#!/bin/sh

# Emit a partition table for a device employing parameters such as the start,

# size, and type.

PROGNAME=`basename "$0"`

THISDIR=`dirname "$0"`

SFDISK="/sbin/sfdisk"

# Cylinder size in sectors for alignment purposes.

HEADS=255

SECTORS=63

CYLINDER_SIZE=$(($HEADS * $SECTORS))

# Global partition number and previous partition details.

PARTNUM=1

PREVSTART=

PREVSIZE=

PREVTYPE=

# Emit any previous partition details as a complete sfdisk-compatible record.

emit_partition()

{

    if [ "$PREVSTART" ] || [ "$PREVSIZE" ] || [ "$PREVTYPE" ] ; then

        echo -n "$PARTNUM : "

        emit_partition_fields | sed 's/^ //;s/ /,/g'

        PARTNUM=$(($PARTNUM + 1))

    fi

}

# Emit the previous partition fields.

emit_partition_fields()

{

    echo -n " start=${PREVSTART}${SFDISK_UNIT_SUFFIX}"

    REMAINING=$(($DEVSIZE - $PREVSTART))

    # Retain any previously calculated size.

    # Without a size, use start details to calculate a size.

    # Without start details, claim the rest of the device.

    if [ "$PREVSIZE" ] ; then

        :

    elif [ "$START" ] ; then

        PREVSIZE=$((`align_cylinder $START` - $PREVSTART))

    else

        PREVSIZE=$REMAINING

    fi

    if [ "$PREVSIZE" -gt "$REMAINING" ] ; then

        PREVSIZE=$REMAINING

    fi

    echo -n " size=${PREVSIZE}${SFDISK_UNIT_SUFFIX}"

    if [ "$PREVTYPE" ] ; then

        echo -n " Id=`partition_type $PREVTYPE`"

    fi

    echo

}

# Retain the current partition details.

store_partition()

{

    # Define the partition start using a specified position.

    # Alternatively, use previous start and size information.

    # Otherwise, the first partition is being defined.

    if [ "$START" ] && [ "$START" != '-' ] ; then

        PREVSTART=`align_cylinder $START`

    elif [ "$PREVSTART" ] && [ "$PREVSIZE" ] ; then

        PREVSTART=`align_cylinder $(($PREVSTART + $PREVSIZE))`

    else

        PREVSTART=0

    fi

    # Ensure that the first partition starts at sector one.

    if [ "$PREVSTART" = '0' ] ; then

        PREVSTART=1

    fi

    # Calculate and align the stated size.

    # Otherwise, defer the calculation until emitting the details.

    if [ "$SIZE" ] && [ "$SIZE" != '-' ] ; then

        PREVSIZE=$(($SIZE * $DEVSIZE / 100))

        PREVSIZE=`align_cylinder $PREVSIZE`

        if [ "$PREVSTART" = '1' ] ; then

            PREVSIZE=$(($PREVSIZE - 1))

        fi

    else

        PREVSIZE=

    fi

    PREVTYPE=$TYPE

}

# Emit the current partition details and proceed to the next partition.

next_partition()

{

    emit_partition

    store_partition

}

# Convert the partition type to an sdisk-compatible identifier.

partition_type()

{

    case "$1" in

        ( ext[2-4]? ) echo "0x83" ;;

        ( swap      ) echo "0x82" ;;

        ( fat       ) echo "0x0c" ;;

        ( *         ) echo "0x83" ;;

    esac

}

# device_size <device>

#

# Obtain the size of the given disk or partition in 1024-byte blocks.

device_size()

{

    "$SFDISK" -s "$1"

}

# Align to cylinders.

align_cylinder()

{

    if [ ! "$ALIGN_CYLINDER" ] ; then

        echo $1

        return

    fi

    # Round up to the nearest cylinder.

    CYLINDER=$((($1 + $CYLINDER_SIZE - 1) / $CYLINDER_SIZE))

    # Emit the number of sectors.

    echo $(($CYLINDER * $CYLINDER_SIZE))

}

# Test sfdisk behaviour and obtain useful information.

init_sfdisk()

{

    SFDISK_UNIT_SUFFIX=

    # Obtain the device size in 512-byte sectors.

    DEVSIZE=$((`device_size "$1"` * 2))

    # Find the cylinder-addressable size.

    if [ "$ALIGN_CYLINDER" ] ; then

        CYLINDERS=$(($DEVSIZE / $CYLINDER_SIZE))

        DEVSIZE=$(($CYLINDERS * $CYLINDER_SIZE))

    fi

}

# Process the arguments, building a partition description.

read_fields()

{

    OLDIFS=$IFS

    IFS=`echo -n '\t'` read START SIZE TYPE

    STATUS=$?

    IFS=$OLDIFS

    return $STATUS

}

# Emit the help message if requested.

if [ "$1" = '--help' ] ; then

    cat 1>&2 <<EOF

Usage: $PROGNAME [ --align ] ( -f <type> | -p <start> | -s <size> )...

Produce partition descriptions, indicating partition type, start position and

size for each partition. Each occurrence of the -f option starts a new partition

description.

Start positions are indicated as numbers of 512-byte sectors.

Sizes are indicated as percentages of the entire device; if omitted, the

remainder of the device will be used.

Types recognised include ext, ext2, ext3, ext4, fat and swap. Other types are

interpreted as Linux partitions.

If the --align option is specified, align partitions to cylinders for the

satisfaction of earlier sfdisk versions that are obsessed with cylinders, heads

and sectors.

EOF

    exit 0

fi

# Test for the cylinder alignment option.

if [ "$1" = '--align' ] ; then

    ALIGN_CYLINDER="$1"

    shift 1

else

    ALIGN_CYLINDER=

fi

# Obtain details of the selected device.

if [ ! "$DEV" ] ; then

    cat 1>&2 <<EOF

No device specified. Use the DEV environment variable to indicate a device.

EOF

    exit 1

fi

if [ ! -e "$DEV" ] ; then

    cat 1>&2 <<EOF

Device not found: $DEV

EOF

    exit 1

fi

# Initialise sfdisk usage.

init_sfdisk "$DEV"

while read_fields ; do

    next_partition

done

# Emit the last partition.

emit_partition