How can I make memcpy faster?

How can I make memcpy faster?

16 Answers. memcpy is likely to be the fastest way you can copy bytes around in memory. If you need something faster – try figuring out a way of not copying things around, e.g. swap pointers only, not the data itself.

Why is memcpy faster?

Like others say memcpy copies larger than 1-byte chunks. Copying in word sized chunks is much faster. However, most implementations take it a step further and run several MOV (word) instructions before looping. The advantage to copying in say, 8 word blocks per loop is that the loop itself is costly.

Which is faster memcpy or Memmove?

When running memcpy twice, then the second run is faster than the first one. When “touching” the destination buffer of memcpy ( memset(b2, 0, BUFFERSIZE…) ) then the first run of memcpy is also faster. memcpy is still a little bit slower than memmove.

Is memcpy faster than std :: copy?

Very informative analysis. Re Total average decrease in speed of std::copy over memcpy: 0.11%, whilst the number is correct, the results aren’t statistically significant. A 95% confidence interval for the difference in means is (-0.013s, 0.025), which includes zero.

Is memcpy faster than strcpy?

If you know the length of a string, you can use mem functions instead of str functions. For example, memcpy is faster than strcpy because it does not have to search for the end of the string.

What can I use instead of memcpy?

memmove() is similar to memcpy() as it also copies data from a source to destination.

What is the difference between Memmove and memcpy?

memcpy() function is is used to copy a specified number of bytes from one memory to another. memmove() function is used to copy a specified number of bytes from one memory to another or to overlap on same memory.

What is the difference between strcpy and memcpy?

The main difference is that memcpy() always copies the exact number of bytes you specify; strcpy() , on the other hand, will copy until it reads a NUL (aka 0) byte, and then stop after that.

Does memcpy add a null terminator?

> strcpy() other than the strcpy() is null terminated by default. memcpy() takes destination, source and number of characters to copy. Null termination is irrelevant to it.

What is the difference between strncpy and memcpy?

The main difference is that memcpy will copy all N characters you ask for, while strncpy will copy up to the first null terminator inclusive, or N characters, whichever is fewer. In the event that it copies less than N characters, it will pad the rest out with null characters.

Is memcpy safer than strcpy?

On almost any platform, memcpy() is going to be faster than strcpy() when copying the same number of bytes. The only time strcpy() or any of its “safe” equivalents would outperform memcpy() would be when the maximum allowable size of a string would be much greater than its actual size.

Does memcpy copy byte by byte?

memcpy() — Copy Bytes Threadsafe: Yes. The memcpy() function copies count bytes of src to dest . The behavior is undefined if copying takes place between objects that overlap. The memmove() function allows copying between objects that might overlap.

Is the C implementation of memcpy faster?

The techniques described here makes the C implementation of memcpy() a lot faster and in many cases faster than commercial ones. The implementation can probably be improved even more, especially by using wider data types when available.

What factors might affect my decision about a memcpy() algorithm?

A variety of hardware and software factors might affect your decision about a memcpy () algorithm. These include the speed of your processor, the width of your memory bus, the availability and features of a data cache, and the size and alignment of the memory transfers your application will make.

What is the story of memcpy?

The story began when a co-worker of mine made an implementation of memcpy that he was very proud of. His implementation was faster than many standardized C library routines found in the embedded market. When looking at his code, I found several places where improvements could be made.

What is the fastest memcpy/memmove ever written in C?

Apex memmove – the fastest memcpy/memmove on x86/x64 EVER, written in C Please Sign up or sign in to vote. 2 years ago I went OCD on memcpy/memmove; and wrote over 140 variations (80,000 lines of code) of memmove; testing, disassembling, optimizing and benchmarking them on multiple machines.