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pub const POINTER_MAX_BYTES: u64 = 1024;
const SPEC_URLS: [&str; 2] = [ "https://git-lfs.github.com/spec/v1", "https://hawser.github.com/spec/v1",];
#[derive(Debug, Clone, PartialEq, Eq)]pub struct LfsPointer { pub oid: LfsOid, pub size: ClaimedSize,}
pub fn parse_pointer(blob: &[u8]) -> Option<LfsPointer> { if blob.len() as u64 > POINTER_MAX_BYTES { return None; } let text = std::str::from_utf8(blob).ok()?; let mut lines = text.lines(); let spec = lines.next()?.strip_prefix("version ")?; SPEC_URLS.contains(&spec).then_some(())?; let fields: Vec<(&str, &str)> = lines.filter_map(|line| line.split_once(' ')).collect(); let value_of = |key: &str| { fields .iter() .find_map(|(name, value)| (*name == key).then_some(*value)) }; let oid = LfsOid::new(value_of("oid")?.strip_prefix("sha256:")?).ok()?; let size = ClaimedSize::new(value_of("size")?.parse().ok()?); Some(LfsPointer { oid, size })}
#[cfg(test)]mod tests { use super::*;
const OID: &str = "6c17f2007cbe934aee6e309b28b2fba3c119d98be6ea4156da3aa3173456ad16";
fn pointer_text() -> String { format!("version https://git-lfs.github.com/spec/v1\noid sha256:{OID}\nsize 12345\n") }
#[test] fn valid_variants_beyond_the_canonical_form_still_parse() { let hawser = pointer_text().replace("git-lfs.github.com", "hawser.github.com"); assert!( parse_pointer(hawser.as_bytes()).is_some(), "the legacy hawser spec still counts" ); let extra = format!( "version https://git-lfs.github.com/spec/v1\nname media/clip.mp4\noid sha256:{OID}\nsize 7\n" ); assert!( parse_pointer(extra.as_bytes()).is_some(), "extra sorted keys are tolerated" ); }
#[test] fn non_pointers_are_rejected() { let cases: Vec<Vec<u8>> = vec![ b"".to_vec(), b"plain source file\n".to_vec(), format!("oid sha256:{OID}\nsize 7\n").into_bytes(), format!("version https://oyster.cafe/spec/v1\noid sha256:{OID}\nsize 7\n").into_bytes(), pointer_text().replace("sha256:", "sha512:").into_bytes(), pointer_text() .replace("size 12345", "size lots") .into_bytes(), format!("version https://git-lfs.github.com/spec/v1\noid sha256:{OID}\n").into_bytes(), b"version https://git-lfs.github.com/spec/v1\nsize 7\n".to_vec(), [pointer_text().into_bytes(), vec![0xff, 0xfe]].concat(), [ pointer_text().into_bytes(), vec![b' '; POINTER_MAX_BYTES as usize], ] .concat(), ]; cases.iter().enumerate().for_each(|(index, blob)| { assert!( parse_pointer(blob).is_none(), "case {index} parsed as a pointer" ); }); }}