thodg/libgit2/src/oid.h

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• Hash : c9b1e646
  Author :
  Date : 2017-08-09T16:54:07
  

  oid: use memcmp in git_oid__hashcmp
  
  The open-coded version was inherited from git.git. But it
  turns out it was based on an older version of glibc, whose
  memcmp was not very optimized.
  
  Modern glibc does much better, and some compilers (like gcc
  7) can even inline the memcmp into a series of multi-byte
  xors.
  
  Upstream is switching to using memcmp in
  git/git@0b006014c87f400bd9a86267ed30fd3e7b383884.
  

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• src/oid.h

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  #ifndef INCLUDE_oid_h__
  #define INCLUDE_oid_h__
  
  #include "git2/oid.h"
  
  /**
   * Format a git_oid into a newly allocated c-string.
   *
   * The c-string is owned by the caller and needs to be manually freed.
   *
   * @param id the oid structure to format
   * @return the c-string; NULL if memory is exhausted. Caller must
   *			deallocate the string with git__free().
   */
  char *git_oid_allocfmt(const git_oid *id);
  
  GIT_INLINE(int) git_oid__hashcmp(const unsigned char *sha1, const unsigned char *sha2)
  {
  	return memcmp(sha1, sha2, GIT_OID_RAWSZ);
  }
  
  /*
   * Compare two oid structures.
   *
   * @param a first oid structure.
   * @param b second oid structure.
   * @return <0, 0, >0 if a < b, a == b, a > b.
   */
  GIT_INLINE(int) git_oid__cmp(const git_oid *a, const git_oid *b)
  {
  	return git_oid__hashcmp(a->id, b->id);
  }
  
  GIT_INLINE(void) git_oid__cpy_prefix(
  	git_oid *out, const git_oid *id, size_t len)
  {
  	memcpy(&out->id, id->id, (len + 1) / 2);
  
  	if (len & 1)
  		out->id[len / 2] &= 0xF0;
  }
  
  #endif
  

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