I have a recursive function which iterates though directory trees listing the file names located in them.
Here is the function:
void WINAPI SearchFile(PSTR Directory)
{
HANDLE hFind;
WIN32_FIND_DATA FindData;
char SearchName[1024],FullPath[1024];
memset(SearchName,0,sizeof(SearchName));
memset(&FindData,0,sizeof(WIN32_FIND_DATA));
sprintf(SearchName,"%s\\*",Directory);
hFind=FindFirstFile(SearchName,&FindData);
if(hFind!=INVALID_HANDLE_VALUE)
{
while(FindNextFile(hFind,&FindData))
{
if(FindData.cFileName[0]=='.')
{
continue;
}
memset(FullPath,0,sizeof(FullPath));
sprintf(FullPath,"%s\\%s",Directory,FindData.cFileName);
if(FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
MessageBoxA(NULL, FullPath, "Directory", MB_OK);
SearchFile(FullPath);
}
else
{
MessageBoxA(NULL, FullPath, "File", MB_OK);
}
}
FindClose(hFind);
}
}
There are obviously differences between both functions but I don't understand what's making them act differently. Does anyone know why I am having this problem?
for fast understand error need look for line
goto label;
//SearchFile(FullPath);
at this point hFind containing valid data and FindClose(hFind); need be called for it. but after goto label; executed - your overwrite hFind with hFind = FindFirstFile(SearchName, &FindData); - so you already never close original hFind, never can return to iterate folder after such go to sub-folder. this is key point - need save original hFind before go to sub directory and restore it after. when you do recursive function call - this is done auto - because every sub directory in this case enumerated in self stack frame, which have separate hFind. this is native solution use recursion here.
but possible convert recursion to loop here because we call self always from the single place and as result to this single place. so we can not save return address in stack but do unconditional jump (goto) to known place.
then code have some extra errors, you never check for string buffers overflow, why 1024 as max length is hard-coded when file path can be up to 32768 chars, you not check for reparse point as result can enter to infinite loop, use FindFirstFile instead FindFirstFileEx, etc.
correct code for enumerate sub-folder in loop can be next
void DoEnum(PCWSTR pcszRoot)
{
SIZE_T FileNameLength = wcslen(pcszRoot);
// initial check for . and ..
switch (FileNameLength)
{
case 2:
if (pcszRoot[1] != '.') break;
case 1:
if (pcszRoot[0] == '.') return;
}
static const WCHAR mask[] = L"\\*";
WCHAR FileName[MAXSHORT + 1];
if (_countof(FileName) < FileNameLength + _countof(mask))
{
return;
}
ULONG dwError;
HANDLE hFindFile = 0;
WIN32_FIND_DATA FindData{};
enum { MaxDeep = 0x200 };
//++ stack
HANDLE hFindFileV[MaxDeep];
PWSTR pszV[MaxDeep];
char prefix[MaxDeep+1];
//--stack
ULONG Level = MaxDeep;
memset(prefix, '\t', MaxDeep);
prefix[MaxDeep] = 0;
PWSTR psz = FileName;
goto __enter;
__loop:
hFindFile = FindFirstFileEx(FileName, FindExInfoBasic, &FindData, FindExSearchNameMatch, 0, FIND_FIRST_EX_LARGE_FETCH);
if (hFindFile != INVALID_HANDLE_VALUE)
{
do
{
pcszRoot = FindData.cFileName;
// skip . and ..
switch (FileNameLength = wcslen(pcszRoot))
{
case 2:
if (pcszRoot[1] != '.') break;
case 1:
if (pcszRoot[0] == '.') continue;
}
if (FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
if ((SIZE_T)(FileName + _countof(FileName) - psz) < FileNameLength + _countof(mask))
{
continue;
}
__enter:
memcpy(psz, pcszRoot, (1 + FileNameLength) * sizeof(WCHAR));
if (FindData.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)
{
DbgPrint("%sreparse point: <%S>\n", prefix + Level, pcszRoot);
}
else
{
if (Level)
{
DbgPrint("%s<%S>\n", prefix + Level, psz);
hFindFileV[--Level] = hFindFile;
pszV[Level] = psz;
memcpy(psz += FileNameLength, mask, sizeof(mask));
psz++;
goto __loop;
__return:
*--psz = 0;
psz = pszV[Level];
hFindFile = hFindFileV[Level++];
DbgPrint("%s</%S>\n", prefix + Level, psz);
}
}
}
else
{
DbgPrint("%s[%u%u] %S\n", prefix + Level, FindData.nFileSizeLow, FindData.nFileSizeHigh, pcszRoot);
}
if (!hFindFile)
{
// top level exit
return ;
}
} while (FindNextFile(hFindFile, &FindData));
if ((dwError = GetLastError()) == ERROR_NO_MORE_FILES)
{
dwError = NOERROR;
}
FindClose(hFindFile);
}
else
{
dwError = GetLastError();
}
if (dwError)
{
DbgPrint("<%S> err = %u\n", FileName, dwError);
}
goto __return;
}
The reason for the difference is actually the confusion brought to you by goto label.If you are using the recursive version, after the recursive execution is completed, it will return to the recursive place to continue execution.
