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/*

* Copyright (C) 2009-2012 the libgit2 contributors

*

* 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_git_oid_h__

#define INCLUDE_git_oid_h__

#include "common.h"

#include "types.h"

/**

* @file git2/oid.h

* @brief Git object id routines

* @defgroup git_oid Git object id routines

* @ingroup Git

* @{

*/

GIT_BEGIN_DECL

/** Size (in bytes) of a raw/binary oid */

#define GIT_OID_RAWSZ 20

/** Size (in bytes) of a hex formatted oid */

#define GIT_OID_HEXSZ (GIT_OID_RAWSZ * 2)

/** Minimum length (in number of hex characters,

* i.e. packets of 4 bits) of an oid prefix */

#define GIT_OID_MINPREFIXLEN 4

/** Unique identity of any object (commit, tree, blob, tag). */

typedef struct _git_oid git_oid;

struct _git_oid {

/** raw binary formatted id */

unsigned char id[GIT_OID_RAWSZ];

};

/**

* Parse a hex formatted object id into a git_oid.

*

* @param out oid structure the result is written into.

* @param str input hex string; must be pointing at the start of

* the hex sequence and have at least the number of bytes

* needed for an oid encoded in hex (40 bytes).

* @return 0 or an error code

*/

GIT_EXTERN(int) git_oid_fromstr(git_oid *out, const char *str);

/**

* Parse N characters of a hex formatted object id into a git_oid

*

* If N is odd, N-1 characters will be parsed instead.

* The remaining space in the git_oid will be set to zero.

*

* @param out oid structure the result is written into.

* @param str input hex string of at least size `length`

* @param length length of the input string

* @return 0 or an error code

*/

GIT_EXTERN(int) git_oid_fromstrn(git_oid *out, const char *str, size_t length);

/**

* Copy an already raw oid into a git_oid structure.

*

* @param out oid structure the result is written into.

* @param raw the raw input bytes to be copied.

*/

GIT_EXTERN(void) git_oid_fromraw(git_oid *out, const unsigned char *raw);

/**

* Format a git_oid into a hex string.

*

* @param str output hex string; must be pointing at the start of

* the hex sequence and have at least the number of bytes

* needed for an oid encoded in hex (40 bytes). Only the

* oid digits are written; a '\\0' terminator must be added

* by the caller if it is required.

* @param oid oid structure to format.

*/

GIT_EXTERN(void) git_oid_fmt(char *str, const git_oid *oid);

/**

* Format a git_oid into a loose-object path string.

*

* The resulting string is "aa/...", where "aa" is the first two

* hex digits of the oid and "..." is the remaining 38 digits.

*

* @param str output hex string; must be pointing at the start of

* the hex sequence and have at least the number of bytes

* needed for an oid encoded in hex (41 bytes). Only the

* oid digits are written; a '\\0' terminator must be added

* by the caller if it is required.

* @param oid oid structure to format.

*/

GIT_EXTERN(void) git_oid_pathfmt(char *str, const git_oid *oid);

/**

* Format a git_oid into a newly allocated c-string.

*

* @param oid the oid structure to format

* @return the c-string; NULL if memory is exhausted. Caller must

* deallocate the string with git__free().

*/

GIT_EXTERN(char *) git_oid_allocfmt(const git_oid *oid);

/**

* Format a git_oid into a buffer as a hex format c-string.

*

* If the buffer is smaller than GIT_OID_HEXSZ+1, then the resulting

* oid c-string will be truncated to n-1 characters. If there are

* any input parameter errors (out == NULL, n == 0, oid == NULL),

* then a pointer to an empty string is returned, so that the return

* value can always be printed.

*

* @param out the buffer into which the oid string is output.

* @param n the size of the out buffer.

* @param oid the oid structure to format.

* @return the out buffer pointer, assuming no input parameter

* errors, otherwise a pointer to an empty string.

*/

GIT_EXTERN(char *) git_oid_tostr(char *out, size_t n, const git_oid *oid);

/**

* Copy an oid from one structure to another.

*

* @param out oid structure the result is written into.

* @param src oid structure to copy from.

*/

GIT_EXTERN(void) git_oid_cpy(git_oid *out, const git_oid *src);

/**

* 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)

{

const unsigned char *sha1 = a->id;

const unsigned char *sha2 = b->id;

int i;

for (i = 0; i < GIT_OID_RAWSZ; i++, sha1++, sha2++) {

if (*sha1 != *sha2)

return *sha1 - *sha2;

}

return 0;

}

/**

* Compare two oid structures for equality

*

* @param a first oid structure.

* @param b second oid structure.

* @return true if equal, false otherwise

*/

GIT_INLINE(int) git_oid_equal(const git_oid *a, const git_oid *b)

{

return !git_oid_cmp(a, b);

}

/**

* Compare the first 'len' hexadecimal characters (packets of 4 bits)

* of two oid structures.

*

* @param a first oid structure.

* @param b second oid structure.

* @param len the number of hex chars to compare

* @return 0 in case of a match

*/

GIT_EXTERN(int) git_oid_ncmp(const git_oid *a, const git_oid *b, size_t len);

/**

* Check if an oid equals an hex formatted object id.

*

* @param a oid structure.

* @param str input hex string of an object id.

* @return GIT_ENOTOID if str is not a valid hex string,

* 0 in case of a match, GIT_ERROR otherwise.

*/

GIT_EXTERN(int) git_oid_streq(const git_oid *a, const char *str);

/**

* Check is an oid is all zeros.

*

* @return 1 if all zeros, 0 otherwise.

*/

GIT_EXTERN(int) git_oid_iszero(const git_oid *a);

/**

* OID Shortener object

*/

typedef struct git_oid_shorten git_oid_shorten;

/**

* Create a new OID shortener.

*

* The OID shortener is used to process a list of OIDs

* in text form and return the shortest length that would

* uniquely identify all of them.

*

* E.g. look at the result of `git log --abbrev`.

*

* @param min_length The minimal length for all identifiers,

* which will be used even if shorter OIDs would still

* be unique.

* @return a `git_oid_shorten` instance, NULL if OOM

*/

GIT_EXTERN(git_oid_shorten *) git_oid_shorten_new(size_t min_length);

/**

* Add a new OID to set of shortened OIDs and calculate

* the minimal length to uniquely identify all the OIDs in

* the set.

*

* The OID is expected to be a 40-char hexadecimal string.

* The OID is owned by the user and will not be modified

* or freed.

*

* For performance reasons, there is a hard-limit of how many

* OIDs can be added to a single set (around ~22000, assuming

* a mostly randomized distribution), which should be enough

* for any kind of program, and keeps the algorithm fast and

* memory-efficient.

*

* Attempting to add more than those OIDs will result in a

* GIT_ENOMEM error

*

* @param os a `git_oid_shorten` instance

* @param text_oid an OID in text form

* @return the minimal length to uniquely identify all OIDs

* added so far to the set; or an error code (<0) if an

* error occurs.

*/

GIT_EXTERN(int) git_oid_shorten_add(git_oid_shorten *os, const char *text_oid);

/**

* Free an OID shortener instance

*

* @param os a `git_oid_shorten` instance

*/

GIT_EXTERN(void) git_oid_shorten_free(git_oid_shorten *os);

/** @} */

GIT_END_DECL

#endif