57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/* sbrk.c -- Implementation of the low-level sbrk() routine
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*
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* Copyright (c) 2004 National Semiconductor Corporation
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*
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* The authors hereby grant permission to use, copy, modify, distribute,
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* and license this software and its documentation for any purpose, provided
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* that existing copyright notices are retained in all copies and that this
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* notice is included verbatim in any distributions. No written agreement,
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* license, or royalty fee is required for any of the authorized uses.
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* Modifications to this software may be copyrighted by their authors
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* and need not follow the licensing terms described here, provided that
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* the new terms are clearly indicated on the first page of each file where
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* they apply.
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*/
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#include <errno.h>
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#include <stddef.h> /* where ptrdiff_t is defined */
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#include <stdlib.h>
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/* Extend heap space by size bytes.
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Return start of new space allocated, or -1 for errors
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Error cases:
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1. Allocation is not within heap range */
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void * _sbrk (ptrdiff_t size)
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{
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/*
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* The following two memory locations should be defined in the linker script file
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*/
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extern const char _HEAP_START; /* start of heap */
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extern const char _HEAP_MAX; /* end of heap (maximum value of heap_ptr) */
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static const char * heap_ptr; /* pointer to head of heap */
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const char * old_heap_ptr;
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static unsigned char init_sbrk = 0;
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/* heap_ptr is initialized to HEAP_START */
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if (init_sbrk == 0)
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{
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heap_ptr = &_HEAP_START;
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init_sbrk = 1;
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}
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old_heap_ptr = heap_ptr;
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if ((heap_ptr + size) > &_HEAP_MAX)
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{
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/* top of heap is bigger than _HEAP_MAX */
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errno = ENOMEM;
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return (void *) -1;
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}
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/* success: update heap_ptr and return previous value */
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heap_ptr += size;
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return (void *)old_heap_ptr;
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}
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