issue/55 simdcompression is a feature.

1 files changed, 34 insertions, 0 deletions

diff --git a/src/common/mod.rs b/src/common/mod.rs
index bf38fee..0c64d5f 100644
--- a/src/common/mod.rs
+++ b/src/common/mod.rs
@@ -25,3 +25,37 @@ pub trait HasLen {
     }
 }
 
+
+fn count_leading_zeros(mut val: u32) -> u8 {
+    if val == 0 {
+        return 32;
+    }
+    let mut result = 0u8;
+    while (val & (1u32 << 31)) == 0 {
+        val <<= 1;
+        result += 1;
+    }
+    result
+}
+
+
+pub fn compute_num_bits(amplitude: u32) -> u8 {
+    32u8 - count_leading_zeros(amplitude)
+}
+
+
+
+#[cfg(test)]
+mod test {
+    use super::compute_num_bits;
+    
+    fn test_compute_num_bits() {
+        assert_eq!(compute_num_bits(1), 1u8);
+        assert_eq!(compute_num_bits(0), 0u8);
+        assert_eq!(compute_num_bits(2), 2u8);
+        assert_eq!(compute_num_bits(3), 2u8);
+        assert_eq!(compute_num_bits(4), 3u8);
+        assert_eq!(compute_num_bits(255), 8u8);
+        assert_eq!(compute_num_bits(256), 9u8);
+    }
+}
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