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Diffstat (limited to 'src/ring.c')
| -rw-r--r-- | src/ring.c | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/src/ring.c b/src/ring.c new file mode 100644 index 0000000..e34ef6d --- /dev/null +++ b/src/ring.c @@ -0,0 +1,211 @@ +/** + * coopgammad -- Cooperative gamma server + * Copyright (C) 2016 Mattias Andrée (maandree@kth.se) + * + * This library is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This library 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this library. If not, see <http://www.gnu.org/licenses/>. + */ +#include "ring.h" + +#include <stdlib.h> +#include <string.h> + + + +/** + * Initialise a ring buffer + * + * @param this The ring buffer + */ +void ring_initialise(struct ring* this) +{ + this->start = 0; + this->end = 0; + this->size = 0; + this->buffer = NULL; +} + + +/** + * Release resource allocated to a ring buffer + * + * @param this The ring buffer + */ +void ring_destroy(struct ring* this) +{ + free(this->buffer); +} + + +/** + * Marshal a ring buffer + * + * @param this The ring buffer + * @param buf Output buffer for the marshalled data, + * `NULL` to only measure how large buffer + * is needed + * @return The number of marshalled bytes + */ +size_t ring_marshal(const struct ring* this, void* buf) +{ + size_t off = 0, n = this->end - this->start; + char* bs = buf; + + if (bs != NULL) + *(size_t*)(bs + off) = n; + off += sizeof(size_t); + + if (bs != NULL) + memcpy(bs + off, this->buffer + this->start, n); + off += n; + + return off; +} + + +/** + * Unmarshal a ring buffer + * + * @param this Output parameter for the ring buffer + * @param buf Buffer with the marshalled data + * @return The number of unmarshalled bytes, 0 on error + */ +size_t ring_unmarshal(struct ring* this, const void* buf) +{ + size_t off = 0; + const char* bs = buf; + + ring_initialise(this); + + this->size = this->end = *(const size_t*)(bs + off); + off += sizeof(size_t); + + if (this->end > 0) + { + if (!(this->buffer = malloc(this->end))) + return 0; + + memcpy(this->buffer, bs + off, this->end); + off += this->end; + } + + return off; +} + + +/** + * Append data to a ring buffer + * + * @param this The ring buffer + * @param data The new data + * @param n The number of bytes in `data` + * @return Zero on success, -1 on error + */ +int ring_push(struct ring* this, void* data, size_t n) +{ + size_t used = 0; + + if (this->start == this->end) + { + if (this->buffer != NULL) + used = this->size; + } + else if (this->start > this->end) + used = this->size - this->start + this->end; + else + used = this->start - this->end; + + if (used + n > this->size) + { + char* new = malloc(used + n); + if (new == NULL) + return -1; + if (this->buffer) + { + if (this->start < this->end) + memcpy(new, this->buffer + this->start, this->end - this->start); + else + { + memcpy(new, this->buffer + this->start, this->size - this->start); + memcpy(new + this->size - this->start, this->buffer, this->end); + } + } + memcpy(new + used, data, n); + this->buffer = new; + this->start = 0; + this->end = used + n; + this->size = used + n; + } + else if ((this->start >= this->end) || (this->end + n <= this->size)) + { + memcpy(this->buffer + this->end, data, n); + this->end += n; + } + else + { + memcpy(this->buffer + this->end, data, this->size - this->end); + data = (char*)data + (this->size - this->end); + n -= this->size - this->end; + memcpy(this->buffer, data, n); + this->end = n; + } + + return 0; +} + + +/** + * Get queued data from a ring buffer + * + * It can take up to two calls (with `ring_pop` between) + * to get all queued data + * + * @param this The ring buffer + * @param n Output parameter for the length + * of the returned segment + * @return The beginning of the queued data, + * `NULL` if there is nothing more + */ +void* ring_peek(struct ring* this, size_t* n) +{ + if (this->buffer == NULL) + return *n = 0, NULL; + + if (this->start < this->end) + *n = this->end - this->start; + else + *n = this->size - this->start; + return this->buffer + this->start; +} + + +/** + * Dequeue data from a ring bubber + * + * @param this The ring buffer + * @param n The number of bytes to dequeue + */ +void ring_pop(struct ring* this, size_t n) +{ + this->start += n; + this->start %= this->size; + if (this->start == this->end) + { + free(this->buffer); + this->start = 0; + this->end = 0; + this->size = 0; + this->buffer = NULL; + } +} + |