/*
 * ggit-oid.c
 * This file is part of libgit2-glib
 *
 * Copyright (C) 2011 - Ignacio Casal Quinteiro
 *
 * libgit2-glib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * libgit2-glib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libgit2-glib. If not, see <http://www.gnu.org/licenses/>.
 */

#include <git2.h>

#include "ggit-oid.h"

struct _GgitOId
{
	git_oid oid;
};

G_DEFINE_BOXED_TYPE (GgitOId, ggit_oid, ggit_oid_copy, ggit_oid_free)

GgitOId *
_ggit_oid_wrap (const git_oid *oid)
{
	GgitOId *glib_oid;

	glib_oid = g_slice_new (GgitOId);
	git_oid_cpy (&glib_oid->oid, oid);

	return glib_oid;
}

const git_oid *
_ggit_oid_get_oid (GgitOId *oid)
{
	return (const git_oid *)&oid->oid;
}

/**
 * ggit_oid_copy:
 * @oid: a #GgitOId.
 *
 * Copies @oid into a newly allocated #GgitOId.
 *
 * Returns: (transfer full) (nullable): a newly allocated #GgitOId.
 */
GgitOId *
ggit_oid_copy (GgitOId *oid)
{
	g_return_val_if_fail (oid != NULL, NULL);

	return _ggit_oid_wrap (&oid->oid);
}

/**
 * ggit_oid_free:
 * @oid: a #GgitOId.
 *
 * Frees @oid.
 */
void
ggit_oid_free (GgitOId *oid)
{
	g_return_if_fail (oid != NULL);

	g_slice_free (GgitOId, oid);
}

/**
 * ggit_oid_new_from_string:
 * @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).
 *
 * Parses a hex formatted object id into a #GgitOId.
 *
 * Returns: (transfer full) (nullable): a newly allocated #GgitOId or %NULL on error.
 */
GgitOId *
ggit_oid_new_from_string (const gchar *str)
{
	GgitOId *glib_oid = NULL;
	git_oid oid;

	g_return_val_if_fail (str != NULL, NULL);

	if (git_oid_fromstr (&oid, str) == GIT_OK)
	{
		glib_oid = _ggit_oid_wrap (&oid);
	}

	return glib_oid;
}

/**
 * ggit_oid_new_from_raw:
 * @raw: (array zero-terminated=1) (element-type guchar): the raw input bytes to be copied.
 *
 * Creates a new #GgitOId from a raw oid.
 *
 * Returns: (transfer full) (nullable): a newly allocated #GgitOId or %NULL on error.
 */
GgitOId *
ggit_oid_new_from_raw (const guchar *raw)
{
	git_oid oid;

	g_return_val_if_fail (raw != NULL, NULL);

	git_oid_fromraw (&oid, raw);

	return _ggit_oid_wrap (&oid);
}

/**
 * ggit_oid_compare:
 * @a: first #GgitOId.
 * @b: second #GgitOId.
 *
 * Compare two #GgitOId structures.
 *
 * Returns: <0, 0, >0 if a < b, a == b, a > b.
 */
gint
ggit_oid_compare (GgitOId *a,
                  GgitOId *b)
{
	g_return_val_if_fail (a != NULL, 0);
	g_return_val_if_fail (b != NULL, 0);

	return git_oid_cmp (&a->oid, &b->oid);
}

/**
 * ggit_oid_to_string:
 * @oid: a #GgitOId.
 *
 * Converts @oid into a readable string.
 *
 * Returns: (transfer full) (nullable): a newly allocated string representing @oid or %NULL.
 */
gchar *
ggit_oid_to_string (GgitOId *oid)
{
	gchar *hex;

	g_return_val_if_fail (oid != NULL, NULL);

	hex = g_new (char, GIT_OID_HEXSZ + 1);

	return git_oid_tostr (hex, GIT_OID_HEXSZ + 1, &oid->oid);
}

/**
 * ggit_oid_hash:
 * @oid: a #GgitOId.
 *
 * Computes a hash value for a git object identifier.
 *
 * Returns: the hash value
 *
 **/
guint
ggit_oid_hash (GgitOId const *oid)
{
	/* This is copied from glib
	 * This function implements the widely used "djb" hash apparently posted
	 * by Daniel Bernstein to comp.lang.c some time ago.  The 32 bit
	 * unsigned hash value starts at 5381 and for each byte 'c' in the
	 * string, is updated: <literal>hash = hash * 33 + c</literal>.  This
	 * function uses the signed value of each byte.
	 */

	guint32 h = 5381;
	guint i;

	for (i = 0; i < GIT_OID_RAWSZ; ++i)
	{
		h = (h << 5) + h + oid->oid.id[i];
	}

	return h;
}

/**
 * ggit_oid_equal:
 * @a: a #GgitOId.
 * @b: a #GgitOId.
 *
 * Compares two #GgitOId for equality.
 *
 * Returns: %TRUE if @a and @b are equal, %FALSE otherwise
 *
 **/
gboolean
ggit_oid_equal (GgitOId const *a,
                GgitOId const *b)
{
	if ((a != NULL) != (b != NULL))
	{
		return FALSE;
	}
	else if (a == b)
	{
		return TRUE;
	}

	return git_oid_cmp (&a->oid, &b->oid) == 0;
}

/**
 * ggit_oid_is_zero:
 * @oid: a #GgitOId.
 *
 * Get whether the oid contains only zeros.
 *
 * Returns: %TRUE if the oid contains only zeros, %FALSE otherwise.
 */
gboolean
ggit_oid_is_zero (GgitOId const *oid)
{
	g_return_val_if_fail (oid != NULL, FALSE);

	return git_oid_iszero (&oid->oid) == 1;
}

static gint
c_to_h (gchar c)
{
	if (c >= '0' && c <= '9')
	{
		return c - '0';
	}
	else if (c >= 'A' && c <= 'F')
	{
		return 10 + (c - 'A');
	}
	else if (c >= 'a' && c <= 'f')
	{
		return 10 + (c - 'a');
	}
	else
	{
		return -1;
	}
}

/**
 * ggit_oid_has_prefix:
 * @oid: a #GgitOId.
 * @prefix: a prefix.
 *
 * Check whether the object id has a given prefix. Note that the prefix is
 * specified in hexadecimal ASCII.
 *
 * Returns: %TRUE if the id has the given prefix, %FALSE otherwise.
 */
gboolean
ggit_oid_has_prefix (GgitOId     *oid,
                     const gchar *prefix)
{
	gint i;

	for (i = 0; i < GIT_OID_RAWSZ; ++i)
	{
		gint v1;

		if (*prefix == '\0')
		{
			return TRUE;
		}

		v1 = c_to_h (*prefix++);

		if (v1 == -1)
		{
			return FALSE;
		}

		if (*prefix != '\0')
		{
			gint v2;

			v2 = c_to_h (*prefix++);

			if (v2 == -1)
			{
				return FALSE;
			}

			if (oid->oid.id[i] != (v1 << 4) + v2)
			{
				return FALSE;
			}
		}
		else if (oid->oid.id[i] >> 4 != v1)
		{
			return FALSE;
		}
	}

	return *prefix == '\0';
}

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