cc65/src/common/alignment.c

/*****************************************************************************/
/*                                                                           */
/*                                alignment.c                                */
/*                                                                           */
/*                             Address aligment                              */
/*                                                                           */
/*                                                                           */
/*                                                                           */
/* (C) 2011,      Ullrich von Bassewitz                                      */
/*                Roemerstrasse 52                                           */
/*                70794 Filderstadt                                          */
/* EMail:         uz@cc65.org                                                */
/*                                                                           */
/*                                                                           */
/* This software is provided 'as-is', without any expressed or implied       */
/* warranty.  In no event will the authors be held liable for any damages    */
/* arising from the use of this software.                                    */
/*                                                                           */
/* Permission is granted to anyone to use this software for any purpose,     */
/* including commercial applications, and to alter it and redistribute it    */
/* freely, subject to the following restrictions:                            */
/*                                                                           */
/* 1. The origin of this software must not be misrepresented; you must not   */
/*    claim that you wrote the original software. If you use this software   */
/*    in a product, an acknowledgment in the product documentation would be  */
/*    appreciated but is not required.                                       */
/* 2. Altered source versions must be plainly marked as such, and must not   */
/*    be misrepresented as being the original software.                      */
/* 3. This notice may not be removed or altered from any source              */
/*    distribution.                                                          */
/*                                                                           */
/*****************************************************************************/



/* common */
#include "alignment.h"
#include "check.h"



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/*                                   Data                                    */
/*****************************************************************************/



/* To factorize an alignment, we will use the following prime table. It lists
 * all primes up to 256, which means we're able to factorize alignments up to
 * 0x10000. This is checked in the code.
 */
static const unsigned char Primes[PRIME_COUNT] = {
      2,   3,   5,   7,  11,  13,  17,  19,  23,  29,
     31,  37,  41,  43,  47,  53,  59,  61,  67,  71,
     73,  79,  83,  89,  97, 101, 103, 107, 109, 113,
    127, 131, 137, 139, 149, 151, 157, 163, 167, 173,
    179, 181, 191, 193, 197, 199, 211, 223, 227, 229,
    233, 239, 241, 251
};
#define LAST_PRIME      ((unsigned long)Primes[PRIME_COUNT-1])

#define FAC_MAX         (LAST_PRIME * LAST_PRIME - 1)



/*****************************************************************************/
/*                                   Code                                    */
/*****************************************************************************/



static void Initialize (FactorizedNumber* F, unsigned long Value)
/* Initialize a FactorizedNumber structure */
{
    unsigned I;

    F->Value = Value;
    for (I = 0; I < PRIME_COUNT; ++I) {
        F->Powers[I] = 0;
    }
}



static unsigned char MaxPower (unsigned char A, unsigned char B)
/* Return the larger of A and B. This will get hopefully inlined by the
 * compiler.
 */
{
    return (A > B)? A : B;
}



static FactorizedNumber* Produce (FactorizedNumber* F)
/* Generate a value from a list of powers of primes and return F */
{
    unsigned I;

    F->Value = 1;
    for (I = 0; I < PRIME_COUNT; ++I) {
        unsigned Count = F->Powers[I];
        while (Count--) {
            F->Value *= Primes[I];
        }
    }
    return F;
}



void Factorize (unsigned long Value, FactorizedNumber* F)
/* Factorize a value between 1 and 0x10000. */
{
    unsigned I;

    /* Initialize F */
    Initialize (F, Value);

    /* If the value is 1 we're already done */
    if (Value == 1) {
        return;
    }

    /* Be sure we can factorize */
    CHECK (Value <= FAC_MAX && Value != 0);

    /* Handle factor 2 separately for speed */
    while ((Value & 0x01UL) == 0UL) {
        ++F->Powers[0];
        Value >>= 1;
    }

    /* Factorize. We don't need to check for array bounds since we checked the
     * maximum value above.
     */
    I = 1;      /* Skip 2 because it was handled above */
    while (Value > 1) {
        unsigned long Tmp = Value / Primes[I];
        if (Tmp * Primes[I] == Value) {
            /* This is a factor */
            ++F->Powers[I];
            Value = Tmp;
        } else {
            /* This is not a factor, try next one */
            ++I;
        }
    }
}



FactorizedNumber* LCM (const FactorizedNumber* Left,
                       const FactorizedNumber* Right,
                       FactorizedNumber* Res)
/* Calculate the least common multiple of two factorized numbers and return
 * the result.
 */
{
    unsigned I;

    /* Generate the powers for the lcm */
    for (I = 0; I < PRIME_COUNT; ++I) {
        Res->Powers[I] = MaxPower (Left->Powers[I], Right->Powers[I]);
    }

    /* Generate the actual lcm value from the powers and return the result */
    return Produce (Res);
}



unsigned long AlignAddr (unsigned long Addr, unsigned long Alignment)
/* Align an address to the given alignment */
{
    return ((Addr + Alignment - 1) / Alignment) * Alignment;
}