util: add portable sort_r()

meson.build

@@ -365,6 +365,74 @@ config.set('TAISEI_BUILDCONF_HAVE_STATIC_ASSERT_WITHOUT_MSG', cc.compiles(
     args : ['-Werror']
 ))
 
+config.set('TAISEI_BUILDCONF_HAVE_GNU_QSORT_R', cc.links(
+    '''
+    #define _GNU_SOURCE
+    #include <stdlib.h>
+    #include <stdint.h>
+    int cmp(const void *a, const void *b, void *ctx) {
+        (*(int*)ctx)++;
+        return *(int*)a - *(int*)b;
+    }
+    int sort_test(size_t size, int array[size]) {
+        int i = 0;
+        qsort_r(array, size, sizeof(*array), cmp, &i);
+        return i;
+    }
+    int main(int argc, char **argv) {
+        volatile int a[] = { 1, 3, 3, 7, 9, 0, 0, 1 };
+        return sort_test(sizeof(a)/sizeof(*a), (int*)a);
+    }
+    ''',
+    name : 'GNU qsort_r()',
+    args : ['-Wall', '-Werror']
+))
+
+config.set('TAISEI_BUILDCONF_HAVE_BSD_QSORT_R', cc.links(
+    '''
+    #define _DEFAULT_SOURCE
+    #include <stdlib.h>
+    #include <stdint.h>
+    int cmp(void *ctx, const void *a, const void *b) {
+        (*(int*)ctx)++;
+        return *(int*)a - *(int*)b;
+    }
+    int sort_test(size_t size, int array[size]) {
+        int i = 0;
+        qsort_r(array, size, sizeof(*array), &i, cmp);
+        return i;
+    }
+    int main(int argc, char **argv) {
+        volatile int a[] = { 1, 3, 3, 7, 9, 0, 0, 1 };
+        return sort_test(sizeof(a)/sizeof(*a), (int*)a);
+    }
+    ''',
+    name : 'BSD qsort_r()',
+    args : ['-Wall', '-Werror']
+))
+
+config.set('TAISEI_BUILDCONF_HAVE_MICROSOFT_QSORT_S', cc.links(
+    '''
+    #include <stdlib.h>
+    #include <stdint.h>
+    int cmp(void *ctx, const void *a, const void *b) {
+        (*(int*)ctx)++;
+        return *(int*)a - *(int*)b;
+    }
+    int sort_test(size_t size, int array[size]) {
+        int i = 0;
+        qsort_s(array, size, sizeof(*array), cmp, &i);
+        return i;
+    }
+    int main(int argc, char **argv) {
+        volatile int a[] = { 1, 3, 3, 7, 9, 0, 0, 1 };
+        return sort_test(sizeof(a)/sizeof(*a), (int*)a);
+    }
+    ''',
+    name : 'Microsoft qsort_s()',
+    args : ['-Wall', '-Werror']
+))
+
 prefer_relpath_systems = [
     'windows',
 ]

src/util/meson.build

@@ -15,6 +15,7 @@ util_src = files(
     'miscmath.c',
     'pngcruft.c',
     'rectpack.c',
+    'sort_r.c',
     'strbuf.c',
     'stringops.c',
 )

