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// See LICENSE for license details.
package Chisel
import internal._
import internal.Builder.pushCommand
import internal.firrtl._
object when { // scalastyle:ignore object.name
/** Create a `when` condition block, where whether a block of logic is
* executed or not depends on the conditional.
*
* @param cond condition to execute upon
* @param block logic that runs only if `cond` is true
*
* @example
* {{{
* when ( myData === UInt(3) ) {
* // Some logic to run when myData equals 3.
* } .elsewhen ( myData === UInt(1) ) {
* // Some logic to run when myData equals 1.
* } .otherwise {
* // Some logic to run when myData is neither 3 nor 1.
* }
* }}}
*/
def apply(cond: Bool)(block: => Unit): WhenContext = {
new WhenContext(cond, !cond)(block)
}
}
/** Internal mechanism for generating a when. Because of the way FIRRTL
* commands are emitted, generating a FIRRTL elsewhen or nested whens inside
* elses would be difficult. Instead, this keeps track of the negative of the
* previous conditions, so when an elsewhen or otherwise is used, it checks
* that both the condition is true and all the previous conditions have been
* false.
*/
class WhenContext(cond: Bool, prevCond: => Bool)(block: => Unit) {
/** This block of logic gets executed if above conditions have been false
* and this condition is true.
*/
def elsewhen (elseCond: Bool)(block: => Unit): WhenContext = {
new WhenContext(prevCond && elseCond, prevCond && !elseCond)(block)
}
/** This block of logic gets executed only if the above conditions were all
* false. No additional logic blocks may be appended past the `otherwise`.
*/
def otherwise(block: => Unit): Unit =
new WhenContext(prevCond, null)(block)
pushCommand(WhenBegin(cond.ref))
block
pushCommand(WhenEnd())
}
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