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callbacks.go
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callbacks.go
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package api
// Check https://akrennmair.github.io/golang-cgo-slides/ to learn
// how this embedded C code works.
/*
#include "bindings.h"
// typedefs for _cgo functions (db)
typedef GoError (*read_db_fn)(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, UnmanagedVector *val, UnmanagedVector *errOut);
typedef GoError (*write_db_fn)(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, U8SliceView val, UnmanagedVector *errOut);
typedef GoError (*remove_db_fn)(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, UnmanagedVector *errOut);
typedef GoError (*scan_db_fn)(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView start, U8SliceView end, int32_t order, GoIter *out, UnmanagedVector *errOut);
// iterator
typedef GoError (*next_db_fn)(iterator_t idx, gas_meter_t *gas_meter, uint64_t *used_gas, UnmanagedVector *key, UnmanagedVector *val, UnmanagedVector *errOut);
// and api
typedef GoError (*humanize_address_fn)(api_t *ptr, U8SliceView src, UnmanagedVector *dest, UnmanagedVector *errOut, uint64_t *used_gas);
typedef GoError (*canonicalize_address_fn)(api_t *ptr, U8SliceView src, UnmanagedVector *dest, UnmanagedVector *errOut, uint64_t *used_gas);
typedef GoError (*query_external_fn)(querier_t *ptr, uint64_t gas_limit, uint64_t *used_gas, U8SliceView request, UnmanagedVector *result, UnmanagedVector *errOut);
// forward declarations (db)
GoError cGet_cgo(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, UnmanagedVector *val, UnmanagedVector *errOut);
GoError cSet_cgo(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, U8SliceView val, UnmanagedVector *errOut);
GoError cDelete_cgo(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView key, UnmanagedVector *errOut);
GoError cScan_cgo(db_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, U8SliceView start, U8SliceView end, int32_t order, GoIter *out, UnmanagedVector *errOut);
// iterator
GoError cNext_cgo(iterator_t *ptr, gas_meter_t *gas_meter, uint64_t *used_gas, UnmanagedVector *key, UnmanagedVector *val, UnmanagedVector *errOut);
// api
GoError cHumanAddress_cgo(api_t *ptr, U8SliceView src, UnmanagedVector *dest, UnmanagedVector *errOut, uint64_t *used_gas);
GoError cCanonicalAddress_cgo(api_t *ptr, U8SliceView src, UnmanagedVector *dest, UnmanagedVector *errOut, uint64_t *used_gas);
// and querier
GoError cQueryExternal_cgo(querier_t *ptr, uint64_t gas_limit, uint64_t *used_gas, U8SliceView request, UnmanagedVector *result, UnmanagedVector *errOut);
*/
import "C"
import (
"encoding/json"
"fmt"
"log"
"reflect"
"runtime/debug"
"unsafe"
"github.com/line/wasmvm/types"
)
// Note: we have to include all exports in the same file (at least since they both import bindings.h),
// or get odd cgo build errors about duplicate definitions
func recoverPanic(ret *C.GoError) {
if rec := recover(); rec != nil {
// This is used to handle ErrorOutOfGas panics.
//
// What we do here is something that should not be done in the first place.
// "A panic typically means something went unexpectedly wrong. Mostly we use it to fail fast
// on errors that shouldn’t occur during normal operation, or that we aren’t prepared to
// handle gracefully." says https://gobyexample.com/panic.
// And 'Ask yourself "when this happens, should the application immediately crash?" If yes,
// use a panic; otherwise, use an error.' says this popular answer on SO: https://stackoverflow.com/a/44505268.
// Oh, and "If you're already worrying about discriminating different kinds of panics, you've lost sight of the ball."
// (Rob Pike) from https://eli.thegreenplace.net/2018/on-the-uses-and-misuses-of-panics-in-go/
//
// We don't want to import Cosmos SDK and also cannot use interfaces to detect these
// error types (as they have no methods). So, let's just rely on the descriptive names.
name := reflect.TypeOf(rec).Name()
switch name {
// These three types are "thrown" (which is not a thing in Go 🙃) in panics from the gas module
// (https://github.com/line/lbm-sdk/blob/main/store/types/gas.go):
// 1. ErrorOutOfGas
// 2. ErrorGasOverflow
// 3. ErrorNegativeGasConsumed
//
// In the baseapp, ErrorOutOfGas gets special treatment:
// - https://github.com/line/lbm-sdk/blob/main/baseapp/baseapp.go#L647
// - https://github.com/line/lbm-sdk/blob/main/baseapp/recovery.go#L50-L60
// This turns the panic into a regular error with a helpful error message.
