// buildConditionalStatement builds the CodeDOM for a conditional statement.
func (db *domBuilder) buildConditionalStatement(node compilergraph.GraphNode) (codedom.Statement, codedom.Statement) {
conditionalExpr := db.getExpression(node, parser.NodeConditionalStatementConditional)
// A conditional is buildd as a jump statement that jumps to the true statement when the
// expression is true and to the false statement (which may have an 'else') when it is false.
// Both statements then jump to a final statement once complete.
finalStatement := codedom.EmptyStatement(node)
trueStart, trueEnd := db.getStatements(node, parser.NodeConditionalStatementBlock)
// The true statement needs to jump to the final statement once complete.
codedom.AssignNextStatement(trueEnd, codedom.UnconditionalJump(finalStatement, node))
elseStart, elseEnd, hasElse := db.tryGetStatements(node, parser.NodeConditionalStatementElseClause)
if hasElse {
// The else statement needs to jump to the final statement once complete.
codedom.AssignNextStatement(elseEnd, codedom.UnconditionalJump(finalStatement, node))
return codedom.ConditionalJump(conditionalExpr, trueStart, elseStart, node), finalStatement
} else {
return codedom.ConditionalJump(conditionalExpr, trueStart, finalStatement, node), finalStatement
}
}
// buildStatementBlock builds the CodeDOM for a statement block.
func (db *domBuilder) buildStatementBlock(node compilergraph.GraphNode) (codedom.Statement, codedom.Statement) {
sit := node.StartQuery().
Out(parser.NodeStatementBlockStatement).
BuildNodeIterator()
startStatement := codedom.EmptyStatement(node)
var current codedom.Statement = startStatement
for sit.Next() {
startStatement, endStatement := db.buildStatements(sit.Node())
codedom.AssignNextStatement(current, startStatement)
current = endStatement
// If the current node is a terminating statement, skip the rest of the block.
scope, hasScope := db.scopegraph.GetScope(sit.Node())
if hasScope && scope.GetIsTerminatingStatement() {
break
}
}
return startStatement, current
}
// buildJumpingCaseStatement builds the CodeDOM for a statement which jumps (branches) based on
// various cases.
func (db *domBuilder) buildJumpingCaseStatement(node compilergraph.GraphNode,
casePredicate compilergraph.Predicate,
caseStatementPredicate compilergraph.Predicate,
caseExpressionPredicate compilergraph.Predicate,
startStatement codedom.Statement,
getCheckExpression checkExpressionGenerator) (codedom.Statement, codedom.Statement) {
// A branching statement is an extended version of a conditional statement. For each branch, we check if the
// branch's value matches the conditional (or "true" if there is no conditional expr). On true, the block
// under the case is executed, followed by a jump to the final statement. Otherwise, the next block
// in the chain is executed.
finalStatement := codedom.EmptyStatement(node)
// Save a break statement reference for the generated statement.
db.breakStatementMap[node.NodeId] = finalStatement
// Generate the statements and check expressions for each of the cases.
var branchJumps = make([]*codedom.ConditionalJumpNode, 0)
cit := node.StartQuery().
Out(casePredicate).
BuildNodeIterator()
for cit.Next() {
caseNode := cit.Node()
caseStart, caseEnd := db.getStatements(caseNode, caseStatementPredicate)
caseExpressionNode, hasCaseExpression := caseNode.TryGetNode(caseExpressionPredicate)
// Generate the expression against which we should check. If there is no expression on
// the case, then this is the default and we compare against "true".
var branchExpression codedom.Expression = nil
if hasCaseExpression {
branchExpression = getCheckExpression(caseExpressionNode)
} else {
branchExpression = codedom.NominalWrapping(
codedom.LiteralValue("true", caseNode),
db.scopegraph.TypeGraph().BoolType(),
caseNode)
}
branchJump := codedom.BranchOn(branchExpression, caseNode)
branchJump.True = caseStart
branchJumps = append(branchJumps, branchJump)
// Jump the end statement, once complete, to the final statement.
codedom.AssignNextStatement(caseEnd, codedom.UnconditionalJump(finalStatement, caseNode))
}
// Generate a "trampoline" that checks each case.
for index, branchJump := range branchJumps {
// Jump the current branch (on false) to the next conditional check.
if index < len(branchJumps)-1 {
branchJump.False = branchJumps[index+1]
} else {
branchJump.False = finalStatement
}
}
// Have the start state jump to the first branch (if any).
if len(branchJumps) > 0 {
codedom.AssignNextStatement(startStatement, branchJumps[0])
}
return startStatement, finalStatement
}
// buildLoopStatement builds the CodeDOM for a loop statement.
func (db *domBuilder) buildLoopStatement(node compilergraph.GraphNode) (codedom.Statement, codedom.Statement) {
startStatement := codedom.EmptyStatement(node)
startStatement.MarkReferenceable()
finalStatement := codedom.EmptyStatement(node)
// Save initial continue and break statements for the loop.
