diff --git a/deltachat-ffi/src/lib.rs b/deltachat-ffi/src/lib.rs
index 0903b84d9..76491351e 100644
--- a/deltachat-ffi/src/lib.rs
+++ b/deltachat-ffi/src/lib.rs
@@ -24,7 +24,9 @@ use num_traits::{FromPrimitive, ToPrimitive};
 
 use deltachat::contact::Contact;
 use deltachat::context::Context;
-use deltachat::dc_tools::{as_path, as_str, dc_strdup, to_string, OsStrExt, StrExt};
+use deltachat::dc_tools::{
+    as_path, as_str, dc_strdup, to_string, to_string_lossy, OsStrExt, StrExt,
+};
 use deltachat::*;
 
 // as C lacks a good and portable error handling,
@@ -186,7 +188,7 @@ pub unsafe extern "C" fn dc_context_new(
     let os_name = if os_name.is_null() {
         String::from("DcFFI")
     } else {
-        dc_tools::to_string_lossy(os_name)
+        to_string_lossy(os_name)
     };
     let ffi_ctx = ContextWrapper {
         cb,
@@ -735,7 +737,7 @@ pub unsafe extern "C" fn dc_send_text_msg(
         return 0;
     }
     let ffi_context = &*context;
-    let text_to_send = dc_tools::to_string_lossy(text_to_send);
+    let text_to_send = to_string_lossy(text_to_send);
     ffi_context
         .with_inner(|ctx| {
             chat::send_text_msg(ctx, chat_id, text_to_send)
@@ -2861,7 +2863,7 @@ fn as_opt_str<'a>(s: *const libc::c_char) -> Option<&'a str> {
         return None;
     }
 
-    Some(dc_tools::as_str(s))
+    Some(as_str(s))
 }
 
 pub mod providers;
diff --git a/examples/repl/cmdline.rs b/examples/repl/cmdline.rs
index 5750efd2f..8824e36c2 100644
--- a/examples/repl/cmdline.rs
+++ b/examples/repl/cmdline.rs
@@ -1,4 +1,4 @@
-use std::ffi::CString;
+use std::path::Path;
 use std::ptr;
 use std::str::FromStr;
 
@@ -20,8 +20,8 @@ use deltachat::message::{self, Message, MessageState};
 use deltachat::peerstate::*;
 use deltachat::qr::*;
 use deltachat::sql;
-use deltachat::x::*;
 use deltachat::Event;
+use libc::free;
 
 /// Reset database tables. This function is called from Core cmdline.
 /// Argument is a bitmask, executing single or multiple actions in one call.
@@ -94,24 +94,20 @@ pub unsafe fn dc_reset_tables(context: &Context, bits: i32) -> i32 {
     1
 }
 
-unsafe fn dc_poke_eml_file(context: &Context, filename: *const libc::c_char) -> libc::c_int {
-    /* mainly for testing, may be called by dc_import_spec() */
-    let mut success: libc::c_int = 0i32;
-    let mut data: *mut libc::c_char = ptr::null_mut();
-    let mut data_bytes = 0;
-    if !(dc_read_file(
-        context,
-        filename,
-        &mut data as *mut *mut libc::c_char as *mut *mut libc::c_void,
-        &mut data_bytes,
-    ) == 0i32)
-    {
-        dc_receive_imf(context, data, data_bytes, "import", 0, 0);
-        success = 1;
-    }
-    free(data as *mut libc::c_void);
+fn dc_poke_eml_file(context: &Context, filename: impl AsRef<Path>) -> Result<(), Error> {
+    let data = dc_read_file(context, filename)?;
 
-    success
+    unsafe {
+        dc_receive_imf(
+            context,
+            data.as_ptr() as *const _,
+            data.len(),
+            "import",
+            0,
+            0,
+        )
+    };
+    Ok(())
 }
 
 /// Import a file to the database.
@@ -130,16 +126,16 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
 
     let ok_to_continue;
     let mut success: libc::c_int = 0;
-    let real_spec: *mut libc::c_char;
+    let real_spec: String;
     let mut suffix: *mut libc::c_char = ptr::null_mut();
     let mut read_cnt: libc::c_int = 0;
 
     /* if `spec` is given, remember it for later usage; if it is not given, try to use the last one */
     if !spec.is_null() {
-        real_spec = dc_strdup(spec);
+        real_spec = to_string(spec);
         context
             .sql
-            .set_config(context, "import_spec", Some(as_str(real_spec)))
+            .set_config(context, "import_spec", Some(&real_spec))
             .unwrap();
         ok_to_continue = true;
     } else {
@@ -150,27 +146,24 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
         } else {
             ok_to_continue = true;
         }
-        real_spec = rs.unwrap_or_default().strdup();
+        real_spec = rs.unwrap_or_default();
     }
     if ok_to_continue {
         let ok_to_continue2;
-        suffix = dc_get_filesuffix_lc(as_str(real_spec));
-        if !suffix.is_null() && strcmp(suffix, b"eml\x00" as *const u8 as *const libc::c_char) == 0
+        suffix = dc_get_filesuffix_lc(&real_spec);
+        if !suffix.is_null()
+            && libc::strcmp(suffix, b"eml\x00" as *const u8 as *const libc::c_char) == 0
         {
-            if 0 != dc_poke_eml_file(context, real_spec) {
+            if dc_poke_eml_file(context, &real_spec).is_ok() {
                 read_cnt += 1
             }
             ok_to_continue2 = true;
         } else {
             /* import a directory */
-            let dir_name = std::path::Path::new(as_str(real_spec));
+            let dir_name = std::path::Path::new(&real_spec);
             let dir = std::fs::read_dir(dir_name);
             if dir.is_err() {
-                error!(
-                    context,
-                    "Import: Cannot open directory \"{}\".",
-                    as_str(real_spec),
-                );
+                error!(context, "Import: Cannot open directory \"{}\".", &real_spec,);
                 ok_to_continue2 = false;
             } else {
                 let dir = dir.unwrap();
@@ -182,10 +175,9 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
                     let name_f = entry.file_name();
                     let name = name_f.to_string_lossy();
                     if name.ends_with(".eml") {
-                        let path_plus_name = format!("{}/{}", as_str(real_spec), name);
+                        let path_plus_name = format!("{}/{}", &real_spec, name);
                         info!(context, "Import: {}", path_plus_name);
-                        let path_plus_name_c = CString::yolo(path_plus_name);
-                        if 0 != dc_poke_eml_file(context, path_plus_name_c.as_ptr()) {
+                        if dc_poke_eml_file(context, path_plus_name).is_ok() {
                             read_cnt += 1
                         }
                     }
@@ -196,9 +188,7 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
         if ok_to_continue2 {
             info!(
                 context,
-                "Import: {} items read from \"{}\".",
-                read_cnt,
-                as_str(real_spec)
+                "Import: {} items read from \"{}\".", read_cnt, &real_spec
             );
             if read_cnt > 0 {
                 context.call_cb(Event::MsgsChanged {
@@ -210,7 +200,6 @@ unsafe fn poke_spec(context: &Context, spec: *const libc::c_char) -> libc::c_int
         }
     }
 
-    free(real_spec as *mut libc::c_void);
     free(suffix as *mut libc::c_void);
     success
 }
@@ -1017,7 +1006,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         "fileinfo" => {
             ensure!(!arg1.is_empty(), "Argument <file> missing.");
 
