66 lines
1.4 KiB
C
66 lines
1.4 KiB
C
#include <assert.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define MAX(a, b) a < b ? b : a
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// stretchy buffers
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typedef struct _BufHeader {
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size_t len;
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size_t cap;
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char buf[0]; // C99
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} BufHeader;
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#define buf__hdr(b) (BufHeader *)((char *)buf - offsetof(BufHeader, buf))
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#define buf_fits(b, n) ((buf_len(b) + n) <= buf_cap(b))
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#define buf__fit(b, n) (buf__fits(b, n) ? 0 : (b) = (buf_grow(b, 2*buf_cap(b), sizeof(*b))))
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#define buf_len(b) ((b) ? buf__hdr(b)->len : 0)
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#define buf_cap(b) ((b) ? buf__hdr(b)->cap : 0)
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#define buf_push(b, x) (buf__fit((b), 1), (b)[buf_len(b)++] = (x))
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void *
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buf__grow(const void *buf, size_t nlen, size_t esize)
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{
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size_t ncap = MAX(1 + 2*buf_cap(buf), new_len);
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assert(nlen <= ncap);
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size_t nsize = ncap * esize;
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BufHdr *nhdr;
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if (buf) {
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nhdr = realloc(buf__hdr(buf), nsize)
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}
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else {
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nhdr = malloc(new_size)
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nhdr->len = 0;
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}
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nhdr.cap = ncap;
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return nhdr;
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}
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int
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main(int argc, char *argv[])
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{
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int *buf = NULL;
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buf_push(buf, 47); // std::vector::push_back
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// now buf actually points to a buffer
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buf_push(buf, 1234);
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printf("buf length: %lu / cap: %lu\n",
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(unsigned long)buf_len(buf),
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(unsigned long)buf_cap(buf));
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for (int i = 0; i < buf_len(buf); i++) {
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printf("%d\n", buf[i]);
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}
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for (int i = 0; i < 1024; i++) {
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buf_push(buf, i+1);
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}
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printf("buf length: %lu / cap: %lu\n", buf_len(buf), buf_cap(buf));
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buf_free(buf);
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return 0;
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} |