зеркало из https://github.com/github/putty.git
221 строка
9.6 KiB
C
221 строка
9.6 KiB
C
/*
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* sshbn.h: the assorted conditional definitions of BignumInt and
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* multiply macros used throughout the bignum code to treat numbers as
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* arrays of the most conveniently sized word for the target machine.
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* Exported so that other code (e.g. poly1305) can use it too.
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*
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* This file must export, in whatever ifdef branch it ends up in:
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*
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* - two types: 'BignumInt' and 'BignumCarry'. BignumInt is an
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* unsigned integer type which will be used as the base word size
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* for all bignum operations. BignumCarry is an unsigned integer
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* type used to hold the carry flag taken as input and output by
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* the BignumADC macro (see below).
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*
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* - four constant macros: BIGNUM_INT_BITS, BIGNUM_INT_BYTES,
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* BIGNUM_TOP_BIT, BIGNUM_INT_MASK. These should be more or less
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* self-explanatory, but just in case, they give the number of bits
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* in BignumInt, the number of bytes that works out to, the
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* BignumInt value consisting of only the top bit, and the
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* BignumInt value with all bits set.
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*
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* - four statement macros: BignumADC, BignumMUL, BignumMULADD,
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* BignumMULADD2. These do various kinds of multi-word arithmetic,
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* and all produce two output values.
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* * BignumADC(ret,retc,a,b,c) takes input BignumInt values a,b
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* and a BignumCarry c, and outputs a BignumInt ret = a+b+c and
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* a BignumCarry retc which is the carry off the top of that
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* addition.
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* * BignumMUL(rh,rl,a,b) returns the two halves of the
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* double-width product a*b.
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* * BignumMULADD(rh,rl,a,b,addend) returns the two halves of the
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* double-width value a*b + addend.
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* * BignumMULADD2(rh,rl,a,b,addend1,addend2) returns the two
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* halves of the double-width value a*b + addend1 + addend2.
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*
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* Every branch of the main ifdef below defines the type BignumInt and
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* the value BIGNUM_INT_BITS. The other three constant macros are
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* filled in by common code further down.
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*
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* Most branches also define a macro DEFINE_BIGNUMDBLINT containing a
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* typedef statement which declares a type _twice_ the length of a
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* BignumInt. This causes the common code further down to produce a
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* default implementation of the four statement macros in terms of
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* that double-width type, and also to defined BignumCarry to be
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* BignumInt.
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*
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* However, if a particular compile target does not have a type twice
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* the length of the BignumInt you want to use but it does provide
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* some alternative means of doing add-with-carry and double-word
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* multiply, then the ifdef branch in question can just define
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* BignumCarry and the four statement macros itself, and that's fine
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* too.
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*/
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#if defined __SIZEOF_INT128__
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/*
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* 64-bit BignumInt using gcc/clang style 128-bit BignumDblInt.
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*
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* gcc and clang both provide a __uint128_t type on 64-bit targets
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* (and, when they do, indicate its presence by the above macro),
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* using the same 'two machine registers' kind of code generation
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* that 32-bit targets use for 64-bit ints.
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*/
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typedef unsigned long long BignumInt;
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#define BIGNUM_INT_BITS 64
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#define DEFINE_BIGNUMDBLINT typedef __uint128_t BignumDblInt
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#elif defined _MSC_VER && defined _M_AMD64
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/*
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* 64-bit BignumInt, using Visual Studio x86-64 compiler intrinsics.
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*
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* 64-bit Visual Studio doesn't provide very much in the way of help
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* here: there's no int128 type, and also no inline assembler giving
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* us direct access to the x86-64 MUL or ADC instructions. However,
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* there are compiler intrinsics giving us that access, so we can
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* use those - though it turns out we have to be a little careful,
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* since they seem to generate wrong code if their pointer-typed
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* output parameters alias their inputs. Hence all the internal temp
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* variables inside the macros.
