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mtlcl410andClaude Opus 5.5
d2776fa350
The file must start with %PDF-1.0 to %PDF-1.7 and an end-of-line marker, followed by a comment of % and four bytes above 127. A document whose next save is a full rewrite is judged by the header that save writes. Save as PDF/A makes the next save full, at version 1.7 when the kept version isn't 1.0 to 1.7. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Pq7HyDBXygTf7jcqdsjcfn
70 lines
2.8 KiB
Rust
70 lines
2.8 KiB
Rust
//! PDF/A-2 6.1.2, the file header: the file starts at its first byte with `%PDF-1.n`, `n` from 0
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//! to 7, and an end-of-line marker; the next line is a comment, `%` and at least four bytes each
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//! above 127, which marks the file as binary (ISO 32000-1 7.5.2).
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//!
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//! A document whose next save rewrites it in full is judged by the header that save writes: the
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//! version it keeps, followed by the writer's own binary comment.
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use pdfcraft_cos::Document;
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/// What the header of `doc`, as it will be saved, breaks of 6.1.2.
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#[derive(Debug, Default, PartialEq, Eq)]
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pub(crate) struct Header {
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/// The first line isn't `%PDF-1.0` to `%PDF-1.7` at the start of the file.
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pub(crate) version: bool,
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/// The second line isn't a comment of at least four bytes above 127.
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pub(crate) comment: bool,
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}
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pub(crate) fn check(doc: &Document) -> Header {
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if doc.full_save_required() || doc.encryption_changed() {
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let written = doc.version().get(..3).unwrap_or_default();
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return Header { version: !allowed(written.as_bytes()), comment: false };
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}
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let data = doc.bytes();
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let Some(rest) = data.strip_prefix(b"%PDF-") else { return Header { version: true, comment: false } };
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let version = rest.get(..3).unwrap_or_default();
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let Some(rest) = rest.get(3..).and_then(eol) else {
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return Header { version: true, comment: !binary_comment(after_line(rest)) };
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};
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Header { version: !allowed(version), comment: !binary_comment(rest) }
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}
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/// Whether a version is `1.0` to `1.7`.
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fn allowed(version: &[u8]) -> bool {
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matches!(version, [b'1', b'.', b'0'..=b'7'])
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}
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/// What follows an end-of-line marker (CR, LF or CR LF) at the start of `data`.
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fn eol(data: &[u8]) -> Option<&[u8]> {
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match data {
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[b'\r', b'\n', rest @ ..] | [b'\r', rest @ ..] | [b'\n', rest @ ..] => Some(rest),
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_ => None,
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}
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}
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/// What follows the first end-of-line marker in `data`, or nothing.
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fn after_line(data: &[u8]) -> &[u8] {
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let end = data.iter().position(|&b| b == b'\r' || b == b'\n').unwrap_or(data.len());
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data.get(end..).and_then(eol).unwrap_or_default()
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}
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/// Whether `data` starts with `%` and four bytes above 127.
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fn binary_comment(data: &[u8]) -> bool {
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matches!(data, [b'%', a, b, c, d, ..] if [a, b, c, d].iter().all(|&&x| x > 127))
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}
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/// Makes the next save of `doc` write a header 6.1.2 allows, when the current one breaks it:
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/// a full save, at version 1.7 when the version kept isn't 1.0 to 1.7. What it fixed, if anything.
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pub(crate) fn rewrite(doc: &mut Document) -> Option<String> {
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let header = check(doc);
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if !header.version && !header.comment {
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return None;
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}
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if !allowed(doc.version().as_bytes().get(..3).unwrap_or_default()) {
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doc.set_version("1.7");
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}
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doc.require_full_save();
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Some("Rewrote the file header".into())
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}
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