ext_header(to_decode: *const libc::c_char) -> *mut libc:
     };
 }
 
+unsafe fn print_hex(target: *mut libc::c_char, cur: *const libc::c_char) {
+    assert!(!target.is_null());
+    assert!(!cur.is_null());
+
+    let bytes = std::slice::from_raw_parts(cur as *const _, strlen(cur));
+    let raw = to_cstring(format!("={}", &hex::encode_upper(bytes)[..2]));
+    libc::memcpy(target as *mut _, raw.as_ptr() as *const _, 4);
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -882,4 +886,16 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn test_print_hex() {
+        let mut hex: [libc::c_char; 4] = [0; 4];
+        let cur = b"helloworld" as *const u8 as *const libc::c_char;
+        unsafe { print_hex(hex.as_mut_ptr(), cur) };
+        assert_eq!(to_string(hex.as_ptr() as *const _), "=68");
+
+        let cur = b":" as *const u8 as *const libc::c_char;
+        unsafe { print_hex(hex.as_mut_ptr(), cur) };
+        assert_eq!(to_string(hex.as_ptr() as *const _), "=3A");
+    }
 }
diff --git a/src/dc_tools.rs b/src/dc_tools.rs
index 6385d15a6..9379607f7 100644
--- a/src/dc_tools.rs
+++ b/src/dc_tools.rs
@@ -243,28 +243,13 @@ pub unsafe fn dc_null_terminate(
 }
 
 pub unsafe fn dc_binary_to_uc_hex(buf: *const uint8_t, bytes: size_t) -> *mut libc::c_char {
-    let mut hex: *mut libc::c_char = 0 as *mut libc::c_char;
-    let mut i;
-    if !(buf.is_null() || bytes <= 0) {
-        hex = calloc(
-            ::std::mem::size_of::<libc::c_char>(),
-            bytes.wrapping_mul(2).wrapping_add(1),
-        ) as *mut libc::c_char;
-        if !hex.is_null() {
-            i = 0;
-            while i < bytes {
-                snprintf(
-                    &mut *hex.offset((i * 2) as isize) as *mut libc::c_char,
-                    3,
-                    b"%02X\x00" as *const u8 as *const libc::c_char,
-                    *buf.offset(i as isize) as libc::c_int,
-                );
-                i += 1
-            }
-        }
+    if buf.is_null() || bytes == 0 {
+        return std::ptr::null_mut();
     }
 
-    hex
+    let buf = std::slice::from_raw_parts(buf, bytes);
+    let raw = hex::encode_upper(buf);
+    strdup(to_cstring(raw).as_ptr())
 }
 
 /* remove all \r characters from string */
@@ -1820,4 +1805,15 @@ mod tests {
             free(str as *mut libc::c_void);
         }
     }
+
+    #[test]
+    fn test_dc_binary_to_uc_hex() {
+        let buf = vec![0, 1, 2, 3, 255];
+
+        let raw = unsafe { dc_binary_to_uc_hex(buf.as_ptr(), buf.len()) };
+        let res = to_string(raw);
+        assert_eq!(res, "00010203FF");
+
+        unsafe { free(raw as *mut _) };
+    }
 }
diff --git a/src/x.rs b/src/x.rs
index ac9703532..0d1643b1c 100644
--- a/src/x.rs
+++ b/src/x.rs
@@ -1,4 +1,5 @@
 use crate::dc_strbuilder::dc_strbuilder_t;
+use crate::dc_tools::*;
 use crate::types::*;
 
 pub use libc::{
@@ -8,16 +9,30 @@ pub use libc::{
 };
 
 pub unsafe fn strdup(s: *const libc::c_char) -> *mut libc::c_char {
-    let slen = libc::strlen(s);
-    let result = libc::malloc(slen + 1);
+    if s.is_null() {
+        return std::ptr::null_mut();
+    }
+
+    let slen = strlen(s);
+    let result = malloc(slen + 1);
     if result.is_null() {
         return std::ptr::null_mut();
     }
 
-    libc::memcpy(result, s as *const _, slen + 1);
+    memcpy(result, s as *const _, slen + 1);
     result as *mut _
 }
 
+pub fn strndup(s: *const libc::c_char, n: libc::c_ulong) -> *mut libc::c_char {
+    if s.is_null() {
+        return std::ptr::null_mut();
+    }
+
+    let s_r = to_str(s);
+    let end = std::cmp::min(n as usize, s_r.len());
+    unsafe { strdup(to_cstring(&s_r[..end]).as_ptr()) }
+}
+
 extern "C" {
     pub fn clock() -> libc::clock_t;
     pub fn qsort(
@@ -29,7 +44,6 @@ extern "C" {
         >,
     );
     pub fn pow(_: libc::c_double, _: libc::c_double) -> libc::c_double;
-    pub fn strndup(_: *const libc::c_char, _: libc::c_ulong) -> *mut libc::c_char;
     pub fn strftime(
         _: *mut libc::c_char,
         _: size_t,
@@ -59,23 +73,12 @@ extern "C" {
         _: *const libc::c_char,
     ) -> !;
 
-    #[cfg(windows)]
-    pub(crate) fn snprintf(
-        s: *mut libc::c_char,
-        n: libc::size_t,
-        format: *const libc::c_char,
-        _: ...
-    ) -> libc::c_int;
-
     // -- DC Methods
 
     pub fn dc_strbuilder_catf(_: *mut dc_strbuilder_t, format: *const libc::c_char, _: ...);
     pub fn dc_mprintf(format: *const libc::c_char, _: ...) -> *mut libc::c_char;
 }
 
-#[cfg(not(windows))]
-pub(crate) use libc::snprintf;
-
 #[cfg(not(target_os = "macos"))]
 pub unsafe extern "C" fn __assert_rtn(
     a: *const libc::c_char,
@@ -132,6 +135,7 @@ pub(crate) unsafe fn strncasecmp(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::dc_tools::to_string;
 
     #[test]
     fn test_atox() {
@@ -140,4 +144,17 @@ mod tests {
             assert_eq!(atoi(b"\x00" as *const u8 as *const libc::c_char), 0);
         }
     }
+
+    #[test]
+    fn test_strndup() {
+        unsafe {
+            let res = strndup(b"helloworld\x00" as *const u8 as *const libc::c_char, 4);
+            assert_eq!(
+                to_string(res),
+                to_string(b"hell\x00" as *const u8 as *const libc::c_char)
+            );
+            assert_eq!(strlen(res), 4);
+            free(res as *mut _);
+        }
+    }
 }