C / C++ / MFC

6-Nov-02 9:54

I can assume CRT functions would probably out perform my own for loop functions...?

The idea is this:

I have a buffer[0xFFFF] I wish to iterate the buffer looking for sequences of characters (carriage returns).

Currently I have something like:

for(int i=0; i<MAX_BUFF_SIZE && m_nLines < iLine; i++)
{  if(buffer[i] == 13) m_nLines++;  }

It occurred to me that this can also be accomplished using CRT functions, which I thought are probably tweaked as tweaked can get...so I should probably use that implementation instead of the above...???

If you know if the CRT would out perform lemme know and if you wanna profile for me or check out the assembly dump and compare instructions, by all means please do so... Poke tongue | ;-P

Save me alot of time...or if your just damn sure that CRT would be faster...lemme know...

Thanx a million

Cheers! Smile | :)

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Tim Smith6-Nov-02 10:09

Tim Smith

6-Nov-02 10:09

I doubt strchr will help much. In fact, it might hurt if you make the following optimization to your routine.

if (m_nLines < iLine)
{
    for (int i = 0; i < MAX_BUFF_SIZE; i++)
    {
        if (buffer [i] == 13)
        {
            m_nLines++;
            if (m_nLines >= iLine)
                break;
        }
    }
}

Now, you might get some improvement with using memchr.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Daniel Turini6-Nov-02 10:06

Daniel Turini

6-Nov-02 10:06

Look under \Program Files\Microsoft Visual Studio\VC98\CRT\SRC\Intel\ for the file STRCHR.ASM

It's fast as hell. Smile | :)

lazy isn't my middle name.. its my first.. people just keep calling me Mel cause that's what they put on my drivers license. - Mel Feik

Paul M Watt6-Nov-02 10:07

Paul M Watt

6-Nov-02 10:07

Where will you be using this loop? If it gets called only once in a while, I would not worry about tweaking its performance because it is relatively simple loop that counts the number or return carraiges in a buffer.

However if you are going to be calling this function every time that a character is pressed that is another issue.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Tim Smith6-Nov-02 10:44

Tim Smith

6-Nov-02 10:44

(for previous message, threading error)

*SLAP* (myself)

When I said it wouldn't help much, I had just seen the C version of the routine. Silly silly me.

But I still think memchr would be a better fit for him.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

alex.barylski6-Nov-02 12:02

6-Nov-02 12:02

Paul Watt wrote:
However if you are going to be calling this function every time that a character is pressed that is another issue.

Yes this correct...I chose this over a line vector(terminology???) so it gets called each time a key is pressed...

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

alex.barylski6-Nov-02 11:52

6-Nov-02 11:52

How is memchr() better than strchr()? Are there fewer instructions...? Faster instructions....? Whats the deal...?

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Tim Smith6-Nov-02 12:24

Tim Smith

6-Nov-02 12:24

strchr assumes NULL terminated string. Thus an extra test for a NULL. memchr doesn't have that.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

alex.barylski6-Nov-02 13:27

6-Nov-02 13:27

Awesome...thanks Smile | :)

I suppose I could have up the *.asm files myself and determined which was faster, but I guess I just wasn't thinking. Blush | :O

Thanx again!

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

alex.barylski6-Nov-02 12:05

waveInOpen - Unresolved External Symbol !

6-Nov-02 12:05

This is what I was thinking, I just needed to hear it form somebody other than myself...

Thanx Smile | :)

p.s - No i don't hear voices

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Paddy6-Nov-02 9:41

Paddy

6-Nov-02 9:41

Hi,

I'm very new to VC++ and I hope someone can help me out!
I'm trying to write a program to take audio samples from the sound card but I keep getting an "unresolved external symbol" error and I have no idea why! I have the code to set up the wave format but once I try and query the soundcard it complains. Am I doing something wrong?

Record Sound error LNK2019: unresolved external symbol__imp__waveInOpen@24 referenced in function "void__cdecl RecordWaveFile(void)" (?RecordWaveFile@@YAXXZ)

void RecordWaveFile()
{

HWAVEIN WaveHandle;
WAVEFORMATEX WaveFormat;

WaveFormat.wFormatTag = WAVE_FORMAT_PCM;
WaveFormat.nChannels = 1;
WaveFormat.nSamplesPerSec = 22050;
WaveFormat.wBitsPerSample = 8;
WaveFormat.nAvgBytesPerSec = 22050;
WaveFormat.nBlockAlign = 1;
WaveFormat.cbSize = 0;

int Res = waveInOpen(&WaveHandle, WAVE_MAPPER, &WaveFormat, 0, 0, WAVE_FORMAT_QUERY);

if (Res == WAVERR_BADFORMAT) return;

}

Thanks in advance,
Paddy.

BlackSmith6-Nov-02 10:01

BlackSmith

6-Nov-02 10:01

Add to your project settings, under 'Link->Object/Library modules' tab, Winmm.lib.
That's bout-it. Cool | :cool:

--BlackSmith--
/*The roof is on fire, we don't need no water, let the MF burn*/. BHG.

Paddy6-Nov-02 10:38

Paddy

6-Nov-02 10:38

Thanks,
You wouldn't believe how long I've been trying to fix that for!!!

User 66586-Nov-02 11:22

User 6658

6-Nov-02 11:22

Alternatively, you can also put #pragma comment(linker, "winmm.lib") to the top of the source file. That's the way I do it whenever I need to link with a new lib file apart from the ones already set in the linker options

regards

modified 12-Sep-18 21:01pm.