[klippa] custom serializer step 1: add struct definition

Also added a few APIs like push/embed/copy_bytes

klippa/src/lib.rs

@@ -14,6 +14,7 @@ mod name;
 mod os2;
 mod parsing_util;
 mod post;
+mod serialize;
 mod stat;
 pub use parsing_util::{
     parse_drop_tables, parse_name_ids, parse_name_languages, parse_unicodes, populate_gids,

klippa/src/serialize.rs

@@ -0,0 +1,369 @@
+//! serializer
+//! ported from Harfbuzz Serializer: <https://github.com/harfbuzz/harfbuzz/blob/5e32b5ca8fe430132b87c0eee6a1c056d37c35eb/src/hb-serialize.hh>
+use fnv::FnvHashMap;
+use write_fonts::types::Scalar;
+
+#[derive(Clone, Copy, Debug)]
+#[allow(dead_code)]
+pub(crate) struct SerializeErrorFlags(u16);
+
+#[allow(dead_code)]
+impl SerializeErrorFlags {
+    pub const SERIALIZE_ERROR_NONE: Self = Self(0x0000);
+    pub const SERIALIZE_ERROR_OTHER: Self = Self(0x0001);
+    pub const SERIALIZE_ERROR_OFFSET_OVERFLOW: Self = Self(0x0002);
+    pub const SERIALIZE_ERROR_OUT_OF_ROOM: Self = Self(0x0004);
+    pub const SERIALIZE_ERROR_INT_OVERFLOW: Self = Self(0x0008);
+    pub const SERIALIZE_ERROR_ARRAY_OVERFLOW: Self = Self(0x0010);
+}
+
+impl Default for SerializeErrorFlags {
+    fn default() -> Self {
+        Self::SERIALIZE_ERROR_NONE
+    }
+}
+
+impl PartialEq for SerializeErrorFlags {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+
+impl std::ops::BitOr for SerializeErrorFlags {
+    type Output = Self;
+
+    /// Returns the union of the two sets of flags.
+    #[inline]
+    fn bitor(self, other: SerializeErrorFlags) -> Self {
+        Self(self.0 | other.0)
+    }
+}
+
+impl std::ops::BitOrAssign for SerializeErrorFlags {
+    /// Adds the set of flags.
+    #[inline]
+    fn bitor_assign(&mut self, other: Self) {
+        self.0 |= other.0;
+    }
+}
+
+impl std::ops::Not for SerializeErrorFlags {
+    type Output = bool;
+    #[inline]
+    fn not(self) -> bool {
+        self == SerializeErrorFlags::SERIALIZE_ERROR_NONE
+    }
+}
+
+#[allow(dead_code)]
+#[derive(Default)]
+// Offset relative to the current object head (default)/tail or
+// Absolute: from the start of the serialize buffer
+enum OffsetWhence {
+    #[default]
+    Head,
+    Tail,
+    Absolute,
+}
+
+type PoolIdx = usize;
+// Reference Harfbuzz implementation:
+// <https://github.com/harfbuzz/harfbuzz/blob/5e32b5ca8fe430132b87c0eee6a1c056d37c35eb/src/hb-serialize.hh#L69>
+#[derive(Default)]
+#[allow(dead_code)]
+struct Object {
+    // head/tail: indices of the output buffer for this object
+    head: usize,
+    tail: usize,
+    // real links are associated with actual offsets
+    real_links: Vec<Link>,
+    // virtual links not associated with actual offsets,
+    // they exist merely to enforce an ordering constraint.
+    virtual_links: Vec<Link>,
+
+    // pool index of the object that will be worked on next
+    next_obj: Option<PoolIdx>,
+}
+
+// LinkWidth:2->offset16, 3->offset24 and 4->offset32
+#[allow(dead_code)]
+#[derive(Default)]
+enum LinkWidth {
+    #[default]
+    Two,
+    Three,
+    Four,
+}
+
+type ObjIdx = u32;
+
+#[allow(dead_code)]
+#[derive(Default)]
+struct Link {
+    width: LinkWidth,
+    is_signed: bool,
+    whence: OffsetWhence,
+    bias: u32,
+    position: u32,
+    objidx: Option<ObjIdx>,
+}
+
+// reference harfbuzz implementation:
+//<https://github.com/harfbuzz/harfbuzz/blob/5e32b5ca8fe430132b87c0eee6a1c056d37c35eb/src/hb-serialize.hh#L57>
+#[derive(Default)]
+#[allow(dead_code)]
