/*
 * Copyright 2012, Jérôme Duval, korli@users.berlios.de.
 * Copyright 2003, Tyler Dauwalder, tyler@dauwalder.net.
 * Distributed under the terms of the MIT License.
 */

/*! \file Utils.cpp - Miscellaneous Udf utility functions. */

#include "UdfStructures.h"
#include "Utils.h"

extern "C" {
	extern int32 timezone_offset;
}

/*! \brief Returns "true" if \a value is true, "false" otherwise. */
const char*
bool_to_string(bool value)
{
	return value ? "true" : "false";
}


/*! \brief Calculates the UDF crc checksum for the given byte stream.

	Based on crc code from UDF-2.50 6.5, as permitted.

	\param data Pointer to the byte stream.
	\param length Length of the byte stream in bytes.

	\return The crc checksum, or 0 if an error occurred.
*/
uint16
calculate_crc(uint8 *data, uint16 length)
{
	uint16 crc = 0;
	if (data) {
		for ( ; length > 0; length--, data++)
			crc = kCrcTable[(crc >> 8 ^ *data) & 0xff] ^ (crc << 8);
	}
	return crc;
}


/*! \brief Takes an overloaded ssize_t return value like those returned
	by BFile::Read() and friends, as well as an expected number of bytes,
	and returns B_OK if the byte counts match, or the appropriate error
	code otherwise.
*/
status_t
check_size_error(ssize_t bytesReturned, ssize_t bytesExpected)
{
	return bytesReturned == bytesExpected
		? B_OK : (bytesReturned >= 0 ? B_IO_ERROR : status_t(bytesReturned));
}


/*! \brief Calculates the block shift amount for the given
 	block size, which must be a positive power of 2.
*/
status_t
get_block_shift(uint32 blockSize, uint32 &blockShift)
{
	if (blockSize == 0)
		return B_BAD_VALUE;	
	uint32 bitCount = 0;
	uint32 result = 0;
	for (int i = 0; i < 32; i++) {
		// Zero out all bits except bit i
		uint32 block = blockSize & (uint32(1) << i);
		if (block) {
			if (++bitCount > 1)
				return B_BAD_VALUE;
			else 
				result = i;
		}
	}
	blockShift = result;
	return B_OK;
}


#define EPOCH_YEAR	1970
#define MAX_YEAR	69
#define SECSPERMIN	60
#define MINSPERHOUR	60
#define HOURSPERDAY	24
#define SECSPERDAY	(SECSPERMIN * MINSPERHOUR * HOURSPERDAY)
#define DAYSPERNYEAR	365

status_t
decode_time(timestamp &timestamp, struct timespec &timespec)
{
	DEBUG_INIT_ETC(NULL, ("timestamp: (tnt: 0x%x, type: %d, timezone: %d = 0x%x, year: %d, " 
	           "month: %d, day: %d, hour: %d, minute: %d, second: %d)", timestamp.type_and_timezone(),
	           timestamp.type(), timestamp.timezone(),
	            timestamp.timezone(),timestamp.year(),
	           timestamp.month(), timestamp.day(), timestamp.hour(), timestamp.minute(), timestamp.second()));

	if (timestamp.year() < EPOCH_YEAR || timestamp.year() >= EPOCH_YEAR + MAX_YEAR)
		return B_BAD_VALUE;

	time_t result = 0;
	const int monthLengths[12]
		= { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

	int year = timestamp.year();
	int month = timestamp.month();
	int day = timestamp.day();
	int hour = timestamp.hour();
	int minute = timestamp.minute();
	int second = timestamp.second();

	// Range check the timezone offset, then round it down
	// to the nearest hour, since no one I know treats timezones
	// with a per-minute granularity, and none of the other OSes
	// I've looked at appear to either.
	int timezone_offset = 0;
	if (timestamp.type() == 1)
		timezone_offset = timestamp.timezone();
	if (-SECSPERDAY > timezone_offset || timezone_offset > SECSPERDAY)
		timezone_offset = 0;
	timezone_offset -= timezone_offset % 60;

	int previousLeapYears = (year - 1968) / 4;
	bool isLeapYear = (year - 1968) % 4 == 0;
	if (isLeapYear)
		--previousLeapYears;

	// Years to days
	result = (year - EPOCH_YEAR) * DAYSPERNYEAR + previousLeapYears;
	// Months to days
	for (int i = 0; i < month-1; i++) {
		result += monthLengths[i];
	}
	if (month > 2 && isLeapYear)
		++result;
	// Days to hours
	result = (result + day - 1) * HOURSPERDAY;
	// Hours to minutes
	result = (result + hour) * MINSPERHOUR + timezone_offset;
	// Minutes to seconds
	result = (result + minute) * SECSPERMIN + second;

	timespec.tv_sec = result;
	timespec.tv_nsec = 1000 * (timestamp.microsecond()
		+ timestamp.hundred_microsecond() * 100
		+ timestamp.centisecond() * 10000);
	return B_OK;
}


long_address
to_long_address(ino_t id, uint32 length)
{
	TRACE(("udf_to_long_address: ino_t = %" B_PRIdINO ", length = %" B_PRIu32,
		id, length));
	long_address result;
	result.set_block((id >> 16) & 0xffffffff);
	result.set_partition(id & 0xffff);
	result.set_length(length);
	DUMP(result);
	return result;
}


ino_t
to_vnode_id(long_address address)
{
	DEBUG_INIT(NULL);
	ino_t result = address.block();
	result <<= 16;
	result |= address.partition();
	TRACE(("block:     %" B_PRIu32 ", 0x%" B_PRIx32 "\n", address.block(),
		address.block()));
	TRACE(("partition: %d, 0x%x\n", address.partition(), address.partition())); 
	TRACE(("length:    %" B_PRIu32 ", 0x%" B_PRIx32 "\n", address.length(),
		address.length()));
	TRACE(("ino_t:     %" B_PRIdINO "\n", result));
	return result;
}