-            if let Some(buf) = dc_read_file_safe(context, &arg1) {
+            if let Ok(buf) = dc_read_file(context, &arg1) {
                 let (width, height) = dc_get_filemeta(&buf)?;
                 println!("width={}, height={}", width, height);
             } else {
diff --git a/examples/repl/main.rs b/examples/repl/main.rs
index 6adbe567e..62839b321 100644
--- a/examples/repl/main.rs
+++ b/examples/repl/main.rs
@@ -23,11 +23,9 @@ use std::sync::{Arc, Mutex, RwLock};
 use deltachat::config;
 use deltachat::configure::*;
 use deltachat::context::*;
-use deltachat::dc_tools::*;
 use deltachat::job::*;
 use deltachat::oauth2::*;
 use deltachat::securejoin::*;
-use deltachat::x::*;
 use deltachat::Event;
 use rustyline::completion::{Completer, FilenameCompleter, Pair};
 use rustyline::config::OutputStreamType;
@@ -441,11 +439,6 @@ unsafe fn handle_cmd(line: &str, ctx: Arc<RwLock<Context>>) -> Result<ExitResult
     let mut args = line.splitn(2, ' ');
     let arg0 = args.next().unwrap_or_default();
     let arg1 = args.next().unwrap_or_default();
-    let arg1_c = if arg1.is_empty() {
-        std::ptr::null()
-    } else {
-        arg1.strdup()
-    };
 
     match arg0 {
         "connect" => {
@@ -521,8 +514,6 @@ unsafe fn handle_cmd(line: &str, ctx: Arc<RwLock<Context>>) -> Result<ExitResult
         _ => dc_cmdline(&ctx.read().unwrap(), line)?,
     }
 
-    free(arg1_c as *mut _);
-
     Ok(ExitResult::Continue)
 }
 
diff --git a/src/configure/auto_mozilla.rs b/src/configure/auto_mozilla.rs
index fd2016682..005cc5fcb 100644
--- a/src/configure/auto_mozilla.rs
+++ b/src/configure/auto_mozilla.rs
@@ -1,3 +1,4 @@
+use libc::free;
 use quick_xml;
 use quick_xml::events::{BytesEnd, BytesStart, BytesText};
 
@@ -5,7 +6,6 @@ use crate::constants::*;
 use crate::context::Context;
 use crate::dc_tools::*;
 use crate::login_param::LoginParam;
-use crate::x::*;
 
 use super::read_autoconf_file;
 /* ******************************************************************************
diff --git a/src/configure/auto_outlook.rs b/src/configure/auto_outlook.rs
index b3fdbe9b5..05018bebf 100644
--- a/src/configure/auto_outlook.rs
+++ b/src/configure/auto_outlook.rs
@@ -1,3 +1,6 @@
+use std::ptr;
+
+use libc::free;
 use quick_xml;
 use quick_xml::events::{BytesEnd, BytesStart, BytesText};
 
@@ -5,8 +8,6 @@ use crate::constants::*;
 use crate::context::Context;
 use crate::dc_tools::*;
 use crate::login_param::LoginParam;
-use crate::x::*;
-use std::ptr;
 
 use super::read_autoconf_file;
 /* ******************************************************************************
@@ -46,7 +47,7 @@ pub unsafe fn outlk_autodiscover(
             ok_to_continue = true;
             break;
         }
-        memset(
+        libc::memset(
             &mut outlk_ad as *mut outlk_autodiscover_t as *mut libc::c_void,
             0,
             ::std::mem::size_of::<outlk_autodiscover_t>(),
diff --git a/src/dc_imex.rs b/src/dc_imex.rs
index 33b196835..7902f44b7 100644
--- a/src/dc_imex.rs
+++ b/src/dc_imex.rs
@@ -2,6 +2,7 @@ use std::ffi::CString;
 use std::path::Path;
 use std::ptr;
 
+use libc::{free, strcmp, strlen, strstr};
 use mmime::mailmime_content::*;
 use mmime::mmapstring::*;
 use mmime::other::*;
@@ -23,7 +24,6 @@ use crate::param::*;
 use crate::pgp::*;
 use crate::sql::{self, Sql};
 use crate::stock::StockMessage;
-use crate::x::*;
 
 // import/export and tools
 // param1 is a directory where the keys are written to
@@ -276,7 +276,7 @@ pub unsafe fn dc_continue_key_transfer(
     }
 
     if let Some(filename) = msg.get_file(context) {
-        if let Some(buf) = dc_read_file_safe(context, filename) {
+        if let Ok(buf) = dc_read_file(context, filename) {
             norm_sc = dc_normalize_setup_code(context, setup_code);
             if norm_sc.is_null() {
                 warn!(context, "Cannot normalize Setup Code.",);
@@ -767,8 +767,8 @@ unsafe fn export_backup(context: &Context, dir: *const libc::c_char) -> bool {
                                                 } else {
                                                     info!(context, "EXPORTing filename={}", name);
                                                     let curr_pathNfilename = context.get_blobdir().join(entry.file_name());
-                                                    if let Some(buf) =
-                                                        dc_read_file_safe(context, &curr_pathNfilename)
+                                                    if let Ok(buf) =
+                                                        dc_read_file(context, &curr_pathNfilename)
                                                     {
                                                         if buf.is_empty() {
                                                             continue;
@@ -874,7 +874,7 @@ unsafe fn import_self_keys(context: &Context, dir_name: *const libc::c_char) ->
                 free(buf.cast());
                 buf = ptr::null_mut();
 
-                if let Some(buf_r) = dc_read_file_safe(context, &path_plus_name) {
+                if let Ok(buf_r) = dc_read_file(context, &path_plus_name) {
                     buf = buf_r.as_ptr() as *mut _;
                     std::mem::forget(buf_r);
                 } else {
diff --git a/src/dc_mimefactory.rs b/src/dc_mimefactory.rs
index a6a1af68e..9e82f8e3d 100644
--- a/src/dc_mimefactory.rs
+++ b/src/dc_mimefactory.rs
@@ -2,6 +2,7 @@ use std::path::Path;
 use std::ptr;
 
 use chrono::TimeZone;
+use libc::{free, strcmp, strlen};
 use mmime::clist::*;
 use mmime::mailimf_types::*;
 use mmime::mailimf_types_helper::*;
@@ -25,7 +26,6 @@ use crate::location;
 use crate::message::{self, Message};
 use crate::param::*;
 use crate::stock::StockMessage;
-use crate::x::*;
 
 #[derive(Clone, Copy, Eq, PartialEq)]
 pub enum Loaded {
diff --git a/src/dc_mimeparser.rs b/src/dc_mimeparser.rs
index c91d1031a..31a8fa09c 100644
--- a/src/dc_mimeparser.rs
+++ b/src/dc_mimeparser.rs
@@ -4,6 +4,7 @@ use std::ptr;
 
 use charset::Charset;
 use deltachat_derive::{FromSql, ToSql};
+use libc::{strcmp, strlen, strncmp};
 use mmime::clist::*;
 use mmime::mailimf::*;
 use mmime::mailimf_types::*;
@@ -25,7 +26,6 @@ use crate::error::Error;
 use crate::location;
 use crate::param::*;
 use crate::stock::StockMessage;
-use crate::x::*;
 
 #[derive(Debug)]
 pub struct MimeParser<'a> {
diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index 6d9476928..266a8d4cc 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -2,6 +2,7 @@ use std::ffi::CString;
 use std::ptr;
 
 use itertools::join;
+use libc::{free, strcmp, strlen};
 use mmime::clist::*;
 use mmime::mailimf::*;
 use mmime::mailimf_types::*;
@@ -28,7 +29,6 @@ use crate::peerstate::*;
 use crate::securejoin::handle_securejoin_handshake;
 use crate::sql;
 use crate::stock::StockMessage;
-use crate::x::*;
 
 #[derive(Debug, PartialEq, Eq)]
 enum CreateEvent {
diff --git a/src/dc_strencode.rs b/src/dc_strencode.rs
index 05481481c..0ec5cd627 100644
--- a/src/dc_strencode.rs
+++ b/src/dc_strencode.rs
@@ -3,13 +3,13 @@ use std::ffi::CString;
 use std::ptr;
 
 use charset::Charset;
+use libc::{free, strlen};
 use mmime::mailmime_decode::*;
 use mmime::mmapstring::*;
 use mmime::other::*;
 use percent_encoding::{percent_decode, utf8_percent_encode, AsciiSet, CONTROLS};
 
 use crate::dc_tools::*;
-use crate::x::*;
 
