[read-fonts] AI unsafe reads

Major speedup observed in HR benchmarks.

Author: behdad

font-codegen/src/fields.rs

@@ -825,13 +825,15 @@ impl Field {
         let range_stmt = self.getter_range_stmt();
         let mut read_stmt = if let Some(args) = &self.attrs.read_with_args {
             let get_args = args.to_tokens_for_table_getter();
-            quote!( self.data.read_with_args(range, &#get_args).unwrap() )
+            quote!( unsafe { self.data.read_with_args_unchecked(range, &#get_args).unwrap() } )
         } else if is_var_array {
-            quote!(VarLenArray::read(self.data.split_off(range.start).unwrap()).unwrap())
+            quote!(
+                unsafe { VarLenArray::read(self.data.split_off_unchecked(range.start)).unwrap() }
+            )
         } else if is_array {
-            quote!(self.data.read_array(range).unwrap())
+            quote!(unsafe { self.data.read_array_unchecked(range) })
         } else {
-            quote!(self.data.read_at(range.start).unwrap())
+            quote!(unsafe { self.data.read_at_unchecked(range.start) })
         };
         if is_versioned {
             read_stmt = quote!(Some(#read_stmt));

read-fonts/generated/font.rs

@@ -71,34 +71,34 @@ impl<'a> TableDirectory<'a> {
     /// 0x00010000 or 0x4F54544F
     pub fn sfnt_version(&self) -> u32 {
         let range = self.sfnt_version_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     /// Number of tables.
     pub fn num_tables(&self) -> u16 {
         let range = self.num_tables_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     pub fn search_range(&self) -> u16 {
         let range = self.search_range_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     pub fn entry_selector(&self) -> u16 {
         let range = self.entry_selector_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     pub fn range_shift(&self) -> u16 {
         let range = self.range_shift_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     /// Table records array—one for each top-level table in the font
     pub fn table_records(&self) -> &'a [TableRecord] {
         let range = self.table_records_byte_range();
-        self.data.read_array(range).unwrap()
+        unsafe { self.data.read_array_unchecked(range) }
     }
 }
 
@@ -287,43 +287,43 @@ impl<'a> TTCHeader<'a> {
     /// Font Collection ID string: \"ttcf\"
     pub fn ttc_tag(&self) -> Tag {
         let range = self.ttc_tag_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     /// Major/minor version of the TTC Header
     pub fn version(&self) -> MajorMinor {
         let range = self.version_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     /// Number of fonts in TTC
     pub fn num_fonts(&self) -> u32 {
         let range = self.num_fonts_byte_range();
-        self.data.read_at(range.start).unwrap()
+        unsafe { self.data.read_at_unchecked(range.start) }
     }
 
     /// Array of offsets to the TableDirectory for each font from the beginning of the file
     pub fn table_directory_offsets(&self) -> &'a [BigEndian<u32>] {
         let range = self.table_directory_offsets_byte_range();
-        self.data.read_array(range).unwrap()
+        unsafe { self.data.read_array_unchecked(range) }
     }
 
     /// Tag indicating that a DSIG table exists, 0x44534947 ('DSIG') (null if no signature)
     pub fn dsig_tag(&self) -> Option<u32> {
         let range = self.dsig_tag_byte_range()?;
-        Some(self.data.read_at(range.start).unwrap())
+        Some(unsafe { self.data.read_at_unchecked(range.start) })
     }
 
     /// The length (in bytes) of the DSIG table (null if no signature)
     pub fn dsig_length(&self) -> Option<u32> {
         let range = self.dsig_length_byte_range()?;
-        Some(self.data.read_at(range.start).unwrap())
+        Some(unsafe { self.data.read_at_unchecked(range.start) })
     }
 
     /// The offset (in bytes) of the DSIG table from the beginning of the TTC file (null if no signature)
     pub fn dsig_offset(&self) -> Option<u32> {
         let range = self.dsig_offset_byte_range()?;
-        Some(self.data.read_at(range.start).unwrap())
+        Some(unsafe { self.data.read_at_unchecked(range.start) })
     }
 }