From: Kostya Shishkov <kostya.shishkov@gmail.com>
Date: Wed, 10 May 2017 17:07:27 +0000 (+0200)
Subject: integer code reader
X-Git-Url: https://git.nihav.org/?a=commitdiff_plain;h=d7fcdd86dd9f353e6f7b19bf84592698c4b020be;hp=0ca65ffdfd8d16f8eb3b13f9a0832c60921934cf;p=nihav.git

integer code reader
---

diff --git a/src/io/intcode.rs b/src/io/intcode.rs
new file mode 100644
index 0000000..141377d
--- /dev/null
+++ b/src/io/intcode.rs
@@ -0,0 +1,144 @@
+use io::bitreader::{BitReader, BitReaderError, BitReaderResult};
+
+#[derive(Debug)]
+pub enum UintCodeType {
+    UnaryOnes,
+    UnaryZeroes,
+    Unary012,
+    Unary210,
+    LimitedUnary(u32, u32),
+    Golomb(u8),
+    Rice(u8),
+    Gamma,
+    GammaP,
+}
+
+pub enum IntCodeType {
+    Golomb(u8),
+    Rice(u8),
+    Gamma,
+    GammaP,
+}
+
+pub trait IntCodeReader {
+    fn read_code(&mut self, t: UintCodeType) -> BitReaderResult<u32>;
+    fn read_code_signed(&mut self, t: IntCodeType) -> BitReaderResult<i32>;
+}
+
+fn read_unary(br: &mut BitReader, terminator: u32) -> BitReaderResult<u32> {
+    let mut res: u32 = 0;
+    loop {
+        if br.read(1)? == terminator { return Ok(res); }
+        res = res + 1;
+    }
+}
+
+fn read_unary_lim(br: &mut BitReader, terminator: u32, len: u32) -> BitReaderResult<u32> {
+    let mut res: u32 = 0;
+    loop {
+        if br.read(1)? == terminator { return Ok(res); }
+        res = res + 1;
+        if res == len { return Ok(res); }
+    }
+}
+
+fn read_unary210(br: &mut BitReader) -> BitReaderResult<u32> {
+    let val = read_unary_lim(br, 2, 0)?;
+    Ok(2 - val)
+}
+
+fn read_golomb(br: &mut BitReader, m: u8) -> BitReaderResult<u32> {
+    if m == 0 { return Err(BitReaderError::InvalidValue); }
+    let nbits = (8 - m.leading_zeros()) as u8;
+    if (m & (m - 1)) == 0 { return read_rice(br, nbits); }
+    let cutoff = ((1 << nbits) - m) as u32;
+    let pfx = read_unary(br, 0)?;
+    let tail = br.read(nbits - 1)?;
+    if tail < cutoff {
+        let res = pfx * (m as u32) + tail;
+        Ok (res)
+    } else {
+        let add = br.read(1)?;
+        let res = pfx * (m as u32) + (tail - cutoff) * 2 + add + cutoff;
+        Ok (res)
+    }
+}
+
+fn read_rice(br: &mut BitReader, k: u8) -> BitReaderResult<u32> {
+    let pfx = read_unary(br, 1)?;
+    let ret = (pfx << k) + br.read(k)?;
+    Ok(ret)
+}
+
+fn read_gamma(br: &mut BitReader) -> BitReaderResult<u32> {
+    let mut ret = 0;
+    while br.read(1)? != 1 {
+        ret = (ret << 1) | br.read(1)?;
+    }
+    Ok(ret)
+}
+
+fn read_gammap(br: &mut BitReader) -> BitReaderResult<u32> {
+    let pfx = read_unary(br, 1)?;
+    if pfx > 32 { return Err(BitReaderError::InvalidValue); }
+    let ret = (1 << pfx) + br.read(pfx as u8)?;
+    Ok(ret)
+}
+
+fn uval_to_sval0mp(uval: u32) -> i32 {
+    if (uval & 1) != 0 { -((uval >> 1) as i32) }
+    else               { (uval >> 1) as i32 }
+}
+
+fn uval_to_sval0pm(uval: u32) -> i32 {
+    if (uval & 1) != 0 { ((uval + 1) >> 1) as i32 }
+    else               { -((uval >> 1) as i32) }
+}
+
+impl<'a> IntCodeReader for BitReader<'a> {
+    fn read_code(&mut self, t: UintCodeType) -> BitReaderResult<u32> {
+        match t {
+            UintCodeType::UnaryOnes               => read_unary(self, 0),
+            UintCodeType::UnaryZeroes             => read_unary(self, 1),
+            UintCodeType::LimitedUnary(len, term) => read_unary_lim(self, term, len),
+            UintCodeType::Unary012                => read_unary_lim(self, 2, 0),
+            UintCodeType::Unary210                => read_unary210(self),
+            UintCodeType::Golomb(m)               => read_golomb(self, m),
+            UintCodeType::Rice(k)                 => read_rice(self, k),
+            UintCodeType::Gamma                   => read_gamma(self),
+            UintCodeType::GammaP                  => read_gammap(self),
+        }
+    }
+    #[allow(unused_variables)]
+    fn read_code_signed(&mut self, t: IntCodeType) -> BitReaderResult<i32> {
+        let uval =
+            match t {
+                IntCodeType::Golomb(m)               => read_golomb(self, m)?,
+                IntCodeType::Rice(k)                 => read_rice(self, k)?,
+                IntCodeType::Gamma                   => read_gamma(self)?,
+                IntCodeType::GammaP                  => read_gammap(self)?,
+            };
+        match t {
+            IntCodeType::Golomb(m)               => Ok(uval_to_sval0mp(uval)),
+            IntCodeType::Rice(k)                 => Ok(uval_to_sval0mp(uval)),
+            IntCodeType::Gamma                   => Ok(uval_to_sval0pm(uval)),
+            IntCodeType::GammaP                  => Ok(uval_to_sval0pm(uval)),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use io::bitreader::*;
+
+    #[test]
+    fn int_codes() {
+        const GDATA: [u8; 6] = [0b000_001_01, 0b0_0110_011, 0b1_1000_100, 0b1_1010_101, 0b10_10111_1, 0b1000_0000];
+        let src = &GDATA;
+        let mut br = BitReader::new(src, src.len(), BitReaderMode::BE);
+        for i in 0..11 {
+            assert_eq!(br.read_code(UintCodeType::Golomb(5)).unwrap(), i);
+        }
+    }
+}
diff --git a/src/io/mod.rs b/src/io/mod.rs
index 17f9c98..bfe78f6 100644
--- a/src/io/mod.rs
+++ b/src/io/mod.rs
@@ -1,5 +1,5 @@
 pub mod bitreader;
 pub mod codebook;
-
+pub mod intcode;
 pub mod byteio;