[Buildroot] [PATCH 2/5 v2] suppot/download: add option parsing to the download wrapper

Yann E. MORIN yann.morin.1998 at free.fr
Sun Dec 7 11:02:35 UTC 2014


Instead of relying on argument ordering, use actual options in the
download wrapper.

Download backends (bzr, cp, hg...) are left as-is, because it does not
make sense to complexifies them, since they are almost very trivial
shell scripts, and adding option parsing would be really overkill.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
---
 package/pkg-download.mk     |  42 ++++++-----
 support/download/dl-wrapper | 166 ++++++++++++++++++++++++++++++++++++++++++++
 support/download/wrapper    |  99 --------------------------
 3 files changed, 192 insertions(+), 115 deletions(-)
 create mode 100755 support/download/dl-wrapper
 delete mode 100755 support/download/wrapper

diff --git a/package/pkg-download.mk b/package/pkg-download.mk
index f3409bd..e76bb38 100644
--- a/package/pkg-download.mk
+++ b/package/pkg-download.mk
@@ -18,6 +18,8 @@ export SCP := $(call qstrip,$(BR2_SCP)) $(QUIET)
 SSH := $(call qstrip,$(BR2_SSH)) $(QUIET)
 export LOCALFILES := $(call qstrip,$(BR2_LOCALFILES))
 
+DL_WRAPPER = support/download/dl-wrapper
+
 # Default spider mode is 'DOWNLOAD'. Other possible values are 'SOURCE_CHECK'
 # used by the _source-check target and 'SHOW_EXTERNAL_DEPS', used by the
 # external-deps target.
@@ -95,8 +97,9 @@ endef
 # problems
 define DOWNLOAD_GIT
 	test -e $(DL_DIR)/$($(PKG)_SOURCE) || \
-	$(EXTRA_ENV) support/download/wrapper git \
-		$(DL_DIR)/$($(PKG)_SOURCE) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b git \
+		-o $(DL_DIR)/$($(PKG)_SOURCE) \
+		-- \
 		$($(PKG)_SITE) \
 		$($(PKG)_DL_VERSION) \
 		$($(PKG)_BASE_NAME)
@@ -115,8 +118,9 @@ endef
 
 define DOWNLOAD_BZR
 	test -e $(DL_DIR)/$($(PKG)_SOURCE) || \
-	$(EXTRA_ENV) support/download/wrapper bzr \
-		$(DL_DIR)/$($(PKG)_SOURCE) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b bzr \
+		-o $(DL_DIR)/$($(PKG)_SOURCE) \
+		-- \
 		$($(PKG)_SITE) \
 		$($(PKG)_DL_VERSION) \
 		$($(PKG)_BASE_NAME)
@@ -132,8 +136,9 @@ endef
 
 define DOWNLOAD_CVS
 	test -e $(DL_DIR)/$($(PKG)_SOURCE) || \
-	$(EXTRA_ENV) support/download/wrapper cvs \
-		$(DL_DIR)/$($(PKG)_SOURCE) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b cvs \
+		-o $(DL_DIR)/$($(PKG)_SOURCE) \
+		-- \
 		$(call stripurischeme,$(call qstrip,$($(PKG)_SITE))) \
 		$($(PKG)_DL_VERSION) \
 		$($(PKG)_RAWNAME) \
@@ -151,8 +156,9 @@ endef
 
 define DOWNLOAD_SVN
 	test -e $(DL_DIR)/$($(PKG)_SOURCE) || \
-	$(EXTRA_ENV) support/download/wrapper svn \
-		$(DL_DIR)/$($(PKG)_SOURCE) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b svn \
+		-o $(DL_DIR)/$($(PKG)_SOURCE) \
+		-- \
 		$($(PKG)_SITE) \
 		$($(PKG)_DL_VERSION) \
 		$($(PKG)_BASE_NAME)
@@ -171,8 +177,9 @@ endef
 # to prepend the path with a slash: scp://[user@]host:/absolutepath
 define DOWNLOAD_SCP
 	test -e $(DL_DIR)/$(2) || \
-	$(EXTRA_ENV) support/download/wrapper scp \
-		$(DL_DIR)/$(2) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b scp \
+		-o $(DL_DIR)/$(2) \
+		-- \
 		'$(call stripurischeme,$(call qstrip,$(1)))' && \
 	$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
 endef
@@ -188,8 +195,9 @@ endef
 
