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Message-ID: <20210818201827.GM13220@brightrain.aerifal.cx>
Date: Wed, 18 Aug 2021 16:18:27 -0400
From: Rich Felker <dalias@...c.org>
To: Olivier Galibert <galibert@...ox.com>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] stdlib: implement qsort_r
On Wed, Aug 18, 2021 at 07:36:53PM +0200, Olivier Galibert wrote:
> The extension qsort_r allows calling qsort on a list of indices
> without having a global variable to hold the data to sort.
> ---
>
> I didn't see a "clean" patch for the wrapper version in the thread, so
> here is one. Passes libc-test, of course.
Here is the original patch, which also handles namespace correctly and
separates the translation units:
https://www.openwall.com/lists/musl/2021/03/09/10
Otherwise I think yours is roughly the same. I haven't checked whether
there are any other differences that should be resolved.
One change that should be made to either is that qsort_r should be
under _BSD_SOURCE, not _GNU_SOURCE.
> include/stdlib.h | 4 ++++
> src/stdlib/qsort.c | 39 +++++++++++++++++++++++++--------------
> 2 files changed, 29 insertions(+), 14 deletions(-)
>
> diff --git a/include/stdlib.h b/include/stdlib.h
> index b54a051f..cacb61bf 100644
> --- a/include/stdlib.h
> +++ b/include/stdlib.h
> @@ -55,6 +55,10 @@ int system (const char *);
> void *bsearch (const void *, const void *, size_t, size_t, int (*)(const void *, const void *));
> void qsort (void *, size_t, size_t, int (*)(const void *, const void *));
>
> +#if defined(_GNU_SOURCE)
> + void qsort_r (void *, size_t, size_t, int (*)(const void *, const void *, void *), void *);
> +#endif
> +
> int abs (int);
> long labs (long);
> long long llabs (long long);
> diff --git a/src/stdlib/qsort.c b/src/stdlib/qsort.c
> index da58fd31..9add0ac5 100644
> --- a/src/stdlib/qsort.c
> +++ b/src/stdlib/qsort.c
> @@ -32,6 +32,7 @@
> #define ntz(x) a_ctz_l((x))
>
> typedef int (*cmpfun)(const void *, const void *);
> +typedef int (*cmpfun_r)(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_r 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_r 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_r cmp, void *arg)
> {
> size_t lp[12*sizeof(size_t)];
> size_t i, size = width * nel;
> @@ -173,14 +174,14 @@ 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) {
> @@ -196,7 +197,7 @@ void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
> 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 +209,21 @@ 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;
> }
> }
> +
> +static int qsort_cmp(const void *e1, const void *e2, void *arg)
> +{
> + return ((cmpfun)arg)(e1, e2);
> +}
> +
> +void qsort(void *base, size_t nel, size_t width, cmpfun cmp)
> +{
> + return qsort_r(base, nel, width, qsort_cmp, cmp);
> +}
> --
> 2.32.0
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