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 /*
  * 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_git_oid_h__
 #define INCLUDE_git_oid_h__
 
 #include "common.h"
 #include "types.h"
 #include "experimental.h"
 
 /**
  * @file git2/oid.h
  * @brief Git object id routines
  * @defgroup git_oid Git object id routines
  * @ingroup Git
  * @{
  */
 GIT_BEGIN_DECL
 
 /** The type of object id. */
 typedef enum {
 
 #ifdef GIT_EXPERIMENTAL_SHA256
     GIT_OID_SHA1 = 1,  /**< SHA1 */
     GIT_OID_SHA256 = 2 /**< SHA256 */
 #else
     GIT_OID_SHA1 = 1   /**< SHA1 */
 #endif
 
 } git_oid_t;
 
 /*
  * SHA1 is currently the only supported object ID type.
  */
 
 /** SHA1 is currently libgit2's default oid type. */
 #define GIT_OID_DEFAULT         GIT_OID_SHA1
 
 /** Size (in bytes) of a raw/binary sha1 oid */
 #define GIT_OID_SHA1_SIZE       20
 /** Size (in bytes) of a hex formatted sha1 oid */
 #define GIT_OID_SHA1_HEXSIZE   (GIT_OID_SHA1_SIZE * 2)
 
 /**
  * The binary representation of the null sha1 object ID.
  */
 #ifndef GIT_EXPERIMENTAL_SHA256
 # define GIT_OID_SHA1_ZERO   { { 0 } }
 #else
 # define GIT_OID_SHA1_ZERO   { GIT_OID_SHA1, { 0 } }
 #endif
 
 /**
  * The string representation of the null sha1 object ID.
  */
 #define GIT_OID_SHA1_HEXZERO   "0000000000000000000000000000000000000000"
 
 /*
  * Experimental SHA256 support is a breaking change to the API.
  * This exists for application compatibility testing.
  */
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 
 /** Size (in bytes) of a raw/binary sha256 oid */
 # define GIT_OID_SHA256_SIZE     32
 /** Size (in bytes) of a hex formatted sha256 oid */
 # define GIT_OID_SHA256_HEXSIZE (GIT_OID_SHA256_SIZE * 2)
 
 /**
  * The binary representation of the null sha256 object ID.
  */
 # define GIT_OID_SHA256_ZERO { GIT_OID_SHA256, { 0 } }
 
 /**
  * The string representation of the null sha256 object ID.
  */
 # define GIT_OID_SHA256_HEXZERO "0000000000000000000000000000000000000000000000000000000000000000"
 
 #endif
 
 /* Maximum possible object ID size in raw / hex string format. */
 #ifndef GIT_EXPERIMENTAL_SHA256
 # define GIT_OID_MAX_SIZE        GIT_OID_SHA1_SIZE
 # define GIT_OID_MAX_HEXSIZE     GIT_OID_SHA1_HEXSIZE
 #else
 # define GIT_OID_MAX_SIZE        GIT_OID_SHA256_SIZE
 # define GIT_OID_MAX_HEXSIZE     GIT_OID_SHA256_HEXSIZE
 #endif
 
 /** 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 {
 
 #ifdef GIT_EXPERIMENTAL_SHA256
     /** type of object id */
     unsigned char type;
 #endif
 
     /** raw binary formatted id */
     unsigned char id[GIT_OID_MAX_SIZE];
 } git_oid;
 
 /**
  * Parse a hex formatted object id into a git_oid.
  *
  * The appropriate number of bytes for the given object ID type will
  * be read from the string - 40 bytes for SHA1, 64 bytes for SHA256.
  * The given string need not be NUL terminated.
  *
  * @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 for sha1,
  *      256 bytes for sha256).
  * @param type the type of object id
  * @return 0 or an error code
  */
 #ifdef GIT_EXPERIMENTAL_SHA256
 GIT_EXTERN(int) git_oid_fromstr(git_oid *out, const char *str, git_oid_t type);
 #else
 GIT_EXTERN(int) git_oid_fromstr(git_oid *out, const char *str);
 #endif
 
 /**
  * Parse a hex formatted NUL-terminated string into a git_oid.
  *
  * @param out oid structure the result is written into.
  * @param str input hex string; must be null-terminated.
  * @param type the type of object id
  * @return 0 or an error code
  */
 #ifdef GIT_EXPERIMENTAL_SHA256
 GIT_EXTERN(int) git_oid_fromstrp(git_oid *out, const char *str, git_oid_t type);
 #else
 GIT_EXTERN(int) git_oid_fromstrp(git_oid *out, const char *str);
 #endif
 
