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/*
* melisma - extensible and scriptable audio engine
* Copyright (C) 2026 Ludvig Gunne Lindström
*
* 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 <https://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <lauxlib.h>
#include "melisma.h"
#include "mutil.h"
#define LOOKBACK_TYPENAME "lookback"
struct lookback
{
ml_node *node;
size_t cursor;
size_t len;
float buf[];
};
static void proc(const ml_proc_args *args)
{
struct lookback *lb = args->userp;
for (size_t i = 0; i < args->nframes; i++)
{
args->out[0][i] = lb->buf[lb->cursor];
lb->buf[lb->cursor] = args->in[0][i];
lb->cursor++;
if (lb->cursor == lb->len)
{
lb->cursor = 0;
}
}
}
static int l_init(lua_State *s)
{
float t = luaL_checknumber(s,1);
ml_channel *src = mutil_get_channel(s,2);
unsigned long sr = ml_sample_rate();
unsigned long len = sr*t;
struct lookback *lb = calloc(1,sizeof(*lb) + len*sizeof(lb->buf[0]));
lb->len = len;
ml_node *node = ml_create_node(proc,lb);
ml_label_node(node,"lookback");
lb->node = node;
ml_channel *dst = ml_add_input(node);
ml_connect(src,dst);
ml_add_output(node);
*(void**) lua_newuserdata(s,sizeof(void*)) = lb;
luaL_setmetatable(s,LOOKBACK_TYPENAME);
return 1;
}
static int l_out(lua_State *s)
{
struct lookback *lb = *(void**) luaL_checkudata(s,1,LOOKBACK_TYPENAME);
*(void**) lua_newuserdata(s,sizeof(void*)) = ml_get_output(lb->node,0);
luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
return 1;
}
int luaopen_melisma_lookback(lua_State *s)
{
lua_newtable(s);
int tbl = lua_gettop(s);
lua_pushcfunction(s,l_init);
lua_setfield(s,tbl,"init");
lua_pushcfunction(s,l_out);
lua_setfield(s,tbl,MUTIL_OUTPUT_CHANNEL_FUNCTION);
luaL_newmetatable(s,LOOKBACK_TYPENAME);
int mt = lua_gettop(s);
lua_pushvalue(s,tbl);
lua_setfield(s,mt,"__index");
lua_settop(s,tbl);
return 1;
}
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