Initial check in of big integer library

third_party/bigint/BigIntegerUtils.hh

+#ifndef BIGINTEGERUTILS_H
+#define BIGINTEGERUTILS_H
+
+#include "BigInteger.hh"
+#include <string>
+#include <iostream>
+
+/* This file provides:
+ * - Convenient std::string <-> BigUnsigned/BigInteger conversion routines
+ * - std::ostream << operators for BigUnsigned/BigInteger */
+
+// std::string conversion routines.  Base 10 only.
+std::string bigUnsignedToString(const BigUnsigned &x);
+std::string bigIntegerToString(const BigInteger &x);
+BigUnsigned stringToBigUnsigned(const std::string &s);
+BigInteger stringToBigInteger(const std::string &s);
+
+// Creates a BigInteger from data such as `char's; read below for details.
+template <class T>
+BigInteger dataToBigInteger(const T* data, BigInteger::Index length, BigInteger::Sign sign);
+
+// Outputs x to os, obeying the flags `dec', `hex', `bin', and `showbase'.
+std::ostream &operator <<(std::ostream &os, const BigUnsigned &x);
+
+// Outputs x to os, obeying the flags `dec', `hex', `bin', and `showbase'.
+// My somewhat arbitrary policy: a negative sign comes before a base indicator (like -0xFF).
+std::ostream &operator <<(std::ostream &os, const BigInteger &x);
+
+// BEGIN TEMPLATE DEFINITIONS.
+
+/*
+ * Converts binary data to a BigInteger.
+ * Pass an array `data', its length, and the desired sign.
+ *
+ * Elements of `data' may be of any type `T' that has the following
+ * two properties (this includes almost all integral types):
+ *
+ * (1) `sizeof(T)' correctly gives the amount of binary data in one
+ * value of `T' and is a factor of `sizeof(Blk)'.
+ *
+ * (2) When a value of `T' is casted to a `Blk', the low bytes of
+ * the result contain the desired binary data.
+ */
+template <class T>
+BigInteger dataToBigInteger(const T* data, BigInteger::Index length, BigInteger::Sign sign) {
+        // really ceiling(numBytes / sizeof(BigInteger::Blk))
+        unsigned int pieceSizeInBits = 8 * sizeof(T);
+        unsigned int piecesPerBlock = sizeof(BigInteger::Blk) / sizeof(T);
+        unsigned int numBlocks = (length + piecesPerBlock - 1) / piecesPerBlock;
+
+        // Allocate our block array
+        BigInteger::Blk *blocks = new BigInteger::Blk[numBlocks];
+
+        BigInteger::Index blockNum, pieceNum, pieceNumHere;
+
+        // Convert
+        for (blockNum = 0, pieceNum = 0; blockNum < numBlocks; blockNum++) {
+                BigInteger::Blk curBlock = 0;
+                for (pieceNumHere = 0; pieceNumHere < piecesPerBlock && pieceNum < length;
+                        pieceNumHere++, pieceNum++)
+                        curBlock |= (BigInteger::Blk(data[pieceNum]) << (pieceSizeInBits * pieceNumHere));
+                blocks[blockNum] = curBlock;
+        }
+
+        // Create the BigInteger.
+        BigInteger x(blocks, numBlocks, sign);
+
+        delete [] blocks;
+        return x;
+}
+
+#endif