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/*
* Copyright (c) 2015-2017 Richard Braun.
*
* 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 <assert.h>
#include <stddef.h>
#include <string.h>
#include <kern/cbuf.h>
#include <kern/error.h>
#include <kern/macros.h>
/* Negative close to 0 so that an overflow occurs early */
#define CBUF_INIT_INDEX ((size_t)-500)
void
cbuf_init(struct cbuf *cbuf, char *buf, size_t capacity)
{
assert(ISP2(capacity));
cbuf->buf = buf;
cbuf->capacity = capacity;
cbuf->start = CBUF_INIT_INDEX;
cbuf->end = cbuf->start;
}
static size_t
cbuf_index(const struct cbuf *cbuf, size_t abs_index)
{
return abs_index & (cbuf->capacity - 1);
}
static void
cbuf_update_start(struct cbuf *cbuf)
{
/* Mind integer overflows */
if (cbuf_size(cbuf) > cbuf->capacity) {
cbuf->start = cbuf->end - cbuf->capacity;
}
}
void
cbuf_push(struct cbuf *cbuf, char byte)
{
cbuf->buf[cbuf_index(cbuf, cbuf->end)] = byte;
cbuf->end++;
cbuf_update_start(cbuf);
}
int
cbuf_pop(struct cbuf *cbuf, char *bytep)
{
if (cbuf_size(cbuf) == 0) {
return ERROR_AGAIN;
}
*bytep = cbuf->buf[cbuf_index(cbuf, cbuf->start)];
cbuf->start++;
return 0;
}
int
cbuf_write(struct cbuf *cbuf, size_t index, const void *buf, size_t size)
{
char *start, *end, *buf_end;
size_t new_end, skip;
if (!cbuf_range_valid(cbuf, index, cbuf->end)) {
return ERROR_INVAL;
}
new_end = index + size;
if (!cbuf_range_valid(cbuf, cbuf->start, new_end)) {
cbuf->end = new_end;
if (size > cbuf_capacity(cbuf)) {
skip = size - cbuf_capacity(cbuf);
buf += skip;
index += skip;
size = cbuf_capacity(cbuf);
}
}
start = &cbuf->buf[cbuf_index(cbuf, index)];
end = start + size;
buf_end = cbuf->buf + cbuf->capacity;
if ((end <= cbuf->buf) || (end > buf_end)) {
skip = buf_end - start;
memcpy(start, buf, skip);
buf += skip;
start = cbuf->buf;
size -= skip;
}
memcpy(start, buf, size);
cbuf_update_start(cbuf);
return 0;
}
int
cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep)
{
const char *start, *end, *buf_end;
size_t size;
/* At least one byte must be available */
if (!cbuf_range_valid(cbuf, index, index + 1)) {
return ERROR_INVAL;
}
size = cbuf->end - index;
if (*sizep > size) {
*sizep = size;
}
start = &cbuf->buf[cbuf_index(cbuf, index)];
end = start + *sizep;
buf_end = cbuf->buf + cbuf->capacity;
if ((end > cbuf->buf) && (end <= buf_end)) {
size = *sizep;
} else {
size = buf_end - start;
memcpy(buf, start, size);
buf += size;
start = cbuf->buf;
size = *sizep - size;
}
memcpy(buf, start, size);
return 0;
}
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