sqlite3_ext 0.2.0

Build loadable extensions for SQLite using Rust
Documentation 
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use super::*;
use std::{
    mem::transmute,
    ops::Deref,
    os::raw::{c_char, c_int},
};

type CEntry = unsafe extern "C" fn(
    db: *mut ffi::sqlite3,
    err_msg: *mut *mut c_char,
    api: *mut ffi::sqlite3_api_routines,
) -> c_int;

/// Represents an SQLite-compatible extension entry point.
///
/// Because the original Rust function is the [Deref] target for Extension, it can be called
/// from Rust easily.
///
/// # Examples
///
/// ```no_run
/// use sqlite3_ext::*;
///
/// #[sqlite3_ext_main(persistent)]
/// fn init(db: &Connection) -> Result<()> {
///     // Automatically load this extension on future connections.
///     per_db_init.register_auto()?;
///     // Load this extension on this connection.
///     per_db_init(db)?;
///     // Add extensions to the VFS system
///     Ok(())
/// }
///
/// #[sqlite3_ext_init]
/// fn per_db_init(db: &Connection) -> Result<()> {
///     // Add extensions to this connection.
///     Ok(())
/// }
/// # fn main() {}
/// ```
#[repr(C)]
pub struct Extension {
    c_entry: unsafe extern "C" fn(),
    init: fn(&Connection) -> Result<()>,
}

impl Extension {
    /// Construct an Extension from parts.
    ///
    /// You generally want to use [sqlite3_ext_init] instead of this function.
    pub const fn new(c_entry: CEntry, init: fn(&Connection) -> Result<()>) -> Self {
        unsafe {
            Extension {
                c_entry: transmute::<CEntry, unsafe extern "C" fn()>(c_entry),
                init,
            }
        }
    }

    /// Register this extension as an automatic extension.
    ///
    /// The provided method will be invoked on all database connections opened in the
    /// future. For more information, consult the SQLite documentation for
    /// `sqlite3_auto_extension`.
    ///
    /// Requires SQLite 3.8.7.
    pub fn register_auto(&'static self) -> Result<()> {
        sqlite3_require_version!(3_008_007, unsafe {
            Error::from_sqlite(ffi::sqlite3_auto_extension(Some(self.c_entry)))
        })
    }

    /// Remove all registered automatic extensions.
    ///
    /// For more information, consult the SQLite documentation for
    /// `sqlite3_reset_auto_extension`.
    ///
    /// Requires SQLite 3.8.7. On earlier verions this method is a no-op.
    pub fn reset_auto() {
        sqlite3_match_version! {
            3_008_007 => unsafe { ffi::sqlite3_reset_auto_extension() },
            _ => (),
        }
    }

    /// Remove a previously-registered automatic extension.
    ///
    /// For more information, consult the SQLite documentation for
    /// `sqlite3_cancel_auto_extension`.
    ///
    /// Requires SQLite 3.8.7.
    pub fn cancel_auto(&'static self) -> Result<bool> {
        sqlite3_require_version!(3_008_007, unsafe {
            Ok(ffi::sqlite3_cancel_auto_extension(Some(self.c_entry)) != 0)
        })
    }
}

impl Deref for Extension {
    type Target = fn(&Connection) -> Result<()>;

    fn deref(&self) -> &Self::Target {
        &self.init
    }
}