feat: import mmime crate

mmime/src/charconv.rs

@@ -0,0 +1,32 @@
+use crate::other::*;
+use libc;
+use std::ffi::{CStr, CString};
+
+pub const MAIL_CHARCONV_ERROR_CONV: libc::c_uint = 3;
+pub const MAIL_CHARCONV_ERROR_MEMORY: libc::c_uint = 2;
+pub const MAIL_CHARCONV_ERROR_UNKNOWN_CHARSET: libc::c_uint = 1;
+pub const MAIL_CHARCONV_NO_ERROR: libc::c_uint = 0;
+
+pub unsafe fn charconv(
+    tocode: *const libc::c_char,
+    fromcode: *const libc::c_char,
+    s: *const libc::c_char,
+    length: size_t,
+    result: *mut *mut libc::c_char,
+) -> libc::c_int {
+    assert!(!fromcode.is_null(), "invalid fromcode");
+    assert!(!s.is_null(), "invalid input string");
+    if let Some(encoding) =
+        charset::Charset::for_label(CStr::from_ptr(fromcode).to_str().unwrap().as_bytes())
+    {
+        let data = std::slice::from_raw_parts(s as *const u8, strlen(s));
+
+        let (res, _, _) = encoding.decode(data);
+        let res_c = CString::new(res.as_bytes()).unwrap();
+        *result = strdup(res_c.as_ptr()) as *mut _;
+
+        MAIL_CHARCONV_NO_ERROR as libc::c_int
+    } else {
+        MAIL_CHARCONV_ERROR_UNKNOWN_CHARSET as libc::c_int
+    }
+}