Method read

src/types/mod.rs:837–894

(ctx: &VmCtx, ptr: u32)

    #[ensures(ctx_safe(ctx))]
    #[ensures(trace_safe(trace, ctx))]
    pub fn read(ctx: &VmCtx, ptr: u32) -> RuntimeResult<Subscription> {
        if !ctx.fits_in_lin_mem_usize(ptr as usize, Self::WASI_SIZE as usize) {
            return Err(RuntimeError::Eoverflow);
        }

        if !is_aligned(Alignment::Eight, ptr) {
            return Err(RuntimeError::Einval);
        }

        // read the subscription struct fields
        let userdata = ctx.read_u64(ptr as usize);
        let tag = ctx.read_u64((ptr + 8) as usize);

        match tag {
            Self::CLOCK_TAG => {
                let v_clock_id = ctx.read_u32((ptr + 16) as usize);
                let v_timeout = ctx.read_u64((ptr + 24) as usize);
                let v_precision = ctx.read_u64((ptr + 32) as usize);
                let v_flags = ctx.read_u64((ptr + 40) as usize);

                let precision = Timestamp::new(v_precision);
                let flags = SubClockFlags::try_from(v_flags)?;

                Ok(Subscription {
                    userdata,
                    subscription_u: SubscriptionInner::Clock(SubscriptionClock {
                        id: v_clock_id,
                        timeout: Timestamp::new(v_timeout),
                        precision,
                        flags,
                    }),
                })
            }
            Self::FD_READ_TAG => {
                let v_fd = ctx.read_u32((ptr + 16) as usize);

                Ok(Subscription {
                    userdata,
                    subscription_u: SubscriptionInner::Fd(SubscriptionFdReadWrite {
                        v_fd,
                        typ: SubscriptionFdType::Read,
                    }),
                })
            }
            Self::FD_WRITE_TAG => {
                let v_fd = ctx.read_u32((ptr + 16) as usize);

                Ok(Subscription {
                    userdata,
                    subscription_u: SubscriptionInner::Fd(SubscriptionFdReadWrite {
                        v_fd,
                        typ: SubscriptionFdType::Write,
                    }),
                })
            }
            _ => Err(RuntimeError::Einval),
        }
    }