1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160

// Copyright 2015-2020 Capital One Services, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! # wapc-guest
//!
//! The `wapc-guest` library provides WebAssembly module developers with access to a
//! [waPC](https://wascap.io/comms)-compliant host runtime. Each guest module has a single
//! call handler, declared with the `wapc_handler!` macro. Inside this call handler, the guest
//! module should check the operation of the delivered message and handle it accordingly,
//! returning any binary payload in response.
//!
//! # Example
//! ```
//! extern crate wapc_guest as guest;
//!
//! use guest::prelude::*;
//!
//! wapc_handler!(handle_wapc);
//!
//! pub fn handle_wapc(operation: &str, msg: &[u8]) -> CallResult {
//!     match operation {
//!         "sample:Guest!Hello" => hello_world(msg),
//!         _ => Err("bad dispatch".into()),
//!     }     
//! }
//!
//! fn hello_world(
//!    _msg: &[u8]) -> CallResult {
//!    let _res = host_call("myBinding", "sample:Host", "Call", b"hello")?;
//!     Ok(vec![])
//! }
//! ```

/// WaPC Guest SDK result type
pub type Result<T> = std::result::Result<T, errors::Error>;

#[link(wasm_import_module = "wapc")]
extern "C" {
    pub fn __console_log(ptr: *const u8, len: usize);
    pub fn __host_call(
        bd_ptr: *const u8,
        bd_len: usize,
        ns_ptr: *const u8,
        ns_len: usize,
        op_ptr: *const u8,
        op_len: usize,
        ptr: *const u8,
        len: usize,
    ) -> usize;
    pub fn __host_response(ptr: *const u8);
    pub fn __host_response_len() -> usize;
    pub fn __host_error_len() -> usize;
    pub fn __host_error(ptr: *const u8);
    pub fn __guest_response(ptr: *const u8, len: usize);
    pub fn __guest_error(ptr: *const u8, len: usize);
    pub fn __guest_request(op_ptr: *const u8, ptr: *const u8);
}

/// The function through which all host calls take place.
pub fn host_call(binding: &str, ns: &str, op: &str, msg: &[u8]) -> Result<Vec<u8>> {
    let callresult = unsafe {
        __host_call(
            binding.as_ptr() as _,
            binding.len() as _,
            ns.as_ptr() as _,
            ns.len() as _,
            op.as_ptr() as _,
            op.len() as _,
            msg.as_ptr() as _,
            msg.len() as _,
        )
    };
    if callresult != 1 {
        // call was not successful
        let errlen = unsafe { __host_error_len() };
        let buf = Vec::with_capacity(errlen as _);
        let retptr = buf.as_ptr();
        let slice = unsafe {
            __host_error(retptr);
            std::slice::from_raw_parts(retptr as _, errlen as _)
        };
        Err(errors::new(errors::ErrorKind::HostError(
            String::from_utf8(slice.to_vec()).unwrap(),
        )))
    } else {
        // call succeeded
        let len = unsafe { __host_response_len() };
        let buf = Vec::with_capacity(len as _);
        let retptr = buf.as_ptr();
        let slice = unsafe {
            __host_response(retptr);
            std::slice::from_raw_parts(retptr as _, len as _)
        };
        Ok(slice.to_vec())
    }
}

#[macro_export]
macro_rules! wapc_handler {
    ($user_handler:ident) => {
        #[no_mangle]
        pub extern "C" fn __guest_call(op_len: i32, req_len: i32) -> i32 {
            use std::slice;
            use $crate::console_log;

            let buf: Vec<u8> = Vec::with_capacity(req_len as _);
            let req_ptr = buf.as_ptr();

            let opbuf: Vec<u8> = Vec::with_capacity(op_len as _);
            let op_ptr = opbuf.as_ptr();

            let (slice, op) = unsafe {
                $crate::__guest_request(op_ptr, req_ptr);
                (
                    slice::from_raw_parts(req_ptr, req_len as _),
                    slice::from_raw_parts(op_ptr, op_len as _),
                )
            };

            let opstr = ::std::str::from_utf8(op).unwrap();

            match $user_handler(&opstr, slice) {
                Ok(msg) => unsafe {
                    $crate::__guest_response(msg.as_ptr(), msg.len() as _);
                    1
                },
                Err(e) => {
                    let errmsg = format!("Guest call failed: {}", e);
                    console_log(&errmsg);
                    unsafe {
                        $crate::__guest_error(errmsg.as_ptr(), errmsg.len() as _);
                    }
                    0
                }
            }
        }
    };
}

#[cold]
#[inline(never)]
pub fn console_log(s: &str) {
    unsafe {
        __console_log(s.as_ptr(), s.len());
    }
}

pub mod errors;
pub mod prelude;