libpq 6.0.1

Safe binding for libpq
Documentation 
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use std::os::raw::c_char;

pub(crate) fn to_cstr(s: &str) -> std::ffi::CString {
    unsafe { std::ffi::CString::from_vec_unchecked(s.as_bytes().to_vec()) }
}

pub(crate) fn to_str(s: *const c_char) -> crate::errors::Result<&'static str> {
    let buffer = unsafe { std::ffi::CStr::from_ptr(s) };

    Ok(buffer.to_str()?)
}

pub(crate) fn to_string(s: *const c_char) -> crate::errors::Result<String> {
    to_str(s).map(|x| x.to_string())
}

pub(crate) fn to_option_str(s: *const c_char) -> crate::errors::Result<Option<&'static str>> {
    if s.is_null() {
        return Ok(None);
    }

    let s = to_str(s)?;

    if s.is_empty() { Ok(None) } else { Ok(Some(s)) }
}

pub(crate) fn to_option_string(s: *const c_char) -> crate::errors::Result<Option<String>> {
    Ok(to_option_str(s)?.map(String::from))
}

pub(crate) fn from_raw(raw: *mut c_char) -> crate::errors::Result<String> {
    let s = unsafe { std::ffi::CString::from_raw(raw).to_str()?.to_string() };

    Ok(s)
}

pub(crate) fn vec_from_nta(raw: *const *const c_char) -> crate::errors::Result<Vec<String>> {
    let mut vec = Vec::new();

    for x in 0.. {
        unsafe {
            if (*raw.offset(x)).is_null() {
                break;
            } else {
                let s = to_string(*raw.offset(x))?;
                vec.push(s);
            }
        }
    }

    Ok(vec)
}

pub(crate) fn new_cstring(size: usize) -> std::ffi::CString {
    unsafe { std::ffi::CString::from_vec_unchecked(vec![0; size]) }
}

pub(crate) fn vec_to_nta<S: ToString>(v: &[S]) -> (Vec<std::ffi::CString>, Vec<*const c_char>) {
    let c = v
        .iter()
        .map(|x| crate::ffi::to_cstr(&x.to_string()))
        .collect::<Vec<_>>();
    let mut ptr = c.iter().map(|x| x.as_ptr()).collect::<Vec<_>>();
    ptr.push(std::ptr::null());

    (c, ptr)
}