//
// The other two gas related panic types indicate programming errors and are handled along
// with all other errors in https://github.com/line/lbm-sdk/blob/main/baseapp/recovery.go#L66-L77.
case "ErrorOutOfGas":
// TODO: figure out how to pass the text in its `Descriptor` field through all the FFI
*ret = C.GoError_OutOfGas
default:
log.Printf("Panic in Go callback: %#v\n", rec)
debug.PrintStack()
*ret = C.GoError_Panic
}
}
}
type Gas = uint64
// GasMeter is a copy of an interface declaration from lfb-sdk
// Defined in https://github.com/line/lfb-sdk/blob/main/store/types/gas.go
type GasMeter interface {
GasConsumed() Gas
}
/****** DB ********/
// KVStore copies a subset of types from lfb-sdk
// We may wish to make this more generic sometime in the future, but not now
// Original KVStore is defined in https://github.com/line/lfb-sdk/blob/main/store/types/store.go
type KVStore interface {
Get(key []byte) []byte
Set(key, value []byte)
Delete(key []byte)
// Iterator over a domain of keys in ascending order. End is exclusive.
// Start must be less than end, or the Iterator is invalid.
// Iterator must be closed by caller.
// To iterate over entire domain, use store.Iterator(nil, nil)
Iterator(start, end []byte) Iterator
// Iterator over a domain of keys in descending order. End is exclusive.
// Start must be less than end, or the Iterator is invalid.
// Iterator must be closed by caller.
ReverseIterator(start, end []byte) Iterator
}
// Iterator copies a subset of types from lfb-sdk
type Iterator interface {
// Valid returns whether the current iterator is valid. Once invalid, the Iterator remains
// invalid forever.
Valid() bool
// Next moves the iterator to the next key in the database, as defined by order of iteration.
// If Valid returns false, this method will panic.
Next()
// Key returns the key at the current position. Panics if the iterator is invalid.
// CONTRACT: key readonly []byte
Key() (key []byte)
// Value returns the value at the current position. Panics if the iterator is invalid.
// CONTRACT: value readonly []byte
Value() (value []byte)
// Error returns the last error encountered by the iterator, if any.
Error() error
// Close closes the iterator, releasing any allocated resources.
Close() error
}
var db_vtable = C.Db_vtable{
read_db: (C.read_db_fn)(C.cGet_cgo),
write_db: (C.write_db_fn)(C.cSet_cgo),
remove_db: (C.remove_db_fn)(C.cDelete_cgo),
scan_db: (C.scan_db_fn)(C.cScan_cgo),
}
type DBState struct {
Store KVStore
// CallID is used to lookup the proper frame for iterators associated with this contract call (iterator.go)
CallID uint64
}
// use this to create C.Db in two steps, so the pointer lives as long as the calling stack
// state := buildDBState(kv, callID)
// db := buildDB(&state, &gasMeter)
// // then pass db into some FFI function
func buildDBState(kv KVStore, callID uint64) DBState {
return DBState{
Store: kv,
CallID: callID,
}
}
// contract: original pointer/struct referenced must live longer than C.Db struct
// since this is only used internally, we can verify the code that this is the case
func buildDB(state *DBState, gm *GasMeter) C.Db {
return C.Db{
gas_meter: (*C.gas_meter_t)(unsafe.Pointer(gm)),
state: (*C.db_t)(unsafe.Pointer(state)),
vtable: db_vtable,
}
}
var iterator_vtable = C.Iterator_vtable{
next_db: (C.next_db_fn)(C.cNext_cgo),
}
// An iterator including referenced objects is 117 bytes large (calculated using https://github.com/DmitriyVTitov/size).
// We limit the number of iterators per contract call ID here in order limit memory usage to 32768*117 = ~3.8 MB as a safety measure.
// In any reasonable contract, gas limits should hit sooner than that though.
