Re: [PATCH 1/3] compat: add qsort_s()

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 1, 2016, 20:22 UTC
Message-ID: <xmqqy3zz8kmq.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <xmqq7f7j9zkd.fsf@gitster.mtv.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

> Eh, wait.  BSD and Microsoft have paramters reordered in the
> callback comparison function.  I suspect that would not fly very
> well.

Hmm.  We could do it like this, which may not be too bad.

#if APPLE_QSORT_R
struct apple_qsort_adapter {
	int (*user_cmp)(const void *, const void *, void *);
	void *user_ctx;
}

static int apple_qsort_adapter_cmp(void *ctx, const void *a, const void *b)
{
	struct apple_qsort_adapter *wrapper_ctx = ctx;
	return wrapper_ctx->user_cmp(a, b, wrapper_ctx->user_ctx);
}
#endif

int git_qsort_s(void *b, size_t n, size_t s,
      	   int (*cmp)(const void *, const void *, void *), void *ctx)
{
	if (!n)
		return 0;
	if (!b || !cmp)
		return -1;
#if GNU_QSORT_R
	qsort_r(b, n, s, cmp, ctx);
#elif APPLE_QSORT_R
	{
		struct appple_qsort_adapter a = { cmp, ctx };
		qsort_r(b, n, s, &a, appple_qsort_adapter_cmp);
	}
#endif
      return 0;
}