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Browse / github.com/storytold/pdfcraft / patch
fix(optimize): size objects in compressed object streams by their compressed share
fix(optimize): size objects in compressed object streams by their compressed share ## What this changes Previously, `audit_space` (`crates/optimize/src/audit.rs`) sized every claimed object via `size(doc, num)` (`pdfcraft_cos::serialize(&obj).len() + 20 + 20`) ? as if each object were written as an uncompressed standalone indirect object with its own `obj`/`endobj` wrapper and 20-byte ASCII cross-reference table entry. When non-stream objects (such as bookmarks, structure tree elements, form fields, annotations, or font dictionaries) were packed into compressed object streams (`/Type /ObjStm`, `XrefEntry::InStream { stream, .. }`), their categories counted much larger than
- Status
- open
- Score
- 0.00
- Adopters
- 0 other operators
- Author
- jonathanwxh-cell (imported from pull request #4951, open)
- Base
1dd2737b47a9c1c9562f0af563053d1bf510e4bf- Size
- +292 −11 in 1 file
- Review
- pending
- Shared
- 2026-10-28
- Id
269f290e517ec00e4e720391
How it went
No other operator has reported using it yet.
Diff
raw · crates/optimize/src/audit.rs
@@ -1,14 +1,15 @@ //! PDF Optimizer ▸ Audit space usage: how many bytes each kind of content takes. //!-//! Every object is sized as it would be written (dictionary plus stream data). Resources go by-//! kind first, wherever they are used: a font or image a form field or comment draws with is-//! still a font or image. Every other object goes to the first category that reaches it; what-//! remains (the catalog, page tree, info, metadata, cross-reference data and anything-//! unreachable) is document overhead.+//! Every standalone object is sized as it would be written (dictionary plus stream data), while+//! objects packed in compressed object streams share their object stream's compressed bytes in+//! proportion to their uncompressed size. Resources go by kind first, wherever they are used: a+//! font or image a form field or comment draws with is still a font or image. Every other object+//! goes to the first category that reaches it; what remains (the catalog, page tree, info,+//! metadata, cross-reference data and anything unreachable) is document overhead. use std::collections::{HashMap, HashSet}; -use pdfcraft_cos::{Dict, Document, ObjRef, Object};+use pdfcraft_cos::{Dict, Document, MAX_DECODED, Object, XrefEntry}; /// The categories, in Acrobat's order. #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]@@ -189,12 +190,27 @@ fn annotation_category(doc: &Document, annot: &Object) -> SpaceCategory { if widget { SpaceCategory::Forms } else { SpaceCategory::Comments } } -fn size(doc: &Document, num: u32) -> u64 {- let obj = doc.get(ObjRef::new(num, doc.generation(num)));+fn serialized_len(doc: &Document, num: u32) -> Option<u64> {+ let obj = doc.try_get(num).ok()?; let mut out = Vec::new(); pdfcraft_cos::serialize(&obj, &mut out);+ Some(out.len() as u64)+}++fn size(doc: &Document, num: u32) -> u64 { // "n g obj\n … \nendobj\n" and its cross-reference entry.- out.len() as u64 + 20 + 20+ serialized_len(doc, num).map_or(0, |len| len + 20 + 20)+}++/// The unedited object stream `num` is packed in, when `num` itself has no unsaved edit.+fn object_stream(doc: &Document, num: u32) -> Option<u32> {+ if doc.is_edited(num) {+ return None;+ }+ match doc.xref_entry(num) {+ Some(XrefEntry::InStream { stream, .. }) if !doc.is_edited(stream) => Some(stream),+ _ => None,+ } } /// Audit the space a document uses; `file_len` is the size of the file on disk (the rest is@@ -253,9 +269,57 @@ pub fn audit_space(doc: &Document, file_len: u64) -> Vec<SpaceUse> { a.claim(e, SpaceCategory::EmbeddedFiles); } let mut bytes: HashMap<SpaceCategory, u64> = HashMap::new();+ let mut streams: HashMap<u32, ([u64; SpaceCategory::ALL.len()], u64, usize)> = HashMap::new();+ for &num in a.owner.keys() {+ if let Some(stream) = object_stream(doc, num)+ && matches!