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99 lines
2.3 KiB
99 lines
2.3 KiB
2 months ago
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/*
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* UCW Library -- A simple growing buffer
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*
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* (c) 2004, Robert Spalek <robert@ucw.cz>
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* (c) 2005, Martin Mares <mj@ucw.cz>
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*
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* Define the following macros:
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*
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* GBUF_TYPE data type of records stored in the buffer
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* GBUF_PREFIX(x) add a name prefix to all global symbols
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* GBUF_TRACE(msg...) log growing of buffer [optional]
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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/**
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* Type identifier of the buffer.
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* The macro is not available outside the header file,
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* but it is used in the definitions of functions.
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**/
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#define BUF_T GBUF_PREFIX(t)
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/**
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* The growing buffer.
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* `ptr` holds the memory and `len` is the current
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* length of available memory.
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**/
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typedef struct BUF_T {
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size_t len;
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GBUF_TYPE *ptr;
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} BUF_T;
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/**
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* Initializes an empty growing buffer in @b.
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**/
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static inline void GBUF_PREFIX(init)(BUF_T *b)
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{
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b->ptr = NULL;
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b->len = 0;
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}
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/**
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* Frees all memory in the buffer and returns it
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* to an empty state.
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**/
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static void UNUSED GBUF_PREFIX(done)(BUF_T *b)
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{
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if (b->ptr)
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xfree(b->ptr);
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b->ptr = NULL;
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b->len = 0;
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}
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/**
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* Sets the length of the buffer @b to exactly @len.
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* Do not use for the growing (you can use this at the end,
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* when you know the exact size), it would be slow.
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*
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* Use <<fun__GENERIC_LINK_|GBUF_PREFIX|grow|,`GBUF_PREFIX(grow)()`>>
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* for growing.
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**/
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static void UNUSED GBUF_PREFIX(set_size)(BUF_T *b, size_t len)
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{
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b->len = len;
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b->ptr = xrealloc(b->ptr, len * sizeof(GBUF_TYPE));
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#ifdef GBUF_TRACE
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GBUF_TRACE(STRINGIFY_EXPANDED(BUF_T) " growing to %zu items", len);
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#endif
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}
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static void UNUSED GBUF_PREFIX(do_grow)(BUF_T *b, size_t len)
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{
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if (len < 2*b->len) // to ensure logarithmic cost
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len = 2*b->len;
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GBUF_PREFIX(set_size)(b, len);
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}
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/**
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* Sets the size of the buffer @b to at last @len.
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* It grows in exponential manner, to ensure the total cost
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* of reallocs is linear with the final size.
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*
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* You can tweak the final size (when you do not need to grow
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* any more) by
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* <<fun__GENERIC_LINK_|GBUF_PREFIX|set_size|,`GBUF_PREFIX(set_size)()`>>.
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**/
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static inline GBUF_TYPE *GBUF_PREFIX(grow)(BUF_T *b, size_t len)
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{
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if (unlikely(len > b->len))
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GBUF_PREFIX(do_grow)(b, len);
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return b->ptr;
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}
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#undef GBUF_TYPE
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#undef GBUF_PREFIX
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#undef GBUF_TRACE
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#undef BUF_T
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