79 lines
3.3 KiB
C
79 lines
3.3 KiB
C
/** X-macro for a minimal dynamic array. `MIN_ARRAY(name, type)`, where `name`
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is an identifier prefix that satisfies `C` naming conventions when mangled and
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`type` is defined tag-type associated therewith. When expanding the array,
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resizing may be necessary and incurs amortised cost; any pointers to this
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memory may become stale. */
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#include <stdlib.h> /* size_t realloc free */
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#include <string.h> /* memmove strcmp memcpy */
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#include <errno.h> /* errno */
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#include <assert.h> /* assert */
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#define MIN_ARRAY_IDLE { 0, 0, 0 }
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#define MIN_ARRAY(name, type) \
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struct name##_array { type *data; size_t size, capacity; }; \
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/** Initialises `a` to idle. */ \
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static void name##_array(struct name##_array *const a) \
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{ assert(a), a->data = 0, a->capacity = a->size = 0; } \
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/** Destroys `a` and returns it to idle. */ \
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static void name##_array_(struct name##_array *const a) \
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{ assert(a), free(a->data), name##_array(a); } \
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/** Ensures `min_capacity` of `a`. @param[min_capacity] If zero, does nothing.
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@return Success; otherwise, `errno` will be set.
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@throws[ERANGE] Tried allocating more then can fit in `size_t` or `realloc`
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doesn't follow POSIX. @throws[realloc, ERANGE] */ \
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static int name##_array_reserve(struct name##_array *const a, \
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const size_t min_capacity) { \
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size_t c0; \
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type *data; \
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const size_t max_size = (size_t)-1 / sizeof *a->data; \
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assert(a); \
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if(a->data) { \
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if(min_capacity <= a->capacity) return 1; \
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c0 = a->capacity; \
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} else { /* Idle. */ \
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if(!min_capacity) return 1; \
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c0 = 1; \
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} \
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if(min_capacity > max_size) return errno = ERANGE, 0; \
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/* `c_n = a1.625^n`, approximation golden ratio `\phi ~ 1.618`. */ \
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while(c0 < min_capacity) { \
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size_t c1 = c0 + (c0 >> 1) + (c0 >> 3) + 1; \
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if(c0 > c1) { c0 = max_size; break; } \
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c0 = c1; \
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} \
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if(!(data = realloc(a->data, sizeof *a->data * c0))) \
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{ if(!errno) errno = ERANGE; return 0; } \
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a->data = data, a->capacity = c0; \
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return 1; \
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} \
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/** Adds at least `buffer` un-initialised and uncounted elements at the back of
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`a`. @return A pointer to the start of `buffer` elements, namely
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`data + size`. If `a` is idle and `buffer` is zero, a null pointer is
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returned, otherwise this indicates an error. @throws[realloc, ERANGE] */ \
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static type *name##_array_buffer(struct name##_array *const a, \
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const size_t buffer) { \
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assert(a); \
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if(a->size > (size_t)-1 - buffer) \
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{ errno = ERANGE; return 0; } /* Unlikely. */ \
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if(!name##_array_reserve(a, a->size + buffer)) return 0; \
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return a->data ? a->data + a->size : 0; \
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} \
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/** Emplaces `n` elements on `a`. `n` must be smaller than or equal to the
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highest remaining <fn:<name>_array_buffer>. */ \
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static void name##_array_emplace(struct name##_array *const a, \
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const size_t n) { \
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assert(a && a->capacity >= a->size && n <= a->capacity - a->size); \
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a->size += n; \
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} \
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/** @return Push back a new un-initialized datum of `a`.
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@throws[realloc, ERANGE] */ \
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static type *name##_array_new(struct name##_array *const a) { \
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type *const data = name##_array_buffer(a, 1); \
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return data ? name##_array_emplace(a, 1), data : 0; \
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} \
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/* They don't have to all be used, (destructor is important.) */ \
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static void name##_unused_coda(void); static void name##_unused(void) { \
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name##_array(0); name##_array_new(0); name##_unused_coda(); } \
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static void name##_unused_coda(void) { name##_unused(); }
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