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C file IO faster than C++ file IO?

Spearhawk · 2003-03-17T04:18:59

Hi, I decided to re-write the OGL for Game Programming''s tga loader with C++ style file reading instead of C style. Only now my egine takes about twice as long to load. Is C++ file IO slower, or did I do someitng wrong? The code for the loading function is below (old C style commented out). Thanks in advance bool GcTarga::Load(char *fileName) { //byte ucharBad; // Garbage byte data //short int sintBad; // Garbage short int data long imageSize; // Since of TGA image int colorMode; // 4 for RGBA or 3 for RGB byte colorSwap; // Swap variable // Open the TGA file //filePtr = fopen(fileName, "rb"); ifstream file(fileName, ios::in | ios::binary); // Check to see if opened if(!file) { MessageBox(NULL, "Failed to open TGA file.", "ERROR", MB_OK); return false; } // Read first two bytes of data not needed file.seekg(sizeof(byte) * 2, ios::cur); //file.read((char*)&ucharBad, sizeof(byte)); //file.read((char*)&ucharBad, sizeof(byte)); // Read the image type //fread(&imageTypeCode, sizeof(byte), 1, filePtr); file.read((char*)&imageTypeCode, sizeof(byte)); // Check that it''s the corect type if((imageTypeCode != 2) && (imageTypeCode != 3)) { fclose(filePtr); MessageBox(NULL, "The TGA file is not of a suported format", "ERROR", MB_OK); return false; } // Skip unneaded data //fread(&sintBad, sizeof(short int), 1, filePtr); //fread(&sintBad, sizeof(short int), 1, filePtr); //fread(&ucharBad, sizeof(byte), 1, filePtr); //fread(&sintBad, sizeof(short int), 1, filePtr); //fread(&sintBad, sizeof(short int), 1, filePtr); file.seekg(sizeof(short int) * 4 + sizeof(byte), ios::cur); // Read image dimensions //fread(&imageWidth, sizeof(short int), 1, filePtr); //fread(&imageHeight, sizeof(short int), 1, filePtr); file.read((char*)&imageWidth, sizeof(short int)); file.read((char*)&imageHeight, sizeof(short int)); // Read bit depth //fread(&bitCount, sizeof(byte), 1, filePtr); file.read((char*)&bitCount, sizeof(byte)); // Read 1 byte of garbage data //fread(&ucharBad, sizeof(byte), 1, filePtr); file.seekg(sizeof(byte), ios::cur); // Check for depth if((bitCount == 24) || (bitCount == 32)) { // colorMode -> 3 = BGR, 4 = BGRA colorMode = bitCount / 8; imageSize = imageWidth * imageHeight * colorMode; // Allocate memory for image data imageData = (byte*)malloc(sizeof(byte) * imageSize); // Read image data //fread(imageData, sizeof(byte), imageSize, filePtr); file.read((char*)imageData, sizeof(byte) * imageSize); // Change BGR to RGB (BGRA to RGBA) for(int i = 0; i < imageSize; i += colorMode) { colorSwap = imageData[i]; imageData[i] = imageData[i + 2]; imageData[i + 2] = colorSwap; } } else if(bitCount == 16) { unsigned short pixels = 0; int r=0, g=0, b=0; // RGB color mode (after conversion) colorMode = 3; imageSize = imageWidth * imageHeight * colorMode; // Allocate memory for image data imageData = (byte*)malloc(sizeof(byte) * imageSize); // Load in all the pixel data pixel by pixel and convert to RGB for(int i = 0; i < imageWidth * imageHeight; i++) { // Read in the current pixel //fread(&pixels, sizeof(unsigned short), 1, filePtr); file.read((char*)&pixels, sizeof(unsigned short)); // Change the pixel to 24 bit b = (pixels & 0x1f) << 3; g = ((pixels >> 5) & 0x1f) << 3; r = ((pixels >> 10) & 0x1f) << 3; // Swap to RGB and save in array imageData[i * 3 + 0] = r; imageData[i * 3 + 1] = g; imageData[i * 3 + 2] = b; } } else { MessageBox(NULL, "TGA file of a not suported bpp", "Error", MB_OK); return false; } // Close the file file.close(); //fclose(filePtr); return true; } -- Spearhawk productions Project Andromeda

General and Gameplay Programming Programming

Started by Spearhawk March 04, 2003 05:52 PM

41 comments, last by Spearhawk 21 years, 1 month ago

LilBudyWizer

491

March 16, 2003 06:59 PM

It has been awhile, but seems when I tested streams were signficantly slower even when doing large reads. Overall it didn''t seem enough to matter. The reason being that you spend very little of your time in a game doing I/O. Doing that I/O in big bursts and making the user wait while you do it is a choice you make. So you are going to choose to do that and then worry about which method is faster? I don''t get the point of that.

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Kylotan

10,510

March 17, 2003 03:39 AM

I always found C++ iostreams to be slightly slower and slightly larger (due to the linkage requirements) than using stdio ''equivalents'', but you have to remember that the iostreams potentially do a lot more than stdio does. Iostreams perform a lot of character conversion and the like which many game applications will not need. Those who truly do have performance problems should consider streambufs or specifically filebufs instead. See also here.

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Tybalt

122

March 17, 2003 04:18 AM

C++ is Slower than C!

What? Me no understand.

C and C++ are both programming languages. How can they have a speed, let alone how can you compare their ''speed''.

You seem to be talking about speed of execution, which is dependent on the machine code instructions produced by a compiler. This then is down to the particular compiler and the methods employed by the programmer.

You can''t make generalisations like this. If you have a method that is faster, then fine. Test it, measure it, prove it.

As a side note, I read somewhere that the Win32 CreateFile/... functions are marginally faster than fread because fread actually wraps the Win32 functions. It could be all baloney though, someone should test it.

C file IO faster than C++ file IO?

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C file IO faster than C++ file IO?

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