 /**
  * Encode non-ascii-strings as `=?UTF-8?Q?Bj=c3=b6rn_Petersen?=`.
@@ -336,6 +336,8 @@ unsafe fn print_hex(target: *mut libc::c_char, cur: *const libc::c_char) {
 #[cfg(test)]
 mod tests {
     use super::*;
+
+    use libc::{strcmp, strncmp};
     use std::ffi::CStr;
 
     #[test]
diff --git a/src/dc_tools.rs b/src/dc_tools.rs
index 85de8d767..eb190c27e 100644
--- a/src/dc_tools.rs
+++ b/src/dc_tools.rs
@@ -9,16 +9,15 @@ use std::time::SystemTime;
 use std::{fmt, fs, ptr};
 
 use chrono::{Local, TimeZone};
-use libc::uintptr_t;
+use libc::{free, memcpy, strcpy, strlen, strstr, uintptr_t};
 use mmime::clist::*;
 use mmime::mailimf_types::*;
 use rand::{thread_rng, Rng};
 
 use crate::context::Context;
 use crate::error::Error;
-use crate::x::*;
 
-pub fn dc_exactly_one_bit_set(v: libc::c_int) -> bool {
+pub(crate) fn dc_exactly_one_bit_set(v: libc::c_int) -> bool {
     0 != v && 0 == v & (v - 1)
 }
 
@@ -43,7 +42,7 @@ pub unsafe fn dc_strdup(s: *const libc::c_char) -> *mut libc::c_char {
         ret = strdup(s);
         assert!(!ret.is_null());
     } else {
-        ret = calloc(1, 1) as *mut libc::c_char;
+        ret = libc::calloc(1, 1) as *mut libc::c_char;
         assert!(!ret.is_null());
     }
 
@@ -51,21 +50,7 @@ pub unsafe fn dc_strdup(s: *const libc::c_char) -> *mut libc::c_char {
 }
 
 /// Duplicates a string, returns null if given string is null
-///
-/// # Examples
-///
-/// ```
-/// use deltachat::dc_tools::{dc_strdup_keep_null, to_string};
-/// use std::ffi::{CStr};
-///
-/// unsafe {
-///     let str_a = b"foobar\x00" as *const u8 as *const libc::c_char;
-///     let str_a_copy = dc_strdup_keep_null(str_a);
-///     assert_eq!(to_string(str_a_copy), "foobar");
-///     assert_ne!(str_a, str_a_copy);
-/// }
-/// ```
-pub unsafe fn dc_strdup_keep_null(s: *const libc::c_char) -> *mut libc::c_char {
+pub(crate) unsafe fn dc_strdup_keep_null(s: *const libc::c_char) -> *mut libc::c_char {
     if !s.is_null() {
         dc_strdup(s)
     } else {
@@ -73,7 +58,7 @@ pub unsafe fn dc_strdup_keep_null(s: *const libc::c_char) -> *mut libc::c_char {
     }
 }
 
-pub unsafe fn dc_atoi_null_is_0(s: *const libc::c_char) -> libc::c_int {
+pub(crate) fn dc_atoi_null_is_0(s: *const libc::c_char) -> libc::c_int {
     if !s.is_null() {
         as_str(s).parse().unwrap_or_default()
     } else {
@@ -81,20 +66,6 @@ pub unsafe fn dc_atoi_null_is_0(s: *const libc::c_char) -> libc::c_int {
     }
 }
 
-pub unsafe fn dc_str_replace(
-    haystack: *mut *mut libc::c_char,
-    needle: *const libc::c_char,
-    replacement: *const libc::c_char,
-) {
-    let haystack_s = to_string(*haystack);
-    let needle_s = to_string(needle);
-    let replacement_s = to_string(replacement);
-
-    free(*haystack as *mut libc::c_void);
-
-    *haystack = haystack_s.replace(&needle_s, &replacement_s).strdup();
-}
-
 unsafe fn dc_ltrim(buf: *mut libc::c_char) {
     let mut len: libc::size_t;
     let mut cur: *const libc::c_uchar;
@@ -106,7 +77,7 @@ unsafe fn dc_ltrim(buf: *mut libc::c_char) {
             len = len.wrapping_sub(1)
         }
         if buf as *const libc::c_uchar != cur {
-            memmove(
+            libc::memmove(
                 buf as *mut libc::c_void,
                 cur as *const libc::c_void,
                 len.wrapping_add(1),
@@ -137,28 +108,13 @@ unsafe fn dc_rtrim(buf: *mut libc::c_char) {
     };
 }
 
-pub unsafe fn dc_trim(buf: *mut libc::c_char) {
+pub(crate) unsafe fn dc_trim(buf: *mut libc::c_char) {
     dc_ltrim(buf);
     dc_rtrim(buf);
 }
 
-/* the result must be free()'d */
-pub unsafe fn dc_null_terminate(
-    in_0: *const libc::c_char,
-    bytes: libc::c_int,
-) -> *mut libc::c_char {
-    let out: *mut libc::c_char = malloc(bytes as usize + 1) as *mut libc::c_char;
-    assert!(!out.is_null());
-    if !in_0.is_null() && bytes > 0 {
-        strncpy(out, in_0, bytes as usize);
-    }
-    *out.offset(bytes as isize) = 0 as libc::c_char;
-
-    out
-}
-
 /* remove all \r characters from string */
-pub unsafe fn dc_remove_cr_chars(buf: *mut libc::c_char) {
+pub(crate) unsafe fn dc_remove_cr_chars(buf: *mut libc::c_char) {
     /* search for first `\r` */
     let mut p1: *const libc::c_char = buf;
     while 0 != *p1 {
@@ -179,84 +135,9 @@ pub unsafe fn dc_remove_cr_chars(buf: *mut libc::c_char) {
     *p2 = 0 as libc::c_char;
 }
 
-/* replace bad UTF-8 characters by sequences of `_` (to avoid problems in filenames, we do not use eg. `?`) the function is useful if strings are unexpectingly encoded eg. as ISO-8859-1 */
-#[allow(non_snake_case)]
-pub unsafe fn dc_replace_bad_utf8_chars(buf: *mut libc::c_char) {
-    let mut OK_TO_CONTINUE = true;
-    if buf.is_null() {
-        return;
-    }
-    /* force unsigned - otherwise the `> ' '` comparison will fail */
-    let mut p1: *mut libc::c_uchar = buf as *mut libc::c_uchar;
-    let p1len: libc::c_int = strlen(buf) as libc::c_int;
-    let mut c: libc::c_int;
-    let mut i: libc::c_int;
-    let ix: libc::c_int;
-    let mut n: libc::c_int;
-    let mut j: libc::c_int;
-    i = 0;
-    ix = p1len;
-    's_36: loop {
-        if !(i < ix) {
-            break;
-        }
-        c = *p1.offset(i as isize) as libc::c_int;
-        if c > 0 && c <= 0x7f {
-            n = 0
-        } else if c & 0xe0 == 0xc0 {
-            n = 1
-        } else if c == 0xed
-            && i < ix - 1
-            && *p1.offset((i + 1) as isize) as libc::c_int & 0xa0 == 0xa0
-        {
-            /* U+d800 to U+dfff */
-            OK_TO_CONTINUE = false;
-            break;
-        } else if c & 0xf0 == 0xe0 {
-            n = 2
-        } else if c & 0xf8 == 0xf0 {
-            n = 3
-        } else {
-            //else if ((c & 0xFC) == 0xF8)                          { n=4; }        /* 111110bb - not valid in https://tools.ietf.org/html/rfc3629 */
-            //else if ((c & 0xFE) == 0xFC)                          { n=5; }        /* 1111110b - not valid in https://tools.ietf.org/html/rfc3629 */
-            OK_TO_CONTINUE = false;
-            break;
-        }
-        j = 0;
-        while j < n && i < ix {
-            /* n bytes matching 10bbbbbb follow ? */
-            i += 1;
-            if i == ix || *p1.offset(i as isize) as libc::c_int & 0xc0 != 0x80 {
-                OK_TO_CONTINUE = false;
-                break 's_36;
-            }
-            j += 1
-        }
-        i += 1
-    }
-    if OK_TO_CONTINUE == false {
-        while 0 != *p1 {
-            if *p1 as libc::c_int > 0x7f {
-                *p1 = '_' as i32 as libc::c_uchar
-            }
-            p1 = p1.offset(1isize)
-        }
-        return;
-    }
-}
-
 /// Shortens a string to a specified length and adds "..." or "[...]" to the end of
 /// the shortened string.
-///
-/// # Examples
-/// ```
-/// use deltachat::dc_tools::dc_truncate;
-///
-/// let s = "this is a little test string";
-/// assert_eq!(dc_truncate(s, 16, false), "this is a [...]");
-/// assert_eq!(dc_truncate(s, 16, true), "this is a ...");
-/// ```
-pub fn dc_truncate(buf: &str, approx_chars: usize, do_unwrap: bool) -> Cow<str> {
+pub(crate) fn dc_truncate(buf: &str, approx_chars: usize, do_unwrap: bool) -> Cow<str> {
     let ellipse = if do_unwrap { "..." } else { "[...]" };
 
     let count = buf.chars().count();
@@ -278,7 +159,7 @@ pub fn dc_truncate(buf: &str, approx_chars: usize, do_unwrap: bool) -> Cow<str>
 }
 
