96 lines
2.6 KiB
C
96 lines
2.6 KiB
C
#ifndef ALLOC_H
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#define ALLOC_H
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struct alloc_state;
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struct tree;
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struct commit;
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struct tag;
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struct repository;
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void *alloc_blob_node(struct repository *r);
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void *alloc_tree_node(struct repository *r);
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void init_commit_node(struct commit *c);
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void *alloc_commit_node(struct repository *r);
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void *alloc_tag_node(struct repository *r);
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void *alloc_object_node(struct repository *r);
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struct alloc_state *allocate_alloc_state(void);
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void clear_alloc_state(struct alloc_state *s);
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#define alloc_nr(x) (((x)+16)*3/2)
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/**
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* Dynamically growing an array using realloc() is error prone and boring.
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*
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* Define your array with:
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*
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* - a pointer (`item`) that points at the array, initialized to `NULL`
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* (although please name the variable based on its contents, not on its
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* type);
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*
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* - an integer variable (`alloc`) that keeps track of how big the current
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* allocation is, initialized to `0`;
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*
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* - another integer variable (`nr`) to keep track of how many elements the
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* array currently has, initialized to `0`.
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*
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* Then before adding `n`th element to the item, call `ALLOC_GROW(item, n,
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* alloc)`. This ensures that the array can hold at least `n` elements by
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* calling `realloc(3)` and adjusting `alloc` variable.
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*
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* ------------
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* sometype *item;
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* size_t nr;
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* size_t alloc
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*
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* for (i = 0; i < nr; i++)
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* if (we like item[i] already)
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* return;
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*
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* // we did not like any existing one, so add one
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* ALLOC_GROW(item, nr + 1, alloc);
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* item[nr++] = value you like;
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* ------------
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*
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* You are responsible for updating the `nr` variable.
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*
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* If you need to specify the number of elements to allocate explicitly
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* then use the macro `REALLOC_ARRAY(item, alloc)` instead of `ALLOC_GROW`.
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*
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* Consider using ALLOC_GROW_BY instead of ALLOC_GROW as it has some
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* added niceties.
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*
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* DO NOT USE any expression with side-effect for 'x', 'nr', or 'alloc'.
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*/
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#define ALLOC_GROW(x, nr, alloc) \
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do { \
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if ((nr) > alloc) { \
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if (alloc_nr(alloc) < (nr)) \
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alloc = (nr); \
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else \
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alloc = alloc_nr(alloc); \
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REALLOC_ARRAY(x, alloc); \
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} \
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} while (0)
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/*
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* Similar to ALLOC_GROW but handles updating of the nr value and
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* zeroing the bytes of the newly-grown array elements.
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*
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* DO NOT USE any expression with side-effect for any of the
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* arguments.
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*/
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#define ALLOC_GROW_BY(x, nr, increase, alloc) \
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do { \
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if (increase) { \
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size_t new_nr = nr + (increase); \
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if (new_nr < nr) \
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BUG("negative growth in ALLOC_GROW_BY"); \
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ALLOC_GROW(x, new_nr, alloc); \
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memset((x) + nr, 0, sizeof(*(x)) * (increase)); \
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nr = new_nr; \
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} \
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} while (0)
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#endif
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