/********************************************************************************************
* Supersingular Isogeny Key Encapsulation Library
*
* Abstract: configuration file and platform-dependent macros
*********************************************************************************************/  

#ifndef __CONFIG_H__
#define __CONFIG_H__

#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>


// Definition of compiler

#define COMPILER_GCC     1
#define COMPILER_CLANG   2

#if defined(__GNUC__)           // GNU GCC compiler
    #define COMPILER COMPILER_GCC   
#elif defined(__clang__)        // Clang compiler
    #define COMPILER COMPILER_CLANG
#else
    #error -- "Unsupported COMPILER"
#endif

#define _AMD64_

// Definition of the targeted architecture and basic data types
    
#define TARGET_AMD64        1
#define TARGET_x86          2
#define TARGET_ARM          3
#define TARGET_ARM64        4

#if defined(_AMD64_)
    #define TARGET TARGET_AMD64
    #define RADIX           64
    #define LOG2RADIX       6  
    typedef uint64_t        digit_t;        // Unsigned 64-bit digit
#elif defined(_X86_)
    #define TARGET TARGET_x86
    #define RADIX           32
    #define LOG2RADIX       5  
    typedef uint32_t        digit_t;        // Unsigned 32-bit digit
#elif defined(_ARM_)
    #define TARGET TARGET_ARM
    #define RADIX           32
    #define LOG2RADIX       5  
    typedef uint32_t        digit_t;        // Unsigned 32-bit digit
#elif defined(_ARM64_)
    #define TARGET TARGET_ARM64
    #define RADIX           64
    #define LOG2RADIX       6  
    typedef uint64_t        digit_t;        // Unsigned 64-bit digit
#else
    #error -- "Unsupported ARCHITECTURE"
#endif

#define RADIX64             64


// Selection of implementation: optimized_generic

#if defined(_OPTIMIZED_GENERIC_)                      
    #define OPTIMIZED_GENERIC_IMPLEMENTATION
#endif


// Extended datatype support
                     
typedef uint64_t uint128_t[2];
    

// Macro definitions

#define NBITS_TO_NBYTES(nbits)      (((nbits)+7)/8)                                          // Conversion macro from number of bits to number of bytes
#define NBITS_TO_NWORDS(nbits)      (((nbits)+(sizeof(digit_t)*8)-1)/(sizeof(digit_t)*8))    // Conversion macro from number of bits to number of computer words
#define NBYTES_TO_NWORDS(nbytes)    (((nbytes)+sizeof(digit_t)-1)/sizeof(digit_t))           // Conversion macro from number of bytes to number of computer words

// Macro to avoid compiler warnings when detecting unreferenced parameters
#define UNREFERENCED_PARAMETER(PAR) ((void)(PAR))


/********************** Constant-time unsigned comparisons ***********************/

// The following functions return 1 (TRUE) if condition is true, 0 (FALSE) otherwise

static __inline unsigned int is_digit_nonzero_ct(digit_t x)
{ // Is x != 0?
    return (unsigned int)((x | (0-x)) >> (RADIX-1));
}

static __inline unsigned int is_digit_zero_ct(digit_t x)
{ // Is x = 0?
    return (unsigned int)(1 ^ is_digit_nonzero_ct(x));
}

static __inline unsigned int is_digit_lessthan_ct(digit_t x, digit_t y)
{ // Is x < y?
    return (unsigned int)((x ^ ((x ^ y) | ((x - y) ^ y))) >> (RADIX-1)); 
}


/********************** Macros for platform-dependent operations **********************/

// Digit multiplication
#define MUL(multiplier, multiplicand, hi, lo)                                                     \
    digit_x_digit((multiplier), (multiplicand), &(lo));
    
// Digit addition with carry
#define ADDC(carryIn, addend1, addend2, carryOut, sumOut)                                         \
    { digit_t tempReg = (addend1) + (digit_t)(carryIn);                                           \
    (sumOut) = (addend2) + tempReg;                                                               \
    (carryOut) = (is_digit_lessthan_ct(tempReg, (digit_t)(carryIn)) | is_digit_lessthan_ct((sumOut), tempReg)); }

// Digit subtraction with borrow
#define SUBC(borrowIn, minuend, subtrahend, borrowOut, differenceOut)                             \
    { digit_t tempReg = (minuend) - (subtrahend);                                                 \
    unsigned int borrowReg = (is_digit_lessthan_ct((minuend), (subtrahend)) | ((borrowIn) & is_digit_zero_ct(tempReg)));  \
    (differenceOut) = tempReg - (digit_t)(borrowIn);                                              \
    (borrowOut) = borrowReg; }
    
// Shift right with flexible datatype
#define SHIFTR(highIn, lowIn, shift, shiftOut, DigitSize)                                         \
    (shiftOut) = ((lowIn) >> (shift)) ^ ((highIn) << (DigitSize - (shift)));
    
// Shift left with flexible datatype
#define SHIFTL(highIn, lowIn, shift, shiftOut, DigitSize)                                         \
    (shiftOut) = ((highIn) << (shift)) ^ ((lowIn) >> (DigitSize - (shift)));

// 64x64-bit multiplication
#define MUL128(multiplier, multiplicand, product)                                                 \
    mp_mul((digit_t*)&(multiplier), (digit_t*)&(multiplicand), (digit_t*)&(product), NWORDS_FIELD/2);

// 128-bit addition, inputs < 2^127
#define ADD128(addend1, addend2, addition)                                                        \
    mp_add((digit_t*)(addend1), (digit_t*)(addend2), (digit_t*)(addition), NWORDS_FIELD);

// 128-bit addition with output carry
#define ADC128(addend1, addend2, carry, addition)                                                 \
    (carry) = mp_add((digit_t*)(addend1), (digit_t*)(addend2), (digit_t*)(addition), NWORDS_FIELD);


#endif