 #[allow(non_snake_case)]
-pub unsafe fn dc_truncate_n_unwrap_str(
+pub(crate) unsafe fn dc_truncate_n_unwrap_str(
     buf: *mut libc::c_char,
     approx_characters: libc::c_int,
     do_unwrap: libc::c_int,
@@ -337,7 +218,7 @@ unsafe fn dc_utf8_strnlen(s: *const libc::c_char, n: libc::size_t) -> libc::size
     j
 }
 
-pub unsafe fn dc_str_from_clist(
+pub(crate) unsafe fn dc_str_from_clist(
     list: *const clist,
     delimiter: *const libc::c_char,
 ) -> *mut libc::c_char {
@@ -369,7 +250,7 @@ pub unsafe fn dc_str_from_clist(
     res.strdup()
 }
 
-pub unsafe fn dc_str_to_clist(
+pub(crate) unsafe fn dc_str_to_clist(
     str: *const libc::c_char,
     delimiter: *const libc::c_char,
 ) -> *mut clist {
@@ -408,7 +289,7 @@ const COLORS: [u32; 16] = [
     0x39b249, 0xbb243b, 0x964078, 0x66874f, 0x308ab9, 0x127ed0, 0xbe450c,
 ];
 
-pub fn dc_str_to_color(s: impl AsRef<str>) -> u32 {
+pub(crate) fn dc_str_to_color(s: impl AsRef<str>) -> u32 {
     let str_lower = s.as_ref().to_lowercase();
     let mut checksum = 0;
     let bytes = str_lower.as_bytes();
@@ -422,8 +303,9 @@ pub fn dc_str_to_color(s: impl AsRef<str>) -> u32 {
 }
 
 /* clist tools */
+
 /* calls free() for each item content */
-pub unsafe fn clist_free_content(haystack: *const clist) {
+pub(crate) unsafe fn clist_free_content(haystack: *const clist) {
     let mut iter = (*haystack).first;
 
     while !iter.is_null() {
@@ -437,7 +319,7 @@ pub unsafe fn clist_free_content(haystack: *const clist) {
     }
 }
 
-pub unsafe fn clist_search_string_nocase(
+pub(crate) unsafe fn clist_search_string_nocase(
     haystack: *const clist,
     needle: *const libc::c_char,
 ) -> bool {
@@ -448,7 +330,7 @@ pub unsafe fn clist_search_string_nocase(
 
 /* date/time tools */
 /* the result is UTC or DC_INVALID_TIMESTAMP */
-pub unsafe fn dc_timestamp_from_date(date_time: *mut mailimf_date_time) -> i64 {
+pub(crate) unsafe fn dc_timestamp_from_date(date_time: *mut mailimf_date_time) -> i64 {
     let sec = (*date_time).dt_sec;
     let min = (*date_time).dt_min;
     let hour = (*date_time).dt_hour;
@@ -482,13 +364,13 @@ pub fn dc_timestamp_to_str(wanted: i64) -> String {
     ts.format("%Y.%m.%d %H:%M:%S").to_string()
 }
 
-pub fn dc_gm2local_offset() -> i64 {
+pub(crate) fn dc_gm2local_offset() -> i64 {
     let lt = Local::now();
     ((lt.offset().local_minus_utc() / (60 * 60)) * 100) as i64
 }
 
 /* timesmearing */
-pub fn dc_smeared_time(context: &Context) -> i64 {
+pub(crate) fn dc_smeared_time(context: &Context) -> i64 {
     /* function returns a corrected time(NULL) */
     let mut now = time();
     let ts = *context.last_smeared_timestamp.clone().read().unwrap();
@@ -499,7 +381,7 @@ pub fn dc_smeared_time(context: &Context) -> i64 {
     now
 }
 
-pub fn dc_create_smeared_timestamp(context: &Context) -> i64 {
+pub(crate) fn dc_create_smeared_timestamp(context: &Context) -> i64 {
     let now = time();
     let mut ret = now;
 
@@ -514,7 +396,7 @@ pub fn dc_create_smeared_timestamp(context: &Context) -> i64 {
     ret
 }
 
-pub fn dc_create_smeared_timestamps(context: &Context, count: usize) -> i64 {
+pub(crate) fn dc_create_smeared_timestamps(context: &Context, count: usize) -> i64 {
     /* get a range to timestamps that can be used uniquely */
     let now = time();
     let start = now + (if count < 5 { count } else { 5 }) as i64 - count as i64;
@@ -528,7 +410,7 @@ pub fn dc_create_smeared_timestamps(context: &Context, count: usize) -> i64 {
 }
 
 /* Message-ID tools */
-pub fn dc_create_id() -> String {
+pub(crate) fn dc_create_id() -> String {
     /* generate an id. the generated ID should be as short and as unique as possible:
     - short, because it may also used as part of Message-ID headers or in QR codes
     - unique as two IDs generated on two devices should not be the same. However, collisions are not world-wide but only by the few contacts.
@@ -568,7 +450,7 @@ fn encode_66bits_as_base64(v1: u32, v2: u32, fill: u32) -> String {
     String::from_utf8(wrapped_writer).unwrap()
 }
 
-pub fn dc_create_incoming_rfc724_mid(
+pub(crate) fn dc_create_incoming_rfc724_mid(
     message_timestamp: i64,
     contact_id_from: u32,
     contact_ids_to: &Vec<u32>,
@@ -590,7 +472,7 @@ pub fn dc_create_incoming_rfc724_mid(
 /// - this function is called for all outgoing messages.
 /// - the message ID should be globally unique
 /// - do not add a counter or any private data as this leaks information unncessarily
-pub fn dc_create_outgoing_rfc724_mid(grpid: Option<&str>, from_addr: &str) -> String {
+pub(crate) fn dc_create_outgoing_rfc724_mid(grpid: Option<&str>, from_addr: &str) -> String {
     let hostname = from_addr
         .find('@')
         .map(|k| &from_addr[k..])
@@ -606,16 +488,7 @@ pub fn dc_create_outgoing_rfc724_mid(grpid: Option<&str>, from_addr: &str) -> St
 /// # Arguments
 ///
 /// * `mid` - A string that holds the message id
-///
-/// # Examples
-///
-/// ```
-/// use deltachat::dc_tools::dc_extract_grpid_from_rfc724_mid;
-/// let mid = "Gr.12345678901.morerandom@domain.de";
-/// let grpid = dc_extract_grpid_from_rfc724_mid(mid);
-/// assert_eq!(grpid, Some("12345678901"));
-/// ```
-pub fn dc_extract_grpid_from_rfc724_mid(mid: &str) -> Option<&str> {
+pub(crate) fn dc_extract_grpid_from_rfc724_mid(mid: &str) -> Option<&str> {
     if mid.len() < 9 || !mid.starts_with("Gr.") {
         return None;
     }
@@ -632,7 +505,9 @@ pub fn dc_extract_grpid_from_rfc724_mid(mid: &str) -> Option<&str> {
     None
 }
 
