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/* io.c -- Code for file and memory I/O.
Copyright (C) 2017 Jakob Tsar-Fox, All Rights Reserved.
This file is part of Nekopack.
Nekopack 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.
Nekopack 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 Nekopack. If not, see <http://www.gnu.org/licenses/>. */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "io.h"
/* Allocates `len` bytes of non-zeroed memory and returns a new stream
structure pointing to it. */
struct stream *stream_new(size_t len) {
struct stream *new = malloc(sizeof(struct stream));
new->len = len;
new->_start = malloc(len);
new->_cur = new->_start;
new->_loc = HEAP;
return new;
}
/* Called to free or unmap the memory chunk associated with the given
stream, as well as the stream structure itself. */
void stream_free(struct stream *s) {
switch (s->_loc) {
case HEAP:
free(s->_start);
}
free(s);
}
/* Copies `n` bytes from the given stream into the memory area specified
by `dest`. The stream's cursor is advanced appropriately. */
void stream_read(void *dest, struct stream *s, size_t n) {
memcpy(dest, s->_cur, n);
s->_cur += n;
}
/* Copies `n` bytes into the given stream from the memory area specified
by `src`. The stream's cursor is advanced appropriately. */
void stream_write(struct stream *s, void *src, size_t n) {
if (s->_cur + n > s->_start + s->len) {
ptrdiff_t dist = (uintptr_t) s->_cur - (uintptr_t) s->_start;
switch(s->_loc) {
case HEAP:
s->len *= 2;
s->_start = realloc(s->_start, s->len);
s->_cur = s->_start + dist;
}
}
memcpy(s->_cur, src, n);
s->_cur += n;
}
/* Applies an initial and primary key to the given stream, effectively
encrypting or decrypting it. */
void stream_xor(struct stream *s, uint8_t initial, uint8_t primary) {
*s->_start ^= initial;
for (char *p = s->_start; p < s->_start + s->len; *p++ ^= primary);
}
/* Obtains the current value of the stream's position indicator. */
size_t stream_tell(struct stream *s) {
return s->_cur - s->_start;
}
/* Sets the stream's position indicator to the given `pos`. */
void stream_seek(struct stream *s, size_t pos) {
s->_cur = s->_start + pos;
}
/* Sets the stream's position indicator to the beginning. */
void stream_rewind(struct stream *s) {
s->_cur = s->_start;
}
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