cros_utils: refine factory and imaging related scripts

lib/cros_image_common.sh

 #!/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 to deal with disk images,
 # especially for being redistributed into platforms without complete Chromium OS
 # developing environment.
 
-# Check if given command is available in current system
-has_command() {
+# Checks if given command is available in current system
+image_has_command() {
   type "$1" >/dev/null 2>&1
 }
 
-err_die() {
+# Prints error message and exit as 1 (error)
+image_die() {
   echo "ERROR: $@" >&2
   exit 1
 }
 
-# Finds the best gzip compressor and invoke it.
-gzip_compress() {
-  if has_command pigz; then
+# Finds the best gzip compressor and invoke it
+image_gzip_compress() {
+  if image_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 the best bzip2 compressor and invoke it
+image_bzip2_compress() {
+  if image_has_command pbzip2; then
+    pbzip2 "$@"
+  else
+    bzip2 "$@"
+  fi
+}
+
 # Finds if current system has tools for part_* commands
-has_part_tools() {
-  has_command cgpt || has_command parted
+image_has_part_tools() {
+  image_has_command cgpt || image_has_command parted
 }
 
 # Finds the best partition tool and print partition offset
-part_offset() {
+image_part_offset() {
   local file="$1"
   local partno="$2"
+  local unpack_file="$(dirname "$file")/unpack_partitions.sh"
 
-  if has_command cgpt; then
+  if image_has_command cgpt; then
     cgpt show -b -i "$partno" "$file"

[Nick Sanders, 2010/11/18 05:12:08]

Can you add parted to the chroot, and just use that in all cases, it's best to
minimize the number of paths through the code.

[Hung-Te, 2010/11/18 05:49:31]

cgpt is always in chroot. I made this because this script may be invoked inside
/ outside chroot, and even for some non-ubuntu Linux in the future, because a
"factory bundle" may not need entire chrome os source tree, so it'd be better to
have a portable library to work with images

[Nick Sanders, 2010/11/18 06:18:35]

Err, what I was saying is that we can easily ensure that parted is always in the
chroot, and therefore always use parted. That way it's potable, with less code
duplication.

Since there are many codepaths here, it's likely that the ones run least will
bitrot. Anyways this can be a fix for a later CL.

[Hung-Te, 2010/11/18 06:46:25]

Thanks for the suggestion. It's a good idea to have parted in chroot so we can
always use parted when writing portable scripts to work inside/outside chroot.

-  elif has_command parted; then
-    parted -m "$file" unit s print |
-      grep "^$partno:" | cut -d ':' -f 2 | sed 's/s$//'
+  elif image_has_command parted; then
+    parted -m "$file" unit s print | awk -F ':' "/^$partno:/ { print int(\$2) }"
+  elif [ -f "$unpack_file" ]; then
+    awk "/ $partno  *Label:/ { print \$2 }" "$unpack_file"
   else
     exit 1
   fi
 }
 
 # Finds the best partition tool and print partition size
-part_size() {
+image_part_size() {
   local file="$1"
   local partno="$2"
+  local unpack_file="$(dirname "$file")/unpack_partitions.sh"
 
-  if has_command cgpt; then
+  if image_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$//'
+  elif image_has_command parted; then
+    parted -m "$file" unit s print | awk -F ':' "/^$partno:/ { print int(\$4) }"
+  elif [ -s "$unpack_file" ]; then
+    awk "/ $partno  *Label:/ { print \$3 }" "$unpack_file"
   else
     exit 1
   fi
 }
 
 # Dumps a file by given offset and size (in sectors)
-dump_partial_file() {
+image_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
+  if image_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))
+      pv -ptreb -B $bs -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() {
+image_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: $file"
+  local offset="$(image_part_offset "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
+  local size="$(image_part_size "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
 
-  dump_partial_file "$file" "$offset" "$size"
+  image_dump_partial_file "$file" "$offset" "$size"
 }
 
+# Maps a specific partition from given image file to a loop device
+image_map_partition() {
+  local file="$1"
+  local part_num="$2"
+  local offset="$(image_part_offset "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
+  local size="$(image_part_size "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
+
+  losetup --offset $((offset * 512)) --sizelimit=$((size * 512)) \
+    -f --show "$file"
+}
+
+# Unmaps a loop device created by image_map_partition
+image_unmap_partition() {
+  local map_point="$1"
+
+  losetup -d "$map_point"
+}
+
+# Mounts a specific partition inside a given image file
+image_mount_partition() {
+  local file="$1"
+  local part_num="$2"
+  local mount_point="$3"
+  local mount_opt="$4"
+  local offset="$(image_part_offset "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
+  local size="$(image_part_size "$file" "$part_num")" ||
+    image_die "failed to find partition #$part_num from: $file"
+
+  if [ -z "$mount_opt" ]; then
+    # by default, mount as read-only.
+    mount_opt=",ro"
+  fi
+
+  mount \
+    -o "loop,offset=$((offset * 512)),sizelimit=$((size * 512)),$mount_opt" \
+    "$file" \
+    "$mount_point"
+}
+
+# Unmounts a partition mount point by mount_partition
+image_umount_partition() {
+  local mount_point="$1"
+
+  umount -d "$mount_point"
+}