In your code, you continue to execute while (FindNextFile(hFind, &FindData)), but when you use goto label, it will jump out of the original loop and restart the program from the label, which leads to what you said list a single directory tree before ending.
If you modify the modified code to the following iterative version, you can understand why there is such a problem.
void fun()
{
char* Directory = "D:\\test";
HANDLE hFind;
WIN32_FIND_DATA FindData;
char SearchName[1024], FullPath[1024];
char LastName[1024] = "";
while (1)
{
memset(SearchName, 0, sizeof(SearchName));
memset(&FindData, 0, sizeof(WIN32_FIND_DATA));
sprintf(SearchName, "%s\\*", Directory);
if (strcmp(SearchName, LastName) == 0)
{
return;
}
strcpy(LastName, SearchName);
hFind = FindFirstFile(SearchName, &FindData);
if (hFind != INVALID_HANDLE_VALUE)
{
while (FindNextFile(hFind, &FindData))
{
if (FindData.cFileName[0] == '.')
{
continue;
}
memset(FullPath, 0, sizeof(FullPath));
sprintf(FullPath, "%s\\%s", Directory, FindData.cFileName);
if (FindData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
MessageBoxA(NULL, Directory, "Directory", MB_OK);
char cArray[1024];
memset(cArray, 0, sizeof(cArray));
sprintf(cArray, "%s", FullPath);
Directory = cArray;
break;
}
else
{
MessageBoxA(NULL, FullPath, "File", MB_OK);
}
}
FindClose(hFind);
}
}
}
So you cannot achieve the same purpose as recursion by using goto, here you can only use recursion. Of course, I have provided a way to traverse directories non-recursively using queues, which is a more scientific way.
One of the key things that you obtain from recursion is a separate set of local variables for each call to the recursive function. When a function calls itself, and in the recursive call modifies local variables, those local-variable changes do not (directly) affect the local variables of the caller. In your original program, this applies to variables hFind, FindData, SearchName, and FullPath.
If you want similar behavior in a non-recursive version of the function then you need to manually preserve the state of your traversal of one level of the tree when you descend to another level. The goto statement doesn't do any such thing -- it just redirects the control flow of your program. Although there are a few good use cases for goto in C, they are uncommon, and yours is not one of them.
There are several ways to implement manually preserving state, but I would suggest
creating a structure type in which to store those data that characterize the state of your traversal of a particular level. Those appear to be only hFind and FindData -- it looks like the other locals don't need to be preserved. Maybe something like this, then:
struct dir_state {
HANDLE hFind;
WIN32_FIND_DATA FindData;
};
Dynamically allocating an array of structures of that type.
unsigned depth_limit = DEFAULT_DEPTH_LIMIT;
struct dir_state *traversal_states
= malloc(depth_limit * sizeof(*traversal_states));
if (traversal_states == NULL) // ... handle allocation error ...
Tracking the depth of your tree traversal, and for each directory you process, using the array element whose index is the relative depth of that directory.
// For example:
traversal_states[depth].hFind
= FindFirstFile(SearchName, &traversal_states[depth].FindData);
// etc.
Remembering the size of the array, so as to be able to reallocate it larger if the traversal descends too deep for its current size.
// For example:
if (depth >= depth_limit) {
depth_limit = depth_limit * 3 / 2;
struct dir_state *temp
= realloc(traversal_states, depth_limit * sizeof(*traversal_states));
if (temp == NULL) {
// handle error, discontinuing traversal
}
traversal_states = temp;
}
Also, use an ordinary for, while, or do loop instead of a backward-jumping goto. There will be a few details to work out to track when to use FindFirstFile and when FindNextFile (which you would still have with goto), but I'm sure you can sort it out.
Details are left as an exercise.
Unless necessary due to memory or processing constraints or infinite recursion tail conditions that would be complication to introduce there really isn't much need to not use recursion here, since it leads to a readable and elegant solution.
I also want to point out that in "modern" C, any solution using a GOTO is likely not a solution you want since they are so often confusing to use and leads to memory issues (we have loops now to make all of that so much simpler).
Instead of the GOTOs I would suggest implementing a stack of the directories. Wrap the printing logic a while or do-while, and as you are iterating over the files add any directories to the stack. At every new iteration pop and walk the directory at the head of the stack. The loop condition just needs to check if the directory stack is empty, before continuing its block.