(doc.try_get(stream).as_deref(), Ok(Object::Stream(_)))+ {+ streams.entry(stream).or_insert(([0; SpaceCategory::ALL.len()], 0, 0));+ }+ } for num in doc.object_numbers() {- if let Some(c) = a.owner.get(&num) {- *bytes.entry(*c).or_default() += size(doc, num);+ if let Some(stream) = object_stream(doc, num)+ && let Some((by_cat, total_u, count)) = streams.get_mut(&stream)+ {+ if let Some(len) = serialized_len(doc, num) {+ let u = len + 1;+ *total_u += u;+ *count += 1;+ if let Some(&c) = a.owner.get(&num) {+ by_cat[c as usize] += u;+ }+ }+ } else if !streams.contains_key(&num)+ && let Some(&c) = a.owner.get(&num)+ {+ *bytes.entry(c).or_default() += size(doc, num);+ }+ }+ for (stream, (by_cat, mut total_u, count)) in streams {+ let Ok(stm_obj) = doc.try_get(stream) else { continue };+ let Object::Stream(stm) = &*stm_obj else { continue };+ let declared_n = usize::try_from(stm.dict.int(b"N").unwrap_or(0).max(0)).unwrap_or(0);+ if count < declared_n+ && let Ok(decoded) = stm.decoded_within(MAX_DECODED)+ {+ let first = usize::try_from(stm.dict.int(b"First").unwrap_or(0).max(0)).unwrap_or(0);+ total_u = total_u.max(decoded.len().saturating_sub(first) as u64);+ }+ if total_u == 0 {+ continue;+ }+ let raw_len = u128::from(stm.raw.len() as u64);+ let total_u = u128::from(total_u);+ let mut acc: u128 = 0;+ for c in SpaceCategory::ALL {+ let cat_u = u128::from(by_cat[c as usize]);+ if cat_u == 0 {+ continue;+ }+ let prev = (acc * raw_len) / total_u;+ acc += cat_u;+ let next = (acc * raw_len) / total_u;+ *bytes.entry(c).or_default() += (next - prev) as u64; } } let counted: u64 = bytes.values().sum();@@ -269,3 +333,220 @@ pub fn audit_space(doc: &Document, file_len: u64) -> Vec<SpaceUse> { }) .collect() }++#[cfg(test)]+mod tests {+ use std::sync::Arc;++ use pdfcraft_cos::{Dict, Document, ObjRef, Object, PdfString, SaveOptions, Stream, write_full};++ use super::*;++ fn one_page_doc() -> (Document, ObjRef) {+ let mut doc = Document::new_empty();+ let pages = doc.root().and_then(|r| doc.get(r).as_dict().and_then(|d| d.reference(b"Pages"))).unwrap();+ let content = doc.add(Object::Stream(Stream::flate(Dict::new(), b"BT ET")));+ let mut page = Dict::new();+ page.set(b"Type".to_vec(), Object::name("Page"));+ page.set(b"Parent".to_vec(), Object::Ref(pages));+ page.set(b"MediaBox".to_vec(), Object::Array(vec![0.into(), 0.into(), 612.into(), 792.into()]));+ page.set(b"Contents".to_vec(), Object::Ref(content));+ let page = doc.add(Object::Dict(page));+ doc.update_dict(pages, |d| {+ d.set(b"Count".to_vec(), Object::Int(1));+ d.set(b"Kids".to_vec(), Object::Array(vec![Object::Ref(page)]));+ })+ .unwrap();+ (doc, page)+ }++ #[test]+ fn space_audit_sizes_objects_packed_in_compressed_object_streams_as_compressed() {+ let (mut doc, page) = one_page_doc();+ let outlines = doc.add(Object::Null);+ let mut items = Vec::new();+ for i in 0..80 {+ let mut item = Dict::new();+ item.set(b"Title".to_vec(), Object::String(PdfString::literal(format!("Chapter {i}: Section heading with repeated text").into_bytes())));+ item.set(b"Parent".to_vec(), Object::Ref(outlines));+ item.set(b"Dest".to_vec(), Object::Array(vec![Object::Ref(page), Object::name("Fit")]));+ items.push(doc.add(Object::Dict(item)));+ }+ let mut root_outlines = Dict::new();+ root_outlines.set(b"First".to_vec(), Object::Ref(items[0]));+ root_outlines.set(b"Last".to_vec(), Object::Ref(*items.last().unwrap()));+ root_outlines.set(b"Count".to_vec(), Object::Int(items.len() as i64));+ doc.set(outlines, Object::Dict(root_outlines));+ for pair in items.windows(2) {+ doc.update_dict(pair[0], |d| d.set(b"Next".to_vec(), Object::Ref(pair[1]))).unwrap();+ doc.update_dict(pair[1], |d| d.set(b"Prev".to_vec(), Object::Ref(pair[0]))).unwrap();+ }+ let root = doc.root().unwrap();+ doc.update_dict(root, |c| c.set(b"Outlines".to_vec(), Object::Ref(outlines))).unwrap();++ let unpacked = write_full(&doc, &SaveOptions { object_streams: false, ..SaveOptions::default() }).unwrap();+ let packed = write_full(&doc, &SaveOptions::default()).unwrap();+ assert!