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event.c
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event.c
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// +build windows
// This file contains convenience stub functions that call Win32 API
// functions and return values suitable for handling in Go.
// Note that some functions such as EvtRender() and EvtFormatMessage() support a model
// where they are called twice - once to determine the necessary buffer size,
// and once to copy values into the supplied buffer.
#define _WIN32_WINNT 0x0602
#include "event.h"
#include "_cgo_export.h"
int CloseEvtHandle(ULONGLONG hEvent) {
EvtClose((EVT_HANDLE)hEvent);
}
int CancelEvtHandle(ULONGLONG hEvent) {
EvtCancel((EVT_HANDLE)hEvent);
}
PVOID RenderEventValues(ULONGLONG hContext, ULONGLONG hEvent) {
DWORD dwBufferSize = 0;
DWORD dwUsed = 0;
DWORD dwPropertyCount = 0;
EvtRender((EVT_HANDLE)hContext, (EVT_HANDLE)hEvent, EvtRenderEventValues, dwBufferSize, NULL, &dwUsed, &dwPropertyCount);
PVOID pRenderedValues = malloc(dwUsed);
if (!pRenderedValues) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
dwBufferSize = dwUsed;
if (! EvtRender((EVT_HANDLE)hContext, (EVT_HANDLE)hEvent, EvtRenderEventValues, dwBufferSize, pRenderedValues, &dwUsed, &dwPropertyCount)){
free(pRenderedValues);
return NULL;
}
return pRenderedValues;
}
// Render the event as XML. The returned buffer must be freed after use.
char* RenderEventXML(ULONGLONG hEvent) {
DWORD dwBufferSize = 0;
DWORD dwUsed = 0;
DWORD dwPropertyCount = 0;
EvtRender(NULL, (EVT_HANDLE)hEvent, EvtRenderEventXml, dwBufferSize, NULL, &dwUsed, &dwPropertyCount);
// Allocate a buffer to hold the utf-16 encoded xml string. Although the xml
// string is utf-16, the dwUsed value is in bytes, not characters
// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa385471(v=vs.85).aspx
LPWSTR xmlWide = malloc(dwUsed);
if (!xmlWide) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
dwBufferSize = dwUsed;
if (! EvtRender(NULL, (EVT_HANDLE)hEvent, EvtRenderEventXml, dwBufferSize, xmlWide, &dwUsed, 0)){
free(xmlWide);
return NULL;
}
// Convert the xml string to multibyte
size_t lenXml = wcstombs(NULL, xmlWide, 0) + 1;
void* xml = malloc(lenXml);
if (!xml) {
free(xmlWide);
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
wcstombs(xml, xmlWide, lenXml);
free(xmlWide);
return xml;
}
char* GetLastErrorString() {
DWORD dwErr = GetLastError();
LPSTR lpszMsgBuf;
FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS, 0, dwErr, 0, (LPSTR)&lpszMsgBuf, 0, NULL);
return (char *)lpszMsgBuf;
}
char* GetFormattedMessage(ULONGLONG hEventPublisher, ULONGLONG hEvent, int format) {
DWORD dwBufferSize = 0;
DWORD dwBufferUsed = 0;
int status;
errno_t decodeReturn = EvtFormatMessage((EVT_HANDLE)hEventPublisher, (EVT_HANDLE)hEvent, 0, 0, NULL, format, 0, NULL, &dwBufferUsed);
if ((status = GetLastError()) != ERROR_INSUFFICIENT_BUFFER) {
return NULL;
}
dwBufferSize = dwBufferUsed + 1;
LPWSTR messageWide = malloc((dwBufferSize) * sizeof(wchar_t));
if (!messageWide) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
decodeReturn = EvtFormatMessage((EVT_HANDLE)hEventPublisher, (EVT_HANDLE)hEvent, 0, 0, NULL, format, dwBufferSize, messageWide, &dwBufferUsed);
if (!decodeReturn) {
free(messageWide);
return NULL;
}
size_t lenMessage = wcstombs(NULL, messageWide, 0) + 1;
void* message = malloc(lenMessage);
if (!message) {
free(messageWide);
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
wcstombs(message, messageWide, lenMessage);
free(messageWide);
return message;
}
ULONGLONG GetEventPublisherHandle(PVOID pRenderedValues) {
LPCWSTR publisher = ((PEVT_VARIANT)pRenderedValues)[EvtSystemProviderName].StringVal;
return (ULONGLONG)EvtOpenPublisherMetadata(NULL, publisher, NULL, 0, 0);
}
ULONGLONG CreateSystemRenderContext() {
return (ULONGLONG)EvtCreateRenderContext(0, NULL, EvtRenderContextSystem);
}
int GetRenderedValueType(PVOID pRenderedValues, int property) {
