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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:16:34 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:16:34 +0000 |
commit | a398d2c2b5fd6ab0545d8bb019f9a970b2309404 (patch) | |
tree | 272fc7ab226258d7ceddee12c8c682c8e711c2b0 /lib/malloc/scratch_buffer.h | |
parent | Initial commit. (diff) | |
download | parted-a398d2c2b5fd6ab0545d8bb019f9a970b2309404.tar.xz parted-a398d2c2b5fd6ab0545d8bb019f9a970b2309404.zip |
Adding upstream version 3.6.upstream/3.6upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | lib/malloc/scratch_buffer.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/lib/malloc/scratch_buffer.h b/lib/malloc/scratch_buffer.h new file mode 100644 index 0000000..33fd2b2 --- /dev/null +++ b/lib/malloc/scratch_buffer.h @@ -0,0 +1,135 @@ +/* Variable-sized buffer with on-stack default allocation. + Copyright (C) 2015-2023 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#ifndef _SCRATCH_BUFFER_H +#define _SCRATCH_BUFFER_H + +/* Scratch buffers with a default stack allocation and fallback to + heap allocation. It is expected that this function is used in this + way: + + struct scratch_buffer tmpbuf; + scratch_buffer_init (&tmpbuf); + + while (!function_that_uses_buffer (tmpbuf.data, tmpbuf.length)) + if (!scratch_buffer_grow (&tmpbuf)) + return -1; + + scratch_buffer_free (&tmpbuf); + return 0; + + The allocation functions (scratch_buffer_grow, + scratch_buffer_grow_preserve, scratch_buffer_set_array_size) make + sure that the heap allocation, if any, is freed, so that the code + above does not have a memory leak. The buffer still remains in a + state that can be deallocated using scratch_buffer_free, so a loop + like this is valid as well: + + struct scratch_buffer tmpbuf; + scratch_buffer_init (&tmpbuf); + + while (!function_that_uses_buffer (tmpbuf.data, tmpbuf.length)) + if (!scratch_buffer_grow (&tmpbuf)) + break; + + scratch_buffer_free (&tmpbuf); + + scratch_buffer_grow and scratch_buffer_grow_preserve are guaranteed + to grow the buffer by at least 512 bytes. This means that when + using the scratch buffer as a backing store for a non-character + array whose element size, in bytes, is 512 or smaller, the scratch + buffer only has to grow once to make room for at least one more + element. +*/ + +#include <stdbool.h> +#include <stddef.h> +#include <stdlib.h> + +/* Scratch buffer. Must be initialized with scratch_buffer_init + before its use. */ +struct scratch_buffer { + void *data; /* Pointer to the beginning of the scratch area. */ + size_t length; /* Allocated space at the data pointer, in bytes. */ + union { max_align_t __align; char __c[1024]; } __space; +}; + +/* Initializes *BUFFER so that BUFFER->data points to BUFFER->__space + and BUFFER->length reflects the available space. */ +static inline void +scratch_buffer_init (struct scratch_buffer *buffer) +{ + buffer->data = buffer->__space.__c; + buffer->length = sizeof (buffer->__space); +} + +/* Deallocates *BUFFER (if it was heap-allocated). */ +static inline void +scratch_buffer_free (struct scratch_buffer *buffer) +{ + if (buffer->data != buffer->__space.__c) + free (buffer->data); +} + +/* Grow *BUFFER by some arbitrary amount. The buffer contents is NOT + preserved. Return true on success, false on allocation failure (in + which case the old buffer is freed). On success, the new buffer is + larger than the previous size. On failure, *BUFFER is deallocated, + but remains in a free-able state, and errno is set. */ +bool __libc_scratch_buffer_grow (struct scratch_buffer *buffer); +libc_hidden_proto (__libc_scratch_buffer_grow) + +/* Alias for __libc_scratch_buffer_grow. */ +static __always_inline bool +scratch_buffer_grow (struct scratch_buffer *buffer) +{ + return __glibc_likely (__libc_scratch_buffer_grow (buffer)); +} + +/* Like __libc_scratch_buffer_grow, but preserve the old buffer + contents on success, as a prefix of the new buffer. */ +bool __libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer); +libc_hidden_proto (__libc_scratch_buffer_grow_preserve) + +/* Alias for __libc_scratch_buffer_grow_preserve. */ +static __always_inline bool +scratch_buffer_grow_preserve (struct scratch_buffer *buffer) +{ + return __glibc_likely (__libc_scratch_buffer_grow_preserve (buffer)); +} + +/* Grow *BUFFER so that it can store at least NELEM elements of SIZE + bytes. The buffer contents are NOT preserved. Both NELEM and SIZE + can be zero. Return true on success, false on allocation failure + (in which case the old buffer is freed, but *BUFFER remains in a + free-able state, and errno is set). It is unspecified whether this + function can reduce the array size. */ +bool __libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer, + size_t nelem, size_t size); +libc_hidden_proto (__libc_scratch_buffer_set_array_size) + +/* Alias for __libc_scratch_set_array_size. */ +static __always_inline bool +scratch_buffer_set_array_size (struct scratch_buffer *buffer, + size_t nelem, size_t size) +{ + return __glibc_likely (__libc_scratch_buffer_set_array_size + (buffer, nelem, size)); +} + +#endif /* _SCRATCH_BUFFER_H */ |