fixed limitedness of PUMP command (closes #40)

PUMP was implemented using dd's bs, which is limited to 2GB. In this fix
the bs is set to fixed 1MB and the block count is calculated and ceiled.

Caveat: Fractions of the block size can not be realized using this
method, but should be not a real problem.

.github/workflows/tests.yml

@@ -17,7 +17,7 @@ jobs:
           submodules: recursive
 
       - name: Install dependencies
-        run: sudo apt-get update && sudo apt-get install -y binfmt-support file kpartx lsof p7zip-full parted qemu qemu-user-static unzip wget xz-utils
+        run: sudo apt-get update && sudo apt-get install -y binfmt-support file kpartx lsof p7zip-full parted qemu qemu-user-static unzip wget xz-utils units
         shell: bash
 
       - name: Run pimod OpenWRT example

Dockerfile

@@ -16,7 +16,8 @@ RUN apt-get update && \
   qemu-user-static \
   unzip \
   wget \
-  xz-utils
+  xz-utils \
+  units
 
 RUN mkdir /pimod
 COPY . /pimod/

action.yml

@@ -14,7 +14,7 @@ runs:
   steps: 
     - run: sudo apt-get update
       shell: bash
-    - run: sudo apt-get install -y binfmt-support file kpartx parted qemu qemu-user-static unzip p7zip-full wget xz-utils
+    - run: sudo apt-get install -y binfmt-support file kpartx parted qemu qemu-user-static unzip p7zip-full wget xz-utils units
       shell: bash
     - run: sudo ${{ github.action_path }}/pimod.sh ${{ inputs.pifile }}
       shell: bash

stages/20-prepare.sh

@@ -1,14 +1,30 @@
 # PUMP increases the image's size about the given amount of megabytes.
 #
-# Usage: PUMP SIZE_IN_MB
+# Usage: PUMP SIZE
 PUMP() {
   if [[ -b "${DEST_IMG}" ]]; then
     echo -e "\033[0;31m### Error: Block device ${DEST_IMG} cannot be pumped.\033[0m"
     return 1
   fi
 
   echo -e "\033[0;32m### PUMP ${1}\033[0m"
-  dd if=/dev/zero bs="${1}" count=1 >> "${DEST_IMG}"
+
+  BS="1M"
+
+  # units does not print to stderr, thus test call before using output
+  echo -n "pump conversion to ${BS} * "
+  units -t "${1}B" "${BS}B"
+
+  COUNT=$(units -t ${1}B ${BS}B)
+
+  # Ceil the number if a decimal is given.
+  if [[ "${COUNT}" == *.* ]]; then
+    COUNT=$(( $(echo "${COUNT}" | cut -d. -f1) + 1 ))
+  fi
+
+  echo "pump ceil: ${BS} * ${COUNT}"
+
+  dd if=/dev/zero bs="${BS}" count="${COUNT}" >> "${DEST_IMG}"
 
   # Fix the GPT if necessary and resize the partition afterwards.
   # The fix is currently kind of hackish..