From 3866ef6158c1ddfe4927e1f88886189ad7a50752 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Fri, 1 Sep 2017 14:42:53 -0700 Subject: [PATCH] scratch_buffer: new module * lib/scratch_buffer.h, lib/scratch_buffer_grow.c: * lib/scratch_buffer_grow_preserve.c: * lib/scratch_buffer_set_array_size.c: New files, copied from glibc with very minor changes that can be copied back. * modules/scratch_buffer: New file. --- ChangeLog | 8 ++ lib/scratch_buffer.h | 135 ++++++++++++++++++++++++++++ lib/scratch_buffer_grow.c | 56 ++++++++++++ lib/scratch_buffer_grow_preserve.c | 67 ++++++++++++++ lib/scratch_buffer_set_array_size.c | 64 +++++++++++++ modules/scratch_buffer | 32 +++++++ 6 files changed, 362 insertions(+) create mode 100644 lib/scratch_buffer.h create mode 100644 lib/scratch_buffer_grow.c create mode 100644 lib/scratch_buffer_grow_preserve.c create mode 100644 lib/scratch_buffer_set_array_size.c create mode 100644 modules/scratch_buffer diff --git a/ChangeLog b/ChangeLog index af34bedbb2..078d5243cc 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,13 @@ 2017-09-01 Paul Eggert + scratch_buffer: new module + * lib/scratch_buffer.h, lib/scratch_buffer_grow.c: + * lib/scratch_buffer_grow_preserve.c: + * lib/scratch_buffer_set_array_size.c: + New files, copied from glibc with very minor changes that can be + copied back. + * modules/scratch_buffer: New file. + libc-config: new module * MODULES.html.sh: Add libc-config. * lib/cdefs.h: New file, copied from the GNU C Library with very diff --git a/lib/scratch_buffer.h b/lib/scratch_buffer.h new file mode 100644 index 0000000000..bb04662eb2 --- /dev/null +++ b/lib/scratch_buffer.h @@ -0,0 +1,135 @@ +/* Variable-sized buffer with on-stack default allocation. + Copyright (C) 2015-2017 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 + . */ + +#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 +#include +#include + +/* 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. */ + max_align_t __space[(1023 + sizeof (max_align_t)) / sizeof (max_align_t)]; +}; + +/* 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; + 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) + 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 */ diff --git a/lib/scratch_buffer_grow.c b/lib/scratch_buffer_grow.c new file mode 100644 index 0000000000..d2df028654 --- /dev/null +++ b/lib/scratch_buffer_grow.c @@ -0,0 +1,56 @@ +/* Variable-sized buffer with on-stack default allocation. + Copyright (C) 2015-2017 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 + . */ + +#ifndef _LIBC +# include +#endif + +#include +#include + +bool +__libc_scratch_buffer_grow (struct scratch_buffer *buffer) +{ + void *new_ptr; + size_t new_length = buffer->length * 2; + + /* Discard old buffer. */ + scratch_buffer_free (buffer); + + /* Check for overflow. */ + if (__glibc_likely (new_length >= buffer->length)) + new_ptr = malloc (new_length); + else + { + __set_errno (ENOMEM); + new_ptr = NULL; + } + + if (__glibc_unlikely (new_ptr == NULL)) + { + /* Buffer must remain valid to free. */ + scratch_buffer_init (buffer); + return false; + } + + /* Install new heap-based buffer. */ + buffer->data = new_ptr; + buffer->length = new_length; + return true; +} +libc_hidden_def (__libc_scratch_buffer_grow) diff --git a/lib/scratch_buffer_grow_preserve.c b/lib/scratch_buffer_grow_preserve.c new file mode 100644 index 0000000000..9268615311 --- /dev/null +++ b/lib/scratch_buffer_grow_preserve.c @@ -0,0 +1,67 @@ +/* Variable-sized buffer with on-stack default allocation. + Copyright (C) 2015-2017 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 + . */ + +#ifndef _LIBC +# include +#endif + +#include +#include +#include + +bool +__libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer) +{ + size_t new_length = 2 * buffer->length; + void *new_ptr; + + if (buffer->data == buffer->__space) + { + /* Move buffer to the heap. No overflow is possible because + buffer->length describes a small buffer on the stack. */ + new_ptr = malloc (new_length); + if (new_ptr == NULL) + return false; + memcpy (new_ptr, buffer->__space, buffer->length); + } + else + { + /* Buffer was already on the heap. Check for overflow. */ + if (__glibc_likely (new_length >= buffer->length)) + new_ptr = realloc (buffer->data, new_length); + else + { + __set_errno (ENOMEM); + new_ptr = NULL; + } + + if (__glibc_unlikely (new_ptr == NULL)) + { + /* Deallocate, but buffer must remain valid to free. */ + free (buffer->data); + scratch_buffer_init (buffer); + return false; + } + } + + /* Install new heap-based buffer. */ + buffer->data = new_ptr; + buffer->length = new_length; + return true; +} +libc_hidden_def (__libc_scratch_buffer_grow_preserve) diff --git a/lib/scratch_buffer_set_array_size.c b/lib/scratch_buffer_set_array_size.c new file mode 100644 index 0000000000..6fcc115340 --- /dev/null +++ b/lib/scratch_buffer_set_array_size.c @@ -0,0 +1,64 @@ +/* Variable-sized buffer with on-stack default allocation. + Copyright (C) 2015-2017 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 + . */ + +#ifndef _LIBC +# include +#endif + +#include +#include +#include + +bool +__libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer, + size_t nelem, size_t size) +{ + size_t new_length = nelem * size; + + /* Avoid overflow check if both values are small. */ + if ((nelem | size) >> (sizeof (size_t) * CHAR_BIT / 2) != 0 + && nelem != 0 && size != new_length / nelem) + { + /* Overflow. Discard the old buffer, but it must remain valid + to free. */ + scratch_buffer_free (buffer); + scratch_buffer_init (buffer); + __set_errno (ENOMEM); + return false; + } + + if (new_length <= buffer->length) + return true; + + /* Discard old buffer. */ + scratch_buffer_free (buffer); + + char *new_ptr = malloc (new_length); + if (new_ptr == NULL) + { + /* Buffer must remain valid to free. */ + scratch_buffer_init (buffer); + return false; + } + + /* Install new heap-based buffer. */ + buffer->data = new_ptr; + buffer->length = new_length; + return true; +} +libc_hidden_def (__libc_scratch_buffer_set_array_size) diff --git a/modules/scratch_buffer b/modules/scratch_buffer new file mode 100644 index 0000000000..7502d707db --- /dev/null +++ b/modules/scratch_buffer @@ -0,0 +1,32 @@ +Description: +Variable-sized buffer with on-stack default allocation. + +Files: +lib/scratch_buffer.h +lib/scratch_buffer_grow.c +lib/scratch_buffer_grow_preserve.c +lib/scratch_buffer_set_array_size.c + +Depends-on: +libc-config +stdbool +stddef + +configure.ac: +AC_CHECK_FUNCS_ONCE([__libc_scratch_buffer_grow]) +if test "$ac_cv_func___libc_scratch_buffer_grow" != yes; then + AC_LIBOBJ([scratch_buffer_grow]) + AC_LIBOBJ([scratch_buffer_grow_preserve]) + AC_LIBOBJ([scratch_buffer_set_array_size]) +fi + +Makefile.am: + +Include: + + +License: +LGPLv2+ + +Maintainer: +all, glibc -- 2.39.5