Prep v240: Add check for qsort_r() and the function if not provided.

As elogind supports musl-libc, we have to remedy the situation that
upstream decided to make use of qsort_r(). This function is not
provided by musl-libc, so we have to provide an own variant.

The variant is an adaption of the qsort_r() algorithm found in
glibc-2.28, the disclaimer from their source files have been added.

Bug: #83
Signed-off-by: Sven Eden <sven.eden@prydeworx.com>

1 files changed, 499 insertions, 0 deletions

diff --git a/src/shared/qsort_r_missing.c b/src/shared/qsort_r_missing.c
new file mode 100644
index 000000000..ae2e63225
--- /dev/null
+++ b/src/shared/qsort_r_missing.c
@@ -0,0 +1,499 @@
+/***
+  This file is part of elogind.
+
+  Copyright 2017-2018 Sven Eden
+
+  elogind is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  elogind is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with elogind; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+
+#include "qsort_r_missing.h"
+
+#if HAVE_QSORT_R == 0
+
+#include <alloca.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+/***
+  Original disclaimer of glibc-2.28 msort.c concerning qsort_r() follows:
+***/
+
+/* An alternative to qsort, with an identical interface.
+   This file is part of the GNU C Library.
+   Copyright (C) 1992-2018 Free Software Foundation, Inc.
+   Written by Mike Haertel, September 1988.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+
+/* qsort_r() calls internal _quicksort() function from qsort.c. Disclaimer is as above. */
+static void quicksort ( void* const pbase, size_t total_elems, size_t size, compare_fn_t cmp, void* arg );
+
+struct msort_param {
+        size_t s;
+        size_t var;
+        compare_fn_t cmp;
+        void* arg;
+        char* t;
+};
+
+static void msort_with_tmp ( const struct msort_param* p, void* b, size_t n ) {
+        char* b1, *b2;
+        size_t n1, n2;
+
+        if ( n <= 1 )
+                return;
+
+        n1 = n / 2;
+        n2 = n - n1;
+        b1 = b;
+        b2 = ( char* ) b + ( n1 * p->s );
+
+        msort_with_tmp ( p, b1, n1 );
+        msort_with_tmp ( p, b2, n2 );
+
+        char* tmp = p->t;
+        const size_t s = p->s;
+        __compar_d_fn_t cmp = p->cmp;
+        void* arg = p->arg;
+        switch ( p->var ) {
+                case 0:
+                        while ( n1 > 0 && n2 > 0 ) {
+                                if ( ( *cmp ) ( b1, b2, arg ) <= 0 ) {
+                                        *( uint32_t* ) tmp = *( uint32_t* ) b1;
+                                        b1 += sizeof ( uint32_t );
+                                        --n1;
+                                } else {
+                                        *( uint32_t* ) tmp = *( uint32_t* ) b2;
+                                        b2 += sizeof ( uint32_t );
+                                        --n2;
+                                }
+                                tmp += sizeof ( uint32_t );
+                        }
+                        break;
+                case 1:
+                        while ( n1 > 0 && n2 > 0 ) {
+                                if ( ( *cmp ) ( b1, b2, arg ) <= 0 ) {
+                                        *( uint64_t* ) tmp = *( uint64_t* ) b1;
+                                        b1 += sizeof ( uint64_t );
+                                        --n1;
+                                } else {
+                                        *( uint64_t* ) tmp = *( uint64_t* ) b2;
+                                        b2 += sizeof ( uint64_t );
+                                        --n2;
+                                }
+                                tmp += sizeof ( uint64_t );
+                        }
+                        break;
+                case 2:
+                        while ( n1 > 0 && n2 > 0 ) {
+                                unsigned long* tmpl = ( unsigned long* ) tmp;
+                                unsigned long* bl;
+
+                                tmp += s;
+                                if ( ( *cmp ) ( b1, b2, arg ) <= 0 ) {
+                                        bl = ( unsigned long* ) b1;
+                                        b1 += s;
+                                        --n1;
+                                } else {
+                                        bl = ( unsigned long* ) b2;
+                                        b2 += s;
+                                        --n2;
+                                }
+                                while ( tmpl < ( unsigned long* ) tmp )
+                                        *tmpl++ = *bl++;
+                        }
+                        break;
+                case 3:
+                        while ( n1 > 0 && n2 > 0 ) {
+                                if ( ( *cmp ) ( *( const void** ) b1, *( const void** ) b2, arg ) <= 0 ) {
+                                        *( void** ) tmp = *( void** ) b1;
+                                        b1 += sizeof ( void* );
+                                        --n1;
+                                } else {
+                                        *( void** ) tmp = *( void** ) b2;
+                                        b2 += sizeof ( void* );
+                                        --n2;
+                                }
+                                tmp += sizeof ( void* );
