| macro_rules! impl_write_unsigned_leb128 { |
| ($fn_name:ident, $int_ty:ident) => { |
| #[inline] |
| pub fn $fn_name(out: &mut Vec<u8>, mut value: $int_ty) { |
| loop { |
| if value < 0x80 { |
| out.push(value as u8); |
| break; |
| } else { |
| out.push(((value & 0x7f) | 0x80) as u8); |
| value >>= 7; |
| } |
| } |
| } |
| }; |
| } |
| |
| impl_write_unsigned_leb128!(write_u16_leb128, u16); |
| impl_write_unsigned_leb128!(write_u32_leb128, u32); |
| impl_write_unsigned_leb128!(write_u64_leb128, u64); |
| impl_write_unsigned_leb128!(write_u128_leb128, u128); |
| impl_write_unsigned_leb128!(write_usize_leb128, usize); |
| |
| macro_rules! impl_read_unsigned_leb128 { |
| ($fn_name:ident, $int_ty:ident) => { |
| #[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); |
| |
| #[inline] |
| /// encodes an integer using signed leb128 encoding and stores |
| /// the result using a callback function. |
| /// |
| /// The callback `write` is called once for each position |
| /// that is to be written to with the byte to be encoded |
| /// at that position. |
| pub fn write_signed_leb128_to<W>(mut value: i128, mut write: W) |
| where |
| W: FnMut(u8), |
| { |
| 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. |
| } |
| |
| write(byte); |
| |
| if !more { |
| break; |
| } |
| } |
| } |
| |
| #[inline] |
| pub fn write_signed_leb128(out: &mut Vec<u8>, value: i128) { |
| write_signed_leb128_to(value, |v| out.push(v)) |
| } |
| |
| #[inline] |
| pub fn read_signed_leb128(data: &[u8], start_position: usize) -> (i128, usize) { |
| let mut result = 0; |
| let mut shift = 0; |
| let mut position = start_position; |
| let mut byte; |
| |
| loop { |
| byte = data[position]; |
| position += 1; |
| result |= i128::from(byte & 0x7F) << shift; |
| shift += 7; |
| |
| if (byte & 0x80) == 0 { |
| break; |
| } |
| } |
| |
| if (shift < 64) && ((byte & 0x40) != 0) { |
| // sign extend |
| result |= -(1 << shift); |
| } |
| |
| (result, position - start_position) |
| } |