rusqlite/src/vtab/csvtab.rs

//! CSV Virtual Table
//! Port of [csv](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/csv.c) C extension.
extern crate csv;
use std::fs::File;
use std::os::raw::{c_char, c_int, c_void};
use std::path::Path;
use std::result;
use std::str;

use {Connection, Error, Result};
use ffi;
use types::Null;
use vtab::{declare_vtab, dequote, escape_double_quote, parse_boolean, Context, IndexInfo, Values, VTab, VTabCursor};

/// Register the "csv" module.
/// ```sql
/// CREATE VIRTUAL TABLE vtab USING csv(
///   filename=FILENAME -- Name of file containing CSV content
///   [, schema=SCHEMA] -- Alternative CSV schema. 'CREATE TABLE x(col1 TEXT NOT NULL, col2 INT, ...);'
///   [, header=YES|NO] -- First row of CSV defines the names of columns if "yes". Default "no".
///   [, columns=N] -- Assume the CSV file contains N columns.
///   [, delimiter=C] -- CSV delimiter. Default ','.
///   [, quote=C] -- CSV quote. Default '"'. 0 means no quote.
/// );
/// ```
pub fn load_module(conn: &Connection) -> Result<()> {
    let aux: Option<()> = None;
    conn.create_module("csv", &CSV_MODULE, aux)
}

init_module!(CSV_MODULE,
             CSVTab,
             CSVTabCursor,
             csv_create,
             csv_connect,
             csv_best_index,
             csv_disconnect,
             csv_disconnect,
             csv_open,
             csv_close,
             csv_filter,
             csv_next,
             csv_eof,
             csv_column,
             csv_rowid);

/// An instance of the CSV virtual table
#[repr(C)]
struct CSVTab {
    /// Base class. Must be first
    base: ffi::sqlite3_vtab,
    /// Name of the CSV file
    filename: String,
    has_headers: bool,
    delimiter: u8,
    quote: u8,
    /// Offset to start of data
    offset_first_row: u64,
}

impl CSVTab {
    fn reader(&self) -> result::Result<csv::Reader<File>, csv::Error> {
        csv::Reader::from_file(&self.filename).map(|reader| {
            reader.has_headers(self.has_headers)
                .delimiter(self.delimiter)
                .quote(self.quote)
        })
    }

    fn parameter(c_slice: &[u8]) -> Result<(&str, &str)> {
        let arg = try!(str::from_utf8(c_slice)).trim();
        let mut split = arg.split('=');
        if let Some(key) = split.next() {
            if let Some(value) = split.next() {
                let param = key.trim();
                let value = dequote(value);
                return Ok((param, value));
            }
        }
        Err(Error::ModuleError(format!("illegal argument: '{}'", arg)))
    }

    fn parse_byte(arg: &str) -> Option<u8> {
        if arg.len() == 1 {
            arg.bytes().next()
        } else {
            None
        }
    }
}

impl VTab for CSVTab {
    type Cursor = CSVTabCursor;

    unsafe fn connect(db: *mut ffi::sqlite3, _aux: *mut c_void, args: &[&[u8]]) -> Result<CSVTab> {
        if args.len() < 4 {
            return Err(Error::ModuleError("no CSV file specified".to_owned()));
        }

        let mut vtab = CSVTab {
            base: Default::default(),
            filename: "".to_owned(),
            has_headers: false,
            delimiter: b',',
            quote: b'"',
            offset_first_row: 0,
        };
        let mut schema = None;
        let mut n_col = None;

        let args = &args[3..];
        for c_slice in args {
            let (param, value) = try!(CSVTab::parameter(c_slice));
            match param {
                "filename" => {
                    if !Path::new(value).exists() {
                        return Err(Error::ModuleError(format!("file '{}' does not exist", value)));
                    }
                    vtab.filename = value.to_owned();
                },
                "schema" => {
                    schema = Some(value.to_owned());
                },
                "columns" => {
                    if let Ok(n) = value.parse::<u16>() {
                        if n_col.is_some() {
                            return Err(Error::ModuleError("more than one 'columns' parameter".to_owned()));
                        } else if n == 0 {
                            return Err(Error::ModuleError("must have at least one column".to_owned()));
                        }
                        n_col = Some(n);
                    } else {
                        return Err(Error::ModuleError(format!("unrecognized argument to 'columns': {}", value)));
                    }
                },
                "header" => {
                    if let Some(b) = parse_boolean(value) {
                        vtab.has_headers = b;
                    } else {
                        return Err(Error::ModuleError(format!("unrecognized argument to 'header': {}", value)));
                    }
                },
                "delimiter" => {
                    if let Some(b) = CSVTab::parse_byte(value) {
                        vtab.delimiter = b;
                    } else {
                        return Err(Error::ModuleError(format!("unrecognized argument to 'delimiter': {}", value)));
                    }
                },
                "quote" => {
                    if let Some(b) = CSVTab::parse_byte(value) {
                        if b == b'0' {
                            vtab.quote = 0;
                        } else {
                            vtab.quote = b;
                        }
                    } else {
                        return Err(Error::ModuleError(format!("unrecognized argument to 'quote': {}", value)));
                    }
                },
                _ => {
                    return Err(Error::ModuleError(format!("unrecognized parameter '{}'", param)));
                },
            }
        }

        if vtab.filename.is_empty() {
            return Err(Error::ModuleError("no CSV file specified".to_owned()));
        }