I recently saw code for reading entire contents of an InputStream into a String in Kotlin, such as:
// input is of type InputStream
val baos = ByteArrayOutputStream()
input.use { it.copyTo(baos) }
val inputAsString = baos.toString()
And also:
val reader = BufferedReader(InputStreamReader(input))
try {
val results = StringBuilder()
while (true) {
val line = reader.readLine()
if (line == null) break
results.append(line)
}
val inputAsString = results.toString()
} finally {
reader.close()
}
And even this that looks smoother since it auto-closes the InputStream:
val inputString = BufferedReader(InputStreamReader(input)).useLines { lines ->
val results = StringBuilder()
lines.forEach { results.append(it) }
results.toString()
}
Or slight variation on that one:
val results = StringBuilder()
BufferedReader(InputStreamReader(input)).forEachLine { results.append(it) }
val resultsAsString = results.toString()
Then this functional fold thingy:
val inputString = input.bufferedReader().useLines { lines ->
lines.fold(StringBuilder()) { buff, line -> buff.append(line) }.toString()
}
Or a bad variation which doesn't close the InputStream:
val inputString = BufferedReader(InputStreamReader(input))
.lineSequence()
.fold(StringBuilder()) { buff, line -> buff.append(line) }
.toString()
But they are all clunky and I keep finding newer and different versions of the same... and some of them never even close the InputStream. What is a non-clunky (idiomatic) way to read the InputStream?
Note: this question is intentionally written and answered by the author (Self-Answered Questions), so that the idiomatic answers to commonly asked Kotlin topics are present in SO.
Kotlin has a specific extension just for this purpose.
The simplest:
val inputAsString = input.bufferedReader().use { it.readText() } // defaults to UTF-8
And in this example, you could decide between bufferedReader() or just reader(). The call to the function Closeable.use() will automatically close the input at the end of the lambda's execution.
Further reading:
If you do this type of thing a lot, you could write this as an extension function:
fun InputStream.readTextAndClose(charset: Charset = Charsets.UTF_8): String {
return this.bufferedReader(charset).use { it.readText() }
}
Which you could then call easily as:
val inputAsString = input.readTextAndClose() // defaults to UTF-8
On a side note, all Kotlin extension functions that require knowing the charset already default to UTF-8, so if you require a different encoding you need to adjust the code above in calls to include encoding for reader(charset) or bufferedReader(charset).
Warning: You might see examples that are shorter:
val inputAsString = input.reader().readText()
But these do not close the stream. Make sure you check the API documentation for all of the IO functions you use to be sure which ones close and which do not. Usually, if they include the word use (such as useLines() or use()) they close the stream after. An exception is that File.readText() differs from Reader.readText() in that the former does not leave anything open and the latter does indeed require an explicit close.
See also: Kotlin IO related extension functions
【Method 1 | Manually Close Stream】
private fun getFileText(uri: Uri):String {
val inputStream = contentResolver.openInputStream(uri)!!
val bytes = inputStream.readBytes() //see below
val text = String(bytes, StandardCharsets.UTF_8) //specify charset
inputStream.close()
return text
}
inputStream.readBytes() requires manually close the stream: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/java.io.-input-stream/read-bytes.html
【Method 2 | Automatically Close Stream】
private fun getFileText(uri: Uri): String {
return contentResolver.openInputStream(uri)!!.bufferedReader().use {it.readText() }
}
You can specify the charset inside bufferedReader(), default is UTF-8:
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/java.io.-input-stream/buffered-reader.html
bufferedReader() is an upgrade version of reader(), it is more versatile:
How exactly does bufferedReader() work in Kotlin?
use() can automatically close the stream when the block is done:
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/use.html
An example that reads contents of an InputStream to a String
import java.io.File
import java.io.InputStream
import java.nio.charset.Charset
fun main(args: Array<String>) {
val file = File("input"+File.separator+"contents.txt")
var ins:InputStream = file.inputStream()
var content = ins.readBytes().toString(Charset.defaultCharset())
println(content)
}
For Reference - Kotlin Read File
Quick solution works well when converting InputStream to string.
val convertedInputStream = String(inputStream.readAllBytes(), StandardCharsets.UTF_8)
I have a barcode reader code was working well with Xcode 6.2 but when you upgraded to Xcode 6.3 I got this error message
Use error message of unresolved identifier 'qrCodeFrameView'
this my code
func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
// Check if the metadataObjects array is not nil and it contains at least one object.
if metadataObjects == nil || metadataObjects.count == 0 {
qrCodeFrameView?.frame = CGRectZero
return
}
// Get the metadata object.
