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#include <stddef.h>
#include <stdint.h>
#include "mbstring.h"
static const char8_t *
memrchr1(const char8_t *s, size_t k, const char8_t *n)
{
for (const char8_t *p = s + k - 1; k-- > 0; p--) {
if (*p == *n)
return p;
}
return nullptr;
}
static const char8_t *
memrchr2(const char8_t *h, size_t k, const char8_t *n)
{
uint16_t hw, nw;
const char8_t *H = h + k - 1;
hw = H[-1] << 8 | H[-0];
nw = n[+0] << 8 | n[+1];
for (H -= 2, k -= 2; k; k--, hw = hw >> 8 | (*H-- << 8)) {
if (hw == nw)
return H + 1;
}
return hw == nw ? H + 1 : nullptr;
}
static const char8_t *
memrchr3(const char8_t *h, size_t k, const char8_t *n)
{
uint32_t hw, nw;
const char8_t *H = h + k - 1;
hw = H[-2] << 24 | H[-1] << 16 | H[-0] << 8;
nw = n[+0] << 24 | n[+1] << 16 | n[+2] << 8;
for (H -= 3, k -= 3; k;
k--, hw = (hw >> 8 | (*H-- << 24)) & UINT32_C(0xFFFFFF00))
{
if (hw == nw)
return H + 1;
}
return hw == nw ? H + 1 : nullptr;
}
static const char8_t *
memrchr4(const char8_t *h, size_t k, const char8_t *n)
{
uint32_t hw, nw;
const char8_t *H = h + k - 1;
hw = H[-3] << 24 | H[-2] << 16 | H[-1] << 8 | H[-0];
nw = n[+0] << 24 | n[+1] << 16 | n[+2] << 8 | n[+3];
for (H -= 4, k -= 4; k; k--, hw = hw >> 8 | (*H-- << 24)) {
if (hw == nw)
return H + 1;
}
return hw == nw ? H + 1 : nullptr;
}
const char8_t *
u8rchr(struct u8view sv, rune ch)
{
char8_t buf[U8_LEN_MAX];
int n = rtou8(buf, ch, sizeof(buf));
if (sv.len < (size_t)n)
return nullptr;
switch (n) {
case 1:
return memrchr1(sv.p, sv.len, buf);
case 2:
return memrchr2(sv.p, sv.len, buf);
case 3:
return memrchr3(sv.p, sv.len, buf);
case 4:
return memrchr4(sv.p, sv.len, buf);
}
unreachable();
}
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