1 files changed, 82 insertions, 0 deletions

diff --git a/bash/denominate-function.bash b/bash/denominate-function.bash
new file mode 100644
index 0000000..9e5cb31
--- /dev/null
+++ b/bash/denominate-function.bash
@@ -0,0 +1,82 @@
+#!/bin/bash
+denominate_function()
+{
+        declare -n func_name="$1"
+        local func_output_b64encoded output_hash
+        read -r -d '' \
+                func_output_b64encoded \
+                < <(base64) || [ "${func_output_b64encoded}" ]
+        read output_hash _ \
+                < <(base64 -d <<< "$func_output_b64encoded" | sha256sum)
+        [ ${#output_hash} = 64 ] || return
+        func_name=SHA256_${output_hash:0:32}
+        source <(cat <<END
+${func_name} ()
+{
+base64 -d <<.
+${func_output_b64encoded}
+.
+}
+END
+)
+}
+
+reverse_hash()
+{
+        case "$#.$1" in
+        2.SHA256 )
+                ;;
+        1.SHA256_???????????????????????????????? )
+                set -- SHA256 "${1#SHA256_}"
+                ;;
+        * )
+                return 1
+                ;;
+        esac
+        case ${#2} in
+        32 | 64 )
+                set -- "${1}_${2: 0 : 32}"
+                ;;
+        * )
+                return 1
+                ;;
+        esac
+        (
+                set -o pipefail
+                set -e
+                declare -f "$1" |
+                sed -n -e '/^[   ]*base64 -d <<[.]$/,/^[.]$/ { p }' |
+                sed -e '1 d ; $ d' |
+                base64 -d
+        )
+}
+
+example_input()
+{
+        sed -n -e '/^reverse_hash *()/ , /^}$/ p' <"$0"
+}
+
+set -e
+set -o pipefail
+
+if [ -t 0 ]
+then
+        if [ $# = 0 ]
+        then
+                denominate_function f < <(example_input)
+        else
+                denominate_function f <<< "$*"
+        fi
+else
+        denominate_function f
+fi
+
+read -r -d '' < <( reverse_hash "$f" | base64) || [ "$REPLY" ]
+if      read s _ < <( base64 -d <<< "$REPLY" | sha256sum ) &&
+        [ ${#s} -eq 64 -a "${s: 0 : 32}" = "${f: -32 : 32}" ]
+then
+        declare -f "$f" | grep . &&
+        printf '%s\n' "$f"
+else
+        false
+fi