oxc/crates/oxc_sourcemap/src/decode.rs

/// Port from https://github.com/getsentry/rust-sourcemap/blob/master/src/decoder.rs
/// It is a helper for decode vlq soucemap string to `SourceMap`.
use crate::error::{Error, Result};
use crate::{SourceMap, Token};

#[derive(serde::Deserialize)]
#[serde(rename_all = "camelCase")]
struct JSONSourceMap {
    file: Option<String>,
    mappings: String,
    sources: Vec<String>,
    sources_content: Option<Vec<String>>,
    names: Vec<String>,
}

pub fn decode(value: &str) -> Result<SourceMap> {
    let json: JSONSourceMap = serde_json::from_str(value)?;
    let file = json.file.map(Into::into);
    let names = json.names.into_iter().map(Into::into).collect::<Vec<_>>();
    let sources = json.sources.into_iter().map(Into::into).collect::<Vec<_>>();
    let source_contents =
        json.sources_content.map(|v| v.into_iter().map(Into::into).collect::<Vec<_>>());
    let tokens = decode_mapping(&json.mappings, names.len(), sources.len())?;
    Ok(SourceMap::new(file, names, sources, source_contents, tokens, None))
}

#[allow(clippy::cast_possible_truncation)]
fn decode_mapping(mapping: &str, names_len: usize, sources_len: usize) -> Result<Vec<Token>> {
    let mut tokens = vec![];

    let mut dst_col;
    let mut src_id = 0;
    let mut src_line = 0;
    let mut src_col = 0;
    let mut name_id = 0;
    let mut nums = Vec::with_capacity(6);

    for (dst_line, line) in mapping.split(';').enumerate() {
        if line.is_empty() {
            continue;
        }

        dst_col = 0;

        for segment in line.split(',') {
            if segment.is_empty() {
                continue;
            }

            nums.clear();
            parse_vlq_segment_into(segment, &mut nums)?;
            dst_col = (i64::from(dst_col) + nums[0]) as u32;

            let mut src = !0;
            let mut name = !0;

            if nums.len() > 1 {
                if nums.len() != 4 && nums.len() != 5 {
                    return Err(Error::BadSegmentSize(nums.len() as u32));
                }
                src_id = (i64::from(src_id) + nums[1]) as u32;
                if src_id >= sources_len as u32 {
                    return Err(Error::BadSourceReference(src_id));
                }

                src = src_id;
                src_line = (i64::from(src_line) + nums[2]) as u32;
                src_col = (i64::from(src_col) + nums[3]) as u32;

                if nums.len() > 4 {
                    name_id = (i64::from(name_id) + nums[4]) as u32;
                    if name_id >= names_len as u32 {
                        return Err(Error::BadNameReference(name_id));
                    }
                    name = name_id;
                }
            }

            tokens.push(Token::new(
                dst_line as u32,
                dst_col,
                src_line,
                src_col,
                if src == !0 { None } else { Some(src) },
                if name == !0 { None } else { Some(name) },
            ));
        }
    }

    Ok(tokens)
}

#[rustfmt::skip]
const B64: [i8; 256] = [ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 - 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, ];

fn parse_vlq_segment_into(segment: &str, rv: &mut Vec<i64>) -> Result<()> {
    let mut cur = 0;
    let mut shift = 0;

    for c in segment.bytes() {
        let enc = i64::from(B64[c as usize]);
        let val = enc & 0b11111;
        let cont = enc >> 5;
        cur += val.checked_shl(shift).ok_or(Error::VlqOverflow)?;
        shift += 5;

        if cont == 0 {
            let sign = cur & 1;
            cur >>= 1;
            if sign != 0 {
                cur = -cur;
            }
            rv.push(cur);
            cur = 0;
            shift = 0;
        }
    }

    if cur != 0 || shift != 0 {
        Err(Error::VlqLeftover)
    } else if rv.is_empty() {
        Err(Error::VlqNoValues)
    } else {
        Ok(())
    }
}

#[test]
fn test_decode_sourcemap() {
    let input = r#"{
        "version": 3,
        "sources": ["coolstuff.js"],
        "sourceRoot": "x",
        "names": ["x","alert"],
        "mappings": "AAAA,GAAIA,GAAI,EACR,IAAIA,GAAK,EAAG,CACVC,MAAM"
    }"#;
    let sm = SourceMap::from_json_string(input).unwrap();
    let mut iter = sm.get_source_view_tokens().filter(|token| token.get_name_id().is_some());
    assert_eq!(iter.next().unwrap().to_tuple(), (Some("coolstuff.js"), 0, 4, Some("x")));
    assert_eq!(iter.next().unwrap().to_tuple(), (Some("coolstuff.js"), 1, 4, Some("x")));
    assert_eq!(iter.next().unwrap().to_tuple(), (Some("coolstuff.js"), 2, 2, Some("alert")));
    assert!(iter.next().is_none());
}