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Message-Id: <20210309210213.29539-1-ericonr@disroot.org>
Date: Tue, 9 Mar 2021 18:02:13 -0300
From: Érico Nogueira <ericonr@...root.org>
To: musl@...ts.openwall.com
Cc: Érico Nogueira <ericonr@...root.org>
Subject: [PATCH v3] add qsort_r and make qsort a wrapper around it
we make qsort a wrapper by providing a wrapper_cmp function that uses
the extra argument as a function pointer. should be optimized to a tail
call on most architectures, as long as it's built with
-fomit-frame-pointer, so the performance impact should be minimal.
to keep the git history clean, for now qsort_r is implemented in qsort.c
and qsort is implemented in qsort_nr.c. qsort.c also received a few
trivial cleanups, including replacing (*cmp)() calls with cmp().
qsort_nr.c contains only wrapper_cmp and qsort as a qsort_r wrapper
itself.
---
Following suggestions from IRC, as few changes as possible to the files,
a final clean up commit after this one would involve some git mv's (I
won't make a patch for it). Added weak_alias to force qsort to use
libc's qsort_r.
If this can't be accepted due to the overhead on some archs (ppc, mips,
arm in some situations?), maybe we could revisit v2 of the patch?
include/stdlib.h | 1 +
src/include/stdlib.h | 1 +
src/stdlib/qsort.c | 37 ++++++++++++++++++++-----------------
src/stdlib/qsort_nr.c | 14 ++++++++++++++
4 files changed, 36 insertions(+), 17 deletions(-)
create mode 100644 src/stdlib/qsort_nr.c
diff --git a/include/stdlib.h b/include/stdlib.h
index b54a051f..0c0ced5f 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -158,6 +158,7 @@ struct __locale_struct;
float strtof_l(const char *__restrict, char **__restrict, struct __locale_struct *);
double strtod_l(const char *__restrict, char **__restrict, struct __locale_struct *);
long double strtold_l(const char *__restrict, char **__restrict, struct __locale_struct *);
+void qsort_r (void *, size_t, size_t, int (*)(const void *, const void *, void *), void *);
#endif
#if defined(_LARGEFILE64_SOURCE) || defined(_GNU_SOURCE)
diff --git a/src/include/stdlib.h b/src/include/stdlib.h
index e9da2015..812b04de 100644
--- a/src/include/stdlib.h
+++ b/src/include/stdlib.h
@@ -8,6 +8,7 @@ hidden void __env_rm_add(char *, char *);
hidden int __mkostemps(char *, int, int);
hidden int __ptsname_r(int, char *, size_t);
hidden char *__randname(char *);
+hidden void __qsort_r (void *, size_t, size_t, int (*)(const void *, const void *, void *), void *);
hidden void *__libc_malloc(size_t);
hidden void *__libc_malloc_impl(size_t);
diff --git a/src/stdlib/qsort.c b/src/stdlib/qsort.c
index da58fd31..20e40dda 100644
--- a/src/stdlib/qsort.c
+++ b/src/stdlib/qsort.c
@@ -24,6 +24,7 @@
/* Smoothsort, an adaptive variant of Heapsort. Memory usage: O(1).
