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April 11, 2026 09:01
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Fast string compare
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| int fast_compare( const char *ptr0, const char *ptr1, int len ){ | |
| int fast = len/sizeof(size_t) + 1; | |
| int offset = (fast-1)*sizeof(size_t); | |
| int current_block = 0; | |
| if( len <= sizeof(size_t)){ fast = 0; } | |
| size_t *lptr0 = (size_t*)ptr0; | |
| size_t *lptr1 = (size_t*)ptr1; | |
| while( current_block < fast ){ | |
| if( (lptr0[current_block] ^ lptr1[current_block] )){ | |
| int pos; | |
| for(pos = current_block*sizeof(size_t); pos < len ; ++pos ){ | |
| if( (ptr0[pos] ^ ptr1[pos]) || (ptr0[pos] == 0) || (ptr1[pos] == 0) ){ | |
| return (int)((unsigned char)ptr0[pos] - (unsigned char)ptr1[pos]); | |
| } | |
| } | |
| } | |
| ++current_block; | |
| } | |
| while( len > offset ){ | |
| if( (ptr0[offset] ^ ptr1[offset] )){ | |
| return (int)((unsigned char)ptr0[offset] - (unsigned char)ptr1[offset]); | |
| } | |
| ++offset; | |
| } | |
| return 0; | |
| } |
I got similar results for this and strncmp
https://github.com/natsys/blog has a test and benchmark. Just clone, cd fast_str, make.
What's the license on this?
@mgronhol What's the license?
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looked at this... it came out to be 11s vs. 7s for strncmp on my mac for some large number of comparisons... :\