mirror of
https://github.com/storytold/craft-libs.git
synced 2026-11-13 22:12:12 +00:00
Dylan M. Taylor
f2d658d08f
The layer every EPS reader and writer in the apps had its own copy of: where the PostScript and the previews are behind the binary header (read and write), the header comments with the bounding boxes (also deferred to the trailer), the EPSI preview bitmap, ASCII85 both ways, and telling EPS, PostScript and PostScript- or PDF-based Illustrator files apart. No PostScript interpreter. From storytold/vectorcraft at 6e873b80 (crates/eps: lib.rs, import.rs, import/preview.rs, ps.rs) and storytold/designcraft at 513f77b8 (crates/images/src/eps.rs).
78 lines
3.7 KiB
Rust
78 lines
3.7 KiB
Rust
//! The binary header of an EPS file with a preview ("DOS EPS binary file header", EPSF 3.0
|
||
//! section 5.2): 30 bytes, little-endian.
|
||
//!
|
||
//! | bytes | |
|
||
//! |---|---|
|
||
//! | 0–3 | `C5 D0 D3 C6` |
|
||
//! | 4–7, 8–11 | offset and length of the PostScript |
|
||
//! | 12–15, 16–19 | offset and length of the Windows metafile preview (0 for none) |
|
||
//! | 20–23, 24–27 | offset and length of the TIFF preview (0 for none) |
|
||
//! | 28–29 | checksum of bytes 0–27 (XOR of the 16-bit words), or `FFFF` for none |
|
||
|
||
use crate::Error;
|
||
|
||
/// The first bytes of an EPS file with a binary header.
|
||
pub const DOS_MAGIC: [u8; 4] = [0xC5, 0xD0, 0xD3, 0xC6];
|
||
/// The binary header's size.
|
||
pub const DOS_HEADER: usize = 30;
|
||
|
||
/// The parts of an EPS file.
|
||
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
|
||
pub struct Sections<'a> {
|
||
/// The PostScript program: the whole file when it has no binary header.
|
||
pub postscript: &'a [u8],
|
||
/// The TIFF preview.
|
||
pub tiff: Option<&'a [u8]>,
|
||
/// The Windows metafile preview.
|
||
pub metafile: Option<&'a [u8]>,
|
||
}
|
||
|
||
/// The sections of an EPS file: its PostScript and previews behind a binary header, or the whole
|
||
/// file as PostScript. A header that points outside the file is an error, whichever section it
|
||
/// is: such a file is cut short or not an EPS.
|
||
pub fn sections(bytes: &[u8]) -> Result<Sections<'_>, Error> {
|
||
if !bytes.starts_with(&DOS_MAGIC) {
|
||
return Ok(Sections { postscript: bytes, tiff: None, metafile: None });
|
||
}
|
||
let word = |at: usize| -> Result<usize, Error> {
|
||
let b = bytes.get(at..at.saturating_add(4)).and_then(|b| <[u8; 4]>::try_from(b).ok()).ok_or(Error::OutsideFile)?;
|
||
usize::try_from(u32::from_le_bytes(b)).map_err(|_| Error::OutsideFile)
|
||
};
|
||
let part = |at: usize| -> Result<&[u8], Error> {
|
||
let (start, len) = (word(at)?, word(at + 4)?);
|
||
start.checked_add(len).and_then(|end| bytes.get(start..end)).ok_or(Error::OutsideFile)
|
||
};
|
||
// A preview with no offset or no length is absent.
|
||
let preview = |at: usize| -> Result<Option<&[u8]>, Error> { if word(at)? == 0 || word(at + 4)? == 0 { Ok(None) } else { part(at).map(Some) } };
|
||
Ok(Sections { postscript: part(4)?, metafile: preview(12)?, tiff: preview(20)? })
|
||
}
|
||
|
||
/// `postscript` behind a binary header, followed by its previews. With neither preview the
|
||
/// PostScript is returned as it is: a header would only hide it from readers of plain EPS.
|
||
pub fn wrap(postscript: &[u8], tiff: Option<&[u8]>, metafile: Option<&[u8]>) -> Result<Vec<u8>, Error> {
|
||
let (tiff, metafile) = (tiff.filter(|t| !t.is_empty()), metafile.filter(|m| !m.is_empty()));
|
||
if tiff.is_none() && metafile.is_none() {
|
||
return Ok(postscript.to_vec());
|
||
}
|
||
let size = |part: Option<&[u8]>| u32::try_from(part.map_or(0, <[u8]>::len)).map_err(|_| Error::TooLarge);
|
||
let ps_len = u32::try_from(postscript.len()).map_err(|_| Error::TooLarge)?;
|
||
let (metafile_len, tiff_len) = (size(metafile)?, size(tiff)?);
|
||
let metafile_at = (DOS_HEADER as u32).checked_add(ps_len).ok_or(Error::TooLarge)?;
|
||
let tiff_at = metafile_at.checked_add(metafile_len).ok_or(Error::TooLarge)?;
|
||
let total = tiff_at.checked_add(tiff_len).ok_or(Error::TooLarge)?;
|
||
let mut out = Vec::with_capacity(usize::try_from(total).map_err(|_| Error::TooLarge)?);
|
||
out.extend(DOS_MAGIC);
|
||
out.extend((DOS_HEADER as u32).to_le_bytes());
|
||
out.extend(ps_len.to_le_bytes());
|
||
for (at, len) in [(metafile_at, metafile_len), (tiff_at, tiff_len)] {
|
||
out.extend((if len == 0 { 0 } else { at }).to_le_bytes());
|
||
out.extend(len.to_le_bytes());
|
||
}
|
||
// No checksum.
|
||
out.extend(0xFFFFu16.to_le_bytes());
|
||
out.extend(postscript);
|
||
out.extend(metafile.unwrap_or_default());
|
||
out.extend(tiff.unwrap_or_default());
|
||
Ok(out)
|
||
}
|