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fix 2's-completement encoding for non full with signed ints

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This commit is contained in:
Robin Appelman 2019-08-28 02:44:35 +02:00
commit 2fd2b49810
3 changed files with 22 additions and 44 deletions
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2
bitstream_reader_derive/Cargo.toml
View file

@ -12,7 +12,7 @@ name = "bitstream_reader_derive"
proc-macro = true proc-macro = true
[dependencies] [dependencies]
syn = { version = "0.15" } syn = "0.15"
quote = "0.6" quote = "0.6"
proc-macro2 = "0.4" proc-macro2 = "0.4"
syn_util = "0.3" syn_util = "0.3"

16
src/buffer.rs
View file

@ -3,7 +3,7 @@ use std::fmt;
use std::fmt::Debug; use std::fmt::Debug;
use std::marker::PhantomData; use std::marker::PhantomData;
use std::mem::size_of; use std::mem::size_of;
use std::ops::BitOrAssign; use std::ops::{BitOrAssign, BitXor};
use std::rc::Rc; use std::rc::Rc;
use num_traits::{Float, PrimInt}; use num_traits::{Float, PrimInt};
@ -190,7 +190,7 @@ where
#[inline] #[inline]
pub fn read_int<T>(&self, position: usize, count: usize) -> Result<T> pub fn read_int<T>(&self, position: usize, count: usize) -> Result<T>
where where
T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt, T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt + BitXor,
{ {
let type_bit_size = size_of::<T>() * 8; let type_bit_size = size_of::<T>() * 8;
@ -227,7 +227,7 @@ where
self.read_no_fit_usize(position, count) self.read_no_fit_usize(position, count)
}; };
if count == type_bit_size && fit_usize { if count == type_bit_size {
Ok(value) Ok(value)
} else { } else {
Ok(self.make_signed(value, count)) Ok(self.make_signed(value, count))
@ -278,13 +278,15 @@ where
fn make_signed<T>(&self, value: T, count: usize) -> T fn make_signed<T>(&self, value: T, count: usize) -> T
where where
T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt, T: PrimInt + BitOrAssign + IsSigned + UncheckedPrimitiveInt + BitXor,
{ {
if T::is_signed() { if T::is_signed() {
let sign_bit = value >> (count - 1) & T::one(); let sign_bit = value >> (count - 1) & T::one();
let absolute_value = value & !(T::max_value() << (count - 1)); if sign_bit == T::one() {
let sign = T::one() - sign_bit - sign_bit; value | (T::zero() - T::one()) ^ ((T::one() << count) - T::one())
absolute_value * sign } else {
value
}
} else { } else {
value value
} }

