Re: [igt-dev] [PATCH i-g-t 1/3] lib/vec: Add igt_vec

Ville Syrjälä
2020-01-30T15:54:14Z

On Thu, Jan 30, 2020 at 03:31:41PM +0000, Chris Wilson wrote:
> Quoting Ville Syrjala (2020-01-30 15:12:27)
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Add a small std::vector lookalike which grows as needed.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > lib/Makefile.sources | 2 ++
> > lib/igt_vec.c | 86 ++++++++++++++++++++++++++++++++++++++++++++
> > lib/igt_vec.h | 40 +++++++++++++++++++++
> > lib/meson.build | 1 +
> > 4 files changed, 129 insertions(+)
> > create mode 100644 lib/igt_vec.c
> > create mode 100644 lib/igt_vec.h
> >
> > diff --git a/lib/Makefile.sources b/lib/Makefile.sources
> > index 631d6714e5ce..3e573f267e15 100644
> > --- a/lib/Makefile.sources
> > +++ b/lib/Makefile.sources
> > @@ -62,6 +62,8 @@ lib_source_list = \
> > igt_sysrq.h \
> > igt_x86.h \
> > igt_x86.c \
> > + igt_vec.c \
> > + igt_vec.h \
> > igt_vgem.c \
> > igt_vgem.h \
> > instdone.c \
> > diff --git a/lib/igt_vec.c b/lib/igt_vec.c
> > new file mode 100644
> > index 000000000000..dc4a6172fc8d
> > --- /dev/null
> > +++ b/lib/igt_vec.c
> > @@ -0,0 +1,86 @@
> > +/*
> > + * Copyright © 2020 Intel Corporation
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining a
> > + * copy of this software and associated documentation files (the "Software"),
> > + * to deal in the Software without restriction, including without limitation
> > + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > + * and/or sell copies of the Software, and to permit persons to whom the
> > + * Software is furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice (including the next
> > + * paragraph) shall be included in all copies or substantial portions of the
> > + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> > + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> > + * IN THE SOFTWARE.
> > + */
> > +
> > +#include <stdlib.h>
> > +#include <string.h>
> > +
> > +#include "igt_core.h"
> > +#include "igt_vec.h"
> > +
> > +void igt_vec_init(struct igt_vec *vec, int elem_size)
> > +{
> > + memset(vec, 0, sizeof(*vec));
> > + vec->elem_size = elem_size;
> > +}
> > +
> > +void igt_vec_fini(struct igt_vec *vec)
> > +{
> > + free(vec->elems);
> > + memset(vec, 0, sizeof(*vec));
> > +}
> > +
> > +void *igt_vec_elem(const struct igt_vec *vec, int idx)
> > +{
> > + igt_assert(idx < vec->len);
> > +
> > + return vec->elems + idx * vec->elem_size;
> > +}
> > +
> > +void igt_vec_push(struct igt_vec *vec, void *elem)
> > +{
> > + if (vec->len >= vec->size) {
> > + vec->size = vec->size ? vec->size * 2 : 8;
> > + vec->elems = realloc(vec->elems, vec->size * vec->elem_size);
> > + igt_assert(vec->elems);
> > + }
> > +
> > + vec->len++;
> > + memcpy(igt_vec_elem(vec, vec->len - 1), elem, vec->elem_size);
>
> I would have split this into
>
> void *igt_vec_grow(struct igt_vec *vec)
> {
> if (vec->len++ >= vec->size) {
> vec->size = vec->size ? vec->size * 2 : 8;
> vec->elems = realloc(vec->elems, vec->size * vec->elem_size);
> igt_assert(vec->elems);
> }
>
> return igt_vec_elem(vec, vec->len - 1);
> }
>
> igt_vec_push(vec, elem)
> {
> memcpy(igt_vec_grow(vec), elem, vec->size);
> }
>
> since we are happy to throw assertions and not worry too much about
> error propagation.

I can paint it like that.

>
> > +
> > + vec->len++;
> > +}
> > +
> > +int igt_vec_length(const struct igt_vec *vec)
> > +{
> > + return vec->len;
> > +}
> > +
> > +int igt_vec_index(const struct igt_vec *vec, void *elem)
> > +{
> > + for (int i = 0; i < vec->len; i++) {
> > + if (!memcmp(igt_vec_elem(vec, i), elem, vec->elem_size))
> > + return i;
> > + }
> > +
> > + return -1;
> > +}
> > +
> > +void igt_vec_remove(struct igt_vec *vec, int idx)
> > +{
> > + igt_assert(idx < vec->len);
> > +
> > + if (idx < vec->len - 1)
> > + memmove(igt_vec_elem(vec, idx),
> > + igt_vec_elem(vec, idx + 1),
> > + (vec->len - 1 - idx) * vec->elem_size);
>
> memmove of 0 not to your liking?

Don't think I've ever figured out if it works as expected.

>
> > +
> > + vec->len--;
> > +}
> > diff --git a/lib/igt_vec.h b/lib/igt_vec.h
> > new file mode 100644
> > index 000000000000..de2549a45841
> > --- /dev/null
> > +++ b/lib/igt_vec.h
> > @@ -0,0 +1,40 @@
> > +/*
> > + * Copyright © 2020 Intel Corporation
> > + *
> > + * Permission is hereby granted, free of charge, to any person obtaining a
> > + * copy of this software and associated documentation files (the "Software"),
> > + * to deal in the Software without restriction, including without limitation
> > + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > + * and/or sell copies of the Software, and to permit persons to whom the
> > + * Software is furnished to do so, subject to the following conditions:
> > + *
> > + * The above copyright notice and this permission notice (including the next
> > + * paragraph) shall be included in all copies or substantial portions of the
> > + * Software.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> > + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> > + * IN THE SOFTWARE.
> > + */
> > +
> > +#ifndef __IGT_VEC_H__
> > +#define __IGT_VEC_H__
> > +
> > +struct igt_vec {
> > + void *elems;
> > + int elem_size, size, len;
>
> I would have used char[0] and casting just to have a variable length
> struct :)

Then we'd have to reallocate the whole struct to grow it.
Wouldn't work since the caller owns the struct.

>
> I might have also used longs throughout instead of ints, or in this day
> and age, size_t.

I was actually thinking of something smaller since I doubt anyone
wants to use this with large amounts of data due to O(n).

>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> -Chris

--
Ville Syrjälä
Intel