-pub unsafe fn dc_extract_grpid_from_rfc724_mid_list(list: *const clist) -> *mut libc::c_char {
+pub(crate) unsafe fn dc_extract_grpid_from_rfc724_mid_list(
+    list: *const clist,
+) -> *mut libc::c_char {
     if !list.is_null() {
         let mut cur: *mut clistiter = (*list).first;
         while !cur.is_null() {
@@ -656,7 +531,7 @@ pub unsafe fn dc_extract_grpid_from_rfc724_mid_list(list: *const clist) -> *mut
     ptr::null_mut()
 }
 
-pub fn dc_ensure_no_slash_safe(path: &str) -> &str {
+pub(crate) fn dc_ensure_no_slash_safe(path: &str) -> &str {
     if path.ends_with('/') || path.ends_with('\\') {
         return &path[..path.len() - 1];
     }
@@ -671,14 +546,6 @@ fn validate_filename(filename: &str) -> String {
         .replace(':', "-")
 }
 
-pub unsafe fn dc_get_filename(path_filename: impl AsRef<str>) -> *mut libc::c_char {
-    if let Some(p) = Path::new(path_filename.as_ref()).file_name() {
-        p.to_string_lossy().strdup()
-    } else {
-        ptr::null_mut()
-    }
-}
-
 // the returned suffix is lower-case
 #[allow(non_snake_case)]
 pub unsafe fn dc_get_filesuffix_lc(path_filename: impl AsRef<str>) -> *mut libc::c_char {
@@ -700,7 +567,7 @@ pub fn dc_get_filemeta(buf: &[u8]) -> Result<(u32, u32), Error> {
 ///
 /// If `path` starts with "$BLOBDIR", replaces it with the blobdir path.
 /// Otherwise, returns path as is.
-pub fn dc_get_abs_path<P: AsRef<std::path::Path>>(
+pub(crate) fn dc_get_abs_path<P: AsRef<std::path::Path>>(
     context: &Context,
     path: P,
 ) -> std::path::PathBuf {
@@ -712,11 +579,11 @@ pub fn dc_get_abs_path<P: AsRef<std::path::Path>>(
     }
 }
 
-pub fn dc_file_exist(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
+pub(crate) fn dc_file_exist(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
     dc_get_abs_path(context, &path).exists()
 }
 
-pub fn dc_get_filebytes(context: &Context, path: impl AsRef<std::path::Path>) -> u64 {
+pub(crate) fn dc_get_filebytes(context: &Context, path: impl AsRef<std::path::Path>) -> u64 {
     let path_abs = dc_get_abs_path(context, &path);
     match fs::metadata(&path_abs) {
         Ok(meta) => meta.len() as u64,
@@ -724,7 +591,7 @@ pub fn dc_get_filebytes(context: &Context, path: impl AsRef<std::path::Path>) ->
     }
 }
 
-pub fn dc_delete_file(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
+pub(crate) fn dc_delete_file(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
     let path_abs = dc_get_abs_path(context, &path);
     if !path_abs.is_file() {
         warn!(
@@ -744,7 +611,7 @@ pub fn dc_delete_file(context: &Context, path: impl AsRef<std::path::Path>) -> b
     }
 }
 
-pub fn dc_copy_file(
+pub(crate) fn dc_copy_file(
     context: &Context,
     src: impl AsRef<std::path::Path>,
     dest: impl AsRef<std::path::Path>,
@@ -765,7 +632,7 @@ pub fn dc_copy_file(
     }
 }
 
-pub fn dc_create_folder(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
+pub(crate) fn dc_create_folder(context: &Context, path: impl AsRef<std::path::Path>) -> bool {
     let path_abs = dc_get_abs_path(context, &path);
     if !path_abs.exists() {
         match fs::create_dir_all(path_abs) {
@@ -785,7 +652,7 @@ pub fn dc_create_folder(context: &Context, path: impl AsRef<std::path::Path>) ->
 }
 
 /// Write a the given content to provied file path.
-pub fn dc_write_file(context: &Context, path: impl AsRef<Path>, buf: &[u8]) -> bool {
+pub(crate) fn dc_write_file(context: &Context, path: impl AsRef<Path>, buf: &[u8]) -> bool {
     let path_abs = dc_get_abs_path(context, &path);
     if let Err(_err) = fs::write(&path_abs, buf) {
         warn!(
@@ -800,42 +667,26 @@ pub fn dc_write_file(context: &Context, path: impl AsRef<Path>, buf: &[u8]) -> b
     }
 }
 
-#[allow(non_snake_case)]
-pub unsafe fn dc_read_file(
+pub fn dc_read_file<P: AsRef<std::path::Path>>(
     context: &Context,
-    pathNfilename: *const libc::c_char,
-    buf: *mut *mut libc::c_void,
-    buf_bytes: *mut libc::size_t,
-) -> libc::c_int {
-    if pathNfilename.is_null() {
-        return 0;
-    }
-    if let Some(mut bytes) = dc_read_file_safe(context, as_str(pathNfilename)) {
-        *buf = &mut bytes[..] as *mut _ as *mut libc::c_void;
-        *buf_bytes = bytes.len();
-        std::mem::forget(bytes);
-        1
-    } else {
-        0
-    }
-}
-
-pub fn dc_read_file_safe<P: AsRef<std::path::Path>>(context: &Context, path: P) -> Option<Vec<u8>> {
+    path: P,
+) -> Result<Vec<u8>, Error> {
     let path_abs = dc_get_abs_path(context, &path);
+
     match fs::read(&path_abs) {
-        Ok(bytes) => Some(bytes),
-        Err(_err) => {
+        Ok(bytes) => Ok(bytes),
+        Err(err) => {
             warn!(
                 context,
                 "Cannot read \"{}\" or file is empty.",
                 path.as_ref().display()
             );
-            None
+            Err(err.into())
         }
     }
 }
 
-pub fn dc_get_fine_path_filename(
+pub(crate) fn dc_get_fine_path_filename(
     context: &Context,
     folder: impl AsRef<Path>,
     desired_filename_suffix: impl AsRef<str>,
@@ -880,7 +731,7 @@ pub fn dc_get_fine_path_filename(
     panic!("Something is really wrong, you need to clean up your disk");
 }
 
-pub fn dc_is_blobdir_path(context: &Context, path: impl AsRef<str>) -> bool {
+pub(crate) fn dc_is_blobdir_path(context: &Context, path: impl AsRef<str>) -> bool {
     context
         .get_blobdir()
         .to_str()
@@ -900,7 +751,7 @@ fn dc_make_rel_path(context: &Context, path: &mut String) {
     }
 }
 
-pub fn dc_make_rel_and_copy(context: &Context, path: &mut String) -> bool {
+pub(crate) fn dc_make_rel_and_copy(context: &Context, path: &mut String) -> bool {
     if dc_is_blobdir_path(context, &path) {
         dc_make_rel_path(context, path);
         return true;
@@ -1148,7 +999,7 @@ fn as_path_unicode<'a>(s: *const libc::c_char) -> &'a std::path::Path {
     std::path::Path::new(as_str(s))
 }
 
-pub fn time() -> i64 {
+pub(crate) fn time() -> i64 {
     SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
         .unwrap()
@@ -1220,36 +1071,64 @@ impl FromStr for EmailAddress {
 