src/util/sort_r.c

@@ -0,0 +1,306 @@
+/*
+ * This software is licensed under the terms of the MIT License.
+ * See COPYING for further information.
+ * ---
+ * Copyright (c) 2011-2024, Lukas Weber <laochailan@web.de>.
+ * Copyright (c) 2012-2024, Andrei Alexeyev <akari@taisei-project.org>.
+ */
+
+//
+// Adapted from https://github.com/noporpoise/sort_r
+//
+
+#include "sort_r.h"
+
+/* Isaac Turner 29 April 2014 Public Domain */
+
+#include <stdlib.h> /* qsort_r(), qsort_s() */
+#include <string.h> /* needed for memcpy() */
+
+/*
+
+sort_r function to be exported.
+
+Parameters:
+  base is the array to be sorted
+  nel is the number of elements in the array
+  width is the size in bytes of each element of the array
+  compar is the comparison function
+  arg is a pointer to be passed to the comparison function
+
+void sort_r(void *base, size_t nel, size_t width,
+            int (*compar)(const void *_a, const void *_b, void *_arg),
+            void *arg);
+
+*/
+
+#if defined TAISEI_BUILDCONF_HAVE_GNU_QSORT_R
+#  define _SORT_R_LINUX
+#elif defined TAISEI_BUILDCONF_HAVE_BSD_QSORT_R
+#  define _SORT_R_BSD
+#elif defined TAISEI_BUILDCONF_HAVE_MICROSOFT_QSORT_S
+#  define _SORT_R_WINDOWS
+#else
+  /* Using our own recursive quicksort sort_r_simple() */
+#endif
+
+#if (defined NESTED_QSORT && NESTED_QSORT == 0)
+#  undef NESTED_QSORT
+#endif
+
+#define SORT_R_SWAP(a,b,tmp) ((tmp) = (a), (a) = (b), (b) = (tmp))
+
+/* swap a and b */
+/* a and b must not be equal! */
+static void sort_r_swap(char *restrict a, char *restrict b, size_t w)
+{
+  char tmp, *end = a+w;
+  for(; a < end; a++, b++) { SORT_R_SWAP(*a, *b, tmp); }
+}
+
+/* swap a, b iff a>b */
+/* a and b must not be equal! */
+/* restrict is same as restrict but better support on old machines */
+static int sort_r_cmpswap(
+	char *restrict a,
+	char *restrict b, size_t w,
+	int (*compar)(const void *_a, const void *_b, void *_arg),
+	void *arg)
+{
+  if(compar(a, b, arg) > 0) {
+    sort_r_swap(a, b, w);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+Swap consecutive blocks of bytes of size na and nb starting at memory addr ptr,
+with the smallest swap so that the blocks are in the opposite order. Blocks may
+be internally re-ordered e.g.
+
+  12345ab  ->   ab34512
+  123abc   ->   abc123
+  12abcde  ->   deabc12
+*/
+static void sort_r_swap_blocks(char *ptr, size_t na, size_t nb)
+{
+  if(na > 0 && nb > 0) {
+    if(na > nb) { sort_r_swap(ptr, ptr+na, nb); }
+    else { sort_r_swap(ptr, ptr+nb, na); }
+  }
+}
+
+/* Implement recursive quicksort ourselves */
+/* Note: quicksort is not stable, equivalent values may be swapped */
+void sort_r_simple(
+	void *base, size_t nel, size_t w,
+	int (*compar)(const void *_a, const void *_b, void *_arg),
+	void *arg)
+{
+  char *b = (char *)base, *end = b + nel*w;
+
+  /* for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
+  printf("\n"); */
+
+  if(nel < 10) {
+    /* Insertion sort for arbitrarily small inputs */
+    char *pi, *pj;
+    for(pi = b+w; pi < end; pi += w) {
+      for(pj = pi; pj > b && sort_r_cmpswap(pj-w,pj,w,compar,arg); pj -= w) {}
+    }
+  }
+  else
+  {
+    /* nel > 6; Quicksort */
+
+    int cmp;
+    char *pl, *ple, *pr, *pre, *pivot;
+    char *last = b+w*(nel-1), *tmp;
+
+    /*
+    Use median of second, middle and second-last items as pivot.
+    First and last may have been swapped with pivot and therefore be extreme
+    */
+    char *l[3];
+    l[0] = b + w;
+    l[1] = b+w*(nel/2);
+    l[2] = last - w;
+
+    /* printf("pivots: %i, %i, %i\n", *(int*)l[0], *(int*)l[1], *(int*)l[2]); */
+
+    if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
+    if(compar(l[1],l[2],arg) > 0) {
+      SORT_R_SWAP(l[1], l[2], tmp);
+      if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
+    }
+
+    /* swap mid value (l[1]), and last element to put pivot as last element */
+    if(l[1] != last) { sort_r_swap(l[1], last, w); }
+
+    /*
+    pl is the next item on the left to be compared to the pivot
+    pr is the last item on the right that was compared to the pivot
+    ple is the left position to put the next item that equals the pivot
+    ple is the last right position where we put an item that equals the pivot
+
+                                           v- end (beyond the array)
+      EEEEEELLLLLLLLuuuuuuuuGGGGGGGEEEEEEEE.
+      ^- b  ^- ple  ^- pl   ^- pr  ^- pre ^- last (where the pivot is)