db.continueStatementMap[node.NodeId] = startStatement
db.breakStatementMap[node.NodeId] = finalStatement
// A loop statement is buildd as a start statement which conditionally jumps to either the loop body
// (on true) or, on false, jumps to a final state after the loop.
if loopExpr, hasLoopExpr := db.tryGetExpression(node, parser.NodeLoopStatementExpression); hasLoopExpr {
// Check for a named value under the loop. If found, this is a loop over a stream or streamable.
namedValue, hasNamedValue := node.TryGetNode(parser.NodeStatementNamedValue)
if hasNamedValue {
namedValueName := namedValue.Get(parser.NodeNamedValueName)
resultVarName := db.generateScopeVarName(node)
namedValueScope, _ := db.scopegraph.GetScope(namedValue)
// Create the stream variable.
streamVarName := db.generateScopeVarName(node)
var streamVariable = codedom.VarDefinitionWithInit(streamVarName, loopExpr, node)
// If the expression is Streamable, first call .Stream() on the expression to get the stream
// for the variable.
if namedValueScope.HasLabel(proto.ScopeLabel_STREAMABLE_LOOP) {
// Call .Stream() on the expression.
streamableMember, _ := db.scopegraph.TypeGraph().StreamableType().GetMember("Stream")
streamExpr := codedom.MemberCall(
codedom.MemberReference(loopExpr, streamableMember, namedValue),
streamableMember,
[]codedom.Expression{},
namedValue)
streamVariable = codedom.VarDefinitionWithInit(streamVarName, streamExpr, node)
}
// Create variables to hold the named value (as requested in the SRG) and the loop result.
namedVariable := codedom.VarDefinition(namedValueName, node)
resultVariable := codedom.VarDefinition(resultVarName, node)
// Create an expression statement to set the result variable to a call to Next().
streamMember, _ := db.scopegraph.TypeGraph().StreamType().GetMember("Next")
nextCallExpr := codedom.MemberCall(
codedom.MemberReference(codedom.LocalReference(streamVarName, node), streamMember, node),
streamMember,
[]codedom.Expression{},
namedValue)
resultExpressionStatement := codedom.ExpressionStatement(codedom.LocalAssignment(resultVarName, nextCallExpr, namedValue), namedValue)
resultExpressionStatement.MarkReferenceable()
// Set the continue statement to call Next() again.
db.continueStatementMap[node.NodeId] = resultExpressionStatement
// Create an expression statement to set the named variable to the first part of the tuple.
namedExpressionStatement := codedom.ExpressionStatement(
codedom.LocalAssignment(namedValueName,
codedom.NativeAccess(
codedom.LocalReference(resultVarName, namedValue), "First", namedValue),
namedValue),
namedValue)
// Jump to the body state if the second part of the tuple in the result variable is true.
bodyStart, bodyEnd := db.getStatements(node, parser.NodeLoopStatementBlock)
checkJump := codedom.ConditionalJump(
codedom.NativeAccess(codedom.LocalReference(resultVarName, node), "Second", node),
bodyStart,
finalStatement,
node)
// Steps:
// 1) Empty statement
// 2) Create the stream's variable (with no value)
// 3) Create the named value variable (with no value)
// 4) Create the result variable (with no value)
// 5) (loop starts here) Pull the Next() result out of the stream
// 6) Pull the true/false bool out of the result
// 7) Pull the named value out of the result
// 8) Jump based on the true/false boolean value
codedom.AssignNextStatement(startStatement, streamVariable)
codedom.AssignNextStatement(streamVariable, namedVariable)
codedom.AssignNextStatement(namedVariable, resultVariable)
codedom.AssignNextStatement(resultVariable, resultExpressionStatement)
codedom.AssignNextStatement(resultExpressionStatement, namedExpressionStatement)
codedom.AssignNextStatement(namedExpressionStatement, checkJump)
// Jump to the result checking expression once the loop body completes.
directJump := codedom.UnconditionalJump(resultExpressionStatement, node)
codedom.AssignNextStatement(bodyEnd, directJump)
return startStatement, finalStatement
} else {
bodyStart, bodyEnd := db.getStatements(node, parser.NodeLoopStatementBlock)
// Loop over a direct boolean expression which is evaluated on each iteration.
initialJump := codedom.ConditionalJump(loopExpr, bodyStart, finalStatement, node)
directJump := codedom.UnconditionalJump(initialJump, node)
codedom.AssignNextStatement(bodyEnd, directJump)
codedom.AssignNextStatement(startStatement, initialJump)
return startStatement, finalStatement
}
} else {
bodyStart, bodyEnd := db.getStatements(node, parser.NodeLoopStatementBlock)
// A loop without an expression just loops infinitely over the body.
directJump := codedom.UnconditionalJump(bodyStart, node)
codedom.AssignNextStatement(bodyEnd, directJump)
codedom.AssignNextStatement(startStatement, bodyStart)
return startStatement, directJump
}
}