大家好，又见面了，我是全栈君。
如题，代码例如以下:
void reverse_words(std::string& original)
{
enum {
scan_normal,
scan_frag,
} state;
char buf[4];
memset(buf, 0, sizeof(buf));
int last = original.size() - 1;
int cur = original.size() - 1;
int n = original.size();
char* p = &original.front(); // scan ptr
char* movep = p; // move ptr
state = scan_normal;
int wfrag_len = 0;
int wlen = 0;
int movel = n;
int scan_ok;
while (n > 0) {
scan_ok = 1;
int end_frag = 0;
wfrag_len = 0;
// scan word until ' ' or word size >= word_buf
while (p[cur] != ' ') {
--cur;
if ( (wfrag_len = (last - cur)) >= sizeof(buf) ) {
scan_ok = 0;
if (scan_normal == state) {
state = scan_frag;
}
break;
}
}
if (state == scan_normal)
wlen = wfrag_len;
else
wlen += wfrag_len;
movel = n - wfrag_len;
if (movel <= 0 || n <= wlen)
break;
if (scan_ok) {
if (state == scan_frag) {
state = scan_normal;
end_frag = 1;
}
}
if (wfrag_len > 0) {
memcpy(buf, p + cur + 1, wfrag_len);
memmove(p + wfrag_len + scan_ok - end_frag, p, movel - (scan_ok - end_frag));
if (end_frag)
memmove(p + wlen, p + wlen - 1, n - wlen);
memcpy(p, buf, wfrag_len);
}
else { // skip empty
memmove(p + wlen + 1, p + wlen, movel - wlen - 1);
}
if (scan_normal == state) {
p[wlen] = ' ';
p += (wlen + 1);
n -= (wlen + 1);
cur = last = (n - 1);
}
else { // scan_frag
cur = last;
}
if (scan_ok || end_frag)
wlen = 0;
memset(buf, 0x0, sizeof(buf));
}
}
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