const frameLenLimit = 32768
// contract: original pointer/struct referenced must live longer than C.Db struct
// since this is only used internally, we can verify the code that this is the case
func buildIterator(callID uint64, it Iterator) (C.iterator_t, error) {
idx, err := storeIterator(callID, it, frameLenLimit)
if err != nil {
return C.iterator_t{}, err
}
return C.iterator_t{
call_id: cu64(callID),
iterator_index: cu64(idx),
}, nil
}
//export cGet
func cGet(ptr *C.db_t, gasMeter *C.gas_meter_t, usedGas *cu64, key C.U8SliceView, val *C.UnmanagedVector, errOut *C.UnmanagedVector) (ret C.GoError) {
defer recoverPanic(&ret)
if ptr == nil || gasMeter == nil || usedGas == nil || val == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*val).is_none || !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
gm := *(*GasMeter)(unsafe.Pointer(gasMeter))
kv := *(*KVStore)(unsafe.Pointer(ptr))
k := copyU8Slice(key)
gasBefore := gm.GasConsumed()
v := kv.Get(k)
gasAfter := gm.GasConsumed()
*usedGas = (cu64)(gasAfter - gasBefore)
// v will equal nil when the key is missing
// https://github.com/line/lbm-sdk/blob/786df84b8e0aaa0a1aff79ffbab0541e597ee004/store/types/store.go#L203
*val = newUnmanagedVector(v)
return C.GoError_None
}
//export cSet
func cSet(ptr *C.db_t, gasMeter *C.gas_meter_t, usedGas *C.uint64_t, key C.U8SliceView, val C.U8SliceView, errOut *C.UnmanagedVector) (ret C.GoError) {
defer recoverPanic(&ret)
if ptr == nil || gasMeter == nil || usedGas == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
gm := *(*GasMeter)(unsafe.Pointer(gasMeter))
kv := *(*KVStore)(unsafe.Pointer(ptr))
k := copyU8Slice(key)
v := copyU8Slice(val)
gasBefore := gm.GasConsumed()
kv.Set(k, v)
gasAfter := gm.GasConsumed()
*usedGas = (C.uint64_t)(gasAfter - gasBefore)
return C.GoError_None
}
//export cDelete
func cDelete(ptr *C.db_t, gasMeter *C.gas_meter_t, usedGas *C.uint64_t, key C.U8SliceView, errOut *C.UnmanagedVector) (ret C.GoError) {
defer recoverPanic(&ret)
if ptr == nil || gasMeter == nil || usedGas == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
gm := *(*GasMeter)(unsafe.Pointer(gasMeter))
kv := *(*KVStore)(unsafe.Pointer(ptr))
k := copyU8Slice(key)
gasBefore := gm.GasConsumed()
kv.Delete(k)
gasAfter := gm.GasConsumed()
*usedGas = (C.uint64_t)(gasAfter - gasBefore)
return C.GoError_None
}
//export cScan
func cScan(ptr *C.db_t, gasMeter *C.gas_meter_t, usedGas *C.uint64_t, start C.U8SliceView, end C.U8SliceView, order ci32, out *C.GoIter, errOut *C.UnmanagedVector) (ret C.GoError) {
defer recoverPanic(&ret)
if ptr == nil || gasMeter == nil || usedGas == nil || out == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
gm := *(*GasMeter)(unsafe.Pointer(gasMeter))
state := (*DBState)(unsafe.Pointer(ptr))
kv := state.Store
s := copyU8Slice(start)
e := copyU8Slice(end)
var iter Iterator
gasBefore := gm.GasConsumed()
switch order {
case 1: // Ascending
iter = kv.Iterator(s, e)
case 2: // Descending
iter = kv.ReverseIterator(s, e)
default:
return C.GoError_BadArgument
}
gasAfter := gm.GasConsumed()
*usedGas = (C.uint64_t)(gasAfter - gasBefore)
cIterator, err := buildIterator(state.CallID, iter)
if err != nil {
// store the actual error message in the return buffer
*errOut = newUnmanagedVector([]byte(err.Error()))
return C.GoError_User
}
out.state = cIterator
out.vtable = iterator_vtable
return C.GoError_None
}
//export cNext
func cNext(ref C.iterator_t, gasMeter *C.gas_meter_t, usedGas *C.uint64_t, key *C.UnmanagedVector, val *C.UnmanagedVector, errOut *C.UnmanagedVector) (ret C.GoError) {
// typical usage of iterator
// for ; itr.Valid(); itr.Next() {
// k, v := itr.Key(); itr.Value()
// ...
// }
defer recoverPanic(&ret)
if ref.call_id == 0 || gasMeter == nil || usedGas == nil || key == nil || val == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*key).is_none || !(*val).is_none || !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
gm := *(*GasMeter)(unsafe.Pointer(gasMeter))
iter := retrieveIterator(uint64(ref.call_id), uint64(ref.iterator_index))
if iter == nil {
panic("Unable to retrieve iterator.")
