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context.go
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context.go
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package fvm
import (
"github.com/onflow/cadence"
"github.com/onflow/flow-go/model/flow"
)
// A Context defines a set of execution parameters used by the virtual machine.
type Context struct {
Chain flow.Chain
ASTCache ASTCache
Blocks Blocks
Metrics *MetricsCollector
GasLimit uint64
BlockHeader *flow.Header
ServiceAccountEnabled bool
RestrictedAccountCreationEnabled bool
RestrictedDeploymentEnabled bool
SetValueHandler SetValueHandler
SignatureVerifier SignatureVerifier
TransactionProcessors []TransactionProcessor
ScriptProcessors []ScriptProcessor
}
// SetValueHandler receives a value written by the Cadence runtime.
type SetValueHandler func(owner flow.Address, key string, value cadence.Value) error
// NewContext initializes a new execution context with the provided options.
func NewContext(opts ...Option) Context {
return newContext(defaultContext(), opts...)
}
// NewContextFromParent spawns a child execution context with the provided options.
func NewContextFromParent(parent Context, opts ...Option) Context {
return newContext(parent, opts...)
}
func newContext(ctx Context, opts ...Option) Context {
for _, applyOption := range opts {
ctx = applyOption(ctx)
}
return ctx
}
const AccountKeyWeightThreshold = 1000
const defaultGasLimit = 100000
func defaultContext() Context {
return Context{
Chain: flow.Mainnet.Chain(),
ASTCache: nil,
Blocks: nil,
Metrics: nil,
GasLimit: defaultGasLimit,
BlockHeader: nil,
ServiceAccountEnabled: true,
RestrictedAccountCreationEnabled: true,
RestrictedDeploymentEnabled: true,
SetValueHandler: nil,
SignatureVerifier: NewDefaultSignatureVerifier(),
TransactionProcessors: []TransactionProcessor{
NewTransactionSignatureVerifier(AccountKeyWeightThreshold),
NewTransactionSequenceNumberChecker(),
NewTransactionFeeDeductor(),
NewTransactionInvocator(),
},
ScriptProcessors: []ScriptProcessor{
NewScriptInvocator(),
},
}
}
// An Option sets a configuration parameter for a virtual machine context.
type Option func(ctx Context) Context
// WithChain sets the chain parameters for a virtual machine context.
func WithChain(chain flow.Chain) Option {
return func(ctx Context) Context {
ctx.Chain = chain
return ctx
}
}
// WithASTCache sets the AST cache for a virtual machine context.
func WithASTCache(cache ASTCache) Option {
return func(ctx Context) Context {
ctx.ASTCache = cache
return ctx
}
}
// WithGasLimit sets the gas limit for a virtual machine context.
func WithGasLimit(limit uint64) Option {
return func(ctx Context) Context {
ctx.GasLimit = limit
return ctx
}
}
// WithBlockHeader sets the block header for a virtual machine context.
//
// The VM uses the header to provide current block information to the Cadence runtime,
// as well as to seed the pseudorandom number generator.
func WithBlockHeader(header *flow.Header) Option {
return func(ctx Context) Context {
ctx.BlockHeader = header
return ctx
}
}
// WithBlocks sets the block storage provider for a virtual machine context.
//
// The VM uses the block storage provider to provide historical block information to
// the Cadence runtime.
func WithBlocks(blocks Blocks) Option {
return func(ctx Context) Context {
ctx.Blocks = blocks
return ctx
}
}
// WithMetricsCollector sets the metrics collector for a virtual machine context.
//
// A metrics collector is used to gather metrics reported by the Cadence runtime.
func WithMetricsCollector(mc *MetricsCollector) Option {
return func(ctx Context) Context {
ctx.Metrics = mc
return ctx
}
}
// WithTransactionSignatureVerifier sets the transaction processors for a
// virtual machine context.
func WithTransactionProcessors(processors ...TransactionProcessor) Option {
return func(ctx Context) Context {
ctx.TransactionProcessors = processors
return ctx
}
}
// WithServiceAccount enables or disables calls to the Flow service account.
func WithServiceAccount(enabled bool) Option {
return func(ctx Context) Context {
ctx.ServiceAccountEnabled = enabled
return ctx
}
}
// WithRestrictedDeployment enables or disables restricted contract deployment for a
// virtual machine context.
func WithRestrictedDeployment(enabled bool) Option {
return func(ctx Context) Context {
ctx.RestrictedDeploymentEnabled = enabled
return ctx
}
}
// WithRestrictedAccountCreation enables or disables restricted account creation for a
// virtual machine context
func WithRestrictedAccountCreation(enabled bool) Option {
return func(ctx Context) Context {
ctx.RestrictedAccountCreationEnabled = enabled
return ctx
}
}
// WithSetValueHandler sets a handler that is called when a value is written
// by the Cadence runtime.
func WithSetValueHandler(handler SetValueHandler) Option {
return func(ctx Context) Context {
ctx.SetValueHandler = handler
return ctx
}
}