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这里result已经是*big.Int类型，左移29/28位没有问题，是指result = result * 2^29，或者result = result * 2^28。limbsToBig方法是从高位开始计算的，所以要不停左移，左移的位数是limbs固定的，29， 28，...这样，和每个limb的系数没有关系。
// The value of a field element is:
// x[0] + (x[1] * 2**29) + (x[2] * 2**57) + (x[3] * 2**86) + (x[4] * 2**114) + (x[5] * 2**143) + (x[6] * 2**171) + (x[7] * 2**200) + (x[8] * 2**228)
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From:"尼维沙·纳默帝敖"< ***@***.*** >;
Date:2022/1/25 16:24
To:"emmansun/gmsm"< ***@***.*** >;
CC:"Subscribed"< ***@***.*** >;
Subject:[emmansun/gmsm] 关于SM2中p256ReduceCarry进位问题 (Discussion #18)
最近尝试用Rust写SM2，参考和学习您的代码，十分感谢您保留的常量预计算的代码，解决了很多困惑。没学过GO，代码也是边看边理解。
问题：在p256Sum方法中调用p256ReduceCarry后，原29bits宽，可能就变成了30bits宽，原28bits可能变成29bits。这时如果调用p256ToBig方法转换为bigint，依旧是按照29或者28bits左移的话，是否有问题？
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哎呀，我去，脑子卒了，之前理解有偏差，谢谢您的回复！！！ |
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byteszard
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最近尝试用Rust写SM2，参考和学习您的代码，十分感谢您保留的常量预计算的代码，解决了很多困惑。没学过GO，代码也是边看边理解。
问题：在p256Sum方法中调用p256ReduceCarry后，原29bits宽，可能就变成了30bits宽，原28bits可能变成29bits。这时如果调用p256ToBig方法转换为bigint，依旧是按照29或者28bits左移的话，是否有问题？
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