// NewPattern returns a new Pattern from the given definition values.
// "ops" is a sequence of op codes. "pool" is a constant pool.
// "verb" is the verb part of the pattern. It is empty if the pattern does not have the part.
// "version" must be 1 for now.
// It returns an error if the given definition is invalid.
func NewPattern(version int, ops []int, pool []string, verb string) (Pattern, error) {
if version != 1 {
grpclog.Printf("unsupported version: %d", version)
return Pattern{}, ErrInvalidPattern
}
l := len(ops)
if l%2 != 0 {
grpclog.Printf("odd number of ops codes: %d", l)
return Pattern{}, ErrInvalidPattern
}
var (
typedOps []op
stack, maxstack int
tailLen int
pushMSeen bool
vars []string
)
for i := 0; i < l; i += 2 {
op := op{code: utilities.OpCode(ops[i]), operand: ops[i+1]}
switch op.code {
case utilities.OpNop:
continue
case utilities.OpPush:
if pushMSeen {
tailLen++
}
stack++
case utilities.OpPushM:
if pushMSeen {
grpclog.Printf("pushM appears twice")
return Pattern{}, ErrInvalidPattern
}
pushMSeen = true
stack++
case utilities.OpLitPush:
if op.operand < 0 || len(pool) <= op.operand {
grpclog.Printf("negative literal index: %d", op.operand)
return Pattern{}, ErrInvalidPattern
}
if pushMSeen {
tailLen++
}
stack++
case utilities.OpConcatN:
if op.operand <= 0 {
grpclog.Printf("negative concat size: %d", op.operand)
return Pattern{}, ErrInvalidPattern
}
stack -= op.operand
if stack < 0 {
grpclog.Print("stack underflow")
return Pattern{}, ErrInvalidPattern
}
stack++
case utilities.OpCapture:
if op.operand < 0 || len(pool) <= op.operand {
grpclog.Printf("variable name index out of bound: %d", op.operand)
return Pattern{}, ErrInvalidPattern
}
v := pool[op.operand]
op.operand = len(vars)
vars = append(vars, v)
stack--
if stack < 0 {
grpclog.Printf("stack underflow")
return Pattern{}, ErrInvalidPattern
}
default:
grpclog.Printf("invalid opcode: %d", op.code)
return Pattern{}, ErrInvalidPattern
}
if maxstack < stack {
maxstack = stack
}
typedOps = append(typedOps, op)
}
return Pattern{
ops: typedOps,
pool: pool,
vars: vars,
stacksize: maxstack,
tailLen: tailLen,
verb: verb,
}, nil
}
func (g *defaultLogger) Print(args ...interface{}) {
grpclog.Print(args...)
}