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
// Here we use filter method to check if the type of metadataObj is supported
// Instead of hardcoding the AVMetadataObjectTypeQRCode, we check if the type
// can be found in the array of supported bar codes.
if supportedBarCodes.filter({ $0 == metadataObj.type }).count > 0 {
// If the found metadata is equal to the QR code metadata then update the status label's text and set the bounds
let barCodeObject = videoPreviewLayer?.transformedMetadataObjectForMetadataObject(metadataObj as AVMetadataMachineReadableCodeObject) as! AVMetadataMachineReadableCodeObject
qrCodeFrameView?.frame = barCodeObject.bounds
if metadataObj.stringValue != nil {
}
I am receiving the error
Operand Types Are Not Compatible With The Operator
in the title when trying to compare two "real" datatypes.
Can anyone help me out with what is wrong?
public void clicked()
{
real localAnnualUsage = itemSetup_DS.AnnualUsage();
real localSalesPrice = itemSetup.StockPrice;
real localCost = itemSetup.StockCost;
real localstockInventAvg = itemSetup.StockInventAvg;
real localTurnAndEarn;
real localAnnualGP;
real localAvgInvCost;
;
localAvgInvCost = itemSetup.StockInventAvg;
if (localStockInventAvg != itemSetup_StockInventAvg)
{
localAvgInvCost = itemSetup_StockInventAvg;
}
//...
}
The error happens with on the line of the conditional.
Most likely your itemSetup_StockInventAvg variable is a real control, not a real.
Try using:
if (localStockInventAvg != itemSetup_StockInventAvg.realValue())
or better (because the control stores the result in itemSetup.StockInventAvg):
if (localStockInventAvg != itemSetup.StockInventAvg)
Update: This makes no sense, since localStockInventAvg was set to itemSetup.StockInventAvg the line before.
Look please below this codes throw me : FormatException was unhandled by user code
Codes:
satis.KDV = Decimal.Parse((from o in genSatisctx.Urun where o.ID == UrunID select o.Kdv).ToString());
How can i rewrite linq query?
You are calling ToString on the query rather than a single result. Even though you may expect only one value to match your query, it will not return just a single value. You have to instruct it to do so using Single, First, Last or the variations of these that also return a default value (SingleOrDefault, FirstOrDefault, LastOrDefault).
In order to avoid an exception, you could change it to use Decimal.TryParse or you could change your code to use a default value if the LINQ query returns something that won't parse properly. I'd recommend the former or a combination.
Note that in the following example, I have added the call to SingleOrDefault. This ensures that only one value is parsed, even if no value is found, and that if there are multiple results, we get an exception (i.e. it enforces that we get exactly zero or one result to the query).
decimal parsedValue;
if (Decimal.TryParse(
genSatisctx
.Urun
.Where(o => o.ID == UrunID)
.Select(o=>o.Kdv)
.SingleOrDefault()
.ToString(), out parsedValue))
{
satis.KDV = parsedValue;
}
You're calling ToString() on an IQueryable<T> - what did you expect the string to be? It's very unlikely to be anything which can be parsed as a decimal number!
My guess is that you want to call First() or Single(), but we can't really tell without more information. What's the type of o.Kdv?
I suspect you either want:
satis.KDV = (from o in genSatisctx.Urun
where o.ID == UrunID
select o.Kdv).First();
or
string kdvString = (from o in genSatisctx.Urun
where o.ID == UrunID
select o.Kdv).First();
decimal kdv;
if (decimal.TryParse(kdvString, out kdv))
{
satis.KDV = kdv;
}
else
{
// What do you want to do if it's not valid?
}
When I use debug mode I see the data is update when over mouse, after end of this method ( it's show this message [input string was not in a correct format]
/* protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
try
{
TextBox name = (TextBox)GridView1.Rows[e.RowIndex].FindControl("txtEditName");
SqlDataSource2.UpdateParameters["Name"].DefaultValue = name.ToString();
TextBox age = (TextBox)GridView1.Rows[e.RowIndex].FindControl("txtEditAge");
SqlDataSource2.UpdateParameters["Age"].DefaultValue = age.ToString();
TextBox birthday = (TextBox)GridView1.Rows[e.RowIndex].FindControl("txtEditBirthday");
SqlDataSource2.UpdateParameters["Birthday"].DefaultValue = birthday.ToString();
DropDownList country = (DropDownList)GridView1.Rows[e.RowIndex].FindControl("DropEditCountry");
SqlDataSource2.UpdateParameters["CountryID"].DefaultValue = country.SelectedValue;
TextBox mobile = (TextBox)GridView1.Rows[e.RowIndex].FindControl("txtEditMobile");
SqlDataSource2.UpdateParameters["Mobile_No"].DefaultValue = mobile.ToString();
SqlDataSource2.Update();
}
catch (Exception j)
{
j.Message.ToString();
}
}
/* }