48
tests/tests.rs
View file

@ -123,7 +123,7 @@ fn read_u64_be() {
fn read_i8_le() { fn read_i8_le() {
let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian); let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian);
assert_eq!(buffer.read_int::<i8>(0, 3).unwrap(), -0b01); assert_eq!(buffer.read_int::<i8>(0, 3).unwrap(), -0b11);
assert_eq!(buffer.read_int::<i8>(0, 8).unwrap(), -0b100_1011); assert_eq!(buffer.read_int::<i8>(0, 8).unwrap(), -0b100_1011);
} }
@ -132,7 +132,7 @@ fn read_i8_be() {
let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian); let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian);
assert_eq!(buffer.read_int::<i8>(1, 2).unwrap(), 0b1); assert_eq!(buffer.read_int::<i8>(1, 2).unwrap(), 0b1);
assert_eq!(buffer.read_int::<i8>(0, 3).unwrap(), -0b01); assert_eq!(buffer.read_int::<i8>(0, 3).unwrap(), -0b11);
assert_eq!(buffer.read_int::<i8>(0, 8).unwrap(), -0b100_1011); assert_eq!(buffer.read_int::<i8>(0, 8).unwrap(), -0b100_1011);
} }
@ -141,7 +141,7 @@ fn read_i16_le() {
let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian); let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian);
assert_eq!(buffer.read_int::<i16>(6, 12).unwrap(), 0b0_0110_1010_10); assert_eq!(buffer.read_int::<i16>(6, 12).unwrap(), 0b0_0110_1010_10);
assert_eq!(buffer.read_int::<i16>(6, 13).unwrap(), -0b00_0110_1010_10); assert_eq!(buffer.read_int::<i16>(6, 13).unwrap(), -0b11_1001_0101_10);
} }
#[test] #[test]
@ -149,7 +149,7 @@ fn read_i16_be() {
let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian); let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian);
assert_eq!(buffer.read_int::<i16>(6, 12).unwrap(), 0b1_0110_1010_10); assert_eq!(buffer.read_int::<i16>(6, 12).unwrap(), 0b1_0110_1010_10);
assert_eq!(buffer.read_int::<i16>(7, 12).unwrap(), -0b0110_1010_101); assert_eq!(buffer.read_int::<i16>(7, 12).unwrap(), -0b1001_0101_011);
} }
#[test] #[test]
@ -160,56 +160,32 @@ fn read_i32_le() {
buffer.read_int::<i32>(6, 24).unwrap(), buffer.read_int::<i32>(6, 24).unwrap(),
0b1_1001_1010_1100_0110_1010_10 0b1_1001_1010_1100_0110_1010_10
); );
assert_eq!( assert_eq!(buffer.read_int::<i32>(6, 26).unwrap(), -26824278);
buffer.read_int::<i32>(6, 26).unwrap(),
-0b001_1001_1010_1100_0110_1010_10
);
} }
#[test] #[test]
fn read_i32_be() { fn read_i32_be() {
let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian); let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian);
assert_eq!( assert_eq!(buffer.read_int::<i32>(7, 24).unwrap(), -4893108);
buffer.read_int::<i32>(7, 24).unwrap(),
-0b0110_1010_1010_1100_1001_100
);
} }
#[test] #[test]
fn read_i64_le() { fn read_i64_le() {
let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian); let buffer = BitBuffer::new(BYTES.to_vec(), LittleEndian);
assert_eq!( assert_eq!(buffer.read_int::<i64>(6, 34).unwrap(), -6871928406);
buffer.read_int::<i64>(6, 34).unwrap(), assert_eq!(buffer.read_int::<i64>(6, 59).unwrap(), -27471957726940758);
-0b001_1001_1001_1001_1010_1100_0110_1010_10 assert_eq!(buffer.read_int::<i64>(1, 64).unwrap(), -879102647262104230);
);
assert_eq!(
buffer.read_int::<i64>(6, 59).unwrap(),
-0b1110_01111001_1001_1001_1001_1001_1001_1001_1001_1010_1100_0110_1010_10
);
assert_eq!(
buffer.read_int::<i64>(1, 64).unwrap(),
-0b1110_01111001_1001_1001_1001_1001_1001_1001_1001_1010_1100_0110_1010_1011_010
);
} }
#[test] #[test]
fn read_i64_be() { fn read_i64_be() {
let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian); let buffer = BitBuffer::new(BYTES.to_vec(), BigEndian);
assert_eq!( assert_eq!(buffer.read_int::<i64>(7, 34).unwrap(), -5010541773);
buffer.read_int::<i64>(7, 34).unwrap(), assert_eq!(buffer.read_int::<i64>(7, 60).unwrap(), -336251766397153476);
-0b0110_1010_1010_1100_1001_1001_1001_1001_1 assert_eq!(buffer.read_int::<i64>(7, 64).unwrap(), -5380028262354455604);
);
assert_eq!(
buffer.read_int::<i64>(7, 60).unwrap(),
-0b0110_1010_1010_1100_1001_1001_1001_1001_1001_1001_1001_1001_1110_0111_100
);
assert_eq!(
buffer.read_int::<i64>(7, 64).unwrap(),
-0b0110_1010_1010_1100_1001_1001_1001_1001_1001_1001_1001_1001_1110_0111_1001_100
);
} }
#[test] #[test]