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#[inline]
fn write_to_vec(vec: &mut Vec<u8>, position: usize, byte: u8) {
if position == vec.len() {
vec.push(byte);
} else {
vec[position] = byte;
}
}
#[inline]
pub fn write_unsigned_leb128_to<W>(mut value: u128, mut write: W) -> usize
where W: FnMut(usize, u8)
{
let mut position = 0;
loop {
let mut byte = (value & 0x7F) as u8;
value >>= 7;
if value != 0 {
byte |= 0x80;
}
write(position, byte);
position += 1;
if value == 0 {
break;
}
}
position
}
pub fn write_unsigned_leb128(out: &mut Vec<u8>, start_position: usize, value: u128) -> usize {
write_unsigned_leb128_to(value, |i, v| write_to_vec(out, start_position+i, v))
}
#[inline]
pub fn read_unsigned_leb128(data: &[u8], start_position: usize) -> (u128, usize) {
let mut result = 0;
let mut shift = 0;
let mut position = start_position;
loop {
let byte = data[position];
position += 1;
result |= ((byte & 0x7F) as u128) << shift;
if (byte & 0x80) == 0 {
break;
}
shift += 7;
}
(result, position - start_position)
}
#[inline]
pub fn write_signed_leb128_to<W>(mut value: i128, mut write: W) -> usize
where W: FnMut(usize, u8)
{
let mut position = 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;
}
write(position, byte);
position += 1;
if !more {
break;
}
}
position
}
pub fn write_signed_leb128(out: &mut Vec<u8>, start_position: usize, value: i128) -> usize {
write_signed_leb128_to(value, |i, v| write_to_vec(out, start_position+i, 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 |= ((byte & 0x7F) as i128) << shift;
shift += 7;
if (byte & 0x80) == 0 {
break;
}
}
if (shift < 64) && ((byte & 0x40) != 0) {
result |= -(1 << shift);
}
(result, position - start_position)
}
#[test]
fn test_unsigned_leb128() {
let mut stream = Vec::with_capacity(10000);
for x in 0..62 {
let pos = stream.len();
let bytes_written = write_unsigned_leb128(&mut stream, pos, 3 << x);
assert_eq!(stream.len(), pos + bytes_written);
}
let mut position = 0;
for x in 0..62 {
let expected = 3 << x;
let (actual, bytes_read) = read_unsigned_leb128(&stream, position);
assert_eq!(expected, actual);
position += bytes_read;
}
assert_eq!(stream.len(), position);
}
#[test]
fn test_signed_leb128() {
let values: Vec<_> = (-500..500).map(|i| i * 0x12345789ABCDEF).collect();
let mut stream = Vec::new();
for &x in &values {
let pos = stream.len();
let bytes_written = write_signed_leb128(&mut stream, pos, x);
assert_eq!(stream.len(), pos + bytes_written);
}
let mut pos = 0;
for &x in &values {
let (value, bytes_read) = read_signed_leb128(&mut stream, pos);
pos += bytes_read;
assert_eq!(x, value);
}
assert_eq!(pos, stream.len());
}