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Reduce the size of some unsafe blocks in shaper.rs (#38597)

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This change ensures that safe operations are done outside of unsafe
blocks as often as possible.

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>
This commit is contained in:
Simon Wülker 2025-08-11 15:39:07 +02:00 • committed by GitHub
parent b75c3feb97
commit abc549eff7
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GPG key ID: B5690EEEBB952194
1 changed files with 34 additions and 39 deletions
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73
components/fonts/shaper.rs
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@ -692,14 +692,12 @@ extern "C" fn glyph_func(
let font: *const Font = font_data as *const Font; let font: *const Font = font_data as *const Font;
assert!(!font.is_null()); assert!(!font.is_null());
unsafe { match unsafe { (*font).glyph_index(char::from_u32(unicode).unwrap()) } {
match (*font).glyph_index(char::from_u32(unicode).unwrap()) { Some(g) => {
Some(g) => { unsafe { *glyph = g as hb_codepoint_t };
*glyph = g as hb_codepoint_t; true as hb_bool_t
true as hb_bool_t },
}, None => false as hb_bool_t,
None => false as hb_bool_t,
}
} }
} }
@ -712,47 +710,44 @@ extern "C" fn glyph_h_advance_func(
let font: *mut Font = font_data as *mut Font; let font: *mut Font = font_data as *mut Font;
assert!(!font.is_null()); assert!(!font.is_null());
unsafe { let advance = unsafe { (*font).glyph_h_advance(glyph as GlyphId) };
let advance = (*font).glyph_h_advance(glyph as GlyphId); Shaper::float_to_fixed(advance)
Shaper::float_to_fixed(advance)
}
} }
// Callback to get a font table out of a font. /// Callback to get a font table out of a font.
extern "C" fn font_table_func( extern "C" fn font_table_func(
_: *mut hb_face_t, _: *mut hb_face_t,
tag: hb_tag_t, tag: hb_tag_t,
user_data: *mut c_void, user_data: *mut c_void,
) -> *mut hb_blob_t { ) -> *mut hb_blob_t {
unsafe { // NB: These asserts have security implications.
// NB: These asserts have security implications. let font = user_data as *const Font;
let font = user_data as *const Font; assert!(!font.is_null());
assert!(!font.is_null());
// TODO(Issue #197): reuse font table data, which will change the unsound trickery here. // TODO(Issue #197): reuse font table data, which will change the unsound trickery here.
match (*font).table_for_tag(tag as FontTableTag) { let Some(font_table) = (unsafe { (*font).table_for_tag(tag as FontTableTag) }) else {
None => ptr::null_mut(), return ptr::null_mut();
Some(font_table) => { };
// `Box::into_raw` intentionally leaks the FontTable so we don't destroy the buffer
// while HarfBuzz is using it. When HarfBuzz is done with the buffer, it will pass
// this raw pointer back to `destroy_blob_func` which will deallocate the Box.
let font_table_ptr = Box::into_raw(Box::new(font_table));
let buf = (*font_table_ptr).buffer(); // `Box::into_raw` intentionally leaks the FontTable so we don't destroy the buffer
// HarfBuzz calls `destroy_blob_func` when the buffer is no longer needed. // while HarfBuzz is using it. When HarfBuzz is done with the buffer, it will pass
let blob = hb_blob_create( // this raw pointer back to `destroy_blob_func` which will deallocate the Box.
buf.as_ptr() as *const c_char, let font_table_ptr = Box::into_raw(Box::new(font_table));
buf.len() as c_uint,
HB_MEMORY_MODE_READONLY,
font_table_ptr as *mut c_void,
Some(destroy_blob_func),
);
assert!(!blob.is_null()); let buf = unsafe { (*font_table_ptr).buffer() };
blob // HarfBuzz calls `destroy_blob_func` when the buffer is no longer needed.
}, let blob = unsafe {
} hb_blob_create(
} buf.as_ptr() as *const c_char,
buf.len() as c_uint,
HB_MEMORY_MODE_READONLY,
font_table_ptr as *mut c_void,
Some(destroy_blob_func),
)
};
assert!(!blob.is_null());
blob
} }
extern "C" fn destroy_blob_func(font_table_ptr: *mut c_void) { extern "C" fn destroy_blob_func(font_table_ptr: *mut c_void) {