/*
* Read bytes from buffer
* (buffer, number, boolean?) -> string
*/
int rb_read(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
size_t r = luaL_checkinteger(L, 2);
int peek = lua_toboolean(L, 3);
if(r > b->blen) {
lua_pushnil(L);
return 1;
}
if((b->rpos + r) > b->alen) {
/* Substring wraps around to the beginning of the buffer */
lua_pushlstring(L, &b->buffer[b->rpos], b->alen - b->rpos);
lua_pushlstring(L, b->buffer, r - (b->alen - b->rpos));
lua_concat(L, 2);
} else {
lua_pushlstring(L, &b->buffer[b->rpos], r);
}
if(!peek) {
b->blen -= r;
b->rpos += r;
modpos(b);
}
return 1;
}
/*
* Move read position forward without returning the data
* (buffer, number) -> boolean
*/
int rb_discard(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
size_t r = luaL_checkinteger(L, 2);
if(r > b->blen) {
lua_pushboolean(L, 0);
return 1;
}
b->blen -= r;
b->rpos += r;
modpos(b);
lua_pushboolean(L, 1);
return 1;
}
/*
* Write bytes into the buffer
* (buffer, string) -> integer
*/
int rb_write(lua_State *L) {
size_t l, w = 0;
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
const char *s = luaL_checklstring(L, 2, &l);
/* Does `l` bytes fit? */
if((l + b->blen) > b->alen) {
lua_pushnil(L);
return 1;
}
while(l-- > 0) {
writechar(b, *s++);
w++;
}
modpos(b);
lua_pushinteger(L, w);
return 1;
}
double fz(int i, int j) //force on i due to j, z component
{
return (G*m[j]*posz(i,j)/pow(modpos(i,j),3));
}
double fx(int i, int j) //acceleration on i due to j, x component
{
return (G*m[j]*posx(i,j)/pow(modpos(i,j),3));
}
