rusqlite/src/vtab/series.rs

//! generate_series virtual table.
//! Port of C [generate_series "function"](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/series.c).
use std::default::Default;
use libc;

use {Connection, Error, Result};
use ffi;
use vtab::{self, declare_vtab, Context, IndexInfo, Values, VTab, VTabCursor};

/// Register the "generate_series" module.
pub fn load_module(conn: &Connection) -> Result<()> {
    let aux: Option<()> = None;
    conn.create_module("generate_series", &SERIES_MODULE, aux)
}


init_module!(SERIES_MODULE,
             SeriesTab,
             SeriesTabCursor,
             None,
             series_connect,
             series_best_index,
             series_disconnect,
             None,
             series_open,
             series_close,
             series_filter,
             series_next,
             series_eof,
             series_column,
             series_rowid);

// Column numbers
// const SERIES_COLUMN_VALUE : libc::c_int = 0;
const SERIES_COLUMN_START: libc::c_int = 1;
const SERIES_COLUMN_STOP: libc::c_int = 2;
const SERIES_COLUMN_STEP: libc::c_int = 3;

bitflags! {
    #[repr(C)]
    flags QueryPlanFlags: ::libc::c_int {
        // start = $value  -- constraint exists
        const START = 1,
        // stop = $value   -- constraint exists
        const STOP  = 2,
        // step = $value   -- constraint exists
        const STEP  = 4,
        // output in descending order
        const DESC  = 8,
        // Both start and stop
        const BOTH  = START.bits | STOP.bits,
    }
}


/// An instance of the Series virtual table
#[repr(C)]
struct SeriesTab {
    /// Base class. Must be first
    base: ffi::sqlite3_vtab,
}


impl VTab<SeriesTabCursor> for SeriesTab {
    fn connect(db: *mut ffi::sqlite3,
               _aux: *mut libc::c_void,
               _args: &[&[u8]])
               -> Result<SeriesTab> {
        let vtab = SeriesTab { base: Default::default() };
        try!(declare_vtab(db,
                          "CREATE TABLE x(value,start hidden,stop hidden,step hidden)"));
        Ok(vtab)
    }

    fn best_index(&self, info: &mut IndexInfo) -> Result<()> {
        // The query plan bitmask
        let mut idx_num: QueryPlanFlags = QueryPlanFlags::empty();
        // Index of the start= constraint
        let mut start_idx = None;
        // Index of the stop= constraint
        let mut stop_idx = None;
        // Index of the step= constraint
        let mut step_idx = None;
        for i in 0..info.num_of_constraint() {
            if !info.is_constraint_usable(i) {
                continue;
            }
            if info.constraint_operator(i) != vtab::SQLITE_INDEX_CONSTRAINT_EQ {
                continue;
            }
            match info.constraint_column(i) {
                SERIES_COLUMN_START => {
                    start_idx = Some(i);
                    idx_num |= START;
                }
                SERIES_COLUMN_STOP => {
                    stop_idx = Some(i);
                    idx_num |= STOP;
                }
                SERIES_COLUMN_STEP => {
                    step_idx = Some(i);
                    idx_num |= STEP;
                }
                _ => {}
            };
        }

        let mut num_of_arg = 0;
        if let Some(start_idx) = start_idx {
            num_of_arg += 1;
            info.set_argv_index(start_idx, num_of_arg);
            info.set_omit(start_idx, true);
        }
        if let Some(stop_idx) = stop_idx {
            num_of_arg += 1;
            info.set_argv_index(stop_idx, num_of_arg);
            info.set_omit(stop_idx, true);
        }
        if let Some(step_idx) = step_idx {
            num_of_arg += 1;
            info.set_argv_index(step_idx, num_of_arg);
            info.set_omit(step_idx, true);
        }
        if idx_num.contains(BOTH) {
            // Both start= and stop= boundaries are available.
            info.set_estimated_cost((2 - if idx_num.contains(STEP) { 1 } else { 0 }) as f64);
            info.set_estimated_rows(1000);
            if info.num_of_order_by() == 1 {
                if info.is_order_by_desc(0) {
                    idx_num |= DESC;
                }
                info.set_order_by_consumed(true);
            }
        } else {
            info.set_estimated_cost(2147483647f64);
            info.set_estimated_rows(2147483647);
        }
        info.set_idx_num(idx_num.bits());
        Ok(())
    }

    fn open(&self) -> Result<SeriesTabCursor> {
        Ok(SeriesTabCursor::new())
    }
}

/// A cursor for the Series virtual table
#[derive(Default)]
#[repr(C)]
struct SeriesTabCursor {
    /// Base class. Must be first
    base: ffi::sqlite3_vtab_cursor,
    /// True to count down rather than up
    is_desc: bool,
    /// The rowid
    row_id: i64,
    /// Current value ("value")
    value: i64,
    /// Mimimum value ("start")
    min_value: i64,
    /// Maximum value ("stop")
    max_value: i64,
    /// Increment ("step")
    step: i64,
}

impl SeriesTabCursor {
    fn new() -> SeriesTabCursor {
        Default::default()
    }
}
impl VTabCursor<SeriesTab> for SeriesTabCursor {
    fn vtab(&self) -> &mut SeriesTab {
        unsafe { &mut *(self.base.pVtab as *mut SeriesTab) }
    }
    fn filter(&mut self,
              idx_num: libc::c_int,
              _idx_str: Option<&str>,
              args: &Values)
              -> Result<()> {
        let idx_num = QueryPlanFlags::from_bits_truncate(idx_num);
        let mut i = 0;
        if idx_num.contains(START) {
            self.min_value = try!(args.get(i));
            i += 1;
        } else {
            self.min_value = 0;
        }
        if idx_num.contains(STOP) {
            self.max_value = try!(args.get(i));
            i += 1;
        } else {
            self.max_value = 0xffffffff;
        }
        if idx_num.contains(STEP) {
            self.step = try!(args.get(i));
            if self.step < 1 {
                self.step = 1;
            }
        } else {
            self.step = 1;
        };
        self.is_desc = idx_num.contains(DESC);
        if self.is_desc {
            self.value = self.max_value;
            if self.step > 1 {
                self.value -= (self.max_value - self.min_value) % self.step;
            }
        } else {
            self.value = self.min_value;
        }
        self.row_id = 0;
        Ok(())
    }
    fn next(&mut self) -> Result<()> {
        if self.is_desc {
            self.value -= self.step;
        } else {
            self.value += self.step;
        }
        self.row_id += 1;
        Ok(())
    }
    fn eof(&self) -> bool {
        if self.is_desc {
            self.value < self.min_value
        } else {
            self.value > self.max_value
        }
    }
    fn column(&self, ctx: &mut Context, i: libc::c_int) -> Result<()> {
        let x = match i {
            SERIES_COLUMN_START => self.min_value,
            SERIES_COLUMN_STOP => self.max_value,
            SERIES_COLUMN_STEP => self.step,
            _ => self.value,
        };
        ctx.set_result(&x);
        Ok(())
    }
    fn rowid(&self) -> Result<i64> {
        Ok(self.row_id)
    }
}