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*/
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#include <intrin.h>
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typedef unsigned char BignumCarry; /* the type _addcarry_u64 likes to use */
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typedef unsigned __int64 BignumInt;
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#define BIGNUM_INT_BITS 64
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#define BignumADC(ret, retc, a, b, c) do \
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{ \
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BignumInt ADC_tmp; \
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(retc) = _addcarry_u64(c, a, b, &ADC_tmp); \
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(ret) = ADC_tmp; \
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} while (0)
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#define BignumMUL(rh, rl, a, b) do \
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{ \
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BignumInt MULADD_hi; \
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(rl) = _umul128(a, b, &MULADD_hi); \
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(rh) = MULADD_hi; \
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} while (0)
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#define BignumMULADD(rh, rl, a, b, addend) do \
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{ \
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BignumInt MULADD_lo, MULADD_hi; \
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MULADD_lo = _umul128(a, b, &MULADD_hi); \
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MULADD_hi += _addcarry_u64(0, MULADD_lo, (addend), &(rl)); \
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(rh) = MULADD_hi; \
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} while (0)
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#define BignumMULADD2(rh, rl, a, b, addend1, addend2) do \
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{ \
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BignumInt MULADD_lo1, MULADD_lo2, MULADD_hi; \
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MULADD_lo1 = _umul128(a, b, &MULADD_hi); \
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MULADD_hi += _addcarry_u64(0, MULADD_lo1, (addend1), &MULADD_lo2); \
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MULADD_hi += _addcarry_u64(0, MULADD_lo2, (addend2), &(rl)); \
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(rh) = MULADD_hi; \
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} while (0)
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#elif defined __GNUC__ || defined _LLP64 || __STDC__ >= 199901L
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/* 32-bit BignumInt, using C99 unsigned long long as BignumDblInt */
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typedef unsigned int BignumInt;
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#define BIGNUM_INT_BITS 32
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#define DEFINE_BIGNUMDBLINT typedef unsigned long long BignumDblInt
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#elif defined _MSC_VER && defined _M_IX86
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/* 32-bit BignumInt, using Visual Studio __int64 as BignumDblInt */
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typedef unsigned int BignumInt;
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#define BIGNUM_INT_BITS 32
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#define DEFINE_BIGNUMDBLINT typedef unsigned __int64 BignumDblInt
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#elif defined _LP64
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/*
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* 32-bit BignumInt, using unsigned long itself as BignumDblInt.
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*
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* Only for platforms where long is 64 bits, of course.
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*/
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typedef unsigned int BignumInt;
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#define BIGNUM_INT_BITS 32
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#define DEFINE_BIGNUMDBLINT typedef unsigned long BignumDblInt
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#else
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/*
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* 16-bit BignumInt, using unsigned long as BignumDblInt.
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*
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* This is the final fallback for real emergencies: C89 guarantees
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* unsigned short/long to be at least the required sizes, so this
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* should work on any C implementation at all. But it'll be
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* noticeably slow, so if you find yourself in this case you
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* probably want to move heaven and earth to find an alternative!
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*/
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typedef unsigned short BignumInt;
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#define BIGNUM_INT_BITS 16
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#define DEFINE_BIGNUMDBLINT typedef unsigned long BignumDblInt
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#endif
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/*
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* Common code across all branches of that ifdef: define the three
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* easy constant macros in terms of BIGNUM_INT_BITS.
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*/
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#define BIGNUM_INT_BYTES (BIGNUM_INT_BITS / 8)
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#define BIGNUM_TOP_BIT (((BignumInt)1) << (BIGNUM_INT_BITS-1))
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#define BIGNUM_INT_MASK (BIGNUM_TOP_BIT | (BIGNUM_TOP_BIT-1))
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/*
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* Common code across _most_ branches of the ifdef: define a set of
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* statement macros in terms of the BignumDblInt type provided. In
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* this case, we also define BignumCarry to be the same thing as
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* BignumInt, for simplicity.
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*/
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#ifdef DEFINE_BIGNUMDBLINT
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typedef BignumInt BignumCarry;
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#define BignumADC(ret, retc, a, b, c) do \
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{ \
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DEFINE_BIGNUMDBLINT; \
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BignumDblInt ADC_temp = (BignumInt)(a); \
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ADC_temp += (BignumInt)(b); \
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ADC_temp += (c); \
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(ret) = (BignumInt)ADC_temp; \
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(retc) = (BignumCarry)(ADC_temp >> BIGNUM_INT_BITS); \
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} while (0)
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#define BignumMUL(rh, rl, a, b) do \
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{ \
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DEFINE_BIGNUMDBLINT; \
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BignumDblInt MUL_temp = (BignumInt)(a); \
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MUL_temp *= (BignumInt)(b); \
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(rh) = (BignumInt)(MUL_temp >> BIGNUM_INT_BITS); \
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(rl) = (BignumInt)(MUL_temp); \
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} while (0)
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#define BignumMULADD(rh, rl, a, b, addend) do \
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{ \
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DEFINE_BIGNUMDBLINT; \
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BignumDblInt MUL_temp = (BignumInt)(a); \
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MUL_temp *= (BignumInt)(b); \
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MUL_temp += (BignumInt)(addend); \
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(rh) = (BignumInt)(MUL_temp >> BIGNUM_INT_BITS); \
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(rl) = (BignumInt)(MUL_temp); \
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} while (0)
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#define BignumMULADD2(rh, rl, a, b, addend1, addend2) do \
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{ \
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DEFINE_BIGNUMDBLINT; \
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BignumDblInt MUL_temp = (BignumInt)(a); \
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MUL_temp *= (BignumInt)(b); \
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MUL_temp += (BignumInt)(addend1); \
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MUL_temp += (BignumInt)(addend2); \
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(rh) = (BignumInt)(MUL_temp >> BIGNUM_INT_BITS); \
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(rl) = (BignumInt)(MUL_temp); \
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} while (0)
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#endif /* DEFINE_BIGNUMDBLINT */
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