xsv: add transpose command

src/cmd/mod.rs

@@ -18,3 +18,4 @@ pub mod sort;
 pub mod split;
 pub mod stats;
 pub mod table;
+pub mod transpose;

src/cmd/transpose.rs

@@ -0,0 +1,98 @@
+use config::{Config, Delimiter};
+use csv::ByteRecord;
+use std::str;
+use util;
+use CliResult;
+
+static USAGE: &'static str = "
+Transpose the rows/columns of CSV data.
+
+Note that by default this reads all of the CSV data into memory,
+unless --multipass is given.
+
+Usage:
+    xsv transpose [options] [<input>]
+
+transpose options:
+    -m, --multipass        Process the transpose by making multiple
+                           passes over the dataset. Useful for really
+                           big datasets. Consumes memory relative to
+                           the number of rows.
+                           Note that in general it is faster to
+                           process the transpose in memory.
+
+Common options:
+    -h, --help             Display this message
+    -o, --output <file>    Write output to <file> instead of stdout.
+    -d, --delimiter <arg>  The field delimiter for reading CSV data.
+                           Must be a single character. (default: ,)
+";
+
+#[derive(Deserialize)]
+struct Args {
+    arg_input: Option<String>,
+    flag_output: Option<String>,
+    flag_delimiter: Option<Delimiter>,
+    flag_multipass: bool,
+}
+
+pub fn run(argv: &[&str]) -> CliResult<()> {
+    let args: Args = util::get_args(USAGE, argv)?;
+
+    let input_is_stdin = match args.arg_input {
+        Some(ref s) if s == "-" => true,
+        None => true,
+        _ => false,
+    };
+
+  if args.flag_multipass && !input_is_stdin {
+        args.multipass_transpose()
+    } else {
+        args.in_memory_transpose()
+    }
+}
+
+impl Args {
+    fn in_memory_transpose(&self) -> CliResult<()> {
+        let mut rdr = self.rconfig().reader()?;
+        let mut wtr = self.wconfig().writer()?;
+        let nrows = rdr.byte_headers()?.len();
+
+        let all = rdr.byte_records().collect::<Result<Vec<_>, _>>()?;
+        for i in 0..nrows {
+            let mut record = ByteRecord::new();
+
+            for row in all.iter() {
+                record.push_field(&row[i]);
+            }
+            wtr.write_byte_record(&record)?;
+        }
+        Ok(wtr.flush()?)
+    }
+
+    fn multipass_transpose(&self) -> CliResult<()> {
+        let mut wtr = self.wconfig().writer()?;
+        let nrows = self.rconfig().reader()?.byte_headers()?.len();
+
+        for i in 0..nrows {
+            let mut rdr = self.rconfig().reader()?;
+
+            let mut record = ByteRecord::new();
+            for row in rdr.byte_records() {
+                record.push_field(&row?[i]);
+            }
+            wtr.write_byte_record(&record)?;
+        }
+      Ok(wtr.flush()?)
+    }
+
+    fn wconfig(&self) -> Config {
+        Config::new(&self.flag_output)
+    }
+
+    fn rconfig(&self) -> Config {
+        Config::new(&self.arg_input)
+            .delimiter(self.flag_delimiter)
+            .no_headers(true)
+    }
+}

src/main.rs

@@ -64,6 +64,7 @@ macro_rules! command_list {
     split       Split CSV data into many files
     stats       Compute basic statistics
     table       Align CSV data into columns
+    transpose   Transpose rows/columns of CSV data
 "
     )
 }
@@ -160,6 +161,7 @@ enum Command {
     Split,
     Stats,
     Table,
+    Transpose,
 }
 
 impl Command {
@@ -189,6 +191,7 @@ impl Command {
             Command::Split => cmd::split::run(argv),
             Command::Stats => cmd::stats::run(argv),
             Command::Table => cmd::table::run(argv),
+            Command::Transpose => cmd::transpose::run(argv),
         }
     }
 }

tests/test_transpose.rs

@@ -0,0 +1,44 @@
+use workdir::Workdir;
+
+use {CsvData, qcheck};
+
+fn prop_transpose(name: &str, rows: CsvData, streaming: bool) -> bool {
+    let wrk = Workdir::new(name);
+    wrk.create("in.csv", rows.clone());
+
+    let mut cmd = wrk.command("transpose");
+    cmd.arg("in.csv");
+    if streaming { cmd.arg("--multipass"); }
+
+    let got: Vec<Vec<String>> = wrk.read_stdout(&mut cmd);
+
+    let mut expected = vec![];
+
+    let nrows = rows.len();
+    let ncols = if !rows.is_empty() {rows[0].len() } else {0};
+
+    for i in 0..ncols {
+        let mut expected_row = vec![];
+        for j in 0..nrows {
+            expected_row.push(rows[j][i].to_owned());
+        }
+        expected.push(expected_row);
+    }
+    rassert_eq!(got, expected)
+}
+
+#[test]
+fn prop_transpose_in_memory() {
+    fn p(rows: CsvData) -> bool {
+        prop_transpose("prop_transpose_in_memory", rows, false)
+    }
+    qcheck(p as fn(CsvData) -> bool);
+}
+
+#[test]
+fn prop_transpose_multipass() {
+    fn p(rows: CsvData) -> bool {
+        prop_transpose("prop_transpose_multipass", rows, true)
+    }
+    qcheck(p as fn(CsvData) -> bool);
+}

tests/tests.rs

@@ -51,6 +51,7 @@ mod test_sort;
 mod test_split;
 mod test_stats;
 mod test_table;
+mod test_transpose;
 
 fn qcheck<T: Testable>(p: T) {
     QuickCheck::new().gen(StdGen::new(thread_rng(), 5)).quickcheck(p);