Bug #1724: LocalProcess portability issue: LocalProcess::Read2 can not return more than 1024B on PLATFORM_WIN but it can on POSIX - U++ - Redmine

Bug #1724

LocalProcess portability issue: LocalProcess::Read2 can not return more than 1024B on PLATFORM_WIN but it can on POSIX

Added by Abdelghani Omari almost 7 years ago. Updated almost 7 years ago.

Status:

Approved

Start date:

05/17/2017

Priority:

Normal

Due date:

Assignee:

Abdelghani Omari

% Done:

Category:

Core

Spent time:

Target version:

Description

test case:

CONSOLE_APP_MAIN
{
    String str = String('A', 1024);
    str << "B";

    String f = GetDataFile("data.txt");
    SaveFile(f, str);

    String cmd;

    #ifdef PLATFORM_POSIX
     cmd << "cat \"" << f << "\"";
    #else
     cmd << "cmd /c Type \"" << f << "\"";
    #endif

    LocalProcess proc;
    proc.Start(cmd);
    Sleep(200);

    String r;
    proc.Read(r);
    DUMP(r.GetCount());
    proc.Read(r);
    DUMP(r.GetCount());
}

output :
POSIX:

  r.GetCount() = 1025
  r.GetCount() = 0

WIN32:

  r.GetCount() = 1024
  r.GetCount() = 1

this is because the WIN32 version use "if" and the POSIX use "while".

the patch :

bool LocalProcess::Read2(String& reso, String& rese)
{
    LLOG("LocalProcess::Read2");
    reso = wreso;
    rese = wrese;
    wreso.Clear();
    wrese.Clear();

#ifdef PLATFORM_WIN32
    LLOG("LocalProcess::Read");
    bool was_running = IsRunning();
    char buffer[1024];
    dword n;
    while(hOutputRead && PeekNamedPipe(hOutputRead, NULL, 0, NULL, &n, NULL) && n &&  //  LINE modified : replace "if" with " "while" 
       ReadFile(hOutputRead, buffer, sizeof(buffer), &n, NULL) && n)
        reso.Cat(buffer, n);

    while(hErrorRead && PeekNamedPipe(hErrorRead, NULL, 0, NULL, &n, NULL) && n &&   //  LINE modified : replace "if" with " "while" 
       ReadFile(hErrorRead, buffer, sizeof(buffer), &n, NULL) && n)
        rese.Cat(buffer, n);

    if(convertcharset) {
        reso = FromOEMCharset(reso);
        rese = FromOEMCharset(rese);
    }

    return .......

History

#1 Updated by Miroslav Fidler almost 7 years ago

Assignee changed from Miroslav Fidler to Abdelghani Omari

I do not think this is an error. Contract is that Read returns "some" data if available. You are supposed to call it again for the next chunk.

Even in this example, reading the output of "ls" can return less and then some more on the next call, as there might not be data in the pide yet.

In fact, if something needs fixing here, it is perhaps posix version - if some process would be producing a lot of data quickly, it would produce very large Strings, which would be bad in some cases. I guess there should be "if" too...

Mirek