1 // Copyright 2014 PDFium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 // Original code by Matt McCutchen, see the LICENSE file.
6 
7 #ifndef BIGINTEGERUTILS_H
8 #define BIGINTEGERUTILS_H
9 
10 #include "BigInteger.hh"
11 #include <string>
12 #include <ostream>
13 
14 /* This file provides:
15  * - Convenient std::string <-> BigUnsigned/BigInteger conversion routines
16  * - std::ostream << operators for BigUnsigned/BigInteger */
17 
18 // std::string conversion routines.  Base 10 only.
19 std::string bigUnsignedToString(const BigUnsigned &x);
20 std::string bigIntegerToString(const BigInteger &x);
21 BigUnsigned stringToBigUnsigned(const std::string &s);
22 BigInteger stringToBigInteger(const std::string &s);
23 
24 // Creates a BigInteger from data such as `char's; read below for details.
25 template <class T>
26 BigInteger dataToBigInteger(const T* data, BigInteger::Index length, BigInteger::Sign sign);
27 
28 // Outputs x to os, obeying the flags `dec', `hex', `bin', and `showbase'.
29 std::ostream &operator <<(std::ostream &os, const BigUnsigned &x);
30 
31 // Outputs x to os, obeying the flags `dec', `hex', `bin', and `showbase'.
32 // My somewhat arbitrary policy: a negative sign comes before a base indicator (like -0xFF).
33 std::ostream &operator <<(std::ostream &os, const BigInteger &x);
34 
35 // BEGIN TEMPLATE DEFINITIONS.
36 
37 /*
38  * Converts binary data to a BigInteger.
39  * Pass an array `data', its length, and the desired sign.
40  *
41  * Elements of `data' may be of any type `T' that has the following
42  * two properties (this includes almost all integral types):
43  *
44  * (1) `sizeof(T)' correctly gives the amount of binary data in one
45  * value of `T' and is a factor of `sizeof(Blk)'.
46  *
47  * (2) When a value of `T' is casted to a `Blk', the low bytes of
48  * the result contain the desired binary data.
49  */
50 template <class T>
51 BigInteger dataToBigInteger(const T* data, BigInteger::Index length, BigInteger::Sign sign) {
52 	// really ceiling(numBytes / sizeof(BigInteger::Blk))
53 	unsigned int pieceSizeInBits = 8 * sizeof(T);
54 	unsigned int piecesPerBlock = sizeof(BigInteger::Blk) / sizeof(T);
55 	unsigned int numBlocks = (length + piecesPerBlock - 1) / piecesPerBlock;
56 
57 	// Allocate our block array
58 	BigInteger::Blk *blocks = new BigInteger::Blk[numBlocks];
59 
60 	BigInteger::Index blockNum, pieceNum, pieceNumHere;
61 
62 	// Convert
63 	for (blockNum = 0, pieceNum = 0; blockNum < numBlocks; blockNum++) {
64 		BigInteger::Blk curBlock = 0;
65 		for (pieceNumHere = 0; pieceNumHere < piecesPerBlock && pieceNum < length;
66 			pieceNumHere++, pieceNum++)
67 			curBlock |= (BigInteger::Blk(data[pieceNum]) << (pieceSizeInBits * pieceNumHere));
68 		blocks[blockNum] = curBlock;
69 	}
70 
71 	// Create the BigInteger.
72 	BigInteger x(blocks, numBlocks, sign);
73 
74 	delete [] blocks;
75 	return x;
76 }
77 
78 #endif
79