Draft to ease PRAGMA usage (#273 and #265)

src/lib.rs

@@ -117,6 +117,7 @@ mod inner_connection;
 pub mod limits;
 #[cfg(feature = "load_extension")]
 mod load_extension_guard;
+mod pragma;
 mod raw_statement;
 mod row;
 #[cfg(feature = "session")]

src/pragma.rs

@@ -0,0 +1,405 @@
+//! Pragma helpers
+
+use std::ops::Deref;
+
+use crate::error::Error;
+use crate::ffi;
+use crate::types::{ToSql, ToSqlOutput, ValueRef};
+use crate::{Connection, DatabaseName, Result, Row, NO_PARAMS};
+
+pub struct Sql {
+    buf: String,
+}
+
+impl Sql {
+    pub fn new() -> Sql {
+        Sql { buf: String::new() }
+    }
+
+    pub fn push_pragma(
+        &mut self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+    ) -> Result<()> {
+        self.push_keyword("PRAGMA")?;
+        self.push_space();
+        if let Some(schema_name) = schema_name {
+            self.push_schema_name(schema_name);
+            self.push_dot();
+        }
+        self.push_keyword(pragma_name)
+    }
+
+    pub fn push_keyword(&mut self, keyword: &str) -> Result<()> {
+        if !keyword.is_empty() && is_identifier(keyword) {
+            self.buf.push_str(keyword);
+            Ok(())
+        } else {
+            Err(Error::SqliteFailure(
+                ffi::Error::new(ffi::SQLITE_MISUSE),
+                Some(format!("Invalid keyword \"{}\"", keyword)),
+            ))
+        }
+    }
+
+    pub fn push_schema_name(&mut self, schema_name: DatabaseName<'_>) {
+        match schema_name {
+            DatabaseName::Main => self.buf.push_str("main"),
+            DatabaseName::Temp => self.buf.push_str("temp"),
+            DatabaseName::Attached(s) => self.push_identifier(s),
+        };
+    }
+
+    pub fn push_identifier(&mut self, s: &str) {
+        if is_identifier(s) {
+            self.buf.push_str(s);
+        } else {
+            self.wrap_and_escape(s, '"');
+        }
+    }
+
+    pub fn push_value(&mut self, value: &dyn ToSql) -> Result<()> {
+        let value = value.to_sql()?;
+        let value = match value {
+            ToSqlOutput::Borrowed(v) => v,
+            ToSqlOutput::Owned(ref v) => ValueRef::from(v),
+            #[cfg(feature = "blob")]
+            ToSqlOutput::ZeroBlob(_) => {
+                return Err(Error::SqliteFailure(
+                    ffi::Error::new(ffi::SQLITE_MISUSE),
+                    Some(format!("Unsupported value \"{:?}\"", value)),
+                ));
+            }
+            #[cfg(feature = "array")]
+            ToSqlOutput::Array(_) => {
+                return Err(Error::SqliteFailure(
+                    ffi::Error::new(ffi::SQLITE_MISUSE),
+                    Some(format!("Unsupported value \"{:?}\"", value)),
+                ));
+            }
+        };
+        match value {
+            ValueRef::Integer(i) => {
+                self.push_int(i);
+            }
+            ValueRef::Real(r) => {
+                self.push_real(r);
+            }
+            ValueRef::Text(s) => {
+                self.push_string_literal(s);
+            }
+            _ => {
+                return Err(Error::SqliteFailure(
+                    ffi::Error::new(ffi::SQLITE_MISUSE),
+                    Some(format!("Unsupported value \"{:?}\"", value)),
+                ));
+            }
+        };
+        Ok(())
+    }
+
+    pub fn push_string_literal(&mut self, s: &str) {
+        self.wrap_and_escape(s, '\'');
+    }
+
+    pub fn push_int(&mut self, i: i64) {
+        self.buf.push_str(&i.to_string());
+    }
+
+    pub fn push_real(&mut self, f: f64) {
+        self.buf.push_str(&f.to_string());
+    }
+
+    pub fn push_space(&mut self) {
+        self.buf.push(' ');
+    }
+
+    pub fn push_dot(&mut self) {
+        self.buf.push('.');
+    }
+
+    pub fn push_equal_sign(&mut self) {
+        self.buf.push('=');
+    }
+
+    pub fn open_brace(&mut self) {
+        self.buf.push('(');
+    }
+
+    pub fn close_brace(&mut self) {
+        self.buf.push(')');
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.buf
+    }
+
+    fn wrap_and_escape(&mut self, s: &str, quote: char) {
+        self.buf.push(quote);
+        let chars = s.chars();
+        for ch in chars {
+            // escape `quote` by doubling it
+            if ch == quote {
+                self.buf.push(ch);
+            }
+            self.buf.push(ch)
+        }
+        self.buf.push(quote);
+    }
+}
+
+impl Deref for Sql {
+    type Target = str;
+
+    fn deref(&self) -> &str {
+        self.as_str()
+    }
+}
+
+impl Connection {
+    /// Query the current value of `pragma_name`.
