nghttp2/src/ringbuf.h

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/*
* nghttp2 - HTTP/2 C Library
*
* Copyright (c) 2014 Tatsuhiro Tsujikawa
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef RINGBUF_H
#define RINGBUF_H
#include "nghttp2_config.h"
#include <sys/uio.h>
#include <cstring>
#include <algorithm>
namespace nghttp2 {
template <size_t N> struct RingBuf {
RingBuf() : pos(0), len(0) {}
// Returns the number of bytes to read.
size_t rleft() const { return len; }
// Returns the number of bytes this buffer can store.
size_t wleft() const { return N - len; }
// Writes up to min(wleft(), |count|) bytes from buffer pointed by
// |buf|. Returns number of bytes written.
size_t write(const void *buf, size_t count) {
count = std::min(count, wleft());
auto last = (pos + len) % N;
if (count > N - last) {
auto c = N - last;
memcpy(begin + last, buf, c);
memcpy(begin, reinterpret_cast<const uint8_t *>(buf) + c, count - c);
} else {
memcpy(begin + last, buf, count);
}
len += count;
return count;
}
size_t write(size_t count) {
count = std::min(count, wleft());
len += count;
return count;
}
// Drains min(rleft(), |count|) bytes from start of the buffer.
size_t drain(size_t count) {
count = std::min(count, rleft());
pos = (pos + count) % N;
len -= count;
return count;
}
// Returns pointer to the next contiguous readable buffer and its
// length.
std::pair<const void *, size_t> get() const {
if (pos + len > N) {
return {begin + pos, N - pos};
}
return {begin + pos, len};
}
void reset() { pos = len = 0; }
// Fills |iov| for reading. |iov| must contain at least 2 elements.
// Returns the number of filled elements.
int riovec(struct iovec *iov) {
if (len == 0) {
return 0;
}
if (pos + len > N) {
auto c = N - pos;
iov[0].iov_base = begin + pos;
iov[0].iov_len = c;
iov[1].iov_base = begin;
iov[1].iov_len = len - c;
return 2;
}
iov[0].iov_base = begin + pos;
iov[0].iov_len = len;
return 1;
}
// Fills |iov| for writing. |iov| must contain at least 2 elements.
// Returns the number of filled elements.
int wiovec(struct iovec *iov) {
if (len == N) {
return 0;
}
if (pos == 0) {
iov[0].iov_base = begin + pos + len;
iov[0].iov_len = N - pos - len;
return 1;
}
if (pos + len < N) {
auto c = N - pos - len;
iov[0].iov_base = begin + pos + len;
iov[0].iov_len = c;
iov[1].iov_base = begin;
iov[1].iov_len = N - len - c;
return 2;
}
auto last = (pos + len) % N;
iov[0].iov_base = begin + last;
iov[0].iov_len = N - len;
return 1;
}
size_t pos;
size_t len;
uint8_t begin[N];
};
inline int limit_iovec(struct iovec *iov, int iovcnt, size_t max) {
if (max == 0) {
return 0;
}
for (int i = 0; i < iovcnt; ++i) {
auto d = std::min(max, iov[i].iov_len);
iov[i].iov_len = d;
max -= d;
if (max == 0) {
return i + 1;
}
}
return iovcnt;
}
} // namespace nghttp2
#endif // RINGBUF_H