(packed.len() * 3 < unpacked.len(), "{} vs {}", packed.len(), unpacked.len());++ let unpacked_doc = Document::open(Arc::new(unpacked.clone())).unwrap();+ let unpacked_bookmarks =+ audit_space(&unpacked_doc, unpacked.len() as u64).into_iter().find(|u| u.category == SpaceCategory::Bookmarks).unwrap().bytes;++ let reopened = Document::open(Arc::new(packed.clone())).unwrap();+ let audit = audit_space(&reopened, packed.len() as u64);+ let get = |c: SpaceCategory| audit.iter().find(|u| u.category == c).unwrap().clone();+ let bookmarks = get(SpaceCategory::Bookmarks);+ let overhead = get(SpaceCategory::DocumentOverhead);++ assert!(bookmarks.bytes > 0 && bookmarks.bytes < packed.len() as u64, "{audit:?}");+ assert!(bookmarks.bytes * 3 < unpacked_bookmarks, "{} vs {}", bookmarks.bytes, unpacked_bookmarks);+ assert!(overhead.bytes > 0, "packed bookmarks must not swallow the file's overhead: {audit:?}");+ assert_eq!(audit.iter().map(|u| u.bytes).sum::<u64>(), packed.len() as u64);+ }++ #[test]+ fn space_audit_shares_an_object_stream_across_categories_and_survives_freed_or_edited_members() {+ let (mut doc, page) = one_page_doc();+ // A small bookmark and a large structure tree packed into the same object stream.+ let mut item = Dict::new();+ item.set(b"Title".to_vec(), Object::String(PdfString::literal(b"Intro".to_vec())));+ item.set(b"Dest".to_vec(), Object::Array(vec![Object::Ref(page), Object::name("Fit")]));+ let item = doc.add(Object::Dict(item));+ let mut outlines = Dict::new();+ outlines.set(b"First".to_vec(), Object::Ref(item));+ outlines.set(b"Last".to_vec(), Object::Ref(item));+ outlines.set(b"Count".to_vec(), Object::Int(1));+ let outlines = doc.add(Object::Dict(outlines));+ doc.update_dict(item, |d| d.set(b"Parent".to_vec(), Object::Ref(outlines))).unwrap();++ let mut kids = Vec::new();+ for i in 0..40 {+ let mut elem = Dict::new();+ elem.set(b"Type".to_vec(), Object::name("StructElem"));+ elem.set(b"S".to_vec(), Object::name("P"));+ elem.set(b"Alt".to_vec(), Object::String(PdfString::literal(format!("Paragraph {i} with descriptive alternate text").into_bytes())));+ kids.push(Object::Ref(doc.add(Object::Dict(elem))));+ }+ let mut struct_root = Dict::new();+ struct_root.set(b"Type".to_vec(), Object::name("StructTreeRoot"));+ struct_root.set(b"K".to_vec(), Object::Array(kids.clone()));+ let struct_root = doc.add(Object::Dict(struct_root));++ let root = doc.root().unwrap();+ doc.update_dict(root, |c| {+ c.set(b"Outlines".to_vec(), Object::Ref(outlines));+ c.set(b"StructTreeRoot".to_vec(), Object::Ref(struct_root));+ })+ .unwrap();++ let packed = write_full(&doc, &SaveOptions::default()).unwrap();+ let reopened = Document::open(Arc::new(packed.clone())).unwrap();+ let before = audit_space(&reopened, packed.len() as u64);+ let bytes_of = |rows: &[SpaceUse], c: SpaceCategory| rows.iter().find(|u| u.category == c).unwrap().bytes;+ let bookmarks_before = bytes_of(&before, SpaceCategory::Bookmarks);+ let struct_before = bytes_of(&before, SpaceCategory::StructureInfo);+ assert!(bookmarks_before > 0 && struct_before > bookmarks_before * 5, "{before:?}");++ // Freeing the structure elements in memory leaves their dead bytes in the object stream on+ // disk as overhead; the surviving bookmark keeps its own small share.+ let mut freed_struct = reopened.clone();+ let cat_ref = freed_struct.root().unwrap();+ let sr = freed_struct.get(cat_ref).as_dict().unwrap().reference(b"StructTreeRoot").unwrap();+ let elem_refs: Vec<ObjRef> =+ freed_struct.get(sr).as_dict().unwrap().get(b"K").unwrap().as_array().unwrap().iter().filter_map(Object::as_ref).collect();+ freed_struct+ .update_dict(cat_ref, |c| {+ c.remove(b"StructTreeRoot");+ })+ .unwrap();+ freed_struct.free(sr);+ for r in elem_refs {+ freed_struct.free(r);+ }+ let after_free = audit_space(&freed_struct, packed.len() as u64);+ assert_eq!