+                        }
+                        break;
+                default:
+                        while ( n1 > 0 && n2 > 0 ) {
+                                if ( ( *cmp ) ( b1, b2, arg ) <= 0 ) {
+                                        tmp = ( char* ) memcpy ( tmp, b1, s );
+                                        b1 += s;
+                                        --n1;
+                                } else {
+                                        tmp = ( char* ) memcpy ( tmp, b2, s );
+                                        b2 += s;
+                                        --n2;
+                                }
+                        }
+                        break;
+        }
+
+        if ( n1 > 0 )
+                memcpy ( tmp, b1, n1 * s );
+        memcpy ( b, p->t, ( n - n2 ) * s );
+}
+
+void qsort_r ( void* b, size_t n, size_t s, compare_fn_t cmp, void* arg ) {
+        size_t size = n * s;
+        char* tmp = NULL;
+        struct msort_param p;
+
+        /* For large object sizes use indirect sorting.  */
+        if ( s > 32 )
+                size = 2 * n * sizeof ( void* ) + s;
+
+        if ( size < 1024 )
+                /* The temporary array is small, so put it on the stack.  */
+                p.t = alloca ( size );
+        else {
+                /* We should avoid allocating too much memory since this might
+                have to be backed up by swap space.  */
+                static long int phys_pages;
+                static int pagesize;
+
+                if ( pagesize == 0 ) {
+                        phys_pages = sysconf ( _SC_PHYS_PAGES );
+
+                        if ( phys_pages == -1 )
+                                /* Error while determining the memory size.  So let's
+                                   assume there is enough memory.  Otherwise the
+                                   implementer should provide a complete implementation of
+                                   the `sysconf' function.  */
+                                phys_pages = ( long int ) ( ~0ul >> 1 );
+
+                        /* The following determines that we will never use more than
+                           a quarter of the physical memory.  */
+                        phys_pages /= 4;
+
+                        /* Make sure phys_pages is written to memory.  */
+                        __asm ( "" ::: "memory" ); /*atomic_write_barrier () */
+
+                        pagesize = sysconf ( _SC_PAGESIZE );
+                }
+
+                /* Just a comment here.  We cannot compute
+                 phys_pages * pagesize
+                 and compare the needed amount of memory against this value.
+                 The problem is that some systems might have more physical
+                 memory then can be represented with a `size_t' value (when
+                 measured in bytes.  */
+
+                /* If the memory requirements are too high don't allocate memory.  */
+                if ( size / pagesize > ( size_t ) phys_pages ) {
+                        quicksort ( b, n, s, cmp, arg );
+                        return;
+                }
+
+                /* It's somewhat large, so malloc it.  */
+                int save = errno;
+                tmp = malloc ( size );
+                errno = ( save );
+                if ( tmp == NULL ) {
+                        /* Couldn't get space, so use the slower algorithm
+                           that doesn't need a temporary array.  */
+                        quicksort ( b, n, s, cmp, arg );
+                        return;
+                }
+                p.t = tmp;
+        }
+
+        p.s = s;
+        p.var = 4;
+        p.cmp = cmp;
+        p.arg = arg;
+
+        if ( s > 32 ) {
+                /* Indirect sorting.  */
+                char* ip = ( char* ) b;
+                void** tp = ( void** ) ( p.t + n * sizeof ( void* ) );
+                void** t = tp;
+                void* tmp_storage = ( void* ) ( tp + n );
+
+                while ( ( void* ) t < tmp_storage ) {
+                        *t++ = ip;
+                        ip += s;
+                }
+                p.s = sizeof ( void* );
+                p.var = 3;
+                msort_with_tmp ( &p, p.t + n * sizeof ( void* ), n );
+
+                /* tp[0] .. tp[n - 1] is now sorted, copy around entries of
+                the original array.  Knuth vol. 3 (2nd ed.) exercise 5.2-10.  */
+                char* kp;
+                size_t i;
+                for ( i = 0, ip = ( char* ) b; i < n; i++, ip += s )
+                        if ( ( kp = tp[i] ) != ip ) {
+                                size_t j = i;
+                                char* jp = ip;
+                                memcpy ( tmp_storage, ip, s );
+
+                                do {
+                                        size_t k = ( kp - ( char* ) b ) / s;
+                                        tp[j] = jp;
+                                        memcpy ( jp, kp, s );
+                                        j = k;
+                                        jp = kp;
+                                        kp = tp[k];
+                                } while ( kp != ip );
+
+                                tp[j] = jp;
+                                memcpy ( jp, tmp_storage, s );
+                        }
+        } else {
