# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1558652724 -7200
# Node ID b3ffe81236d8746dd547e2c33bd40023869c96a4
# Parent  a3585c5fc0d1d435161980a530b3632ceb4a5649
Introduced sectors as the working unit and cylinder alignment.

diff -r a3585c5fc0d1 -r b3ffe81236d8 makesd-partition-table
--- a/makesd-partition-table	Thu May 23 22:30:49 2019 +0200
+++ b/makesd-partition-table	Fri May 24 01:05:24 2019 +0200
@@ -10,6 +10,12 @@
 
 
 
+# Cylinder size in sectors for alignment purposes.
+
+HEADS=255
+SECTORS=63
+CYLINDER_SIZE=$(($HEADS * $SECTORS))
+
 # Global partition number and previous partition details.
 
 PARTNUM=1
@@ -32,10 +38,20 @@
 
 emit_partition_fields()
 {
-    if [ "$PREVSTART" ] ; then
-        echo -n " start=${PREVSTART}${SFDISK_UNIT_SUFFIX}"
+    if [ "$PREVSTART" = '0' ] ; then
+        FIRSTPART=yes
+    else
+        FIRSTPART=
     fi
 
+    PREVSTART=`align_cylinder $PREVSTART`
+
+    if [ "$PREVSTART" = '0' ] ; then
+        PREVSTART=1
+    fi
+
+    echo -n " start=${PREVSTART}${SFDISK_UNIT_SUFFIX}"
+
     # Obtain any explicitly stated size.
     # Without a size, use start details to calculate a size.
     # Without start details, claim the rest of the device.
@@ -43,9 +59,15 @@
     REMAINING=$(($DEVSIZE - $PREVSTART))
 
     if [ "$PREVSIZE" ] ; then
-        PREVSIZE=$(($PREVSIZE * $DEVSIZE / 100))
+        PREVSIZE=$((($PREVSIZE * $DEVSIZE) / 100))
+        PREVSIZE=`align_cylinder $PREVSIZE`
+
+        if [ "$FIRSTPART" ] ; then
+            PREVSIZE=$(($PREVSIZE - 1))
+        fi
+
     elif [ "$START" ] ; then
-        PREVSIZE=$(($START - $PREVSTART))
+        PREVSIZE=$((`align_cylinder $START` - $PREVSTART))
     else
         PREVSIZE=$REMAINING
     fi
@@ -59,6 +81,7 @@
     if [ "$PREVTYPE" ] ; then
         echo -n " Id=`partition_type $PREVTYPE`"
     fi
+
     echo
 }
 
@@ -70,6 +93,7 @@
         PREVSTART=$START
     elif [ "$PREVSTART" ] && [ "$PREVSIZE" ] ; then
         PREVSIZE=$(($PREVSIZE * $DEVSIZE / 100))
+        PREVSIZE=`align_cylinder $PREVSIZE`
         PREVSTART=$(($PREVSTART + $PREVSIZE))
     else
         PREVSTART=0
@@ -122,19 +146,33 @@
     "$SFDISK" -s "$1"
 }
 
+# Align to cylinders.
+
+align_cylinder()
+{
+    # 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()
 {
-    if "$SFDISK" -uB -s "$1" > /dev/null 2>&1 ; then
-        SFDISK_UNIT_SUFFIX=
-    else
-        SFDISK_UNIT_SUFFIX="K"
-    fi
+    SFDISK_UNIT_SUFFIX=
+
+    # Obtain the device size in 512-byte sectors.
 
-    # Obtain the device size in blocks.
+    DEVSIZE=$((`device_size "$1"` * 2))
 
-    DEVSIZE=`device_size "$1"`
+    # Find the cylinder-addressable size.
+
+    CYLINDERS=$(($DEVSIZE / $CYLINDER_SIZE))
+    DEVSIZE=$(($CYLINDERS * $CYLINDER_SIZE))
 }
 
 
@@ -149,7 +187,7 @@
 size for each partition. Each occurrence of the -f option starts a new partition
 description.
 
-Start positions are indicated as numbers of 1024-byte blocks.
+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.