 define DOWNLOAD_HG
 	test -e $(DL_DIR)/$($(PKG)_SOURCE) || \
-	$(EXTRA_ENV) support/download/wrapper hg \
-		$(DL_DIR)/$($(PKG)_SOURCE) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b hg \
+		-o $(DL_DIR)/$($(PKG)_SOURCE) \
+		-- \
 		$($(PKG)_SITE) \
 		$($(PKG)_DL_VERSION) \
 		$($(PKG)_BASE_NAME)
@@ -208,8 +216,9 @@ endef
 
 define DOWNLOAD_WGET
 	test -e $(DL_DIR)/$(2) || \
-	$(EXTRA_ENV) support/download/wrapper wget \
-		$(DL_DIR)/$(2) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b wget \
+		-o $(DL_DIR)/$(2) \
+		-- \
 		'$(call qstrip,$(1))' && \
 	$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
 endef
@@ -224,8 +233,9 @@ endef
 
 define DOWNLOAD_LOCALFILES
 	test -e $(DL_DIR)/$(2) || \
-	$(EXTRA_ENV) support/download/wrapper cp \
-		$(DL_DIR)/$(2) \
+	$(EXTRA_ENV) $(DL_WRAPPER) -b cp \
+		-o $(DL_DIR)/$(2) \
+		-- \
 		$(call stripurischeme,$(call qstrip,$(1))) && \
 	$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
 endef
diff --git a/support/download/dl-wrapper b/support/download/dl-wrapper
new file mode 100755
index 0000000..078ae33
--- /dev/null
+++ b/support/download/dl-wrapper
@@ -0,0 +1,166 @@
+#!/usr/bin/env bash
+
+# This script is a wrapper to the other download backends.
+# Its role is to ensure atomicity when saving downloaded files
+# back to BR2_DL_DIR, and not clutter BR2_DL_DIR with partial,
+# failed downloads.
+#
+# Call it with:
+#   -b BACKEND  name of the backend (eg. cvs, git, cp...)
+#   -o FILE     full path to the file in which to save the download
+#   --          everything after '--' are options for the backend
+# Environment:
+#   BUILD_DIR: the path to Buildroot's build dir
+
+# To avoid cluttering BR2_DL_DIR, we download to a trashable
+# location, namely in $(BUILD_DIR).
+# Then, we move the downloaded file to a temporary file in the
+# same directory as the final output file.
+# This allows us to finally atomically rename it to its final
+# name.
+# If anything goes wrong, we just remove all the temporaries
+# created so far.
+
+# We want to catch any unexpected failure, and exit immediately.
+set -e
+
+main() {
+    local OPT OPTARG
+    local backend output
+
+    # Parse our options; anythong after '--' is for the backend
+    # Sop we only care to -b (backend) and -o (output file)
+    while getopts :hb:o: OPT; do
+        case "${OPT}" in
+        h)  help; exit 0;;
+        b)  backend="${OPTARG}";;
+        o)  output="${OPTARG}";;
+        :)  error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
+        \?) error "unknown option '%s'\n" "${OPTARG}";;
+        esac
+    done
+    # Forget our options, and keep only those for the backend
+    shift $((OPTIND-1))
+
+    if [ -z "${backend}" ]; then
+        error "no backend specified, use -b\n"
+    fi
+    if [ -z "${output}" ]; then
+        error "no output specified, use -o\n"
+    fi
+
+    # tmpd is a temporary directory in which backends may store intermediate
+    # by-products of the download.
+    # tmpf is the file in which the backends should put the downloaded content.
+    # tmpd is located in $(BUILD_DIR), so as not to clutter the (precious)
+    # $(BR2_DL_DIR)
+    # We let the backends create tmpf, so they are able to set whatever
+    # permission bits they want (although we're only really interested in
+    # the executable bit.)
+    tmpd="$( mktemp -d "${BUILD_DIR}/.${output##*/}.XXXXXX" )"
+    tmpf="${tmpd}/output"
+
+    # Helpers expect to run in a directory that is *really* trashable, so
+    # they are free to create whatever files and/or sub-dirs they might need.
+    # Doing the 'cd' here rather than in all backends is easier.
+    cd "${tmpd}"
+
+    # If the backend fails, we can just remove the temporary directory to
+    # remove all the cruft it may have left behind. Then we just exit in
+    # error too.
+    if ! "${OLDPWD}/support/download/${backend}" "${tmpf}" "${@}"; then
+        rm -rf "${tmpd}"
+        exit 1
