3  * SPDX-License-Identifier: Apache-2.0
8 /* This code may be used (e.g. for trace/logging) in very early
22  * (arm64 excepted) either promise firm ordering (x86) or are in-order
31 	return idx >= ws->len ? idx - ws->len : idx;  in idx_mod()
34 /* Computes modular a - b, assuming a and b are in [0:len) */
37 	return idx_mod(ws, a + (ws->len - b));  in idx_sub()
44 	uint32_t start = ws->start, end = ws->end, seq = ws->seq;  in sys_winstream_write()
47 	 * (Max bytes buffered is actually len-1 because start==end is  in sys_winstream_write()
50 	if (len > ws->len - 1) {  in sys_winstream_write()
52 		len = ws->len - 1;  in sys_winstream_write()
55 	/* Make room in the buffer by advancing start first (note same  in sys_winstream_write()
56 	 * len-1 from above)  in sys_winstream_write()
58 	len = MIN(len, ws->len);  in sys_winstream_write()
60 		uint32_t avail = (ws->len - 1) - idx_sub(ws, end, start);  in sys_winstream_write()
63 			ws->start = idx_mod(ws, start + (len - avail));  in sys_winstream_write()
70 		ws->start = end;  in sys_winstream_write()
71 		data += len0 - len;  in sys_winstream_write()
74 	suffix = MIN(len, ws->len - end);  in sys_winstream_write()
75 	MEMCPY(&ws->data[end], data, suffix);  in sys_winstream_write()
77 		MEMCPY(&ws->data[0], data + suffix, len - suffix);  in sys_winstream_write()
80 	ws->end = idx_mod(ws, end + len);  in sys_winstream_write()
81 	ws->seq += len0; /* seq represents dropped bytes too! */  in sys_winstream_write()
91 		start = ws->start; end = ws->end; wseq = ws->seq;  in sys_winstream_read()
94 		/* No change in buffer state or empty initial stream are easy */  in sys_winstream_read()
104 		behind = wseq - *seq;  in sys_winstream_read()
105 		if (behind > idx_sub(ws, ws->end, ws->start)) {  in sys_winstream_read()
111 		copy = idx_sub(ws, ws->end, behind);  in sys_winstream_read()
112 		len = MIN(buflen, behind);  in sys_winstream_read()
113 		suffix = MIN(len, ws->len - copy);  in sys_winstream_read()
114 		MEMCPY(buf, &ws->data[copy], suffix);  in sys_winstream_read()
116 			MEMCPY(buf + suffix, &ws->data[0], len - suffix);  in sys_winstream_read()
126 	} while (start != ws->start || wseq != ws->seq);  in sys_winstream_read()