+                if ( ( s & ( sizeof ( uint32_t ) - 1 ) ) == 0
+                                && ( ( char* ) b - ( char* ) 0 ) % __alignof__ ( uint32_t ) == 0 ) {
+                        if ( s == sizeof ( uint32_t ) )
+                                p.var = 0;
+                        else if ( s == sizeof ( uint64_t )
+                                        && ( ( char* ) b - ( char* ) 0 ) % __alignof__ ( uint64_t ) == 0 )
+                                p.var = 1;
+                        else if ( ( s & ( sizeof ( unsigned long ) - 1 ) ) == 0
+                                        && ( ( char* ) b - ( char* ) 0 )
+                                        % __alignof__ ( unsigned long ) == 0 )
+                                p.var = 2;
+                }
+                msort_with_tmp ( &p, b, n );
+        }
+        free ( tmp );
+}
+
+/**** quicksort from qsort.c follows ****/
+
+/* Byte-wise swap two items of size SIZE. */
+#define SWAP(a, b, size)           \
+  do                               \
+    {                              \
+      size_t __size = (size);      \
+      char *__a = (a), *__b = (b); \
+      do                           \
+    {                              \
+      char __tmp = *__a;           \
+      *__a++ = *__b;               \
+      *__b++ = __tmp;              \
+    } while (--__size > 0);        \
+    } while (0)
+
+/* Discontinue quicksort algorithm when partition gets below this size.
+   This particular magic number was chosen to work best on a Sun 4/260. */
+#define MAX_THRESH 4
+
+/* Stack node declarations used to store unfulfilled partition obligations. */
+typedef struct {
+        char* lo;
+        char* hi;
+} stack_node;
+
+/* The next 4 #defines implement a very fast in-line stack abstraction. */
+/* The stack needs log (total_elements) entries (we could even subtract
+   log(MAX_THRESH)).  Since total_elements has type size_t, we get as
+   upper bound for log (total_elements):
+   bits per byte (CHAR_BIT) * sizeof(size_t).  */
+#define STACK_SIZE      (CHAR_BIT * sizeof(size_t))
+#define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
+#define POP(low, high)  ((void) (--top, (low = top->lo), (high = top->hi)))
+#define STACK_NOT_EMPTY (stack < top)
+
+/* Order size using quicksort.  This implementation incorporates
+   four optimizations discussed in Sedgewick:
+
+   1. Non-recursive, using an explicit stack of pointer that store the
+      next array partition to sort.  To save time, this maximum amount
+      of space required to store an array of SIZE_MAX is allocated on the
+      stack.  Assuming a 32-bit (64 bit) integer for size_t, this needs
+      only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).
+      Pretty cheap, actually.
+
+   2. Chose the pivot element using a median-of-three decision tree.
+      This reduces the probability of selecting a bad pivot value and
+      eliminates certain extraneous comparisons.
+
+   3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
+      insertion sort to order the MAX_THRESH items within each partition.
+      This is a big win, since insertion sort is faster for small, mostly
+      sorted array segments.
+
+   4. The larger of the two sub-partitions is always pushed onto the
+      stack first, with the algorithm then concentrating on the
+      smaller partition.  This *guarantees* no more than log (total_elems)
+      stack size is needed (actually O(1) in this case)!  */
+
+static void quicksort ( void* const pbase, size_t total_elems, size_t size, compare_fn_t cmp, void* arg ) {
+        char* base_ptr = ( char* ) pbase;
+
+        const size_t max_thresh = MAX_THRESH * size;
+
+        if ( total_elems == 0 )
+                /* Avoid lossage with unsigned arithmetic below.  */
+                return;
+
+        if ( total_elems > MAX_THRESH ) {
+                char* lo = base_ptr;
+                char* hi = &lo[size * ( total_elems - 1 )];
+                stack_node stack[STACK_SIZE];
+                stack_node* top = stack;
+
+                PUSH ( NULL, NULL );
+
+                while ( STACK_NOT_EMPTY ) {
+                        char* left_ptr;
+                        char* right_ptr;
+
+                        /* Select median value from among LO, MID, and HI. Rearrange
+                           LO and HI so the three values are sorted. This lowers the
+                           probability of picking a pathological pivot value and
+                           skips a comparison for both the LEFT_PTR and RIGHT_PTR in
+                           the while loops. */
+
+                        char* mid = lo + size * ( ( hi - lo ) / size >> 1 );
+
+                        if ( ( *cmp ) ( ( void* ) mid, ( void* ) lo, arg ) < 0 )
+                                SWAP ( mid, lo, size );
+                        if ( ( *cmp ) ( ( void* ) hi, ( void* ) mid, arg ) < 0 )
+                                SWAP ( mid, hi, size );
+                        else
+                                goto jump_over;
+                        if ( ( *cmp ) ( ( void* ) mid, ( void* ) lo, arg ) < 0 )
+                                SWAP ( mid, lo, size );
+                        jump_over:
+                        ;
+
+                        left_ptr  = lo + size;
+                        right_ptr = hi - size;
+
+                        /* Here's the famous ``collapse the walls'' section of quicksort.
