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Diffstat (limited to 'src/shared/ring.c')
| -rw-r--r-- | src/shared/ring.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/src/shared/ring.c b/src/shared/ring.c new file mode 100644 index 0000000000..8ae61234c7 --- /dev/null +++ b/src/shared/ring.c @@ -0,0 +1,208 @@ +/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ + +/*** + This file is part of systemd. + + Copyright 2014 David Herrmann <dh.herrmann@gmail.com> + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +***/ + +#include <errno.h> +#include <inttypes.h> +#include <stdlib.h> +#include <string.h> +#include <sys/uio.h> +#include "macro.h" +#include "ring.h" + +#define RING_MASK(_r, _v) ((_v) & ((_r)->size - 1)) + +void ring_flush(struct ring *r) { + assert(r); + + r->start = 0; + r->used = 0; +} + +void ring_clear(struct ring *r) { + free(r->buf); + zero(*r); +} + +/* + * Get data pointers for current ring-buffer data. @vec must be an array of 2 + * iovec objects. They are filled according to the data available in the + * ring-buffer. 0, 1 or 2 is returned according to the number of iovec objects + * that were filled (0 meaning buffer is empty). + * + * Hint: "struct iovec" is defined in <sys/uio.h> and looks like this: + * struct iovec { + * void *iov_base; + * size_t iov_len; + * }; + */ +size_t ring_peek(struct ring *r, struct iovec *vec) { + assert(r); + + if (r->used == 0) { + return 0; + } else if (r->start + r->used <= r->size) { + if (vec) { + vec[0].iov_base = &r->buf[r->start]; + vec[0].iov_len = r->used; + } + return 1; + } else { + if (vec) { + vec[0].iov_base = &r->buf[r->start]; + vec[0].iov_len = r->size - r->start; + vec[1].iov_base = r->buf; + vec[1].iov_len = r->used - (r->size - r->start); + } + return 2; + } +} + +/* + * Copy data from the ring buffer into the linear external buffer @buf. Copy + * at most @size bytes. If the ring buffer size is smaller, copy less bytes and + * return the number of bytes copied. + */ +size_t ring_copy(struct ring *r, void *buf, size_t size) { + size_t l; + + assert(r); + assert(buf); + + if (size > r->used) + size = r->used; + + if (size > 0) { + l = r->size - r->start; + if (size <= l) { + memcpy(buf, &r->buf[r->start], size); + } else { + memcpy(buf, &r->buf[r->start], l); + memcpy((uint8_t*)buf + l, r->buf, size - l); + } + } + + return size; +} + +/* + * Resize ring-buffer to size @nsize. @nsize must be a power-of-2, otherwise + * ring operations will behave incorrectly. + */ +static int ring_resize(struct ring *r, size_t nsize) { + uint8_t *buf; + size_t l; + + assert(r); + assert(nsize > 0); + + buf = malloc(nsize); + if (!buf) + return -ENOMEM; + + if (r->used > 0) { + l = r->size - r->start; + if (r->used <= l) { + memcpy(buf, &r->buf[r->start], r->used); + } else { + memcpy(buf, &r->buf[r->start], l); + memcpy(&buf[l], r->buf, r->used - l); + } + } + + free(r->buf); + r->buf = buf; + r->size = nsize; + r->start = 0; + + return 0; +} + +/* + * Resize ring-buffer to provide enough room for @add bytes of new data. This + * resizes the buffer if it is too small. It returns -ENOMEM on OOM and 0 on + * success. + */ +static int ring_grow(struct ring *r, size_t add) { + size_t need; + + assert(r); + + if (r->size - r->used >= add) + return 0; + + need = r->used + add; + if (need <= r->used) + return -ENOMEM; + else if (need < 4096) + need = 4096; + + need = ALIGN_POWER2(need); + if (need == 0) + return -ENOMEM; + + return ring_resize(r, need); +} + +/* + * Push @len bytes from @u8 into the ring buffer. The buffer is resized if it + * is too small. -ENOMEM is returned on OOM, 0 on success. + */ +int ring_push(struct ring *r, const void *u8, size_t size) { + int err; + size_t pos, l; + + assert(r); + assert(u8); + + if (size == 0) + return 0; + + err = ring_grow(r, size); + if (err < 0) + return err; + + pos = RING_MASK(r, r->start + r->used); + l = r->size - pos; + if (l >= size) { + memcpy(&r->buf[pos], u8, size); + } else { + memcpy(&r->buf[pos], u8, l); + memcpy(r->buf, (const uint8_t*)u8 + l, size - l); + } + + r->used += size; + + return 0; +} + +/* + * Remove @len bytes from the start of the ring-buffer. Note that we protect + * against overflows so removing more bytes than available is safe. + */ +void ring_pull(struct ring *r, size_t size) { + assert(r); + + if (size > r->used) + size = r->used; + + r->start = RING_MASK(r, r->start + size); + r->used -= size; +} |