init

.gitignore

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+target/
+**/*.rs.bk
+Cargo.lock

Cargo.toml

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+[package]
+name = "permute"
+version = "0.1.0"
+authors = ["hellerve <veit@veitheller.de>"]
+
+[dependencies]

README.md

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+# permute
+
+A Rust implementation of the unique random integer generation described
+[here](http://preshing.com/20121224/how-to-generate-a-sequence-of-unique-random-integers/).

src/lib.rs

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+pub struct RandomSeq {
+    idx: u32,
+    offs: u32,
+}
+
+
+fn permute_qpr(i: u32) -> u32 {
+    let x = i as u64;
+    let prime = 4294967291;
+    if x >= prime { return x as u32; }
+
+    let residue = (x * x) % prime;
+    if x <= prime / 2 {
+        return residue as u32;
+    }
+    return (prime - residue) as u32;
+}
+
+impl RandomSeq {
+    pub fn new(base: u32, offset: u32) -> RandomSeq {
+        RandomSeq {
+            idx: permute_qpr(permute_qpr(base) + 0x682f0161),
+            offs: permute_qpr(permute_qpr(offset) + 0x46790905),
+        }
+    }
+
+    pub fn next(&mut self) -> u32 {
+        let res =  permute_qpr((permute_qpr(self.idx) + self.offs) ^ 0x5bf03635);
+        self.idx += 1;
+        return res;
+    }
+}