+    ///
+    /// Some pragmas will return multiple rows/values which cannot be retrieved
+    /// with this method.
+    pub fn pragma_query_value<T, F>(
+        &self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+        f: F,
+    ) -> Result<T>
+    where
+        F: FnOnce(Row<'_, '_>) -> Result<T>,
+    {
+        let mut query = Sql::new();
+        query.push_pragma(schema_name, pragma_name)?;
+        let mut stmt = self.prepare(&query)?;
+        let mut rows = stmt.query(NO_PARAMS)?;
+        if let Some(result_row) = rows.next() {
+            let row = result_row?;
+            f(row)
+        } else {
+            Err(Error::QueryReturnedNoRows)
+        }
+    }
+
+    /// Query the current rows/values of `pragma_name`.
+    pub fn pragma_query<F>(
+        &self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+        mut f: F,
+    ) -> Result<()>
+    where
+        F: FnMut(&Row<'_, '_>) -> Result<()>,
+    {
+        let mut query = Sql::new();
+        query.push_pragma(schema_name, pragma_name)?;
+        let mut stmt = self.prepare(&query)?;
+        let mut rows = stmt.query(NO_PARAMS)?;
+        while let Some(result_row) = rows.next() {
+            let row = result_row?;
+            f(&row)?;
+        }
+        Ok(())
+    }
+
+    /// Query the current value(s) of `pragma_name` associated to
+    /// `pragma_value`.
+    ///
+    /// This method can be used with query-only pragmas which need an argument
+    /// (e.g. `table_info('one_tbl')`) or pragmas which return the updated value
+    /// (e.g. `journal_mode`).
+    pub fn pragma<F>(
+        &self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+        pragma_value: &dyn ToSql,
+        mut f: F,
+    ) -> Result<()>
+    where
+        F: FnMut(&Row<'_, '_>) -> Result<()>,
+    {
+        let mut sql = Sql::new();
+        sql.push_pragma(schema_name, pragma_name)?;
+        // The argument is may be either in parentheses
+        // or it may be separated from the pragma name by an equal sign.
+        // The two syntaxes yield identical results.
+        sql.open_brace();
+        sql.push_value(pragma_value)?;
+        sql.close_brace();
+        let mut stmt = self.prepare(&sql)?;
+        let mut rows = stmt.query(NO_PARAMS)?;
+        while let Some(result_row) = rows.next() {
+            let row = result_row?;
+            f(&row)?;
+        }
+        Ok(())
+    }
+
+    /// Set a new value to `pragma_name`.
+    ///
+    /// Some pragmas will return the updated value which cannot be retrieved
+    /// with this method.
+    pub fn pragma_update(
+        &self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+        pragma_value: &dyn ToSql,
+    ) -> Result<()> {
+        let mut sql = Sql::new();
+        sql.push_pragma(schema_name, pragma_name)?;
+        // The argument is may be either in parentheses
+        // or it may be separated from the pragma name by an equal sign.
+        // The two syntaxes yield identical results.
+        sql.push_equal_sign();
+        sql.push_value(pragma_value)?;
+        self.execute_batch(&sql)
+    }
+
+    /// Set a new value to `pragma_name` and return the updated value.
+    ///
+    /// Only few pragmas automatically return the updated value.
+    pub fn pragma_update_and_check<F, T>(
+        &self,
+        schema_name: Option<DatabaseName<'_>>,
+        pragma_name: &str,
+        pragma_value: &dyn ToSql,
+        f: F,
+    ) -> Result<T>
+    where
+        F: FnOnce(Row<'_, '_>) -> Result<T>,
+    {
+        let mut sql = Sql::new();
+        sql.push_pragma(schema_name, pragma_name)?;
+        // The argument is may be either in parentheses
+        // or it may be separated from the pragma name by an equal sign.
