| Index: base/crc.h
|
| diff --git a/base/crc.h b/base/crc.h
|
| deleted file mode 100644
|
| index 26abe59eb4bc52a649da803e85aa174ea7ad14d3..0000000000000000000000000000000000000000
|
| --- a/base/crc.h
|
| +++ /dev/null
|
| @@ -1,140 +0,0 @@
|
| -// Copyright 2003-2009 Google Inc.
|
| -//
|
| -// Licensed under the Apache License, Version 2.0 (the "License");
|
| -// you may not use this file except in compliance with the License.
|
| -// You may obtain a copy of the License at
|
| -//
|
| -// http://www.apache.org/licenses/LICENSE-2.0
|
| -//
|
| -// Unless required by applicable law or agreed to in writing, software
|
| -// distributed under the License is distributed on an "AS IS" BASIS,
|
| -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
| -// See the License for the specific language governing permissions and
|
| -// limitations under the License.
|
| -// ========================================================================
|
| -
|
| -#ifndef _CRC_H_
|
| -#define _CRC_H_
|
| -
|
| -#include "base/basictypes.h"
|
| -
|
| -namespace omaha {
|
| -
|
| -// This class implements CRCs (aka Rabin Fingerprints).
|
| -// Treats the input as a polynomial with coefficients in Z(2),
|
| -// and finds the remainder when divided by an irreducible polynomial
|
| -// of the appropriate length.
|
| -// It handles all CRC sizes from 8 to 128 bits.
|
| -// The input string is prefixed with a "1" bit, and has "degree" "0" bits
|
| -// appended to it before the remainder is found. This ensures that
|
| -// short strings are scrambled somewhat.
|
| -
|
| -// A polynomial is represented by the bit pattern formed by its coefficients,
|
| -// but with the highest order bit not stored.
|
| -// The highest degree coefficient is stored in the lowest numbered bit
|
| -// in the the lowest adderessed byte. Thus, in what follows,
|
| -// the highest degree coeficient that is stored is in the low order bit
|
| -// of "lo" or "*lo".
|
| -
|
| -// Typical usage:
|
| -//
|
| -// // prepare to do 32-bit CRCs using the default polynomial. No rolling hash.
|
| -// scoped_ptr<CRC> crc(CRC::Default(32, 0));
|
| -// ...
|
| -// uint64 lo; // declare a lo,hi pair to hold the CRC
|
| -// uint64 hi;
|
| -// crc->Empty(&lo, &hi); // Initialize to CRC of empty string
|
| -// crc->Extend(&lo, &hi, "hello", 5); // Get CRC of "hello"
|
| -// ...
|
| -//
|
| -// // prepare to use a 32-bit rolling hash over 6 bytes
|
| -// scoped_ptr<CRC> crc(CRC::Default(32, 6));
|
| -// ...
|
| -// uint64 lo; // declare a lo,hi pair to hold the CRC
|
| -// uint64 hi;
|
| -// crc->Empty(&lo, &hi); // Initialize to CRC of empty string
|
| -// crc->Extend(&lo, &hi, data, 6); // Get CRC of first 6 bytes
|
| -// for (int i = 6; i != sizeof (data); i++) {
|
| -// crc->Roll(&lo, &hi, data[i-6], data[i]); // Move window by one byte
|
| -// // lo,hi is CRC of bytes data[i-5...i]
|
| -// }
|
| -// ...
|
| -//
|
| -
|
| -class CRC {
|
| -public:
|
| - // Initialize all the tables for CRC's of a given bit length "degree"
|
| - // using a default polynomial of the given length.
|
| - //
|
| - // The argument "roll_length" is used by subsequent calls to
|
| - // Roll().
|
| - // Returns a handle that MUST NOT be destroyed with delete.
|
| - // The default polynomials are those in POLYS[8...128].
|
| - // Handles returned by Default() MUST NOT be deleted.
|
| - // Identical calls to Default() yield identical handles.
|
| - static CRC *Default(int degree, size_t roll_length);
|
| -
|
| - // Initialize all the tables for CRC's of a given bit length "degree"
|
| - // using an arbitrary CRC polynomial.
|
| - // Normally, you would use Default() instead of New()---see above.
|
| - //
|
| - // Requires that "lo,hi" contain an irreducible polynomial of degree "degree"
|
| - // Requires 8 <= degree && degree <= 128
|
| - // Any irreducible polynomial of the correct degree will work.
|
| - // See the POLYS array for suitable irredicible polynomials.
|
| - //
|
| - // The argument "roll_length" is used by subsequent calls to
|
| - // Roll().
|
| - // Each call to New() yeilds a pointer to a new object
|
| - // that may be deallocated with delete.
|
| - static CRC *New(uint64 lo, uint64 hi, int degree, size_t roll_length);
|
| -
|
| - virtual ~CRC();
|
| -
|
| - // Place the CRC of the empty string in "*lo,*hi"
|
| - virtual void Empty(uint64 *lo, uint64 *hi) const = 0;
|
| -
|
| - // If "*lo,*hi" is the CRC of bytestring A, place the CRC of
|
| - // the bytestring formed from the concatenation of A and the "length"
|
| - // bytes at "bytes" into "*lo,*hi".
|
| - virtual void Extend(/*INOUT*/ uint64 *lo, /*INOUT*/ uint64 *hi,
|
| - const void *bytes, size_t length) const = 0;
|
| -
|
| - // Equivalent to Extend(lo, hi, bytes, length) where "bytes"
|
| - // points to an array of "length" zero bytes.
|
| - virtual void ExtendByZeroes(/*INOUT*/ uint64 *lo, /*INOUT*/ uint64 *hi,
|
| - size_t length) const = 0;
|
| -
|
| - // If "*lo,*hi" is the CRC of a byte string of length "roll_length"
|
| - // (which is an argument to New() and Default()) that consists of
|
| - // byte "o_byte" followed by string S, set "*lo,*hi" to the CRC of
|
| - // the string that consists of S followed by the byte "i_byte".
|
| - virtual void Roll(/*INOUT*/ uint64 *lo, /*INOUT*/ uint64 *hi,
|
| - uint8 o_byte, uint8 i_byte) const = 0;
|
| -
|
| - // POLYS[] is an array of valid triples that may be given to New()
|
| - static const struct Poly {
|
| - uint64 lo; // first half suitable CRC polynomial
|
| - uint64 hi; // second half of suitable CRC polynomial
|
| - int degree; // degree of suitable CRC polynomial
|
| - } *const POLYS;
|
| - // It is guaranteed that no two entries in POLYS[] are identical,
|
| - // that POLYS[i] cnotains a polynomial of degree i for 8 <= i <= 128,
|
| - // that POLYS[0] and POLYS[1] contains polynomials of degree 32,
|
| - // that POLYS[2] and POLYS[3] contains polynomials of degree 64,
|
| - // that POLYS[4] and POLYS[5] contains polynomials of degree 96, and
|
| - // that POLYS[6] and POLYS[7] contains polynomials of degree 128.
|
| -
|
| - static const int N_POLYS; // Number of elements in POLYS array.
|
| -
|
| -protected:
|
| - CRC(); // Clients may not call constructor;
|
| - // use Default() or New() instead.
|
| -
|
| -private:
|
| - DISALLOW_EVIL_CONSTRUCTORS(CRC);
|
| -};
|
| -
|
| -} // namespace omaha
|
| -
|
| -#endif
|
|
|