--- /dev/null
+#!/bin/sh
+
+[ "$include_multipart" ] && return 0
+inlude_multipart="$0"
+
+# Copyright 2022 - 2023 Paul Hänsch
+#
+# Permission to use, copy, modify, and/or distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+# SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+# IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+if [ "${CONTENT_TYPE}" -a ! "${CONTENT_TYPE##multipart/form-data;*}" ]; then
+ multipart_boundary="${CONTENT_TYPE#*; boundary=}"
+ multipart_boundary="${multipart_boundary%%;*}"
+ multipart_boundary="${multipart_boundary%${CR}}"
+fi
+multipart_cachefile="/tmp/multipart.$$"
+
+readbytes(){
+ # read n bytes, like `head -c` but do not consume input
+ local size="$1" block
+
+ for block in 65536 32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1; do
+ if [ $size -ge $block ]; then
+ dd status=none bs="$block" count="$((size / block))"
+ size="$((size % block))"
+ fi
+ done
+}
+
+multipart_cache() {
+ multipart_cachefile="${1:-${multipart_cachefile}}" # global
+
+ if [ "${multipart_boundary}" ]; then
+ # readbytes "$(( CONTENT_LENGTH ))" >"${multipart_cachefile}"
+ head -c "$(( CONTENT_LENGTH ))" >"${multipart_cachefile}"
+ else
+ return 1
+ fi
+}
+
+multipart(){
+ local name="$1" count="${2:-1}"
+ local formdata state=begin
+
+ while IFS='' read -r formdata; do case "$formdata" in
+ "--${multipart_boundary}--${CR}")
+ [ $state = data ] && return 0 \
+ || return 1
+ ;;
+ "--${multipart_boundary}${CR}")
+ [ $state = data ] && return 0 \
+ || state=header
+ ;;
+ "Content-Disposition: form-data; name=\"${name}\""*"${CR}")
+ [ $state = header -a $count -eq 1 ] && state=dheader
+ [ $state = header -a $count -gt 1 ] && count=$((count - 1))
+ [ $state = data ] && printf "%s\n" "$formdata"
+ ;;
+ "${CR}")
+ if [ $state = dheader ]; then
+ # Do not use `sed -n` (or busybox sed will "convert" NULL to LF)
+ sed "/--${multipart_boundary}\(--\)\?${CR}/{x;q;}" \
+ | head -c-3
+ return 0;
+ fi
+ [ $state = header ] && state=junk
+ ;;
+ esac; done <"${multipart_cachefile}"
+}
+
+multipart_filename(){
+ local name="$1" count="${2:-1}"
+ local formdata state=begin
+
+ while read -r formdata; do case "$formdata" in
+ "--${multipart_boundary}--${CR}")
+ return 1
+ ;;
+ "--${multipart_boundary}${CR}")
+ state=header
+ ;;
+ "Content-Disposition: form-data; name=\"${name}\"; filename=\""*"\""*"${CR}")
+ [ $state = header -a $count -eq 1 ] && break
+ [ $state = header -a $count -gt 1 ] && count=$((count - 1))
+ ;;
+ "${CR}")
+ [ $state = header ] && state=junk
+ ;;
+ esac; done <"${multipart_cachefile}"
+
+ filename="${formdata#*; filename=\"}"
+ filename="${filename%%\"${CR}}"
+ filename="${filename%%\";*}"
+
+ HEX_DECODE % "$filename"
+}