rusqlite/src/row.rs

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use std::{convert, result};
use std::marker::PhantomData;
use super::{Statement, Error, Result};
use types::{FromSql, FromSqlError};
use statement::StatementCrateImpl;
/// An handle for the resulting rows of a query.
pub struct Rows<'stmt> {
stmt: Option<&'stmt Statement<'stmt>>,
}
impl<'stmt> Rows<'stmt> {
fn reset(&mut self) {
if let Some(stmt) = self.stmt.take() {
stmt.reset();
}
}
/// Attempt to get the next row from the query. Returns `Some(Ok(Row))` if there
/// is another row, `Some(Err(...))` if there was an error getting the next
/// row, and `None` if all rows have been retrieved.
///
/// ## Note
///
/// This interface is not compatible with Rust's `Iterator` trait, because the
/// lifetime of the returned row is tied to the lifetime of `self`. This is a
/// "streaming iterator". For a more natural interface, consider using `query_map`
/// or `query_and_then` instead, which return types that implement `Iterator`.
pub fn next<'a>(&'a mut self) -> Option<Result<Row<'a, 'stmt>>> {
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self.stmt
.and_then(|stmt| match stmt.step() {
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Ok(true) => {
Some(Ok(Row {
stmt: stmt,
phantom: PhantomData,
}))
}
Ok(false) => {
self.reset();
None
}
Err(err) => {
self.reset();
Some(Err(err))
}
})
}
}
// TODO: This trait lets us have "pub(crate)" visibility on some methods. Remove this
// once pub(crate) is stable.
pub trait RowsCrateImpl<'stmt> {
fn new(stmt: &'stmt Statement<'stmt>) -> Rows<'stmt>;
fn get_expected_row<'a>(&'a mut self) -> Result<Row<'a, 'stmt>>;
}
impl<'stmt> RowsCrateImpl<'stmt> for Rows<'stmt> {
fn new(stmt: &'stmt Statement<'stmt>) -> Rows<'stmt> {
Rows { stmt: Some(stmt) }
}
fn get_expected_row<'a>(&'a mut self) -> Result<Row<'a, 'stmt>> {
match self.next() {
Some(row) => row,
None => Err(Error::QueryReturnedNoRows),
}
}
}
impl<'stmt> Drop for Rows<'stmt> {
fn drop(&mut self) {
self.reset();
}
}
/// An iterator over the mapped resulting rows of a query.
pub struct MappedRows<'stmt, F> {
rows: Rows<'stmt>,
map: F,
}
// TODO: This trait lets us have "pub(crate)" visibility on some methods. Remove this
// once pub(crate) is stable.
pub trait MappedRowsCrateImpl<'stmt, T, F> {
fn new(rows: Rows<'stmt>, f: F) -> MappedRows<'stmt, F>;
}
impl<'stmt, T, F> MappedRowsCrateImpl<'stmt, T, F> for MappedRows<'stmt, F>
where F: FnMut(&Row) -> T
{
fn new(rows: Rows<'stmt>, f: F) -> MappedRows<'stmt, F> {
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MappedRows { rows: rows, map: f }
}
}
impl<'conn, T, F> Iterator for MappedRows<'conn, F>
where F: FnMut(&Row) -> T
{
type Item = Result<T>;
fn next(&mut self) -> Option<Result<T>> {
let map = &mut self.map;
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self.rows
.next()
.map(|row_result| row_result.map(|row| (map)(&row)))
}
}
/// An iterator over the mapped resulting rows of a query, with an Error type
/// unifying with Error.
pub struct AndThenRows<'stmt, F> {
rows: Rows<'stmt>,
map: F,
}
// TODO: This trait lets us have "pub(crate)" visibility on some methods. Remove this
// once pub(crate) is stable.
pub trait AndThenRowsCrateImpl<'stmt, T, E, F> {
fn new(rows: Rows<'stmt>, f: F) -> AndThenRows<'stmt, F>;
}
impl<'stmt, T, E, F> AndThenRowsCrateImpl<'stmt, T, E, F> for AndThenRows<'stmt, F>
where F: FnMut(&Row) -> result::Result<T, E>
{
fn new(rows: Rows<'stmt>, f: F) -> AndThenRows<'stmt, F> {
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AndThenRows { rows: rows, map: f }
}
}
impl<'stmt, T, E, F> Iterator for AndThenRows<'stmt, F>
where E: convert::From<Error>,
F: FnMut(&Row) -> result::Result<T, E>
{
type Item = result::Result<T, E>;
fn next(&mut self) -> Option<Self::Item> {
let map = &mut self.map;
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self.rows
.next()
.map(|row_result| row_result.map_err(E::from).and_then(|row| (map)(&row)))
}
}
/// A single result row of a query.
pub struct Row<'a, 'stmt> {
stmt: &'stmt Statement<'stmt>,
phantom: PhantomData<&'a ()>,
}
impl<'a, 'stmt> Row<'a, 'stmt> {
/// Get the value of a particular column of the result row.
///
/// ## Failure
///
/// Panics if calling `row.get_checked(idx)` would return an error, including:
///
/// * If the underlying SQLite column type is not a valid type as a source for `T`
/// * If the underlying SQLite integral value is outside the range representable by `T`
/// * If `idx` is outside the range of columns in the returned query
pub fn get<I: RowIndex, T: FromSql>(&self, idx: I) -> T {
self.get_checked(idx).unwrap()
}
/// Get the value of a particular column of the result row.
///
/// ## Failure
///
/// Returns an `Error::InvalidColumnType` if the underlying SQLite column
/// type is not a valid type as a source for `T`.
///
/// Returns an `Error::InvalidColumnIndex` if `idx` is outside the valid column range
/// for this row.
///
/// Returns an `Error::InvalidColumnName` if `idx` is not a valid column name
/// for this row.
pub fn get_checked<I: RowIndex, T: FromSql>(&self, idx: I) -> Result<T> {
let idx = try!(idx.idx(self.stmt));
let value = self.stmt.value_ref(idx);
FromSql::column_result(value).map_err(|err| match err {
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FromSqlError::InvalidType => {
Error::InvalidColumnType(idx,
value.data_type())
}
FromSqlError::OutOfRange(i) => {
Error::IntegralValueOutOfRange(idx, i)
}
FromSqlError::Other(err) => {
Error::FromSqlConversionFailure(idx as usize, value.data_type(), err)
}
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})
}
/// Return the number of columns in the current row.
pub fn column_count(&self) -> i32 {
self.stmt.column_count()
}
}
/// A trait implemented by types that can index into columns of a row.
pub trait RowIndex {
/// Returns the index of the appropriate column, or `None` if no such
/// column exists.
fn idx(&self, stmt: &Statement) -> Result<i32>;
}
impl RowIndex for i32 {
#[inline]
fn idx(&self, stmt: &Statement) -> Result<i32> {
if *self < 0 || *self >= stmt.column_count() {
Err(Error::InvalidColumnIndex(*self))
} else {
Ok(*self)
}
}
}
impl<'a> RowIndex for &'a str {
#[inline]
fn idx(&self, stmt: &Statement) -> Result<i32> {
stmt.column_index(*self)
}
}