tikz-gallery-generator

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//! Safe MuPDF wrappers
use std::{ptr, slice, ops::Deref, ffi::CStr};
use mupdf_sys::*;

#[derive(Debug)]
pub struct Document {
  ctx:   *mut fz_context,
  inner: *mut fz_document,

  page_count: usize,
}

#[derive(Debug)]
pub struct Buffer<'doc> {
  doc:   &'doc Document,
  inner: *mut fz_buffer,
}

impl Document {
  pub fn open_from_bytes(bytes: &[u8]) -> Result<Self, String> {
    let ctx = unsafe {
      fz_new_context(ptr::null(), ptr::null(), FZ_STORE_DEFAULT as usize)
    };
    assert!(!ctx.is_null());

    // SAFETY: this should really be wrapped with fz_try, but it can only
    //         fail if ctx does not contain a document handler list (?) or
    //         the list is already full. seems safe to assume
    //         fz_new_documment will handle us a sane ctx
    unsafe { fz_register_document_handlers(ctx); }

    unsafe {
      fz_set_warning_callback(ctx, None, ptr::null_mut());
      fz_set_error_callback(ctx, None, ptr::null_mut());
    }

    let mut doc = ptr::null_mut();
    let mut page_count = 0;
    let result = unsafe {
      mupdf_open_doc_from_bytes(
        ctx,
        bytes.as_ptr() as *mut _,
        bytes.len(),
        &mut doc,
        &mut page_count,
      )
    };

    if result.type_ != FZ_ERROR_NONE {
      return Err(unsafe {
        CStr::from_ptr(result.err_msg).to_string_lossy().to_string()
      });
    }

    assert!(!doc.is_null());
    let page_count = page_count as usize;
    Ok(Self { ctx, inner: doc, page_count, })
  }

  pub fn render_page_to_svg(
    &self,
    page: usize,
  ) -> Result<Buffer<'_>, String> {
    assert!(page < self.page_count,
      "page {page} is out of bounds: document only has {} pages",
      self.page_count);

    let mut buf = ptr::null_mut();
    let result = unsafe {
      mupdf_page_to_svg(self.ctx, self.inner, page, &mut buf)
    };

    if result.type_ != FZ_ERROR_NONE {
      return Err(unsafe {
        CStr::from_ptr(result.err_msg).to_string_lossy().to_string()
      });
    }

    assert!(!buf.is_null());
    Ok(Buffer { doc: self, inner: buf, })
  }
}

impl Drop for Document {
  fn drop(&mut self) {
    unsafe {
      fz_drop_document(self.ctx, self.inner);
      fz_drop_context(self.ctx);
    }
  }
}

impl<'doc> Deref for Buffer<'doc> {
  type Target = [u8];

  fn deref(&self) -> &[u8] {
    unsafe {
      slice::from_raw_parts(
        (*self.inner).data as *const _,
        (*self.inner).len
      )
    }
  }
}

impl<'doc> Drop for Buffer<'doc> {
  fn drop(&mut self) {
    unsafe { fz_drop_buffer(self.doc.ctx, self.inner); }
  }
}