--- /dev/null
+#![macro_use]
+
+macro_rules! max_leb128_len {
+ ($int_ty:ty) => {
+ // The longest LEB128 encoding for an integer uses 7 bits per byte.
+ (std::mem::size_of::<$int_ty>() * 8 + 6) / 7
+ };
+}
+
+// Returns the longest LEB128 encoding of all supported integer types.
+pub const fn max_leb128_len() -> usize {
+ max_leb128_len!(u128)
+}
+
+macro_rules! impl_write_unsigned_leb128 {
+ ($fn_name:ident, $int_ty:ty) => {
+ #[inline]
+ pub fn $fn_name(
+ out: &mut [::std::mem::MaybeUninit<u8>; max_leb128_len!($int_ty)],
+ mut value: $int_ty,
+ ) -> &[u8] {
+ let mut i = 0;
+
+ loop {
+ if value < 0x80 {
+ unsafe {
+ *out.get_unchecked_mut(i).as_mut_ptr() = value as u8;
+ }
+
+ i += 1;
+ break;
+ } else {
+ unsafe {
+ *out.get_unchecked_mut(i).as_mut_ptr() = ((value & 0x7f) | 0x80) as u8;
+ }
+
+ value >>= 7;
+ i += 1;
+ }
+ }
+
+ unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) }
+ }
+ };
+}
+
+impl_write_unsigned_leb128!(write_u16_leb128, u16);
+impl_write_unsigned_leb128!(write_u32_leb128, u32);
+impl_write_unsigned_leb128!(write_u64_leb128, u64);
+impl_write_unsigned_leb128!(write_u128_leb128, u128);
+impl_write_unsigned_leb128!(write_usize_leb128, usize);
+
+macro_rules! impl_read_unsigned_leb128 {
+ ($fn_name:ident, $int_ty:ty) => {
+ #[inline]
+ pub fn $fn_name(slice: &[u8]) -> ($int_ty, usize) {
+ let mut result = 0;
+ let mut shift = 0;
+ let mut position = 0;
+ loop {
+ let byte = slice[position];
+ position += 1;
+ if (byte & 0x80) == 0 {
+ result |= (byte as $int_ty) << shift;
+ return (result, position);
+ } else {
+ result |= ((byte & 0x7F) as $int_ty) << shift;
+ }
+ shift += 7;
+ }
+ }
+ };
+}
+
+impl_read_unsigned_leb128!(read_u16_leb128, u16);
+impl_read_unsigned_leb128!(read_u32_leb128, u32);
+impl_read_unsigned_leb128!(read_u64_leb128, u64);
+impl_read_unsigned_leb128!(read_u128_leb128, u128);
+impl_read_unsigned_leb128!(read_usize_leb128, usize);
+
+macro_rules! impl_write_signed_leb128 {
+ ($fn_name:ident, $int_ty:ty) => {
+ #[inline]
+ pub fn $fn_name(
+ out: &mut [::std::mem::MaybeUninit<u8>; max_leb128_len!($int_ty)],
+ mut value: $int_ty,
+ ) -> &[u8] {
+ let mut i = 0;
+
+ loop {
+ let mut byte = (value as u8) & 0x7f;
+ value >>= 7;
+ let more = !(((value == 0) && ((byte & 0x40) == 0))
+ || ((value == -1) && ((byte & 0x40) != 0)));
+
+ if more {
+ byte |= 0x80; // Mark this byte to show that more bytes will follow.
+ }
+
+ unsafe {
+ *out.get_unchecked_mut(i).as_mut_ptr() = byte;
+ }
+
+ i += 1;
+
+ if !more {
+ break;
+ }
+ }
+
+ unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) }
+ }
+ };
+}
+
+impl_write_signed_leb128!(write_i16_leb128, i16);
+impl_write_signed_leb128!(write_i32_leb128, i32);
+impl_write_signed_leb128!(write_i64_leb128, i64);
+impl_write_signed_leb128!(write_i128_leb128, i128);
+impl_write_signed_leb128!(write_isize_leb128, isize);
+
+macro_rules! impl_read_signed_leb128 {
+ ($fn_name:ident, $int_ty:ty) => {
+ #[inline]
+ pub fn $fn_name(slice: &[u8]) -> ($int_ty, usize) {
+ let mut result = 0;
+ let mut shift = 0;
+ let mut position = 0;
+ let mut byte;
+
+ loop {
+ byte = slice[position];
+ position += 1;
+ result |= <$int_ty>::from(byte & 0x7F) << shift;
+ shift += 7;
+
+ if (byte & 0x80) == 0 {
+ break;
+ }
+ }
+
+ if (shift < <$int_ty>::BITS) && ((byte & 0x40) != 0) {
+ // sign extend
+ result |= (!0 << shift);
+ }
+
+ (result, position)
+ }
+ };
+}
+
+impl_read_signed_leb128!(read_i16_leb128, i16);
+impl_read_signed_leb128!(read_i32_leb128, i32);
+impl_read_signed_leb128!(read_i64_leb128, i64);
+impl_read_signed_leb128!(read_i128_leb128, i128);
+impl_read_signed_leb128!(read_isize_leb128, isize);