+pub(crate) struct Serializer {
+    start: usize,
+    end: usize,
+    head: usize,
+    tail: usize,
+    // TODO: zerocopy, debug_depth
+    errors: SerializeErrorFlags,
+
+    data: Vec<u8>,
+    object_pool: ObjectPool,
+    // index for current Object in the object_pool
+    current: Option<PoolIdx>,
+
+    packed: Vec<Option<ObjIdx>>,
+    packed_map: FnvHashMap<usize, ObjIdx>,
+}
+
+#[allow(dead_code)]
+impl Serializer {
+    pub(crate) fn new(size: u32) -> Self {
+        let buf_size = size as usize;
+        let mut this = Serializer {
+            data: vec![0; buf_size],
+            end: buf_size,
+            tail: buf_size,
+            packed: Vec::new(),
+            ..Default::default()
+        };
+
+        this.packed.push(None);
+        this
+    }
+
+    // Embed a single Scalar type
+    pub(crate) fn embed(&mut self, obj: impl Scalar) -> Result<usize, SerializeErrorFlags> {
+        let raw = obj.to_raw();
+        let bytes = raw.as_ref();
+        let size = bytes.len();
+
+        let ret = self.allocate_size(size)?;
+        self.data[ret..ret + size].copy_from_slice(bytes);
+        Ok(ret)
+    }
+
+    // Allocate size
+    pub(crate) fn allocate_size(&mut self, size: usize) -> Result<usize, SerializeErrorFlags> {
+        if self.in_error() {
+            return Err(self.errors);
+        }
+
+        if size > u32::MAX as usize || self.tail - self.head < size {
+            return Err(self.set_err(SerializeErrorFlags::SERIALIZE_ERROR_OUT_OF_ROOM));
+        }
+
+        //TODO: add support for clear?
+        let ret = self.head;
+        self.head += size;
+        Ok(ret)
+    }
+
+    pub(crate) fn successful(&self) -> bool {
+        !self.errors
+    }
+
+    pub(crate) fn in_error(&self) -> bool {
+        !!self.errors
+    }
+
+    pub(crate) fn set_err(&mut self, error_type: SerializeErrorFlags) -> SerializeErrorFlags {
+        self.errors |= error_type;
+        self.errors
+    }
+
+    pub(crate) fn push(&mut self) -> Result<(), SerializeErrorFlags> {
+        if self.in_error() {
+            return Err(self.errors);
+        }
+
+        let pool_idx = self.object_pool.alloc();
+        let Some(obj) = self.object_pool.get_obj(pool_idx) else {
+            return Err(self.set_err(SerializeErrorFlags::SERIALIZE_ERROR_OTHER));
+        };
+
+        obj.head = self.head;
+        obj.tail = self.tail;
+        obj.next_obj = self.current;
+        self.current = Some(pool_idx);
+
+        Ok(())
+    }
+
+    pub(crate) fn copy_bytes(mut self) -> Result<Vec<u8>, SerializeErrorFlags> {
+        if !self.successful() {
+            return Err(self.errors);
+        }
+        let len = (self.head - self.start) + (self.end - self.tail);
+        if len == 0 {
+            return Ok(Vec::new());
+        }
+
+        self.data.copy_within(self.tail..self.end, self.head);
+        self.data.truncate(len);
+        Ok(self.data)
+    }
+}
+
+#[allow(dead_code)]
+#[derive(Default)]
+struct ObjectWrap {
+    pub obj: Object,
+    pub next: Option<PoolIdx>,
+}
+
+// reference Harfbuzz implementation:
+//<https://github.com/harfbuzz/harfbuzz/blob/5e32b5ca8fe430132b87c0eee6a1c056d37c35eb/src/hb-pool.hh>
+#[allow(dead_code)]
+#[derive(Default)]
+struct ObjectPool {
+    chunks: Vec<ObjectWrap>,
+    next: Option<PoolIdx>,
+}
+
+#[allow(dead_code)]
+impl ObjectPool {
+    const ALLOC_CHUNKS_LEN: usize = 64;
+    pub fn alloc(&mut self) -> PoolIdx {
+        let len = self.chunks.len();