+        // The two syntaxes yield identical results.
+        sql.push_equal_sign();
+        sql.push_value(pragma_value)?;
+        let mut stmt = self.prepare(&sql)?;
+        let mut rows = stmt.query(NO_PARAMS)?;
+        if let Some(result_row) = rows.next() {
+            let row = result_row?;
+            f(row)
+        } else {
+            Err(Error::QueryReturnedNoRows)
+        }
+    }
+}
+
+fn is_identifier(s: &str) -> bool {
+    let chars = s.char_indices();
+    for (i, ch) in chars {
+        if i == 0 {
+            if !is_identifier_start(ch) {
+                return false;
+            }
+        } else if !is_identifier_continue(ch) {
+            return false;
+        }
+    }
+    true
+}
+
+fn is_identifier_start(c: char) -> bool {
+    (c >= 'A' && c <= 'Z') || c == '_' || (c >= 'a' && c <= 'z') || c > '\x7F'
+}
+
+fn is_identifier_continue(c: char) -> bool {
+    c == '$'
+        || (c >= '0' && c <= '9')
+        || (c >= 'A' && c <= 'Z')
+        || c == '_'
+        || (c >= 'a' && c <= 'z')
+        || c > '\x7F'
+}
+
+#[cfg(test)]
+mod test {
+    use super::Sql;
+    use crate::pragma;
+    use crate::{Connection, DatabaseName};
+
+    #[test]
+    fn pragma_query_value() {
+        let db = Connection::open_in_memory().unwrap();
+        let user_version: i32 = db
+            .pragma_query_value(None, "user_version", |row| row.get_checked(0))
+            .unwrap();
+        assert_eq!(0, user_version);
+    }
+
+    #[test]
+    fn pragma_query_no_schema() {
+        let db = Connection::open_in_memory().unwrap();
+        let mut user_version = -1;
+        db.pragma_query(None, "user_version", |row| {
+            user_version = row.get_checked(0)?;
+            Ok(())
+        })
+        .unwrap();
+        assert_eq!(0, user_version);
+    }
+
+    #[test]
+    fn pragma_query_with_schema() {
+        let db = Connection::open_in_memory().unwrap();
+        let mut user_version = -1;
+        db.pragma_query(Some(DatabaseName::Main), "user_version", |row| {
+            user_version = row.get_checked(0)?;
+            Ok(())
+        })
+        .unwrap();
+        assert_eq!(0, user_version);
+    }
+
+    #[test]
+    fn pragma() {
+        let db = Connection::open_in_memory().unwrap();
+        let mut columns = Vec::new();
+        db.pragma(None, "table_info", &"sqlite_master", |row| {
+            let column: String = row.get_checked(1)?;
+            columns.push(column);
+            Ok(())
+        })
+        .unwrap();
+        assert_eq!(5, columns.len());
+    }
+
+    #[test]
+    fn pragma_update() {
+        let db = Connection::open_in_memory().unwrap();
+        db.pragma_update(None, "user_version", &1).unwrap();
+    }
+
+    #[test]
+    fn pragma_update_and_check() {
+        let db = Connection::open_in_memory().unwrap();
+        let journal_mode: String = db
+            .pragma_update_and_check(None, "journal_mode", &"OFF", |row| row.get_checked(0))
+            .unwrap();
+        assert_eq!("off", &journal_mode);
+    }
+
+    #[test]
+    fn is_identifier() {
+        assert!(pragma::is_identifier("full"));
+        assert!(pragma::is_identifier("r2d2"));
+        assert!(!pragma::is_identifier("sp ce"));
+        assert!(!pragma::is_identifier("semi;colon"));
+    }
+
+    #[test]
+    fn double_quote() {
+        let mut sql = Sql::new();
+        sql.push_schema_name(DatabaseName::Attached(r#"schema";--"#));
+        assert_eq!(r#""schema"";--""#, sql.as_str());
+    }
+
+    #[test]
+    fn wrap_and_escape() {
+        let mut sql = Sql::new();
+        sql.push_string_literal("value'; --");
+        assert_eq!("'value''; --'", sql.as_str());
+    }
+}