+    fi
+
+    # cd back to free the temp-dir, so we can remove it later
+    cd "${OLDPWD}"
+
+    # tmp_output is in the same directory as the final output, so we can
+    # later move it atomically.
+    tmp_output="$( mktemp "${output}.XXXXXX" )"
+
+    # 'mktemp' creates files with 'go=-rwx', so the files are not accessible
+    # to users other than the one doing the download (and root, of course).
+    # This can be problematic when a shared BR2_DL_DIR is used by different
+    # users (e.g. on a build server), where all users may write to the shared
+    # location, since other users would not be allowed to read the files
+    # another user downloaded.
+    # So, we restore the 'go' access rights to a more sensible value, while
+    # still abiding by the current user's umask. We must do that before the
+    # final 'mv', so just do it now.
+    # Some backends (cp and scp) may create executable files, so we need to
+    # carry the executable bit if needed.
+    [ -x "${tmpf}" ] && new_mode=755 || new_mode=644
+    new_mode=$( printf "%04o" $((0${new_mode} & ~0$(umask))) )
+    chmod ${new_mode} "${tmp_output}"
+
+    # We must *not* unlink tmp_output, otherwise there is a small window
+    # during which another download process may create the same tmp_output
+    # name (very, very unlikely; but not impossible.)
+    # Using 'cp' is not reliable, since 'cp' may unlink the destination file
+    # if it is unable to open it with O_WRONLY|O_TRUNC; see:
+    #   http://pubs.opengroup.org/onlinepubs/9699919799/utilities/cp.html
+    # Since the destination filesystem can be anything, it might not support
+    # O_TRUNC, so 'cp' would unlink it first.
+    # Use 'cat' and append-redirection '>>' to save to the final location,
+    # since that is the only way we can be 100% sure of the behaviour.
+    if ! cat "${tmpf}" >>"${tmp_output}"; then
+        rm -rf "${tmpd}" "${tmp_output}"
+        exit 1
+    fi
+    rm -rf "${tmpd}"
+
+    # tmp_output and output are on the same filesystem, so POSIX guarantees
+    # that 'mv' is atomic, because it then uses rename() that POSIX mandates
+    # to be atomic, see:
+    #   http://pubs.opengroup.org/onlinepubs/9699919799/functions/rename.html
+    if ! mv -f "${tmp_output}" "${output}"; then
+        rm -f "${tmp_output}"
+        exit 1
+    fi
+}
+
+help() {
+    cat <<_EOF_
+NAME
+    ${my_name} - downlaod wrapper for Buildroot
+
+SYNOPSIS
+    ${my_name} [OPTION]... -- [BACKEND OPTION]...
+
+DESCRIPTIOM
+    Wrapper script around different download mechanisms. Ensure that
+    concurrent downloads do not conflict, that partial downloads are
+    properly evicted without leaving temporary files, and that access
+    rights are maintained.
+
+    -h  This help text.
+
+    -b BACKEND
+        Wrap the specified BACKEND. Known backends are:
+            bzr     Bazaar
+            cp      local files via simple copy
+            cvs     Concurrent Versions System
+            git     git
+            hg      Mercurial
+            scp     remote files via Secure copy
+            svn     Subversion
+            wget    remote files via HTTP download
+
+    -o FILE
+        Store the downloaded archive in FILE.
+
+  Exit status:
+    0   if OK
+    !0  in case of error
+_EOF_
+}
+
+trace()  { local msg="${1}"; shift; printf "%s: ${msg}" "${my_name}" "${@}"; }
+warn()   { trace "${@}" >&2; }
+errorN() { local ret="${1}"; shift; warn "${@}"; exit ${ret}; }
+error()  { errorN 1 "${@}"; }
+
+my_name="${0##*/}"
+main "${@}"
diff --git a/support/download/wrapper b/support/download/wrapper
deleted file mode 100755
index 320a37e..0000000
--- a/support/download/wrapper
+++ /dev/null
@@ -1,99 +0,0 @@
-#!/usr/bin/env bash
-
-# This script is a wrapper to the other download helpers.
-# Its role is to ensure atomicity when saving downloaded files
-# back to BR2_DL_DIR, and not clutter BR2_DL_DIR with partial,
-# failed downloads.
-#