+        if self.next.is_none() {
+            let new_len = len + Self::ALLOC_CHUNKS_LEN;
+            self.chunks.resize_with(new_len, Default::default);
+
+            for (idx, obj) in self
+                .chunks
+                .get_mut(len..new_len - 1)
+                .unwrap()
+                .iter_mut()
+                .enumerate()
+            {
+                obj.next = Some(len + idx + 1);
+            }
+
+            self.chunks.last_mut().unwrap().next = None;
+            self.next = Some(len);
+        }
+
+        let ret = self.next;
+        self.next = self.chunks[self.next.unwrap()].next;
+
+        ret.unwrap()
+    }
+
+    pub fn release(&mut self, pool_idx: PoolIdx) {
+        let Some(obj) = self.chunks.get_mut(pool_idx) else {
+            return;
+        };
+
+        obj.next = self.next;
+        self.next = Some(pool_idx);
+    }
+
+    pub fn get_obj(&mut self, pool_idx: PoolIdx) -> Option<&mut Object> {
+        self.chunks.get_mut(pool_idx).map(|o| &mut o.obj)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use write_fonts::types::{Offset16, UfWord, Uint24};
+
+    use super::*;
+
+    // test Serializer::embed() works for different Scalar types
+    #[test]
+    fn test_serializer_embed() {
+        let mut s = Serializer::new(2);
+        let gid = 1_u32;
+        //fail when out of room
+        assert_eq!(
+            s.embed(gid),
+            Err(SerializeErrorFlags::SERIALIZE_ERROR_OUT_OF_ROOM)
+        );
+
+        let mut s = Serializer::new(16384);
+        assert_eq!(s.embed(gid), Ok(0));
+
+        //check that head is advancing accordingly
+        let offset = Offset16::new(20);
+        assert_eq!(s.embed(offset), Ok(4));
+
+        let n = Uint24::new(30);
+        assert_eq!(s.embed(n), Ok(6));
+
+        let w = UfWord::new(40);
+        assert_eq!(s.embed(w), Ok(9));
+        assert_eq!(s.head, 11);
+        assert_eq!(s.start, 0);
+        assert_eq!(s.tail, 16384);
+        assert_eq!(s.end, 16384);
+
+        let out = s.copy_bytes().unwrap();
+        assert_eq!(out, [0, 0, 0, 1, 0, 20, 0, 0, 30, 0, 40]);
+    }
+
+    #[test]
+    fn test_push() {
+        let mut s = Serializer::new(2);
+        assert_eq!(s.push(), Ok(()));
+        assert_eq!(
+            s.embed(1_u32),
+            Err(SerializeErrorFlags::SERIALIZE_ERROR_OUT_OF_ROOM)
+        );
+        assert_eq!(
+            s.push(),
+            Err(SerializeErrorFlags::SERIALIZE_ERROR_OUT_OF_ROOM)
+        );
+    }
+
+    #[test]
+    fn test_object_pool() {
+        let mut p = ObjectPool::default();
+
+        let i = p.alloc();
+        assert_eq!(i, 0);
+        let i = p.alloc();
+        assert_eq!(i, 1);
+        let i = p.alloc();
+        assert_eq!(i, 2);
+        let i = p.alloc();
+        assert_eq!(i, 3);
+
+        p.release(1);
+        let i = p.alloc();
+        assert_eq!(i, 1);
+
+        p.release(3);
+        let i = p.alloc();
+        assert_eq!(i, 3);
+
+        let i = p.alloc();
+        assert_eq!(i, 4);
+
+        let o = p.get_obj(0).unwrap();
+        assert_eq!(o.head, 0);
+        assert_eq!(o.tail, 0);
+        assert!(o.real_links.is_empty());
+        assert!(o.virtual_links.is_empty());
+        assert_eq!(o.next_obj, None);
+
+        //test alloc more than 64 chunks, which would grow the internal vector
+        for i in 0..64 {
+            let idx = p.alloc();
+            assert_eq!(idx, 5 + i);
+        }
+    }
+}