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Diffstat (limited to 'malloc/dynarray.h')
| -rw-r--r-- | malloc/dynarray.h | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/malloc/dynarray.h b/malloc/dynarray.h new file mode 100644 index 0000000000..0b171da78c --- /dev/null +++ b/malloc/dynarray.h @@ -0,0 +1,179 @@ +/* Type-safe arrays which grow dynamically. Shared definitions. + Copyright (C) 2017-2018 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 + <http://www.gnu.org/licenses/>. */ + +/* To use the dynarray facility, you need to include + <malloc/dynarray-skeleton.c> and define the parameter macros + documented in that file. + + A minimal example which provides a growing list of integers can be + defined like this: + + struct int_array + { + // Pointer to result array followed by its length, + // as required by DYNARRAY_FINAL_TYPE. + int *array; + size_t length; + }; + + #define DYNARRAY_STRUCT dynarray_int + #define DYNARRAY_ELEMENT int + #define DYNARRAY_PREFIX dynarray_int_ + #define DYNARRAY_FINAL_TYPE struct int_array + #include <malloc/dynarray-skeleton.c> + + To create a three-element array with elements 1, 2, 3, use this + code: + + struct dynarray_int dyn; + dynarray_int_init (&dyn); + for (int i = 1; i <= 3; ++i) + { + int *place = dynarray_int_emplace (&dyn); + assert (place != NULL); + *place = i; + } + struct int_array result; + bool ok = dynarray_int_finalize (&dyn, &result); + assert (ok); + assert (result.length == 3); + assert (result.array[0] == 1); + assert (result.array[1] == 2); + assert (result.array[2] == 3); + free (result.array); + + If the elements contain resources which must be freed, define + DYNARRAY_ELEMENT_FREE appropriately, like this: + + struct str_array + { + char **array; + size_t length; + }; + + #define DYNARRAY_STRUCT dynarray_str + #define DYNARRAY_ELEMENT char * + #define DYNARRAY_ELEMENT_FREE(ptr) free (*ptr) + #define DYNARRAY_PREFIX dynarray_str_ + #define DYNARRAY_FINAL_TYPE struct str_array + #include <malloc/dynarray-skeleton.c> + + Compared to scratch buffers, dynamic arrays have the following + features: + + - They have an element type, and are not just an untyped buffer of + bytes. + + - When growing, previously stored elements are preserved. (It is + expected that scratch_buffer_grow_preserve and + scratch_buffer_set_array_size eventually go away because all + current users are moved to dynamic arrays.) + + - Scratch buffers have a more aggressive growth policy because + growing them typically means a retry of an operation (across an + NSS service module boundary), which is expensive. + + - For the same reason, scratch buffers have a much larger initial + stack allocation. */ + +#ifndef _DYNARRAY_H +#define _DYNARRAY_H + +#include <stdbool.h> +#include <stddef.h> +#include <string.h> + +struct dynarray_header +{ + size_t used; + size_t allocated; + void *array; +}; + +/* Marker used in the allocated member to indicate that an error was + encountered. */ +static inline size_t +__dynarray_error_marker (void) +{ + return -1; +} + +/* Internal function. See the has_failed function in + dynarray-skeleton.c. */ +static inline bool +__dynarray_error (struct dynarray_header *list) +{ + return list->allocated == __dynarray_error_marker (); +} + +/* Internal function. Enlarge the dynamically allocated area of the + array to make room for one more element. SCRATCH is a pointer to + the scratch area (which is not heap-allocated and must not be + freed). ELEMENT_SIZE is the size, in bytes, of one element. + Return false on failure, true on success. */ +bool __libc_dynarray_emplace_enlarge (struct dynarray_header *, + void *scratch, size_t element_size); + +/* Internal function. Enlarge the dynamically allocated area of the + array to make room for at least SIZE elements (which must be larger + than the existing used part of the dynamic array). SCRATCH is a + pointer to the scratch area (which is not heap-allocated and must + not be freed). ELEMENT_SIZE is the size, in bytes, of one element. + Return false on failure, true on success. */ +bool __libc_dynarray_resize (struct dynarray_header *, size_t size, + void *scratch, size_t element_size); + +/* Internal function. Like __libc_dynarray_resize, but clear the new + part of the dynamic array. */ +bool __libc_dynarray_resize_clear (struct dynarray_header *, size_t size, + void *scratch, size_t element_size); + +/* Internal type. */ +struct dynarray_finalize_result +{ + void *array; + size_t length; +}; + +/* Internal function. Copy the dynamically-allocated area to an + explicitly-sized heap allocation. SCRATCH is a pointer to the + embedded scratch space. ELEMENT_SIZE is the size, in bytes, of the + element type. On success, true is returned, and pointer and length + are written to *RESULT. On failure, false is returned. The caller + has to take care of some of the memory management; this function is + expected to be called from dynarray-skeleton.c. */ +bool __libc_dynarray_finalize (struct dynarray_header *list, void *scratch, + size_t element_size, + struct dynarray_finalize_result *result); + + +/* Internal function. Terminate the process after an index error. + SIZE is the number of elements of the dynamic array. INDEX is the + lookup index which triggered the failure. */ +void __libc_dynarray_at_failure (size_t size, size_t index) + __attribute__ ((noreturn)); + +#ifndef _ISOMAC +libc_hidden_proto (__libc_dynarray_emplace_enlarge) +libc_hidden_proto (__libc_dynarray_resize) +libc_hidden_proto (__libc_dynarray_resize_clear) +libc_hidden_proto (__libc_dynarray_finalize) +libc_hidden_proto (__libc_dynarray_at_failure) +#endif + +#endif /* _DYNARRAY_H */ |