Run time: Worst case O(n log n), close to O(n) in the mostly-sorted case. */
+#define _GNU_SOURCE
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
@@ -31,7 +32,7 @@
#include "atomic.h"
#define ntz(x) a_ctz_l((x))
-typedef int (*cmpfun)(const void *, const void *);
+typedef int (*cmpfun)(const void *, const void *, void *);
static inline int pntz(size_t p[2]) {
int r = ntz(p[0] - 1);
@@ -88,7 +89,7 @@ static inline void shr(size_t p[2], int n)
p[1] >>= n;
}
-static void sift(unsigned char *head, size_t width, cmpfun cmp, int pshift, size_t lp[])
+static void sift(unsigned char *head, size_t width, cmpfun cmp, void *arg, int pshift, size_t lp[])
{
unsigned char *rt, *lf;
unsigned char *ar[14 * sizeof(size_t) + 1];
@@ -99,10 +100,10 @@ static void sift(unsigned char *head, size_t width, cmpfun cmp, int pshift, size
rt = head - width;
lf = head - width - lp[pshift - 2];
- if((*cmp)(ar[0], lf) >= 0 && (*cmp)(ar[0], rt) >= 0) {
+ if(cmp(ar[0], lf, arg) >= 0 && cmp(ar[0], rt, arg) >= 0) {
break;
}
- if((*cmp)(lf, rt) >= 0) {
+ if(cmp(lf, rt, arg) >= 0) {
ar[i++] = lf;
head = lf;
pshift -= 1;
@@ -115,7 +116,7 @@ static void sift(unsigned char *head, size_t width, cmpfun cmp, int pshift, size
cycle(width, ar, i);
}
-static void trinkle(unsigned char *head, size_t width, cmpfun cmp, size_t pp[2], int pshift, int trusty, size_t lp[])
+static void trinkle(unsigned char *head, size_t width, cmpfun cmp, void *arg, size_t pp[2], int pshift, int trusty, size_t lp[])
{
unsigned char *stepson,
*rt, *lf;
@@ -130,13 +131,13 @@ static void trinkle(unsigned char *head, size_t width, cmpfun cmp, size_t pp[2],
ar[0] = head;
while(p[0] != 1 || p[1] != 0) {
stepson = head - lp[pshift];
- if((*cmp)(stepson, ar[0]) <= 0) {
+ if(cmp(stepson, ar[0], arg) <= 0) {
break;
}
if(!trusty && pshift > 1) {
rt = head - width;
lf = head - width - lp[pshift - 2];
- if((*cmp)(rt, stepson) >= 0 || (*cmp)(lf, stepson) >= 0) {
+ if(cmp(rt, stepson, arg) >= 0 || cmp(lf, stepson, arg) >= 0) {
break;
}
}
@@ -150,11 +151,11 @@ static void trinkle(unsigned char *head, size_t width, cmpfun cmp, size_t pp[2],
}
if(!trusty) {
cycle(width, ar, i);
- sift(head, width, cmp, pshift, lp);
+ sift(head, width, cmp, arg, pshift, lp);
}
}
-void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
+void __qsort_r(void *base, size_t nel, size_t width, cmpfun cmp, void *arg)
{
size_t lp[12*sizeof(size_t)];
size_t i, size = width * nel;
@@ -173,16 +174,16 @@ void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
while(head < high) {
if((p[0] & 3) == 3) {
- sift(head, width, cmp, pshift, lp);
+ sift(head, width, cmp, arg, pshift, lp);
shr(p, 2);
pshift += 2;
} else {
if(lp[pshift - 1] >= high - head) {
- trinkle(head, width, cmp, p, pshift, 0, lp);
+ trinkle(head, width, cmp, arg, p, pshift, 0, lp);
} else {
- sift(head, width, cmp, pshift, lp);
+ sift(head, width, cmp, arg, pshift, lp);
}
-
+
if(pshift == 1) {
shl(p, 1);
pshift = 0;
@@ -191,12 +192,12 @@ void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
pshift = 1;
}
}
-
+
p[0] |= 1;
head += width;
}
- trinkle(head, width, cmp, p, pshift, 0, lp);
+ trinkle(head, width, cmp, arg, p, pshift, 0, lp);
while(pshift != 1 || p[0] != 1 || p[1] != 0) {
if(pshift <= 1) {
@@ -208,11 +209,13 @@ void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
pshift -= 2;
p[0] ^= 7;
shr(p, 1);
- trinkle(head - lp[pshift] - width, width, cmp, p, pshift + 1, 1, lp);
+ trinkle(head - lp[pshift] - width, width, cmp, arg, p, pshift + 1, 1, lp);
shl(p, 1);
p[0] |= 1;
- trinkle(head - width, width, cmp, p, pshift, 1, lp);
+ trinkle(head - width, width, cmp, arg, p, pshift, 1, lp);
}
head -= width;
}
}
+
+weak_alias(__qsort_r, qsort_r);
diff --git a/src/stdlib/qsort_nr.c b/src/stdlib/qsort_nr.c
new file mode 100644
index 00000000..fe408fb1
--- /dev/null
+++ b/src/stdlib/qsort_nr.c
@@ -0,0 +1,14 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+
+typedef int (*cmpfun)(const void *, const void *);
+
+static int wrapper_cmp(const void *v1, const void *v2, void *cmp)
+{
+ return ((cmpfun)cmp)(v1, v2);
+}
+
+void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
+{
+ __qsort_r(base, nel, width, wrapper_cmp, cmp);
+}
--
2.30.2
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