 /**
  * Parse N characters of a hex formatted object id into a git_oid.
  *
  * If N is odd, the last byte's high nibble will be read in and the
  * low nibble 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
  * @param type the type of object id
  * @return 0 or an error code
  */
 #ifdef GIT_EXPERIMENTAL_SHA256
 GIT_EXTERN(int) git_oid_fromstrn(git_oid *out, const char *str, size_t length, git_oid_t type);
 #else
 GIT_EXTERN(int) git_oid_fromstrn(git_oid *out, const char *str, size_t length);
 #endif
 
 /**
  * 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.
  * @return 0 on success or error code
  */
 #ifdef GIT_EXPERIMENTAL_SHA256
 GIT_EXTERN(int) git_oid_fromraw(git_oid *out, const unsigned char *raw, git_oid_t type);
 #else
 GIT_EXTERN(int) git_oid_fromraw(git_oid *out, const unsigned char *raw);
 #endif
 
 /**
  * Format a git_oid into a hex string.
  *
  * @param out 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 for SHA1,
  *      64 bytes for SHA256). Only the oid digits are written;
  *      a '\\0' terminator must be added by the caller if it is
  *      required.
  * @param id oid structure to format.
  * @return 0 on success or error code
  */
 GIT_EXTERN(int) git_oid_fmt(char *out, const git_oid *id);
 
 /**
  * Format a git_oid into a partial hex string.
  *
  * @param out output hex string; you say how many bytes to write.
  *      If the number of bytes is > GIT_OID_SHA1_HEXSIZE, extra bytes
  *      will be zeroed; if not, a '\0' terminator is NOT added.
  * @param n number of characters to write into out string
  * @param id oid structure to format.
  * @return 0 on success or error code
  */
 GIT_EXTERN(int) git_oid_nfmt(char *out, size_t n, const git_oid *id);
 
 /**
  * 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 out 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 for SHA1,
  *      65 bytes for SHA256). Only the oid digits are written;
  *      a '\\0' terminator must be added by the caller if it
  *      is required.
  * @param id oid structure to format.
  * @return 0 on success, non-zero callback return value, or error code
  */
 GIT_EXTERN(int) git_oid_pathfmt(char *out, const git_oid *id);
 
 /**
  * Format a git_oid into a statically allocated c-string.
  *
  * The c-string is owned by the library and should not be freed
  * by the user. If libgit2 is built with thread support, the string
  * will be stored in TLS (i.e. one buffer per thread) to allow for
  * concurrent calls of the function.
  *
  * @param oid The oid structure to format
  * @return the c-string or NULL on failure
  */
 GIT_EXTERN(char *) git_oid_tostr_s(const git_oid *oid);
 
 /**
  * Format a git_oid into a buffer as a hex format c-string.
  *
  * If the buffer is smaller than the size of a hex-formatted oid string
  * plus an additional byte (GIT_OID_SHA_HEXSIZE + 1 for SHA1 or
  * GIT_OID_SHA256_HEXSIZE + 1 for SHA256), then the resulting
  * oid c-string will be truncated to n-1 characters (but will still be
  * NUL-byte terminated).
  *
  * 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 id 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 *id);
 
 /**
  * Copy an oid from one structure to another.
  *
  * @param out oid structure the result is written into.
  * @param src oid structure to copy from.
  * @return 0 on success or error code
  */
 GIT_EXTERN(int) 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_EXTERN(int) git_oid_cmp(const git_oid *a, const git_oid *b);
 
 /**
  * Compare two oid structures for equality
  *
  * @param a first oid structure.
  * @param b second oid structure.
  * @return true if equal, false otherwise
  */
 GIT_EXTERN(int) git_oid_equal(const git_oid *a, const git_oid *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 id oid structure.
  * @param str input hex string of an object id.
  * @return 0 in case of a match, -1 otherwise.
  */
 GIT_EXTERN(int) git_oid_streq(const git_oid *id, const char *str);
 
 /**
  * Compare an oid to an hex formatted object id.
  *
  * @param id oid structure.
  * @param str input hex string of an object id.
  * @return -1 if str is not valid, <0 if id sorts before str,
  *         0 if id matches str, >0 if id sorts after str.
  */
 GIT_EXTERN(int) git_oid_strcmp(const git_oid *id, const char *str);
 
 /**
  * Check is an oid is all zeros.
  *
  * @return 1 if all zeros, 0 otherwise.
  */
 GIT_EXTERN(int) git_oid_is_zero(const git_oid *id);
 
 /**
  * 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 ~32000, 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_ERROR_INVALID error
  *
  * @param os a `git_oid_shorten` instance
  * @param text_id 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_id);
 
 /**
  * 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

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