}
if !iter.Valid() {
// end of iterator, return as no-op, nil key is considered end
return C.GoError_None
}
gasBefore := gm.GasConsumed()
// call Next at the end, upon creation we have first data loaded
k := iter.Key()
v := iter.Value()
// check iter.Error() ????
iter.Next()
gasAfter := gm.GasConsumed()
*usedGas = (C.uint64_t)(gasAfter - gasBefore)
*key = newUnmanagedVector(k)
*val = newUnmanagedVector(v)
return C.GoError_None
}
/***** GoAPI *******/
type (
HumanizeAddress func([]byte) (string, uint64, error)
CanonicalizeAddress func(string) ([]byte, uint64, error)
)
type GoAPI struct {
HumanAddress HumanizeAddress
CanonicalAddress CanonicalizeAddress
}
var api_vtable = C.GoApi_vtable{
humanize_address: (C.humanize_address_fn)(C.cHumanAddress_cgo),
canonicalize_address: (C.canonicalize_address_fn)(C.cCanonicalAddress_cgo),
}
// contract: original pointer/struct referenced must live longer than C.GoApi struct
// since this is only used internally, we can verify the code that this is the case
func buildAPI(api *GoAPI) C.GoApi {
return C.GoApi{
state: (*C.api_t)(unsafe.Pointer(api)),
vtable: api_vtable,
}
}
//export cHumanAddress
func cHumanAddress(ptr *C.api_t, src C.U8SliceView, dest *C.UnmanagedVector, errOut *C.UnmanagedVector, used_gas *cu64) (ret C.GoError) {
defer recoverPanic(&ret)
if dest == nil || errOut == nil {
return C.GoError_BadArgument
}
if !(*dest).is_none || !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
api := (*GoAPI)(unsafe.Pointer(ptr))
s := copyU8Slice(src)
h, cost, err := api.HumanAddress(s)
*used_gas = cu64(cost)
if err != nil {
// store the actual error message in the return buffer
*errOut = newUnmanagedVector([]byte(err.Error()))
return C.GoError_User
}
if len(h) == 0 {
panic(fmt.Sprintf("`api.HumanAddress()` returned an empty string for %q", s))
}
*dest = newUnmanagedVector([]byte(h))
return C.GoError_None
}
//export cCanonicalAddress
func cCanonicalAddress(ptr *C.api_t, src C.U8SliceView, dest *C.UnmanagedVector, errOut *C.UnmanagedVector, used_gas *cu64) (ret C.GoError) {
defer recoverPanic(&ret)
if dest == nil || errOut == nil {
return C.GoError_BadArgument
}
if !(*dest).is_none || !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
api := (*GoAPI)(unsafe.Pointer(ptr))
s := string(copyU8Slice(src))
c, cost, err := api.CanonicalAddress(s)
*used_gas = cu64(cost)
if err != nil {
// store the actual error message in the return buffer
*errOut = newUnmanagedVector([]byte(err.Error()))
return C.GoError_User
}
if len(c) == 0 {
panic(fmt.Sprintf("`api.CanonicalAddress()` returned an empty string for %q", s))
}
*dest = newUnmanagedVector(c)
return C.GoError_None
}
/****** Go Querier ********/
var querier_vtable = C.Querier_vtable{
query_external: (C.query_external_fn)(C.cQueryExternal_cgo),
}
// contract: original pointer/struct referenced must live longer than C.GoQuerier struct
// since this is only used internally, we can verify the code that this is the case
func buildQuerier(q *Querier) C.GoQuerier {
return C.GoQuerier{
state: (*C.querier_t)(unsafe.Pointer(q)),
vtable: querier_vtable,
}
}
//export cQueryExternal
func cQueryExternal(ptr *C.querier_t, gasLimit C.uint64_t, usedGas *C.uint64_t, request C.U8SliceView, result *C.UnmanagedVector, errOut *C.UnmanagedVector) (ret C.GoError) {
defer recoverPanic(&ret)
if ptr == nil || usedGas == nil || result == nil || errOut == nil {
// we received an invalid pointer
return C.GoError_BadArgument
}
if !(*result).is_none || !(*errOut).is_none {
panic("Got a non-none UnmanagedVector we're about to override. This is a bug because someone has to drop the old one.")
}
// query the data
querier := *(*Querier)(unsafe.Pointer(ptr))
req := copyU8Slice(request)
gasBefore := querier.GasConsumed()
res := types.RustQuery(querier, req, uint64(gasLimit))
gasAfter := querier.GasConsumed()
*usedGas = (C.uint64_t)(gasAfter - gasBefore)
// serialize the response
bz, err := json.Marshal(res)
if err != nil {
*errOut = newUnmanagedVector([]byte(err.Error()))
return C.GoError_CannotSerialize
}
*result = newUnmanagedVector(bz)
return C.GoError_None
}