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Foreach loop in C
/* Foreach loop in GNU C, released in the public domain by Joe Davis.
* Credit would be nice ;)
*/
#ifndef FOREACH_H_
#define FOREACH_H_
#include <stdbool.h>
#include <string.h>
/* Utility functions */
#define CONCAT(a,b) CONCAT_(a,b)
#define CONCAT_(a,b) a ## b
/* Hygiene in macros */
#define GENSYM(name) \
CONCAT(CONCAT(CONCAT(_anon_variable_, name),__LINE__),__COUNTER__)
/* Helper functions for foreach */
/* FOREACH_COMP
Checks if the value of INDEX, is greater than the length of ARRAY.
*/
#define FOREACH_COMP(INDEX, ARRAY, ARRAY_TYPE, SIZE) \
FOREACH_COMP_ (INDEX, ARRAY, ARRAY_TYPE, SIZE, GENSYM (ret))
#define FOREACH_COMP_(INDEX, ARRAY, ARRAY_TYPE, SIZE, ret) \
__extension__ \
({ \
bool ret = 0; \
if (__builtin_types_compatible_p (const char*, ARRAY_TYPE)) \
ret = INDEX < strlen ((const char*)ARRAY); \
else \
ret = INDEX < SIZE; \
ret; \
})
/* FOREACH_ELEM
Return a pointer to the element at INDEX in ARRAY.
*/
#define FOREACH_ELEM(INDEX, ARRAY, TYPE) \
FOREACH_ELEM_ (INDEX, ARRAY, TYPE, GENSYM (tmp_array))
#define FOREACH_ELEM_(INDEX, ARRAY, TYPE, tmp_array) \
__extension__ \
({ \
TYPE *tmp_array_ = ARRAY; \
&tmp_array_[INDEX]; \
})
/* Foreach loop itself */
/* FOREACH
A for-each loop implemented in GNU C.
The variable b at the end of FOREACH is there to make sure that the final
for loop eventually terminates.
*/
#define FOREACH(VAR, ARRAY) \
FOREACH_ (VAR, ARRAY, GENSYM (array), GENSYM (i), GENSYM (b))
#define FOREACH_(VAR, ARRAY, array, i, b) \
for (void *array = (void*)(ARRAY); array; array = 0) \
for (size_t i = 0; array && FOREACH_COMP (i, array, \
__typeof__ (ARRAY), \
sizeof (ARRAY) / sizeof ((ARRAY)[0])); \
i++) \
for (bool b = 1; b; (b) ? array = 0 : 0, b = 0) \
for (VAR = FOREACH_ELEM (i, array, __typeof__ ((ARRAY)[0])); b; b = 0)
#endif /* FOREACH_H_ */
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