// User-level IPC library routines

#include <inc/lib.h>
// Receive a value via IPC and return it.
// If 'pg' is nonnull, then any page sent by the sender will be mapped at
//	that address.
// If 'fromenv' is nonnull, then store the IPC sender's envid in *fromenv.
// If 'perm' is nonnull, then store the IPC sender's page permission in *perm
//	(this is nonzero iff a page was successfully transferred to 'pg').
// If the system call fails, then store 0 in *fromenv and *perm (if
//	they're nonnull) and return the error.
//
// Hint:
//   Use 'env' to discover the value and who sent it.
//   If 'pg' is null, pass sys_ipc_recv a value that it will understand
//   as meaning "no page".  (Zero is not the right value.)
int32_t
ipc_recv(envid_t *from_env_store, void *pg, int *perm_store)
{
    //cprintf("env %08x trying to receive\n",env->env_id);
	// LAB 4: Your code here.
    if (pg == 0)
        pg = (void *)UTOP;

	int ret = 0;
    ret = sys_ipc_recv(pg);
    if (ret < 0)
        return ret;
    
    //cprintf("env %08x received %d from %08x\n",env->env_id,value,env->env_ipc_from);
	
    if (from_env_store != 0)
        *from_env_store = env->env_ipc_from;
    if (perm_store != 0)
        *perm_store = env->env_ipc_perm;

    return env->env_ipc_value;
}

// Send 'val' (and 'pg' with 'perm', assuming 'pg' is nonnull) to 'toenv'.
// This function keeps trying until it succeeds.
// It should panic() on any error other than -E_IPC_NOT_RECV.
//
// Hint:
//   Use sys_yield() to be CPU-friendly.
//   If 'pg' is null, pass sys_ipc_recv a value that it will understand
//   as meaning "no page".  (Zero is not the right value.)
void
ipc_send(envid_t to_env, uint32_t val, void *pg, int perm)
{
    //cprintf("ipc send %d to %08x\n",val,to_env);
    
	// LAB 4: Your code here.
    if (pg == 0)
        pg = (void *)UTOP;

    int ret = -E_IPC_NOT_RECV;
    while (ret == -E_IPC_NOT_RECV) {
        sys_yield();  
        ret = sys_ipc_try_send(to_env, val, pg, perm);
    }

    if (ret < 0)
        panic("error in ipc send: %e, %08x",ret,to_env);
}