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/**
* coopgammad -- Cooperative gamma server
* Copyright (C) 2016 Mattias Andrée (maandree@kth.se)
*
* This program 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 program 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 program. 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;
}
}
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