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Add support for node-thermal-printer by solving issue with buffer ref not working with n-api #2

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Merged
ssxv merged 1 commit into from
Feb 8, 2026
Merged

Add support for node-thermal-printer by solving issue with buffer ref not working with n-api #2

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37 changes: 3 additions & 34 deletions src/node_printer_win.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -541,21 +541,8 @@ Napi::Value PrintDirectWrapped(const Napi::CallbackInfo& args) {
wd->errorPrefix = "PrintDirect";

bool usedTemp = false;
Napi::Reference<Napi::Buffer<char>> bufRef;
bool haveBufferRef = false;
if (args[0].IsBuffer()) {
Napi::Buffer<char> b = args[0].As<Napi::Buffer<char>>();
if (dataLen <= STREAM_THRESHOLD) {
// keep buffer alive via reference and avoid copying
bufRef = Napi::Persistent(b);
haveBufferRef = true;
} else {
// large buffer -> write to temp file for streaming
// fallthrough to write using dataVec
}
}

if (!haveBufferRef && dataLen > STREAM_THRESHOLD) {
if (dataLen > STREAM_THRESHOLD) {
// write to temp file and let worker stream it
char tmpPath[MAX_PATH];
if (GetTempPathA(MAX_PATH, tmpPath) > 0) {
Expand All @@ -579,10 +566,7 @@ Napi::Value PrintDirectWrapped(const Napi::CallbackInfo& args) {
class PrintWorker : public Napi::AsyncWorker {
public:
PrintWorker(Napi::Env env, WorkerData* d, Napi::Promise::Deferred def)
: Napi::AsyncWorker(env), data(d), deferred(def), hasBufferRef(false) {}

PrintWorker(Napi::Env env, WorkerData* d, Napi::Promise::Deferred def, Napi::Reference<Napi::Buffer<char>>&& ref)
: Napi::AsyncWorker(env), data(d), deferred(def), bufferRef(std::move(ref)), hasBufferRef(true) {}
: Napi::AsyncWorker(env), data(d), deferred(def) {}

~PrintWorker() { delete data; }

Expand Down Expand Up @@ -647,14 +631,6 @@ Napi::Value PrintDirectWrapped(const Napi::CallbackInfo& args) {
}
}
ifs.close();
} else if (hasBufferRef) {
auto buf = bufferRef.Value();
written = WritePrinter((HANDLE)printerHandle, (LPVOID)buf.Data(), (DWORD)buf.Length(), &dwBytesWritten);
if (!written || dwBytesWritten != (DWORD)buf.Length()) {
data->errorInfo = getLastErrorInfo();
data->errorPrefix = "WritePrinter";
return;
}
} else {
written = WritePrinter((HANDLE)printerHandle, (LPVOID)data->data.data(), (DWORD)data->data.size(), &dwBytesWritten);
if (!written || dwBytesWritten != (DWORD)data->data.size()) {
Expand Down Expand Up @@ -689,16 +665,9 @@ Napi::Value PrintDirectWrapped(const Napi::CallbackInfo& args) {
private:
WorkerData* data;
Napi::Promise::Deferred deferred;
Napi::Reference<Napi::Buffer<char>> bufferRef;
bool hasBufferRef;
};

PrintWorker* w = nullptr;
if (haveBufferRef) {
w = new PrintWorker(env, wd, deferred, std::move(bufRef));
} else {
w = new PrintWorker(env, wd, deferred);
}
PrintWorker* w = new PrintWorker(env, wd, deferred);
w->Queue();
return deferred.Promise();
}
Expand Down