This is highly optimized code that in the normal case loads 4 bytes at a time, checks if any of the 4 is z a null (0) and handles accordingly. If the string doesn't start on a 4-byte boundary, the str_misaligned counts 1, 2, or 3 characters until a null or alignment boundary is found. The tricky computation in main_loop is
(~ax ^ (ax + 0x7efefeff) ) & 0x81010100 == 0 This test is true if and only if none of the four bytes in ax is initially 0 (null). If the test fails (i.e. the terminating null is found), there are four cases to deal with computing the length by subtracting pointers. (The lea instruction is a cheap way of subtracting a constant from one register and placing the result into another.) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to algogeeks@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/algogeeks -~----------~----~----~----~------~----~------~--~---