        let mut cols: Vec<String> = Vec::new();
        if vtab.has_headers || (n_col.is_none() && schema.is_none()) {
            let mut reader = try!(vtab.reader());
            if vtab.has_headers {
                let headers = try!(reader.headers());
                vtab.offset_first_row = reader.byte_offset();
                // headers ignored if cols is not empty
                if n_col.is_none() && schema.is_none() {
                    cols = headers.into_iter().map(|header| escape_double_quote(&header).into_owned()).collect();
                }
            } else {
                let mut count = 0;
                while let Some(col) = reader.next_bytes().into_iter_result() {
                    try!(col);
                    cols.push(format!("c{}", count));
                    count+=1;
                }
            }
        }

        if cols.is_empty() && schema.is_none() {
            return Err(Error::ModuleError("no column specified".to_owned()));
        }

        if schema.is_none() {
            let mut sql = String::from("CREATE TABLE x(");
            for (i, col) in cols.iter().enumerate() {
                sql.push('"');
                sql.push_str(col);
                sql.push_str("\" TEXT");
                if i == cols.len() - 1 {
                    sql.push_str(");");
                } else {
                    sql.push_str(", ");
                }
            }
            schema = Some(sql);
        }

        try!(declare_vtab(db, &schema.unwrap()));
        Ok(vtab)
    }

    // Only a forward full table scan is supported.
    fn best_index(&self, info: &mut IndexInfo) -> Result<()> {
        info.set_estimated_cost(1000000.);
        Ok(())
    }

    fn open(&self) -> Result<CSVTabCursor> {
        Ok(CSVTabCursor::new(try!(self.reader())))
    }
}

/// A cursor for the CSV virtual table
#[repr(C)]
struct CSVTabCursor {
    /// Base class. Must be first
    base: ffi::sqlite3_vtab_cursor,
    /// The CSV reader object
    reader: csv::Reader<File>,
    /// Current cursor position used as rowid
    row_number: usize,
    /// Values of the current row
    cols: Vec<String>,
    eof: bool,
}

impl CSVTabCursor {
    fn new(reader: csv::Reader<File>) -> CSVTabCursor {
        CSVTabCursor {
            base: Default::default(),
            reader,
            row_number: 0,
            cols: Vec::new(),
            eof: false,
        }
    }
}

impl VTabCursor for CSVTabCursor {
    type Table = CSVTab;

    fn vtab(&self) -> &CSVTab {
        unsafe { & *(self.base.pVtab as *const CSVTab) }
    }

    // Only a full table scan is supported.  So `filter` simply rewinds to
    // the beginning.
    fn filter(&mut self,
              _idx_num: c_int,
              _idx_str: Option<&str>,
              _args: &Values)
              -> Result<()> {
        {
            let offset_first_row = self.vtab().offset_first_row;
            try!(self.reader.seek(offset_first_row));
        }
        self.row_number = 0;
        self.next()
    }
    fn next(&mut self) -> Result<()> {
        {
            self.eof = self.reader.done();
            if self.eof {
                return Ok(());
            }

            self.cols.clear();
            while let Some(col) = self.reader.next_str().into_iter_result() {
                self.cols.push(String::from(try!(col)));
            }
        }

        self.row_number += 1;
        Ok(())
    }
    fn eof(&self) -> bool {
        self.eof
    }
    fn column(&self, ctx: &mut Context, col: c_int) -> Result<()> {
        if col < 0 || col as usize >= self.cols.len() {
            return Err(Error::ModuleError(format!("column index out of bounds: {}", col)));
        }
        if self.cols.is_empty() {
            ctx.set_result(&Null);
            return Ok(());
        }
        // TODO Affinity
        ctx.set_result(&self.cols[col as usize]);
        Ok(())
    }
    fn rowid(&self) -> Result<i64> {
        Ok(self.row_number as i64)
    }
}

impl From<csv::Error> for Error {
    fn from(err: csv::Error) -> Error {
        use std::error::Error as StdError;
        Error::ModuleError(String::from(err.description()))
    }
}

#[cfg(test)]
mod test {
    use {Connection, Result};
    use vtab::csvtab;

    #[test]
    fn test_csv_module() {
        let db = Connection::open_in_memory().unwrap();
        csvtab::load_module(&db).unwrap();
        db.execute_batch("CREATE VIRTUAL TABLE vtab USING csv(filename='test.csv', header=yes)").unwrap();

        {
            let mut s = db.prepare("SELECT rowid, * FROM vtab").unwrap();
            {
                let headers = s.column_names();
                assert_eq!(vec!["rowid", "colA", "colB", "colC"], headers);
            }

            let ids: Result<Vec<i32>> =
                s.query_map(&[], |row| row.get::<i32, i32>(0)).unwrap().collect();
            let sum = ids.unwrap().iter().fold(0, |acc, &id| acc + id);
            assert_eq!(sum, 15);
        }
        db.execute_batch("DROP TABLE vtab").unwrap();
    }

    #[test]
    fn test_csv_cursor() {
        let db = Connection::open_in_memory().unwrap();
        csvtab::load_module(&db).unwrap();
        db.execute_batch("CREATE VIRTUAL TABLE vtab USING csv(filename='test.csv', header=yes)").unwrap();

        {
            let mut s =
                db.prepare("SELECT v1.rowid, v1.* FROM vtab v1 NATURAL JOIN vtab v2 WHERE \
                              v1.rowid < v2.rowid")
                    .unwrap();

            let mut rows = s.query(&[]).unwrap();
            let row = rows.next().unwrap().unwrap();
            assert_eq!(row.get::<i32, i32>(0), 2);
        }
        db.execute_batch("DROP TABLE vtab").unwrap();
    }
}