-# Call it with:
-#   $1: name of the helper (eg. cvs, git, cp...)
-#   $2: full path to the file in which to save the download
-#   $*: additional arguments to the helper in $1
-# Environment:
-#   BUILD_DIR: the path to Buildroot's build dir
-
-# To avoid cluttering BR2_DL_DIR, we download to a trashable
-# location, namely in $(BUILD_DIR).
-# Then, we move the downloaded file to a temporary file in the
-# same directory as the final output file.
-# This allows us to finally atomically rename it to its final
-# name.
-# If anything goes wrong, we just remove all the temporaries
-# created so far.
-
-# We want to catch any unexpected failure, and exit immediately.
-set -e
-
-helper="${1}"
-output="${2}"
-shift 2
-
-# tmpd is a temporary directory in which helpers may store intermediate
-# by-products of the download.
-# tmpf is the file in which the helpers should put the downloaded content.
-# tmpd is located in $(BUILD_DIR), so as not to clutter the (precious)
-# $(BR2_DL_DIR)
-# We let the helpers create tmpf, so they are able to set whatever
-# permission bits they want (although we're only really interested in
-# the executable bit.)
-tmpd="$( mktemp -d "${BUILD_DIR}/.${output##*/}.XXXXXX" )"
-tmpf="${tmpd}/output"
-
-# Helpers expect to run in a directory that is *really* trashable, so
-# they are free to create whatever files and/or sub-dirs they might need.
-# Doing the 'cd' here rather than in all helpers is easier.
-cd "${tmpd}"
-
-# If the helper fails, we can just remove the temporary directory to
-# remove all the cruft it may have left behind. Then we just exit in
-# error too.
-if ! "${OLDPWD}/support/download/${helper}" "${tmpf}" "${@}"; then
-    rm -rf "${tmpd}"
-    exit 1
-fi
-
-# cd back to free the temp-dir, so we can remove it later
-cd "${OLDPWD}"
-
-# tmp_output is in the same directory as the final output, so we can
-# later move it atomically.
-tmp_output="$( mktemp "${output}.XXXXXX" )"
-
-# 'mktemp' creates files with 'go=-rwx', so the files are not accessible
-# to users other than the one doing the download (and root, of course).
-# This can be problematic when a shared BR2_DL_DIR is used by different
-# users (e.g. on a build server), where all users may write to the shared
-# location, since other users would not be allowed to read the files
-# another user downloaded.
-# So, we restore the 'go' access rights to a more sensible value, while
-# still abiding by the current user's umask. We must do that before the
-# final 'mv', so just do it now.
-# Some helpers (cp and scp) may create executable files, so we need to
-# carry the executable bit if needed.
-[ -x "${tmpf}" ] && new_mode=755 || new_mode=644
-new_mode=$( printf "%04o" $((0${new_mode} & ~0$(umask))) )
-chmod ${new_mode} "${tmp_output}"
-
-# We must *not* unlink tmp_output, otherwise there is a small window
-# during which another download process may create the same tmp_output
-# name (very, very unlikely; but not impossible.)
-# Using 'cp' is not reliable, since 'cp' may unlink the destination file
-# if it is unable to open it with O_WRONLY|O_TRUNC; see:
-#   http://pubs.opengroup.org/onlinepubs/9699919799/utilities/cp.html
-# Since the destination filesystem can be anything, it might not support
-# O_TRUNC, so 'cp' would unlink it first.
-# Use 'cat' and append-redirection '>>' to save to the final location,
-# since that is the only way we can be 100% sure of the behaviour.
-if ! cat "${tmpf}" >>"${tmp_output}"; then
-    rm -rf "${tmpd}" "${tmp_output}"
-    exit 1
-fi
-rm -rf "${tmpd}"
-# tmp_output and output are on the same filesystem, so POSIX guarantees
-# that 'mv' is atomic, because it then uses rename() that POSIX mandates
-# to be atomic, see:
-#   http://pubs.opengroup.org/onlinepubs/9699919799/functions/rename.html
-if ! mv "${tmp_output}" "${output}"; then
-    rm -f "${tmp_output}"
-    exit 1
-fi
-- 
1.9.1




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