[PATCH v2 1/5] compat: add qsort_s()
- From
René Scharfe <l.s.r@web.de>
- Date
- Jan 22, 2017, 17:51 UTC
- Message-ID
- <1caa38ac-0214-441f-8e8a-1ade0839337e@web.de>
- In-Reply-To
- <67ac53cd-3fc0-8bd0-30f4-129281c3090f@web.de>
The function qsort_s() was introduced with C11 Annex K; it provides the ability to pass a context pointer to the comparison function, supports the convention of using a NULL pointer for an empty array and performs a few safety checks.
Add an implementation based on compat/qsort.c for platforms that lack a native standards-compliant qsort_s() (i.e. basically everyone). It doesn't perform the full range of possible checks: It uses size_t instead of rsize_t and doesn't check nmemb and size against RSIZE_MAX because we probably don't have the restricted size type defined. For the same reason it returns int instead of errno_t.
Signed-off-by: Rene Scharfe <l.s.r@web.de> --- Makefile | 8 +++++++ compat/qsort_s.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ git-compat-util.h | 6 +++++ 3 files changed, 83 insertions(+) create mode 100644 compat/qsort_s.c
diff --git a/Makefile b/Makefile index 27afd0f378..53ecc84e28 100644 --- a/Makefile +++ b/Makefile @@ -279,6 +279,9 @@ all:: # is a simplified version of the merge sort used in glibc. This is # recommended if Git triggers O(n^2) behavior in your platform's qsort(). # +# Define HAVE_ISO_QSORT_S if your platform provides a qsort_s() that's +# compatible with the one described in C11 Annex K. +# # Define UNRELIABLE_FSTAT if your system's fstat does not return the same # information on a not yet closed file that lstat would return for the same # file after it was closed. @@ -1418,6 +1421,11 @@ ifdef INTERNAL_QSORT COMPAT_CFLAGS += -DINTERNAL_QSORT COMPAT_OBJS += compat/qsort.o endif +ifdef HAVE_ISO_QSORT_S + COMPAT_CFLAGS += -DHAVE_ISO_QSORT_S +else + COMPAT_OBJS += compat/qsort_s.o +endif ifdef RUNTIME_PREFIX COMPAT_CFLAGS += -DRUNTIME_PREFIX endif diff --git a/compat/qsort_s.c b/compat/qsort_s.c new file mode 100644 index 0000000000..52d1f0a73d --- /dev/null +++ b/compat/qsort_s.c @@ -0,0 +1,69 @@ +#include "../git-compat-util.h" + +/* + * A merge sort implementation, simplified from the qsort implementation + * by Mike Haertel, which is a part of the GNU C Library. + * Added context pointer, safety checks and return value. + */ + +static void msort_with_tmp(void *b, size_t n, size_t s, + int (*cmp)(const void *, const void *, void *), + char *t, void *ctx) +{ + char *tmp; + char *b1, *b2; + size_t n1, n2; + + if (n <= 1) + return; + + n1 = n / 2; + n2 = n - n1; + b1 = b; + b2 = (char *)b + (n1 * s); + + msort_with_tmp(b1, n1, s, cmp, t, ctx); + msort_with_tmp(b2, n2, s, cmp, t, ctx); + + tmp = t; + + while (n1 > 0 && n2 > 0) { + if (cmp(b1, b2, ctx) <= 0) { + memcpy(tmp, b1, s); + tmp += s; + b1 += s; + --n1; + } else { + memcpy(tmp, b2, s); + tmp += s; + b2 += s; + --n2; + } + } + if (n1 > 0) + memcpy(tmp, b1, n1 * s); + memcpy(b, t, (n - n2) * s); +} + +int git_qsort_s(void *b, size_t n, size_t s, + int (*cmp)(const void *, const void *, void *), void *ctx) +{ + const size_t size = st_mult(n, s); + char buf[1024]; + + if (!n) + return 0; + if (!b || !cmp) + return -1; + + if (size < sizeof(buf)) { + /* The temporary array fits on the small on-stack buffer. */ + msort_with_tmp(b, n, s, cmp, buf, ctx); + } else { + /* It's somewhat large, so malloc it. */ + char *tmp = xmalloc(size); + msort_with_tmp(b, n, s, cmp, tmp, ctx); + free(tmp); + } + return 0; +} diff --git a/git-compat-util.h b/git-compat-util.h index 87237b092b..f706744e6a 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -988,6 +988,12 @@ static inline void sane_qsort(void *base, size_t nmemb, size_t size, qsort(base, nmemb, size, compar); } +#ifndef HAVE_ISO_QSORT_S +int git_qsort_s(void *base, size_t nmemb, size_t size, + int (*compar)(const void *, const void *, void *), void *ctx); +#define qsort_s git_qsort_s +#endif + #ifndef REG_STARTEND #error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd" #endif
-- 2.11.0