return (int)((PEVT_VARIANT)pRenderedValues)[property].Type;
}
char* GetRenderedStringValue(PVOID pRenderedValues, int property) {
wchar_t const * propVal = ((PEVT_VARIANT)pRenderedValues)[property].StringVal;
size_t lenNarrowPropVal = wcstombs(NULL, propVal, 0) + 1;
char* value = malloc(lenNarrowPropVal);
if (!value) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return NULL;
}
wcstombs(value, propVal, lenNarrowPropVal);
return value;
}
ULONGLONG GetRenderedByteValue(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].ByteVal;
}
ULONGLONG GetRenderedUInt16Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].UInt16Val;
}
ULONGLONG GetRenderedUInt32Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].UInt32Val;
}
ULONGLONG GetRenderedUInt64Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].UInt64Val;
}
LONGLONG GetRenderedSByteValue(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].SByteVal;
}
LONGLONG GetRenderedInt16Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].Int16Val;
}
LONGLONG GetRenderedInt32Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].Int32Val;
}
LONGLONG GetRenderedInt64Value(PVOID pRenderedValues, int property) {
return ((PEVT_VARIANT)pRenderedValues)[property].Int64Val;
}
//FILETIME to unix epoch: https://support.microsoft.com/en-us/kb/167296
ULONGLONG GetRenderedFileTimeValue(PVOID pRenderedValues, int property) {
FILETIME* ft = (FILETIME*) &(((PEVT_VARIANT)pRenderedValues)[property].FileTimeVal);
ULONGLONG time = ft->dwHighDateTime;
time = (time << 32) | ft->dwLowDateTime;
return (time / 10000000) - 11644473600;
}
// Dispatch events and errors appropriately
DWORD WINAPI SubscriptionCallback(EVT_SUBSCRIBE_NOTIFY_ACTION action, PVOID pContext, EVT_HANDLE hEvent)
{
switch(action)
{
case EvtSubscribeActionError:
// In this case, hEvent is an error code, not a handle to an event
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa385596(v=vs.85).aspx
eventCallbackError((ULONGLONG)hEvent, pContext);
break;
case EvtSubscribeActionDeliver:
eventCallback((ULONGLONG)hEvent, pContext);
break;
default:
// TODO: signal unknown error
eventCallbackError(0, pContext);
}
return ERROR_SUCCESS; // The service ignores the returned status.
}
ULONGLONG SetupListener(char* channel, char* query, PVOID pWatcher, EVT_HANDLE hBookmark, EVT_SUBSCRIBE_FLAGS flags)
{
DWORD status = ERROR_SUCCESS;
EVT_HANDLE hSubscription = NULL;
size_t wideChannelLen;
size_t maxWideChannelLen = mbstowcs(NULL, channel, 0) + 1;
LPWSTR lChannel = malloc(maxWideChannelLen * sizeof(wchar_t));
if (!lChannel) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return 0;
}
size_t maxWideQueryLen = mbstowcs(NULL, query, 0) + 1;
LPWSTR lQuery = malloc(maxWideQueryLen * sizeof(wchar_t));
if (!lQuery) {
SetLastError(ERROR_NOT_ENOUGH_MEMORY);
return 0;
}
// Convert Go string to wide characters
mbstowcs(lChannel, channel, maxWideChannelLen);
mbstowcs(lQuery, query, maxWideQueryLen);
// Subscribe to events beginning in the present. All future events will trigger the callback.
hSubscription = EvtSubscribe(NULL, NULL, lChannel, lQuery, hBookmark, pWatcher, (EVT_SUBSCRIBE_CALLBACK)SubscriptionCallback, flags);
free(lChannel);
return (ULONGLONG)hSubscription;
}
ULONGLONG CreateListener(char* channel, char* query, int startPos, PVOID pWatcher) {
return SetupListener(channel, query, pWatcher, NULL, startPos);
}
ULONGLONG CreateListenerFromBookmark(char* channel, char* query, PVOID pWatcher, ULONGLONG hBookmark) {
return SetupListener(channel, query, pWatcher, (EVT_HANDLE)hBookmark, EvtSubscribeStartAfterBookmark);
}
ULONGLONG GetTestEventHandle() {
DWORD status = ERROR_SUCCESS;
EVT_HANDLE record = 0;
DWORD recordsReturned;
EVT_HANDLE result = EvtQuery(NULL, L"Application", L"*", EvtQueryChannelPath);
if (result == 0) {
return 0;
}
if (!EvtNext(result, 1, &record, 500, 0, &recordsReturned)) {
EvtClose(result);
return 0;
}
EvtClose(result);
return (ULONGLONG)record;
}