thodg/libgit2/src/delta-apply.h

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• Hash : a97b769a
  Author :
  Date : 2016-04-27T12:00:31
  

  odb: avoid inflating the full delta to read the header
  
  When we read the header, we want to know the size and type of the
  object. We're currently inflating the full delta in order to read the
  first few bytes. This can mean hundreds of kB needlessly inflated for
  large objects.
  
  Instead use a packfile stream to read just enough so we can read the two
  varints in the header and avoid inflating most of the delta.
  

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• src/delta-apply.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_delta_apply_h__
  #define INCLUDE_delta_apply_h__
  
  #include "odb.h"
  #include "pack.h"
  
  /**
   * Apply a git binary delta to recover the original content.
   *
   * @param out the output buffer to receive the original data.
   *		Only out->data and out->len are populated, as this is
   *		the only information available in the delta.
   * @param base the base to copy from during copy instructions.
   * @param base_len number of bytes available at base.
   * @param delta the delta to execute copy/insert instructions from.
   * @param delta_len total number of bytes in the delta.
   * @return
   * - 0 on a successful delta unpack.
   * - GIT_ERROR if the delta is corrupt or doesn't match the base.
   */
  extern int git__delta_apply(
  	git_rawobj *out,
  	const unsigned char *base,
  	size_t base_len,
  	const unsigned char *delta,
  	size_t delta_len);
  
  /**
   * Read the header of a git binary delta.
   *
   * @param delta the delta to execute copy/insert instructions from.
   * @param delta_len total number of bytes in the delta.
   * @param base_sz pointer to store the base size field.
   * @param res_sz pointer to store the result size field.
   * @return
   * - 0 on a successful decoding the header.
   * - GIT_ERROR if the delta is corrupt.
   */
  extern int git__delta_read_header(
  	const unsigned char *delta,
  	size_t delta_len,
  	size_t *base_sz,
  	size_t *res_sz);
  
  /**
   * Read the header of a git binary delta
   *
   * This variant reads just enough from the packfile stream to read the
   * delta header.
   */
  extern int git__delta_read_header_fromstream(
  	size_t *base_sz,
  	size_t *res_sz,
  	git_packfile_stream *stream);
  
  #endif
  

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