 /// Utility to check if a in the binary represantion of listflags
 /// the bit at position bitindex is 1.
-///
-///
-/// # Example
-///
-/// ```
-/// use std::convert::TryInto;
-/// use deltachat::dc_tools::listflags_has;
-/// use deltachat::constants::{DC_GCL_ADD_SELF, DC_GCL_VERIFIED_ONLY};
-/// let listflags: u32 = 0x1101;
-/// assert!(listflags_has(listflags, 0x1) == true);
-/// assert!(listflags_has(listflags, 0x10) == false);
-/// assert!(listflags_has(listflags, 0x100) == true);
-/// assert!(listflags_has(listflags, 0x1000) == true);
-/// let listflags: u32 = (DC_GCL_ADD_SELF | DC_GCL_VERIFIED_ONLY).try_into().unwrap();
-/// assert!(listflags_has(listflags, DC_GCL_VERIFIED_ONLY) == true);
-/// assert!(listflags_has(listflags, DC_GCL_ADD_SELF) == true);
-/// let listflags: u32 = DC_GCL_VERIFIED_ONLY.try_into().unwrap();
-/// assert!(listflags_has(listflags, DC_GCL_ADD_SELF) == false);
-/// ```
-pub fn listflags_has(listflags: u32, bitindex: usize) -> bool {
+pub(crate) fn listflags_has(listflags: u32, bitindex: usize) -> bool {
     let listflags = listflags as usize;
     (listflags & bitindex) == bitindex
 }
 
+pub(crate) unsafe fn strdup(s: *const libc::c_char) -> *mut libc::c_char {
+    if s.is_null() {
+        return std::ptr::null_mut();
+    }
+
+    let slen = strlen(s);
+    let result = libc::malloc(slen + 1);
+    if result.is_null() {
+        return std::ptr::null_mut();
+    }
+
+    memcpy(result, s as *const _, slen + 1);
+    result as *mut _
+}
+
+pub(crate) 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 end = std::cmp::min(n as usize, unsafe { strlen(s) });
+    unsafe {
+        let result = libc::malloc(end + 1);
+        memcpy(result, s as *const _, end);
+        std::ptr::write_bytes(result.offset(end as isize), b'\x00', 1);
+
+        result as *mut _
+    }
+}
+
+pub(crate) unsafe fn strcasecmp(s1: *const libc::c_char, s2: *const libc::c_char) -> libc::c_int {
+    let s1 = std::ffi::CStr::from_ptr(s1)
+        .to_string_lossy()
+        .to_lowercase();
+    let s2 = std::ffi::CStr::from_ptr(s2)
+        .to_string_lossy()
+        .to_lowercase();
+    if s1 == s2 {
+        0
+    } else {
+        1
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    use libc::strcmp;
+    use std::convert::TryInto;
     use std::ffi::CStr;
 
+    use crate::constants::*;
     use crate::test_utils::*;
 
     #[test]
@@ -1348,23 +1227,6 @@ mod tests {
         assert_eq!("1.22", format!("{}", 1.22));
     }
 
-    #[test]
-    fn test_dc_str_replace() {
-        unsafe {
-            let mut str: *mut libc::c_char = strdup(b"aaa\x00" as *const u8 as *const libc::c_char);
-            dc_str_replace(
-                &mut str,
-                b"a\x00" as *const u8 as *const libc::c_char,
-                b"ab\x00" as *const u8 as *const libc::c_char,
-            );
-            assert_eq!(
-                CStr::from_ptr(str as *const libc::c_char).to_str().unwrap(),
-                "ababab"
-            );
-            free(str as *mut libc::c_void);
-        }
-    }
-
     #[test]
     fn test_dc_truncate_1() {
         let s = "this is a little test string";
@@ -1420,45 +1282,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn test_dc_null_terminate_1() {
-        unsafe {
-            let str: *mut libc::c_char =
-                dc_null_terminate(b"abcxyz\x00" as *const u8 as *const libc::c_char, 3);
-            assert_eq!(
-                CStr::from_ptr(str as *const libc::c_char).to_str().unwrap(),
-                "abc"
-            );
-            free(str as *mut libc::c_void);
-        }
-    }
-
-    #[test]
-    fn test_dc_null_terminate_2() {
-        unsafe {
-            let str: *mut libc::c_char =
-                dc_null_terminate(b"abcxyz\x00" as *const u8 as *const libc::c_char, 0);
-            assert_eq!(
-                CStr::from_ptr(str as *const libc::c_char).to_str().unwrap(),
-                ""
-            );
-            free(str as *mut libc::c_void);
-        }
-    }
-
-    #[test]
-    fn test_dc_null_terminate_3() {
-        unsafe {
-            let str: *mut libc::c_char =
-                dc_null_terminate(0 as *const u8 as *const libc::c_char, 0);
-            assert_eq!(
-                CStr::from_ptr(str as *const libc::c_char).to_str().unwrap(),
-                ""
-            );
-            free(str as *mut libc::c_void);
-        }
-    }
-
     #[test]
     fn test_dc_str_to_clist_1() {
         unsafe {
@@ -1517,63 +1340,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_dc_replace_bad_utf8_chars_1() {
-        unsafe {
-            let buf1 = strdup(b"ol\xc3\xa1 mundo <>\"\'& \xc3\xa4\xc3\x84\xc3\xb6\xc3\x96\xc3\xbc\xc3\x9c\xc3\x9f foo\xc3\x86\xc3\xa7\xc3\x87 \xe2\x99\xa6&noent;\x00" as *const u8 as *const libc::c_char);
-            let buf2 = strdup(buf1);
-
-            dc_replace_bad_utf8_chars(buf2);
-
-            assert_eq!(strcmp(buf1, buf2), 0);
-
-            free(buf1 as *mut libc::c_void);
-            free(buf2 as *mut libc::c_void);
-        }
-    }
-
-    #[test]
-    fn test_dc_replace_bad_utf8_chars_2() {
-        unsafe {
-            let buf1 = strdup(b"ISO-String with Ae: \xc4\x00" as *const u8 as *const libc::c_char);
-            let buf2 = strdup(buf1);
-
-            dc_replace_bad_utf8_chars(buf2);
-
-            assert_eq!(
-                CStr::from_ptr(buf2 as *const libc::c_char)
-                    .to_str()
-                    .unwrap(),
-                "ISO-String with Ae: _"
-            );
-
-            free(buf1 as *mut libc::c_void);
-            free(buf2 as *mut libc::c_void);
-        }
-    }
-
-    #[test]
-    fn test_dc_replace_bad_utf8_chars_3() {
-        unsafe {
-            let buf1 = strdup(b"\x00" as *const u8 as *const libc::c_char);
-            let buf2 = strdup(buf1);
-
-            dc_replace_bad_utf8_chars(buf2);
-
-            assert_eq!(*buf2.offset(0), 0);
-
-            free(buf1 as *mut libc::c_void);
-            free(buf2 as *mut libc::c_void);
-        }
-    }
-
-    #[test]
-    fn test_dc_replace_bad_utf8_chars_4() {
-        unsafe {
-            dc_replace_bad_utf8_chars(ptr::null_mut());
-        }
-    }
-
     #[test]
     fn test_dc_create_id() {
         let buf = dc_create_id();
@@ -1809,4 +1575,85 @@ mod tests {
         dc_make_rel_path(&t.ctx, &mut foo);
         assert_eq!(foo, format!("$BLOBDIR{}foo", std::path::MAIN_SEPARATOR));
     }
+
+    #[test]
+    fn test_strndup() {
+        unsafe {
+            let res = strndup(b"helloworld\x00" as *const u8 as *const libc::c_char, 4);
+            assert_eq!(
+                to_string(res),
+                to_string(b"hell\x00" as *const u8 as *const libc::c_char)
+            );
+            assert_eq!(strlen(res), 4);
+            free(res as *mut _);
+        }
+    }
+
+    #[test]
+    fn test_file_handling() {
+        let t = dummy_context();
+        let context = &t.ctx;
+
+        if dc_file_exist(context, "$BLOBDIR/foobar")
+            || dc_file_exist(context, "$BLOBDIR/dada")
+            || dc_file_exist(context, "$BLOBDIR/foobar.dadada")
+            || dc_file_exist(context, "$BLOBDIR/foobar-folder")
+        {
+            dc_delete_file(context, "$BLOBDIR/foobar");
+            dc_delete_file(context, "$BLOBDIR/dada");
+            dc_delete_file(context, "$BLOBDIR/foobar.dadada");
+            dc_delete_file(context, "$BLOBDIR/foobar-folder");
+        }
+        assert!(dc_write_file(context, "$BLOBDIR/foobar", b"content"));
+        assert!(dc_file_exist(context, "$BLOBDIR/foobar",));
+        assert!(!dc_file_exist(context, "$BLOBDIR/foobarx"));
+        assert_eq!(dc_get_filebytes(context, "$BLOBDIR/foobar"), 7);
+
+        let abs_path = context
+            .get_blobdir()
+            .join("foobar")
+            .to_string_lossy()
+            .to_string();
+
+        assert!(dc_is_blobdir_path(context, &abs_path));
+        assert!(dc_is_blobdir_path(context, "$BLOBDIR/fofo",));
+        assert!(!dc_is_blobdir_path(context, "/BLOBDIR/fofo",));
+        assert!(dc_file_exist(context, &abs_path));
+
+        assert!(dc_copy_file(context, "$BLOBDIR/foobar", "$BLOBDIR/dada",));
+        assert_eq!(dc_get_filebytes(context, "$BLOBDIR/dada",), 7);
+
+        let buf = dc_read_file(context, "$BLOBDIR/dada").unwrap();
+
+        assert_eq!(buf.len(), 7);
+        assert_eq!(&buf, b"content");
+
+        assert!(dc_delete_file(context, "$BLOBDIR/foobar"));
+        assert!(dc_delete_file(context, "$BLOBDIR/dada"));
+        assert!(dc_create_folder(context, "$BLOBDIR/foobar-folder"));
+        assert!(dc_file_exist(context, "$BLOBDIR/foobar-folder",));
+        assert!(!dc_delete_file(context, "$BLOBDIR/foobar-folder"));
+        let fn0 = dc_get_fine_path_filename(context, "$BLOBDIR", "foobar.dadada");
+        assert_eq!(fn0, PathBuf::from("$BLOBDIR/foobar.dadada"));
+
+        assert!(dc_write_file(context, &fn0, b"content"));
+        let fn1 = dc_get_fine_path_filename(context, "$BLOBDIR", "foobar.dadada");
+        assert_eq!(fn1, PathBuf::from("$BLOBDIR/foobar-1.dadada"));
+
+        assert!(dc_delete_file(context, &fn0));
+    }
+
+    #[test]
+    fn test_listflags_has() {
+        let listflags: u32 = 0x1101;
+        assert!(listflags_has(listflags, 0x1) == true);
+        assert!(listflags_has(listflags, 0x10) == false);
+        assert!(listflags_has(listflags, 0x100) == true);
+        assert!(listflags_has(listflags, 0x1000) == true);
+        let listflags: u32 = (DC_GCL_ADD_SELF | DC_GCL_VERIFIED_ONLY).try_into().unwrap();
+        assert!(listflags_has(listflags, DC_GCL_VERIFIED_ONLY) == true);
+        assert!(listflags_has(listflags, DC_GCL_ADD_SELF) == true);
+        let listflags: u32 = DC_GCL_VERIFIED_ONLY.try_into().unwrap();
+        assert!(listflags_has(listflags, DC_GCL_ADD_SELF) == false);
+    }
 }
diff --git a/src/e2ee.rs b/src/e2ee.rs
index 55c6bc6ab..f47c97ecd 100644
--- a/src/e2ee.rs
+++ b/src/e2ee.rs
@@ -6,6 +6,7 @@ use std::ffi::CStr;
 use std::ptr;
 use std::str::FromStr;
 
