diff options
Diffstat (limited to 'core/src/main/java/org/bouncycastle/pqc/math/linearalgebra/Permutation.java')
| -rw-r--r-- | core/src/main/java/org/bouncycastle/pqc/math/linearalgebra/Permutation.java | 247 |
1 files changed, 0 insertions, 247 deletions
diff --git a/core/src/main/java/org/bouncycastle/pqc/math/linearalgebra/Permutation.java b/core/src/main/java/org/bouncycastle/pqc/math/linearalgebra/Permutation.java deleted file mode 100644 index 28b58d34..00000000 --- a/core/src/main/java/org/bouncycastle/pqc/math/linearalgebra/Permutation.java +++ /dev/null @@ -1,247 +0,0 @@ -package org.bouncycastle.pqc.math.linearalgebra; - -import java.security.SecureRandom; - -/** - * This class implements permutations of the set {0,1,...,n-1} for some given n - * > 0, i.e., ordered sequences containing each number <tt>m</tt> (<tt>0 <= - * m < n</tt>) - * once and only once. - */ -public class Permutation -{ - - /** - * perm holds the elements of the permutation vector, i.e. <tt>[perm(0), - * perm(1), ..., perm(n-1)]</tt> - */ - private int[] perm; - - /** - * Create the identity permutation of the given size. - * - * @param n the size of the permutation - */ - public Permutation(int n) - { - if (n <= 0) - { - throw new IllegalArgumentException("invalid length"); - } - - perm = new int[n]; - for (int i = n - 1; i >= 0; i--) - { - perm[i] = i; - } - } - - /** - * Create a permutation using the given permutation vector. - * - * @param perm the permutation vector - */ - public Permutation(int[] perm) - { - if (!isPermutation(perm)) - { - throw new IllegalArgumentException( - "array is not a permutation vector"); - } - - this.perm = IntUtils.clone(perm); - } - - /** - * Create a permutation from an encoded permutation. - * - * @param enc the encoded permutation - */ - public Permutation(byte[] enc) - { - if (enc.length <= 4) - { - throw new IllegalArgumentException("invalid encoding"); - } - - int n = LittleEndianConversions.OS2IP(enc, 0); - int size = IntegerFunctions.ceilLog256(n - 1); - - if (enc.length != 4 + n * size) - { - throw new IllegalArgumentException("invalid encoding"); - } - - perm = new int[n]; - for (int i = 0; i < n; i++) - { - perm[i] = LittleEndianConversions.OS2IP(enc, 4 + i * size, size); - } - - if (!isPermutation(perm)) - { - throw new IllegalArgumentException("invalid encoding"); - } - - } - - /** - * Create a random permutation of the given size. - * - * @param n the size of the permutation - * @param sr the source of randomness - */ - public Permutation(int n, SecureRandom sr) - { - if (n <= 0) - { - throw new IllegalArgumentException("invalid length"); - } - - perm = new int[n]; - - int[] help = new int[n]; - for (int i = 0; i < n; i++) - { - help[i] = i; - } - - int k = n; - for (int j = 0; j < n; j++) - { - int i = RandUtils.nextInt(sr, k); - k--; - perm[j] = help[i]; - help[i] = help[k]; - } - } - - /** - * Encode this permutation as byte array. - * - * @return the encoded permutation - */ - public byte[] getEncoded() - { - int n = perm.length; - int size = IntegerFunctions.ceilLog256(n - 1); - byte[] result = new byte[4 + n * size]; - LittleEndianConversions.I2OSP(n, result, 0); - for (int i = 0; i < n; i++) - { - LittleEndianConversions.I2OSP(perm[i], result, 4 + i * size, size); - } - return result; - } - - /** - * @return the permutation vector <tt>(perm(0),perm(1),...,perm(n-1))</tt> - */ - public int[] getVector() - { - return IntUtils.clone(perm); - } - - /** - * Compute the inverse permutation <tt>P<sup>-1</sup></tt>. - * - * @return <tt>this<sup>-1</sup></tt> - */ - public Permutation computeInverse() - { - Permutation result = new Permutation(perm.length); - for (int i = perm.length - 1; i >= 0; i--) - { - result.perm[perm[i]] = i; - } - return result; - } - - /** - * Compute the product of this permutation and another permutation. - * - * @param p the other permutation - * @return <tt>this * p</tt> - */ - public Permutation rightMultiply(Permutation p) - { - if (p.perm.length != perm.length) - { - throw new IllegalArgumentException("length mismatch"); - } - Permutation result = new Permutation(perm.length); - for (int i = perm.length - 1; i >= 0; i--) - { - result.perm[i] = perm[p.perm[i]]; - } - return result; - } - - /** - * checks if given object is equal to this permutation. - * <p> - * The method returns false whenever the given object is not permutation. - * - * @param other - - * permutation - * @return true or false - */ - public boolean equals(Object other) - { - - if (!(other instanceof Permutation)) - { - return false; - } - Permutation otherPerm = (Permutation)other; - - return IntUtils.equals(perm, otherPerm.perm); - } - - /** - * @return a human readable form of the permutation - */ - public String toString() - { - String result = "[" + perm[0]; - for (int i = 1; i < perm.length; i++) - { - result += ", " + perm[i]; - } - result += "]"; - return result; - } - - /** - * @return the hash code of this permutation - */ - public int hashCode() - { - return perm.hashCode(); - } - - /** - * Check that the given array corresponds to a permutation of the set - * <tt>{0, 1, ..., n-1}</tt>. - * - * @param perm permutation vector - * @return true if perm represents an n-permutation and false otherwise - */ - private boolean isPermutation(int[] perm) - { - int n = perm.length; - boolean[] onlyOnce = new boolean[n]; - - for (int i = 0; i < n; i++) - { - if ((perm[i] < 0) || (perm[i] >= n) || onlyOnce[perm[i]]) - { - return false; - } - onlyOnce[perm[i]] = true; - } - - return true; - } - -} |