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([2a02:810d:4b3f:ee94:abf:b8ff:feee:998b]) by smtp.gmail.com with ESMTPSA id v22-20020a1709061dd600b00a3d8fb05c0csm141614ejh.86.2024.02.16.09.11.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Feb 2024 09:11:31 -0800 (PST) Message-ID: <18a49662-3640-49c1-9587-db5cc9d62fbc@redhat.com> Date: Fri, 16 Feb 2024 18:11:30 +0100 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] rust: str: add {make,to}_{upper,lower}case() to CString To: Alice Ryhl Cc: a.hindborg@samsung.com, alex.gaynor@gmail.com, benno.lossin@proton.me, bjorn3_gh@protonmail.com, boqun.feng@gmail.com, gary@garyguo.net, linux-kernel@vger.kernel.org, ojeda@kernel.org, rust-for-linux@vger.kernel.org, wedsonaf@gmail.com References: <20240214172505.5044-1-dakr@redhat.com> <20240216165320.1820346-1-aliceryhl@google.com> From: Danilo Krummrich Organization: RedHat In-Reply-To: <20240216165320.1820346-1-aliceryhl@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/16/24 17:53, Alice Ryhl wrote: >> + pub fn make_ascii_lowercase(&mut self) { >> + self.0.make_ascii_lowercase(); >> + } > > It's important to note here that this doesn't remove or introduce NUL > bytes. > > pub fn make_ascii_lowercase(&mut self) { > // INVARIANT: This doesn't introduce or remove NUL bytes in the c > // string. > self.0.make_ascii_lowercase(); > } > > Ditto for make_ascii_uppercase. (But not the to_* methods.) > >> + /// Returns a copy of this [`CString`] where each character is mapped to its >> + /// ASCII lower case equivalent. >> + /// >> + /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', >> + /// but non-ASCII letters are unchanged. >> + /// >> + /// To lowercase the value in-place, use [`make_ascii_lowercase`]. >> + /// >> + /// [`make_ascii_lowercase`]: str::make_ascii_lowercase >> + pub fn to_ascii_lowercase(&self) -> Result { >> + let mut s = (*self).to_cstring()?; >> + >> + s.make_ascii_lowercase(); >> + >> + return Ok(s); >> + } >> + >> + /// Returns a copy of this [`CString`] where each character is mapped to its >> + /// ASCII upper case equivalent. >> + /// >> + /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', >> + /// but non-ASCII letters are unchanged. >> + /// >> + /// To uppercase the value in-place, use [`make_ascii_uppercase`]. >> + /// >> + /// [`make_ascii_uppercase`]: str::make_ascii_uppercase >> + pub fn to_ascii_uppercase(&self) -> Result { >> + let mut s = (*self).to_cstring()?; >> + >> + s.make_ascii_uppercase(); >> + >> + return Ok(s); >> + } > > Please move these to `CStr` as well. That would result into two copies if I actually want a CString, wouldn't it? Also, what would be the use case? And even if someone wants to have a CStr again, couldn't we just deref the resulting CString? - Danilo > >> +impl DerefMut for CString { >> + fn deref_mut(&mut self) -> &mut Self::Target { >> + unsafe { CStr::from_bytes_with_nul_unchecked_mut(&mut *self.buf) } >> + } >> +} > > Needs a safety comment. > > impl DerefMut for CString { > fn deref_mut(&mut self) -> &mut Self::Target { > // SAFETY: A `CString` is always NUL-terminated and contains no > // other NUL bytes. > unsafe { CStr::from_bytes_with_nul_unchecked_mut(&mut *self.buf) } > } > } > > Alice >