+use libc::{free, strcmp, strlen, strncmp};
 use mmime::clist::*;
 use mmime::mailimf::*;
 use mmime::mailimf_types::*;
@@ -30,7 +31,6 @@ use crate::keyring::*;
 use crate::peerstate::*;
 use crate::pgp::*;
 use crate::securejoin::handle_degrade_event;
-use crate::x::*;
 
 #[derive(Debug, Default)]
 pub struct E2eeHelper {
diff --git a/src/job.rs b/src/job.rs
index 3d21537ba..59a637314 100644
--- a/src/job.rs
+++ b/src/job.rs
@@ -19,7 +19,6 @@ use crate::login_param::LoginParam;
 use crate::message::{self, Message, MessageState};
 use crate::param::*;
 use crate::sql;
-use crate::x::*;
 
 /// Thread IDs
 #[derive(Debug, Display, Copy, Clone, PartialEq, Eq, FromPrimitive, ToPrimitive, FromSql, ToSql)]
@@ -140,7 +139,7 @@ impl Job {
         }
 
         if let Some(filename) = self.param.get(Param::File) {
-            if let Some(body) = dc_read_file_safe(context, filename) {
+            if let Ok(body) = dc_read_file(context, filename) {
                 if let Some(recipients) = self.param.get(Param::Recipients) {
                     let recipients_list = recipients
                         .split("\x1e")
@@ -670,7 +669,7 @@ pub unsafe fn job_send_msg(context: &Context, msg_id: u32) -> libc::c_int {
                     mimefactory.msg.param.set_int(Param::Width, 0);
                     mimefactory.msg.param.set_int(Param::Height, 0);
 
-                    if let Some(buf) = dc_read_file_safe(context, pathNfilename) {
+                    if let Ok(buf) = dc_read_file(context, pathNfilename) {
                         if let Ok((width, height)) = dc_get_filemeta(&buf) {
                             mimefactory.msg.param.set_int(Param::Width, width as i32);
                             mimefactory.msg.param.set_int(Param::Height, height as i32);
@@ -1047,7 +1046,7 @@ fn add_smtp_job(context: &Context, action: Action, mimefactory: &MimeFactory) ->
         success = 1;
     }
     unsafe {
-        free(recipients.cast());
+        libc::free(recipients.cast());
     }
     success
 }
diff --git a/src/lib.rs b/src/lib.rs
index 20954f241..87cf915be 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -54,7 +54,6 @@ pub mod qr;
 mod smtp;
 pub mod sql;
 mod stock;
-pub mod x;
 
 pub mod dc_array;
 mod dc_dehtml;
diff --git a/src/message.rs b/src/message.rs
index fc7619406..edf54655b 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -2,6 +2,7 @@ use std::path::{Path, PathBuf};
 use std::ptr;
 
 use deltachat_derive::{FromSql, ToSql};
+use libc::{free, strcmp};
 use phf::phf_map;
 
 use crate::chat::{self, Chat};
@@ -18,7 +19,6 @@ use crate::param::*;
 use crate::pgp::*;
 use crate::sql;
 use crate::stock::StockMessage;
-use crate::x::*;
 
 /// In practice, the user additionally cuts the string himself pixel-accurate.
 const SUMMARY_CHARACTERS: usize = 160;
@@ -351,7 +351,7 @@ impl Message {
         }
 
         if let Some(filename) = self.get_file(context) {
-            if let Some(mut buf) = dc_read_file_safe(context, filename) {
+            if let Ok(mut buf) = dc_read_file(context, filename) {
                 unsafe {
                     // just a pointer inside buf, MUST NOT be free()'d
                     let mut buf_headerline = ptr::null();
diff --git a/src/pgp.rs b/src/pgp.rs
index 84c300ce6..96b144700 100644
--- a/src/pgp.rs
+++ b/src/pgp.rs
@@ -3,6 +3,7 @@ use std::convert::TryInto;
 use std::io::Cursor;
 use std::ptr;
 
+use libc::{strchr, strlen, strncmp, strspn, strstr};
 use pgp::composed::{
     Deserializable, KeyType as PgpKeyType, Message, SecretKeyParamsBuilder, SignedPublicKey,
     SignedSecretKey, SubkeyParamsBuilder,
@@ -15,7 +16,6 @@ use crate::dc_tools::*;
 use crate::error::Error;
 use crate::key::*;
 use crate::keyring::*;
-use crate::x::*;
 
 pub unsafe fn dc_split_armored_data(
     buf: *mut libc::c_char,
diff --git a/src/stock.rs b/src/stock.rs
index 28481d5c5..e92b08d2c 100644
--- a/src/stock.rs
+++ b/src/stock.rs
@@ -7,7 +7,6 @@ use crate::contact::*;
 use crate::context::Context;
 use crate::dc_tools::*;
 use crate::events::Event;
-use libc::free;
 