+                           Gotta like those tight inner loops!  They are the main reason
+                           that this algorithm runs much faster than others. */
+                        do {
+                                while ( ( *cmp ) ( ( void* ) left_ptr, ( void* ) mid, arg ) < 0 )
+                                        left_ptr += size;
+
+                                while ( ( *cmp ) ( ( void* ) mid, ( void* ) right_ptr, arg ) < 0 )
+                                        right_ptr -= size;
+
+                                if ( left_ptr < right_ptr ) {
+                                        SWAP ( left_ptr, right_ptr, size );
+                                        if ( mid == left_ptr )
+                                                mid = right_ptr;
+                                        else if ( mid == right_ptr )
+                                                mid = left_ptr;
+                                        left_ptr += size;
+                                        right_ptr -= size;
+                                } else if ( left_ptr == right_ptr ) {
+                                        left_ptr += size;
+                                        right_ptr -= size;
+                                        break;
+                                }
+                        } while ( left_ptr <= right_ptr );
+
+                        /* Set up pointers for next iteration.  First determine whether
+                           left and right partitions are below the threshold size.  If so,
+                           ignore one or both.  Otherwise, push the larger partition's
+                           bounds on the stack and continue sorting the smaller one. */
+
+                        if ( ( size_t ) ( right_ptr - lo ) <= max_thresh ) {
+                                if ( ( size_t ) ( hi - left_ptr ) <= max_thresh )
+                                        /* Ignore both small partitions. */
+                                        POP ( lo, hi );
+                                else
+                                        /* Ignore small left partition. */
+                                        lo = left_ptr;
+                        } else if ( ( size_t ) ( hi - left_ptr ) <= max_thresh )
+                                /* Ignore small right partition. */
+                                hi = right_ptr;
+                        else if ( ( right_ptr - lo ) > ( hi - left_ptr ) ) {
+                                /* Push larger left partition indices. */
+                                PUSH ( lo, right_ptr );
+                                lo = left_ptr;
+                        } else {
+                                /* Push larger right partition indices. */
+                                PUSH ( left_ptr, hi );
+                                hi = right_ptr;
+                        }
+                }
+        }
+
+        /* Once the BASE_PTR array is partially sorted by quicksort the rest
+           is completely sorted using insertion sort, since this is efficient
+           for partitions below MAX_THRESH size. BASE_PTR points to the beginning
+           of the array to sort, and END_PTR points at the very last element in
+           the array (*not* one beyond it!). */
+
+#define min(x, y) ((x) < (y) ? (x) : (y))
+
+        {
+                char* const end_ptr = &base_ptr[size * ( total_elems - 1 )];
+                char* tmp_ptr = base_ptr;
+                char* thresh = min( end_ptr, base_ptr + max_thresh );
+                char* run_ptr;
+
+                /* Find smallest element in first threshold and place it at the
+                   array's beginning.  This is the smallest array element,
+                   and the operation speeds up insertion sort's inner loop. */
+
+                for ( run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size )
+                        if ( ( *cmp ) ( ( void* ) run_ptr, ( void* ) tmp_ptr, arg ) < 0 )
+                                tmp_ptr = run_ptr;
+
+                if ( tmp_ptr != base_ptr )
+                        SWAP ( tmp_ptr, base_ptr, size );
+
+                /* Insertion sort, running from left-hand-side up to right-hand-side.  */
+
+                run_ptr = base_ptr + size;
+                while ( ( run_ptr += size ) <= end_ptr ) {
+                        tmp_ptr = run_ptr - size;
+                        while ( ( *cmp ) ( ( void* ) run_ptr, ( void* ) tmp_ptr, arg ) < 0 )
+                                tmp_ptr -= size;
+
+                        tmp_ptr += size;
+                        if ( tmp_ptr != run_ptr ) {
+                                char* trav;
+
+                                trav = run_ptr + size;
+                                while ( --trav >= run_ptr ) {
+                                        char c = *trav;
+                                        char* hi, *lo;
+
+                                        for ( hi = lo = trav; ( lo -= size ) >= tmp_ptr; hi = lo )
+                                                * hi = *lo;
+                                        *hi = c;
+                                }
+                        }
+                }
+        }
+}
+
+#endif // HAVE_QSORT_R