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52 lines
1.8 KiB
C
52 lines
1.8 KiB
C
22 years ago
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#include "array.h"
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#if 0
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static array x;
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t *p;
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int64 pos;
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p = array_allocate(&x,sizeof(t),pos);
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array_allocate makes sure that enough bytes are allocated in x for at
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least pos+1 objects of type t. (The size of t must be positive;
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otherwise the effects are undefined.) If not enough bytes are
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allocated (or x is unallocated), array_allocate allocates more bytes,
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moving the dynamically allocated region if necessary. array_allocate
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often allocates somewhat more bytes than necessary, to save time
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later.
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array_allocate then makes sure that the number of bytes initialized
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covers at least those pos+1 objects. If not enough bytes are
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initialized, array_allocate initializes more bytes (setting them to
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0), up to exactly the end of the pos+1st object.
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array_allocate then returns a pointer to the pos+1st object; i.e.,
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object number pos, with objects numbered starting at 0. This pointer
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can be used to change or inspect the object. The pointer can continue
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to be used through subsequent calls to array_get, array_start,
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array_length, and array_bytes, but it must not be used after any
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other operations on this array.
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If something goes wrong, array_allocate returns 0, setting errno
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appropriately, without touching x. In particular, array_allocate
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returns 0 if
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* x has failed, or
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* pos is negative, or
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* not enough memory is available.
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array_allocate does not change x to have failed; if you want to do
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that, use array_fail.
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#endif
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void* array_allocate(array* x,int64 membersize,int64 pos) {
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int64 wanted;
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if (membersize<128)
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wanted=(pos+127)&(-128ll); /* round up to multiple of 128 */
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else
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wanted=(pos+4095)&(-4096ll); /* round up to 4k pages */
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/* detect numeric overflow */
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if (wanted<0) return 0;
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wanted=membersize*(pos+1);
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}
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