diff options
Diffstat (limited to 'gbdk/gbdk-lib/libc/malloc.c')
| -rw-r--r-- | gbdk/gbdk-lib/libc/malloc.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/gbdk/gbdk-lib/libc/malloc.c b/gbdk/gbdk-lib/libc/malloc.c new file mode 100644 index 00000000..965e47dd --- /dev/null +++ b/gbdk/gbdk-lib/libc/malloc.c @@ -0,0 +1,114 @@ +/*------------------------------------------------------------------------- + malloc.c - allocate memory. + + Copyright (C) 2015, Philipp Klaus Krause, pkk@spth.de + + This library is free software; you can redistribute it and/or modify it + under the terms of the GNU General Public License as published by the + Free Software Foundation; either version 2, or (at your option) any + later version. + + This 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this library; see the file COPYING. If not, write to the + Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston, + MA 02110-1301, USA. + + As a special exception, if you link this library with other files, + some of which are compiled with SDCC, to produce an executable, + this library does not by itself cause the resulting executable to + be covered by the GNU General Public License. This exception does + not however invalidate any other reasons why the executable file + might be covered by the GNU General Public License. +-------------------------------------------------------------------------*/ + +#include <stdlib.h> +#include <stddef.h> + +#if defined(__SDCC_mcs51) || defined(__SDCC_ds390) || defined(__SDCC_ds400) +#define HEAPSPACE __xdata +#elif defined(__SDCC_pdk13) || defined(__SDCC_pdk14) || defined(__SDCC_pdk15) +#define HEAPSPACE __near +#else +#define HEAPSPACE +#endif + +typedef struct header HEAPSPACE header_t; + +struct header +{ + header_t *next; // Next block. Linked list of all blocks, terminated by pointer to end of heap (or to the byte beyond the end of the heap). + header_t *next_free; // Next free block. Used in free blocks only. Overlaps with user data in non-free blocks. Linked list of free blocks, 0-terminated. +}; + +header_t *HEAPSPACE __sdcc_heap_free; // First free block, 0 if no free blocks. + +extern header_t __sdcc_heap; +#define HEAP_START &__sdcc_heap + +#if defined(__SDCC_mcs51) || defined(__SDCC_ds390) || defined(__SDCC_ds400) || defined(__SDCC_hc08) || defined(__SDCC_s08) + +extern const unsigned int __sdcc_heap_size; +#define HEAP_END (struct header HEAPSPACE *)((char HEAPSPACE *)&__sdcc_heap + (__sdcc_heap_size - 1)) // -1 To be sure that HEAP_END is bigger than HEAP_START. + +#else + +extern header_t __sdcc_heap_end; // Just beyond the end of the heap. Must be higher in memory than _sdcc_heap_start. +#define HEAP_END &__sdcc_heap_end + +#endif + +void __sdcc_heap_init(void) +{ + __sdcc_heap_free = HEAP_START; + __sdcc_heap_free->next = HEAP_END; + __sdcc_heap_free->next_free = 0; +} + +#if defined(__SDCC_mcs51) || defined(__SDCC_ds390) || defined(__SDCC_ds400) +void HEAPSPACE *malloc(size_t size) +#else +void *malloc(size_t size) +#endif +{ + header_t *h; + header_t *HEAPSPACE *f; + +#if defined(__SDCC_mcs51) || defined(__SDCC_ds390) || defined(__SDCC_ds400) || defined(__SDCC_hc08) || defined(__SDCC_s08) + if(!__sdcc_heap_free) + __sdcc_heap_init(); +#endif + + if(!size || size + offsetof(struct header, next_free) < size) + return(0); + size += offsetof(struct header, next_free); + if(size < sizeof(struct header)) // Requiring a minimum size makes it easier to implement free(), and avoid memory leaks. + size = sizeof(struct header); + + for(h = __sdcc_heap_free, f = &__sdcc_heap_free; h; f = &(h->next_free), h = h->next_free) + { + size_t blocksize = (char HEAPSPACE *)(h->next) - (char HEAPSPACE *)h; + if(blocksize >= size) // Found free block of sufficient size. + { + if(blocksize >= size + sizeof(struct header)) // It is worth creating a new free block + { + header_t *const newheader = (header_t *const)((char HEAPSPACE *)h + size); + newheader->next = h->next; + newheader->next_free = h->next_free; + *f = newheader; + h->next = newheader; + } + else + *f = h->next_free; + + return(&(h->next_free)); + } + } + + return(0); +} + |