查找子装配 [英] Finding substring in assembly

问题描述

我想知道如果有一个更有效的方法，以找到在组件中的子凭什么我目前打算这样做。

I'm wondering if there is a more efficient method to finding a substring in assembly then what I am currently planning to do.

我知道这个字符串命令scansb / scasw /鲹可以在EAX的值进行比较，以通过EDI解决的一个值。不过，据我了解，我只能在同一时间使用这种方法搜索一个字符。

I know the string instruction "scansb/scasw/scads" can compare a value in EAX to a value addressed by EDI. However, as far as I understand, I can only search for one character at a time using this methodology.

所以，如果我想找到的帮助字符串pleasehelpme的位置，我可以用scansb找到的小时偏移，然后跳到另一个，我比较其余功能。如果余数是不正确的，我的previous抵消关口后跳回scansb并尝试再次搜索，这个时候。

So, if I want to find the location of "help" in string "pleasehelpme", I could use scansb to find the offset of the h, then jump to another function where I compare the remainder. If the remainder isn't correct, I jump back to scansb and try searching again, this time after the previous offset mark.

不过，我不想这样做，然后发现有一个更有效的方法。任何建议？在此先感谢

However, I would hate to do this and then discover there is a more efficient method. Any advice? Thanks in advance

推荐答案

有确实更有效的方式，这两种指令明智和算法。

There are indeed more efficient ways, both instruction-wise and algorithmically.

如果您有硬件，你可以使用SSE 4.2比较字符串函数，这是非常快的。见概述<一href="http://software.intel.com/sites/products/documentation/studio/composer/en-us/2009/compiler_c/intref_cls/common/intref_sse42_comp.htm" rel="nofollow">http://software.intel.com/sites/products/documentation/studio/composer/en-us/2009/compiler_c/intref_cls/common/intref_sse42_comp.htm和使用C instrinsics一个例子<一href="http://software.intel.com/en-us/articles/xml-parsing-accelerator-with-intel-streaming-simd-extensions-4-intel-sse4/" rel="nofollow">http://software.intel.com/en-us/articles/xml-parsing-accelerator-with-intel-streaming-simd-extensions-4-intel-sse4/

If you have the hardware you can use the sse 4.2 compare string functions, which are very fast. See an overview http://software.intel.com/sites/products/documentation/studio/composer/en-us/2009/compiler_c/intref_cls/common/intref_sse42_comp.htm and an example using the C instrinsics http://software.intel.com/en-us/articles/xml-parsing-accelerator-with-intel-streaming-simd-extensions-4-intel-sse4/

如果你有长串或多个搜索模式，在博耶 - 穆尔，克努特 - 莫里斯 - 普拉特并拉宾-卡普的算法可以是更有效的。

If you have long substrings or multiple search patterns, the Boyer-Moore, Knuth-Morris-Pratt and Rabin-Karp algorithms may be more efficient.

这篇关于查找子装配的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！