Commit 428d3b02 authored by David Gibson's avatar David Gibson

mem: Add memswap() function

Add a memswap() function to the mem module, which exchanges two (equal
sized, non-overlapping) memory regions.
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent 8f612600
......@@ -2,6 +2,7 @@
#include "config.h"
#include <assert.h>
#include <string.h>
#include <ccan/mem/mem.h>
......@@ -64,3 +65,26 @@ void *memcchr(void const *data, int c, size_t data_len)
return NULL;
}
#define MEMSWAP_TMP_SIZE 256
void memswap(void *a, void *b, size_t n)
{
char *ap = a;
char *bp = b;
char tmp[MEMSWAP_TMP_SIZE];
assert(!memoverlaps(a, n, b, n));
while (n) {
size_t m = n > MEMSWAP_TMP_SIZE ? MEMSWAP_TMP_SIZE : n;
memcpy(tmp, bp, m);
memcpy(bp, ap, m);
memcpy(ap, tmp, m);
ap += m;
bp += m;
n -= m;
}
}
......@@ -217,4 +217,14 @@ static inline bool memoverlaps(const void *a_, size_t al,
return (a < (b + bl)) && (b < (a + al));
}
/*
* memswap - Exchange two memory regions
* @a: first region
* @b: second region
* @n: length of the regions
*
* Undefined results if the two memory regions overlap.
*/
void memswap(void *a, void *b, size_t n);
#endif /* CCAN_MEM_H */
#include "config.h"
#include <assert.h>
#include <ccan/mem/mem.h>
#include <ccan/tap/tap.h>
#define SWAPSIZE 12
int main(void)
{
char haystack1[] = "abcd\0efgh";
......@@ -9,9 +15,10 @@ int main(void)
char needle2[] = "d\0e";
char scan1[] = "aaaab";
char scan2[] = "\0\0\0b";
char tmp1[SWAPSIZE], tmp2[SWAPSIZE];
/* This is how many tests you plan to run */
plan_tests(60);
plan_tests(62);
ok1(memmem(haystack1, sizeof(haystack1), needle1, 2) == haystack1);
ok1(memmem(haystack1, sizeof(haystack1), needle1, 3) == NULL);
......@@ -96,6 +103,16 @@ int main(void)
ok1(memoverlaps(haystack1 + 4, 7, haystack1, 5));
ok1(!memoverlaps(haystack1 + 5, 6, haystack1, 5));
assert(sizeof(haystack1) <= SWAPSIZE);
assert(sizeof(haystack2) <= SWAPSIZE);
memset(tmp1, 0, sizeof(tmp1));
memset(tmp2, 0, sizeof(tmp2));
memcpy(tmp1, haystack1, sizeof(haystack1));
memcpy(tmp2, haystack2, sizeof(haystack2));
memswap(tmp1, tmp2, SWAPSIZE);
ok1(memcmp(tmp1, haystack2, sizeof(haystack2)) == 0);
ok1(memcmp(tmp2, haystack1, sizeof(haystack1)) == 0);
/* This exits depending on whether all tests passed */
return exit_status();
}
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