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Add shortcut for empty memload/memstore #221

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merged 1 commit into from
Oct 17, 2017
Merged

Add shortcut for empty memload/memstore #221

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13 changes: 12 additions & 1 deletion lib/opFns.js
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Original file line number Diff line number Diff line change
Expand Up @@ -867,7 +867,7 @@ function trap (err) {
* @return {String}
*/
function subMemUsage (runState, offset, length) {
// abort if no usage
// YP (225): access with zero length will not extend the memory
if (!length) return

// hacky: if the dataOffset is larger than the largest safeInt then just
Expand Down Expand Up @@ -907,6 +907,12 @@ function subMemUsage (runState, offset, length) {
function memLoad (runState, offset, length) {
// check to see if we have enougth gas for the mem read
subMemUsage(runState, offset, length)

// shortcut
if (length === 0) {
return new Buffer('')
}

var loaded = runState.memory.slice(offset, offset + length)
// fill the remaining lenth with zeros
for (var i = loaded.length; i < length; i++) {
Expand All @@ -928,6 +934,11 @@ function memStore (runState, offset, val, valOffset, length, skipSubMem) {
subMemUsage(runState, offset, length)
}

// shortcut
if (length === 0) {
return
}

var valLength = Math.min(val.length, length)

// read max possible from the value
Expand Down