来自苹果的libdispatch中的凭证意味着什么？

Question

我刚刚阅读了libdispatch的源代码，但我发现有一个词，＆＃34;凭证＆＃34;，只是出现了很多次，但我不知道它究竟是什么意思。    所以能告诉我这个词的真实含义，非常感谢你的帮助。

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Answer 1

我只是从源代码中找到答案：

/*
 * Mach Voucher - an immutable collection of attribute value handles.
 *
 * The mach voucher is such that it can be passed between processes
 * as a Mach port send right (by convention in the mach_msg_header_t’s
 * msgh_voucher field).
 *
 * You may construct a new mach voucher by passing a construction
 * recipe to host_create_mach_voucher().  The construction recipe supports
 * generic commands for copying, removing, and redeeming attribute value
 * handles from previous vouchers, or running attribute-mananger-specific
 * commands within the recipe.
 *
 * Once the set of attribute value handles is constructed and returned,
 * that set will not change for the life of the voucher (just because the
 * attribute value handle itself doesn't change, the value the handle refers
 * to is free to change at will).
 */

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