cellbinutils
2.17cvs20070401

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Defines  
#define  UCHAR_MAX ((unsigned char)(1)) 
#define  DIGIT_MAX (UCHAR_MAX + 1) 
Functions  
void  sort_pointers (size_t n, void **pointers, void **work) 
void sort_pointers  (  size_t  n, 
void **  pointers,  
void **  work  
) 
Definition at line 47 of file sort.c.
{ /* The type of a single digit. This can be any unsigned integral type. When changing this, DIGIT_MAX should be changed as well. */ typedef unsigned char digit_t; /* The maximum value a single digit can have. */ #define DIGIT_MAX (UCHAR_MAX + 1) /* The Ith entry is the number of elements in *POINTERSP that have I in the digit on which we are currently sorting. */ unsigned int count[DIGIT_MAX]; /* Nonzero if we are running on a bigendian machine. */ int big_endian_p; size_t i; size_t j; /* The algorithm used here is radix sort which takes time linear in the number of elements in the array. */ /* The algorithm here depends on being able to swap the two arrays an even number of times. */ if ((sizeof (void *) / sizeof (digit_t)) % 2 != 0) abort (); /* Figure out the endianness of the machine. */ for (i = 0, j = 0; i < sizeof (size_t); ++i) { j *= (UCHAR_MAX + 1); j += i; } big_endian_p = (((char *)&j)[0] == 0); /* Move through the pointer values from least significant to most significant digits. */ for (i = 0; i < sizeof (void *) / sizeof (digit_t); ++i) { digit_t *digit; digit_t *bias; digit_t *top; unsigned int *countp; void **pointerp; /* The offset from the start of the pointer will depend on the endianness of the machine. */ if (big_endian_p) j = sizeof (void *) / sizeof (digit_t)  i; else j = i; /* Now, perform a stable sort on this digit. We use counting sort. */ memset (count, 0, DIGIT_MAX * sizeof (unsigned int)); /* Compute the address of the appropriate digit in the first and onepasttheend elements of the array. On a littleendian machine, the leastsignificant digit is closest to the front. */ bias = ((digit_t *) pointers) + j; top = ((digit_t *) (pointers + n)) + j; /* Count how many there are of each value. At the end of this loop, COUNT[K] will contain the number of pointers whose Ith digit is K. */ for (digit = bias; digit < top; digit += sizeof (void *) / sizeof (digit_t)) ++count[*digit]; /* Now, make COUNT[K] contain the number of pointers whose Ith digit is less than or equal to K. */ for (countp = count + 1; countp < count + DIGIT_MAX; ++countp) *countp += countp[1]; /* Now, drop the pointers into their correct locations. */ for (pointerp = pointers + n  1; pointerp >= pointers; pointerp) work[count[((digit_t *) pointerp)[j]]] = *pointerp; /* Swap WORK and POINTERS so that POINTERS contains the sorted array. */ pointerp = pointers; pointers = work; work = pointerp; } }