diff options
Diffstat (limited to 'tvix/eval/src/builtins/mod.rs')
-rw-r--r-- | tvix/eval/src/builtins/mod.rs | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs index aeffca49950d..4bcaaf7a00e5 100644 --- a/tvix/eval/src/builtins/mod.rs +++ b/tvix/eval/src/builtins/mod.rs @@ -4,6 +4,7 @@ //! available builtins in Nix. use std::{ + cmp, collections::{BTreeMap, HashMap}, path::PathBuf, rc::Rc, @@ -192,6 +193,34 @@ fn pure_builtins() -> Vec<Builtin> { let a = args.pop().unwrap(); arithmetic_op!(a, b, -) }), + Builtin::new("substring", 3, |args, vm| { + let beg = args[0].force(vm)?.as_int()?; + let len = args[1].force(vm)?.as_int()?; + let x = args[2].force(vm)?.to_str()?; + + if beg < 0 { + return Err(ErrorKind::IndexOutOfBounds { index: beg }); + } + let beg = beg as usize; + + // Nix doesn't assert that the length argument is + // non-negative when the starting index is GTE the + // string's length. + if beg >= x.as_str().len() { + return Ok(Value::String("".into())); + } + + if len < 0 { + return Err(ErrorKind::NegativeLength { length: len }); + } + + let len = len as usize; + let end = cmp::min(beg + len, x.as_str().len()); + + Ok(Value::String( + x.as_str()[(beg as usize)..(end as usize)].into(), + )) + }), Builtin::new("throw", 1, |mut args, _| { return Err(ErrorKind::Throw( args.pop().unwrap().to_str()?.as_str().to_owned(), |