 /// Stock strings
 ///
@@ -133,7 +132,7 @@ impl Context {
             Cow::Borrowed(id.fallback())
         } else {
             let ret = to_string(ptr);
-            unsafe { free(ptr as *mut libc::c_void) };
+            unsafe { libc::free(ptr as *mut libc::c_void) };
             Cow::Owned(ret)
         }
     }
diff --git a/src/top_evil_rs.py b/src/top_evil_rs.py
index 2976b0de1..633017a6b 100755
--- a/src/top_evil_rs.py
+++ b/src/top_evil_rs.py
@@ -15,19 +15,21 @@ if __name__ == "__main__":
         unsafe = s.count("unsafe")
         free = s.count("free(")
         gotoblocks = s.count("ok_to_continue") + s.count('OK_TO_CONTINUE')
-        filestats.append((fn, unsafe, free, gotoblocks))
+        chars = s.count("c_char") + s.count("CStr")
+        filestats.append((fn, unsafe, free, gotoblocks, chars))
 
-    sum_unsafe, sum_free, sum_gotoblocks = 0, 0, 0
+    sum_unsafe, sum_free, sum_gotoblocks, sum_chars = 0, 0, 0, 0
 
-    for fn, unsafe, free, gotoblocks in reversed(sorted(filestats, key=lambda x: sum(x[1:]))):
-        print("{0: <30} unsafe: {1: >3} free: {2: >3} ok_to_continue: {3: >3}".format(str(fn), unsafe, free, gotoblocks))
+    for fn, unsafe, free, gotoblocks, chars in reversed(sorted(filestats, key=lambda x: sum(x[1:]))):
+        print("{0: <25} unsafe: {1: >3} free: {2: >3} ok_to_cont: {3: >3} chars: {4: >3}".format(str(fn), unsafe, free, gotoblocks, chars))
         sum_unsafe += unsafe
         sum_free += free
         sum_gotoblocks += gotoblocks
+        sum_chars += chars
 
 
     print()
     print("total unsafe:", sum_unsafe)
     print("total free:", sum_free)
     print("total ok_to_continue:", sum_gotoblocks)
-
+    print("total c_chars:", sum_chars)
diff --git a/src/x.rs b/src/x.rs
deleted file mode 100644
index 481f837ca..000000000
--- a/src/x.rs
+++ /dev/null
@@ -1,67 +0,0 @@
-pub use libc::{
-    calloc, exit, free, malloc, memcmp, memcpy, memmove, memset, realloc, strcat, strchr, strcmp,
-    strcpy, strcspn, strlen, strncmp, strncpy, strrchr, strspn, strstr, strtol, system,
-};
-
-pub unsafe fn strdup(s: *const libc::c_char) -> *mut libc::c_char {
-    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();
-    }
-
-    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 end = std::cmp::min(n as usize, unsafe { strlen(s) });
-    unsafe {
-        let result = malloc(end + 1);
-        memcpy(result, s as *const _, end);
-        std::ptr::write_bytes(result.offset(end as isize), b'\x00', 1);
-
-        result as *mut _
-    }
-}
-
-pub(crate) unsafe fn strcasecmp(s1: *const libc::c_char, s2: *const libc::c_char) -> libc::c_int {
-    let s1 = std::ffi::CStr::from_ptr(s1)
-        .to_string_lossy()
-        .to_lowercase();
-    let s2 = std::ffi::CStr::from_ptr(s2)
-        .to_string_lossy()
-        .to_lowercase();
-    if s1 == s2 {
-        0
-    } else {
-        1
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::dc_tools::to_string;
-
-    #[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 _);
-        }
-    }
-}
diff --git a/tests/stress.rs b/tests/stress.rs
index bb71e89e4..91d700ea9 100644
--- a/tests/stress.rs
+++ b/tests/stress.rs
@@ -1,11 +1,8 @@
 //! Stress some functions for testing; if used as a lib, this file is obsolete.
 
 use std::collections::HashSet;
-use std::path::PathBuf;
 use std::ptr;
 
-use tempfile::{tempdir, TempDir};
-
 use deltachat::chat::{self, Chat};
 use deltachat::config;
 use deltachat::contact::*;
@@ -15,9 +12,9 @@ use deltachat::dc_tools::*;
 use deltachat::keyring::*;
 use deltachat::oauth2::*;
 use deltachat::pgp::*;
-use deltachat::x::*;
 use deltachat::Event;
-use libc;
+use libc::{free, strcmp, strdup, strlen, strncmp};
+use tempfile::{tempdir, TempDir};
 
 /* some data used for testing
  ******************************************************************************/
@@ -30,68 +27,6 @@ static mut S_EM_SETUPFILE: *const libc::c_char =
         as *const u8 as *const libc::c_char;
 
 unsafe fn stress_functions(context: &Context) {
-    if dc_file_exist(context, "$BLOBDIR/foobar")
-        || dc_file_exist(context, "$BLOBDIR/dada")
-        || dc_file_exist(context, "$BLOBDIR/foobar.dadada")
-        || dc_file_exist(context, "$BLOBDIR/foobar-folder")
-    {
-        dc_delete_file(context, "$BLOBDIR/foobar");
-        dc_delete_file(context, "$BLOBDIR/dada");
-        dc_delete_file(context, "$BLOBDIR/foobar.dadada");
-        dc_delete_file(context, "$BLOBDIR/foobar-folder");
-    }
-    assert!(dc_write_file(context, "$BLOBDIR/foobar", b"content"));
-    assert!(dc_file_exist(context, "$BLOBDIR/foobar",));
-    assert!(!dc_file_exist(context, "$BLOBDIR/foobarx"));
-    assert_eq!(dc_get_filebytes(context, "$BLOBDIR/foobar"), 7);
-
-    let abs_path = context
-        .get_blobdir()
-        .join("foobar")
-        .to_string_lossy()
-        .to_string();
-
-    assert!(dc_is_blobdir_path(context, &abs_path));
-    assert!(dc_is_blobdir_path(context, "$BLOBDIR/fofo",));
-    assert!(!dc_is_blobdir_path(context, "/BLOBDIR/fofo",));
-    assert!(dc_file_exist(context, &abs_path));
-
-    assert!(dc_copy_file(context, "$BLOBDIR/foobar", "$BLOBDIR/dada",));
-    assert_eq!(dc_get_filebytes(context, "$BLOBDIR/dada",), 7);
-
-    let mut buf: *mut libc::c_void = ptr::null_mut();
-    let mut buf_bytes: libc::size_t = 0;
-
-    assert_eq!(
-        dc_read_file(
-            context,
-            b"$BLOBDIR/dada\x00" as *const u8 as *const libc::c_char,
-            &mut buf,
-            &mut buf_bytes,
-        ),
-        1
-    );
-    assert_eq!(buf_bytes, 7);
-    assert_eq!(
-        std::str::from_utf8(std::slice::from_raw_parts(buf as *const u8, buf_bytes)).unwrap(),
-        "content"
-    );
-
-    free(buf as *mut _);
-    assert!(dc_delete_file(context, "$BLOBDIR/foobar"));
-    assert!(dc_delete_file(context, "$BLOBDIR/dada"));
-    assert!(dc_create_folder(context, "$BLOBDIR/foobar-folder"));
-    assert!(dc_file_exist(context, "$BLOBDIR/foobar-folder",));
-    assert!(!dc_delete_file(context, "$BLOBDIR/foobar-folder"));
-    let fn0 = dc_get_fine_path_filename(context, "$BLOBDIR", "foobar.dadada");
-    assert_eq!(fn0, PathBuf::from("$BLOBDIR/foobar.dadada"));
-
-    assert!(dc_write_file(context, &fn0, b"content"));
-    let fn1 = dc_get_fine_path_filename(context, "$BLOBDIR", "foobar.dadada");
-    assert_eq!(fn1, PathBuf::from("$BLOBDIR/foobar-1.dadada"));
-
-    assert!(dc_delete_file(context, &fn0));
-
     let res = context.get_config(config::Config::SysConfigKeys).unwrap();
 
     assert!(!res.contains(" probably_never_a_key "));