/**
 * @file block.c Tar block functions
 * 
 * $Id: block.c,v 1.8 2003/01/01 06:22:32 chipx86 Exp $
 *
 * @Copyright (C) 1999-2003 The GNUpdate Project.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 */
#include "tar.h"

#define __readBlock(fp, block) \
	cxRead((block)->buffer, 1, TAR_BLOCK_SIZE, (fp))

#define __writeBlock(fp, block) \
	cxWrite((block)->buffer, 1, TAR_BLOCK_SIZE, (fp))

#define __getCrc(block) (cxTarOctalToInt((block)->header.checksum))
#define __checkCrc(block) (__getCrc(block) == __calcCrc(block))

static int
__calcCrc(TarBlock *block)
{
	int i, sum = 0;

	for (i = 0; i < 512; i++)
		sum += block->buffer[i];

	for (i = 0; i < 8; i++)
		sum += (' ' - block->header.checksum[i]);

	return sum;
}

static int
__readInternal(CxFP *fp, TarBlock *block)
{
	int i = 0;
	int zeroBlockCount = 0;

	while ((i = __readBlock(fp, block)) == TAR_BLOCK_SIZE)
	{
		/* Two all-zero blocks mark EOF */
		if (block->header.name[0] == '\0')
		{
			zeroBlockCount++;

			if (zeroBlockCount == 2)
				return 0;
			else
				continue;
		}

		/* Verify magic and version */
		if (!strncmp(block->header.magic, TAR_MAGIC, TAR_MAGIC_LEN - 1))
		{
			/* Ustar */
			
#if 0
			if (strncmp(block->header.version, "00", 2))
			{
				/* Unknown version. */
				return -3;
			}
#endif
		}
		else if (memcmp(block->header.magic, "\0\0\0\0\0\0\0\0", 8))
		{
			return -2;
		}

		if (!__checkCrc(block))
		{
			/* Checksum error. */
			return -4;
		}

		break;
	}

	return i;
}

CxStatus
cxTarReadBlock(CxFP *fp, TarBlock *block)
{
	int i, j;
	size_t size;
	char *ptr;

	memset(block->buffer, 0, TAR_BLOCK_SIZE);
	block->header.gnu_longname = NULL;
	block->header.gnu_longlink = NULL;

	i = __readInternal(fp, block);

	if (i != TAR_BLOCK_SIZE)
	{
		if (i == 0)
			return CX_EOF;
		else if (i == -2)
			return CX_INVALID_FORMAT;
		else if (i == -3)
			return CX_INVALID_VERSION;
		else if (i == -4)
			return CX_CORRUPT;

		errno = EINVAL;
		return CX_ERROR; /* XXX */
	}

	if (block->header.typeFlag == GNU_LONGLINK)
	{
		size = cxTarOctalToInt(block->header.size);

		j = (size / TAR_BLOCK_SIZE) + ((size % TAR_BLOCK_SIZE) ? 1 : 0);

		MEM_CHECK(block->header.gnu_longlink =
				  (char *)malloc(j * TAR_BLOCK_SIZE));

		for (ptr = block->header.gnu_longlink;
			 j > 0;
			 j--, ptr += TAR_BLOCK_SIZE)
		{
			i = __readBlock(fp, block);

			if (i != TAR_BLOCK_SIZE)
			{
				if (i != -1)
					errno = EINVAL;

				return CX_ERROR;
			}
		}

		i = __readInternal(fp, block);

		if (i != TAR_BLOCK_SIZE)
		{
			if (i != -1)
				errno = EINVAL;

			return CX_ERROR;
		}
	}

	if (block->header.typeFlag == GNU_LONGNAME)
	{
		size = cxTarOctalToInt(block->header.size);

		j = (size / TAR_BLOCK_SIZE) + ((size % TAR_BLOCK_SIZE) ? 1 : 0);

		MEM_CHECK(block->header.gnu_longname =
				  (char *)malloc(j * TAR_BLOCK_SIZE));

		for (ptr = block->header.gnu_longname;
			 j > 0;
			 j--, ptr += TAR_BLOCK_SIZE)
		{
			i = __readBlock(fp, block);

			if (i != TAR_BLOCK_SIZE)
			{
				if (i != -1)
					errno = EINVAL;

				return CX_CORRUPT;
			}
		}

		i = __readInternal(fp, block);
		
		if (i != TAR_BLOCK_SIZE)
		{
			if (i != -1)
				errno = EINVAL;

			return CX_CORRUPT;
		}
	}

	return CX_SUCCESS;
}