+
+    Pivot comparison key:
+      E = equal, L = less than, u = unknown, G = greater than, E = equal
+    */
+    pivot = last;
+    ple = pl = b;
+    pre = pr = last;
+
+    /*
+    Strategy:
+    Loop into the list from the left and right at the same time to find:
+    - an item on the left that is greater than the pivot
+    - an item on the right that is less than the pivot
+    Once found, they are swapped and the loop continues.
+    Meanwhile items that are equal to the pivot are moved to the edges of the
+    array.
+    */
+    while(pl < pr) {
+      /* Move left hand items which are equal to the pivot to the far left.
+         break when we find an item that is greater than the pivot */
+      for(; pl < pr; pl += w) {
+        cmp = compar(pl, pivot, arg);
+        if(cmp > 0) { break; }
+        else if(cmp == 0) {
+          if(ple < pl) { sort_r_swap(ple, pl, w); }
+          ple += w;
+        }
+      }
+      /* break if last batch of left hand items were equal to pivot */
+      if(pl >= pr) { break; }
+      /* Move right hand items which are equal to the pivot to the far right.
+         break when we find an item that is less than the pivot */
+      for(; pl < pr; ) {
+        pr -= w; /* Move right pointer onto an unprocessed item */
+        cmp = compar(pr, pivot, arg);
+        if(cmp == 0) {
+          pre -= w;
+          if(pr < pre) { sort_r_swap(pr, pre, w); }
+        }
+        else if(cmp < 0) {
+          if(pl < pr) { sort_r_swap(pl, pr, w); }
+          pl += w;
+          break;
+        }
+      }
+    }
+
+    pl = pr; /* pr may have gone below pl */
+
+    /*
+    Now we need to go from: EEELLLGGGGEEEE
+                        to: LLLEEEEEEEGGGG
+
+    Pivot comparison key:
+      E = equal, L = less than, u = unknown, G = greater than, E = equal
+    */
+    sort_r_swap_blocks(b, ple-b, pl-ple);
+    sort_r_swap_blocks(pr, pre-pr, end-pre);
+
+    /*for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
+    printf("\n");*/
+
+    sort_r_simple(b, (pl-ple)/w, w, compar, arg);
+    sort_r_simple(end-(pre-pr), (pre-pr)/w, w, compar, arg);
+  }
+}
+
+
+#if defined NESTED_QSORT
+
+  static void sort_r(void *base, size_t nel, size_t width,
+                                    int (*compar)(const void *_a,
+                                                  const void *_b,
+                                                  void *aarg),
+                                    void *arg)
+  {
+    int nested_cmp(const void *a, const void *b)
+    {
+      return compar(a, b, arg);
+    }
+
+    qsort(base, nel, width, nested_cmp);
+  }
+
+#else /* !NESTED_QSORT */
+
+  /* Declare structs and functions */
+
+  #if defined _SORT_R_BSD
+
+    /* Ensure qsort_r is defined */
+    extern void qsort_r(
+			void *base, size_t nel, size_t width, void *thunk,
+			int (*compar)(void *_thunk, const void *_a, const void *_b));
+
+  #endif
+
+  #if defined _SORT_R_BSD || defined _SORT_R_WINDOWS
+
+    /* BSD (qsort_r), Windows (qsort_s) require argument swap */
+
+    struct sort_r_data
+    {
+      void *arg;
+      int (*compar)(const void *_a, const void *_b, void *_arg);
+    };
+
+    static int sort_r_arg_swap(void *s, const void *a, const void *b)
+    {
+      struct sort_r_data *ss = (struct sort_r_data*)s;
+      return (ss->compar)(a, b, ss->arg);
+    }
+
+  #endif
+
+  #if defined _SORT_R_LINUX
+
+    typedef int(* __compar_d_fn_t)(const void *, const void *, void *);
+    extern void (qsort_r)(void *base, size_t nel, size_t width,
+                          __compar_d_fn_t __compar, void *arg)
+      __attribute__((nonnull (1, 4)));
+
+  #endif
+
+  /* implementation */
+	void sort_r(
+		void *base, size_t nel, size_t width,
+		int (*compar)(const void *_a, const void *_b, void *_arg),
+		void *arg)
+  {
+    #if defined _SORT_R_LINUX
+
+        qsort_r(base, nel, width, compar, arg);
+
+    #elif defined _SORT_R_BSD
+
+      struct sort_r_data tmp;
+      tmp.arg = arg;
+      tmp.compar = compar;
+      qsort_r(base, nel, width, &tmp, sort_r_arg_swap);
+
+    #elif defined _SORT_R_WINDOWS
+
+      struct sort_r_data tmp;
+      tmp.arg = arg;
+      tmp.compar = compar;
+      qsort_s(base, nel, width, sort_r_arg_swap, &tmp);
+
+    #else
+
+      /* Fall back to our own quicksort implementation */
+      sort_r_simple(base, nel, width, compar, arg);
+
+    #endif
+  }
+
+#endif /* !NESTED_QSORT */