(bytes_of(&after_free, SpaceCategory::StructureInfo), 0);+ assert_eq!(bytes_of(&after_free, SpaceCategory::Bookmarks), bookmarks_before, "bookmark share stays unchanged after freeing other members");++ // Editing the bookmark in memory moves it out of the object stream and sizes its new value.+ let mut edited = reopened;+ let outlines_ref = edited.get(cat_ref).as_dict().unwrap().reference(b"Outlines").unwrap();+ let first_ref = edited.get(outlines_ref).as_dict().unwrap().reference(b"First").unwrap();+ edited+ .update_dict(first_ref, |d| {+ d.set(b"Title".to_vec(), Object::String(PdfString::literal(vec![b'X'; 400])));+ })+ .unwrap();+ let after_edit = audit_space(&edited, packed.len() as u64);+ assert!(bytes_of(&after_edit, SpaceCategory::Bookmarks) > bookmarks_before + 400);+ assert_eq!(bytes_of(&after_edit, SpaceCategory::StructureInfo), struct_before);++ // A malformed reference pointing directly at the object stream itself must not count the+ // stream a second time alongside its members.+ let Some(XrefEntry::InStream { stream: stm_num, .. }) = edited.xref_entry(outlines_ref.num) else {+ panic!("expected outlines in an object stream");+ };+ let mut self_ref = edited.clone();+ self_ref+ .update_dict(outlines_ref, |d| {+ d.set(b"Last".to_vec(), Object::Ref(ObjRef::new(stm_num, 0)));+ })+ .unwrap();+ let after_self_ref = audit_space(&self_ref, packed.len() as u64);+ assert_eq!(bytes_of(&after_self_ref, SpaceCategory::StructureInfo), struct_before);++ // Editing the object stream itself detaches its members from compressed stream sizing.+ edited+ .update_dict(ObjRef::new(stm_num, 0), |d| {+ d.set(b"First".to_vec(), Object::Int(999_999));+ })+ .unwrap();+ let after_stream_edit = audit_space(&edited, 0);+ assert!(bytes_of(&after_stream_edit, SpaceCategory::StructureInfo) > struct_before);+ }++ #[test]+ fn space_audit_skips_corrupted_object_streams() {+ let (mut doc, page) = one_page_doc();+ // Fill the first object stream (100 objects) with structure elements so the bookmark item+ // lands in the second object stream while the catalog stays readable in the first.+ let mut kids = Vec::new();+ for i in 0..105 {+ let mut elem = Dict::new();+ elem.set(b"Type".to_vec(), Object::name("StructElem"));+ elem.set(b"S".to_vec(), Object::name("P"));+ elem.set(b"Alt".to_vec(), Object::String(PdfString::literal(format!("Item {i}").into_bytes())));+ kids.push(Object::Ref(doc.add(Object::Dict(elem))));+ }+ let mut struct_root = Dict::new();+ struct_root.set(b"Type".to_vec(), Object::name("StructTreeRoot"));+ struct_root.set(b"K".to_vec(), Object::Array(kids));+ let struct_root = doc.add(Object::Dict(struct_root));++ let mut item = Dict::new();+ item.set(b"Title".to_vec(), Object::String(PdfString::literal(b"Broken".to_vec())));+ item.set(b"Dest".to_vec(), Object::Array(vec![Object::Ref(page), Object::name("Fit")]));+ let item = doc.add(Object::Dict(item));+ let mut outlines = Dict::new();+ outlines.set(b"First".to_vec(), Object::Ref(item));+ outlines.set(b"Last".to_vec(), Object::Ref(item));+ let outlines = doc.add(Object::Dict(outlines));+ let root = doc.root().unwrap();+ doc.update_dict(root, |c| {+ c.set(b"StructTreeRoot".to_vec(), Object::Ref(struct_root));+ c.set(b"Outlines".to_vec(), Object::Ref(outlines));+ })+ .unwrap();++ let mut packed = write_full(&doc, &SaveOptions::default()).unwrap();+ // Corrupt the last object stream's Flate payload while keeping the catalog's stream intact.+ let marker = b"/Type /ObjStm";+ let pos = packed.windows(marker.len()).rposition(|w| w == marker).unwrap();+ let stream_kw = packed[pos..].windows(8).position(|w| w == b"\nstream\n").unwrap() + pos + 8;+ for b in &mut packed[stream_kw..stream_kw + 8] {+ *b ^= 0xFF;+ }+ let corrupted = Document::open(Arc::new(packed.clone())).unwrap();+ let audit = audit_space(&corrupted, packed.len() as u64);+ assert_eq!(audit.iter().map(|u| u.bytes).sum::<u64>(), packed.len() as u64);+ }+}