crosutils: refine memento image / factory package creation

image_common.sh

Index: image_common.sh
diff --git a/image_common.sh b/image_common.sh
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+++ b/image_common.sh
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+#!/bin/bash
+
+# Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This script contains common utility function for dealing with image,
+# especially for being redistributed into platforms without complete Chromium OS
+# development environment.
+
+# Check if given command is available in current system
+has_command() {
+  type "$1" >/dev/null 2>&1
+}
+
+err_die() {
+  echo "ERROR: $@" >&2
+  exit 1
+}
+
+# Finds the best gzip compressor and invoke it.
+gzip_compress() {
+  if has_command pigz; then
+    # echo " ** Using parallel gzip **" >&2
+    # Tested with -b 32, 64, 128(default), 256, 1024, 16384, and -b 32 (max
+    # window size of Deflate) seems to be the best in output size.
+    pigz -b 32 "$@"
+  else
+    gzip "$@"
+  fi
+}
+
+# Finds if current system has tools for part_* commands
+has_part_tools() {
+  has_command cgpt || has_command parted
+}
+
+# Finds the best partition tool and print partition offset
+part_offset() {
+  local file="$1"
+  local partno="$2"
+
+  if has_command cgpt; then
+    cgpt show -b -i "$partno" "$file"
+  elif has_command parted; then
+    parted -m "$file" unit s print |
+      grep "^$partno:" | cut -d ':' -f 2 | sed 's/s$//'
+  else
+    exit 1
+  fi
+}
+
+# Finds the best partition tool and print partition size
+part_size() {
+  local file="$1"
+  local partno="$2"
+
+  if has_command cgpt; then
+    cgpt show -s -i "$partno" "$file"
+  elif has_command parted; then
+    parted -m "$file" unit s print |
+      grep "^$partno:" | cut -d ':' -f 4 | sed 's/s$//'
+  else
+    exit 1
+  fi
+}
+
+# Dumps a file by given offset and size (in sectors)
+dump_partial_file() {
+  local file="$1"
+  local offset="$2"
+  local sectors="$3"
+  local bs=512
+
+  # Try to use larger buffer if offset/size can be re-aligned.
+  # 2M / 512 = 4096
+  local buffer_ratio=4096
+  if [ $((offset % buffer_ratio)) -eq 0 -a \
+       $((sectors % buffer_ratio)) -eq 0 ]; then
+    offset=$((offset / buffer_ratio))
+    sectors=$((sectors / buffer_ratio))
+    bs=$((bs * buffer_ratio))
+  fi
+
+  if has_command pv; then
+    dd if="$file" bs=$bs skip="$offset" count="$sectors" \
+      oflag=sync status=noxfer 2>/dev/null |
+      pv -ptreb -B 4m -s $((sectors * $bs))
+  else
+    dd if="$file" bs=$bs skip="$offset" count="$sectors" \
+      oflag=sync status=noxfer 2>/dev/null
+  fi
+}
+
+# Dumps a specific partition from given image file
+dump_partition() {
+  local file="$1"
+  local part_num="$2"
+  local offset="$(part_offset "$file" "$part_num")" ||
+    err_die "failed to dump partition #$part_num from: $file"
+  local size="$(part_size "$file" "$part_num")" ||
+    err_die "failed to dump partition #$part_num from: $file"
+
+  dump_partial_file "$file" "$offset" "$size"
+}
+