Rust

The crate reads the same .tdc config and, for the same seed, produces the same output as the TypeScript, Python, Java and C# implementations — byte for byte, on all three engines and in Parquet.

One crate, library and command line together.

Getting it

On crates.io — version 0.1.7

cargo add tdcv2      # as a dependency
cargo install tdcv2  # as a command

The crate takes no dependencies, and the starter data packs are compiled into the binary, so an installed crate needs nothing else on disk. See Installation.

Using it

use tdcv2::Tdc;

let data = Tdc::from_file("users.tdc")?;
println!("{data}");

for row in data.rows() {
    println!("{:?}", row.get("Gender"));
}

data.write_file("users.csv")?;

Rows, not strings

A row is the reason to use the library rather than the command line. A test that asserts on row.get("Gender") says what it means; the same test parsing CSV back out of a string spends most of its lines on the parsing.

Text output and row output read the same generated values, so the two can never disagree. The row view ignores <block> and the text wrappers entirely — those describe a file format, and a row has no format.

use tdcv2::{Options, Tdc};

let data = Tdc::new(Options {
    config_file: Some("users.tdc".into()),
    count: Some(100),                 // overrides what <env> declared
    seed: Some("test".into()),        // pins the run
    ..Options::default()
})?;

let first = data.row(0).unwrap();
println!("{:?}", first.get("Address.city"));   // a compound's field
println!("{:?}", first.nested()["Address"]);   // or the whole address at once

A sequence that does not apply to a row returns None, never Some(""). A column declared parent="Gender.Male" has no value on a female row, and a blank would claim it had one that happened to be empty.

Options

config_file / config_string	Exactly one of the two
count, seed, locale	Override what <env> declared
engine	Force engine 1, 2 or 3 instead of letting the config route
now_millis	Pin the clock, so a test asserting on a date does not expire overnight
packs_dir, data_paths	Where packs and @data/… sources are found
base_dir	What a relative src= is relative to

A refused config comes back as TdcError::Refused, which carries the diagnostics and the source they point into — so a caller can render the offending line rather than only quote the message. diagnostics() on a successful run carries what the config was warned about but not refused for. seed() reports whether the seed was generated: an unseeded run is not reproducible, which is almost never what was wanted.

One value, without a config

Quick draws a single value from the same data packs a config reads — no file, no <env>, one call:

use tdcv2::quick::Quick;

let mut tdc = Quick::new();

tdc.get("person.lastName")?;      // Jones
tdc.get("usa.docs.ssn")?;         // 699209702, with its real check digits
tdc.many("person.lastName", 5)?;  // five of them
Quick::seeded("demo").locale("ru").get("person.lastName")?;  // pinned and in Russian

The address is a string here, where TypeScript, Python and C# walk it as members. The member shape needs one generated function per address, and a generated surface could only cover the packs compiled into the binary — while most packs arrive at run time, and get("ru.person.lastName") works the moment the download finishes. One value at a time is the whole surface.

No dependencies

The crate depends on nothing. Its lexer and parser are written by hand against the shared grammar; so are the PRNG, the DEFLATE decompressor, SHA-256, the Thrift and Snappy encoders behind the Parquet writer, and the PNG decoder that reads a drawing into a curve.

That is not minimalism for its own sake. Every one of those has to produce the same bytes as the other four implementations, and a crate that fixed a rounding rule or a hash in a minor release would break the guarantee this project is built on without changing a line of TDC.

The one exception is HTTPS, which needs a TLS stack nobody should hand-write. tdcv2 pack and <gen type="http"> run curl as a child process; if it is missing, the command says so and prints the install line for the platform it is on. Everything else — generating data, reading local packs, every output format — works without it.

Requirements

Rust 1.74 or newer.