Data commit

Task/Base64-decode-data/UNIX-Shell/base64-decode-data.sh

@@ -0,0 +1,55 @@
+#! /bin/bash
+declare -a encodeTable=(
+# +   ,   -   .   /   0   1   2   3   4   5   6   7   8   9   :
+ 62  -1  -1  -1  63  52  53  54  55  56  57  58  59  60  61  -1
+# ;   <   =   >   ?   @   A   B   C   D   E   F   G   H   I   J
+ -1  -1  -1  -1  -1  -1   0   1   2   3   4   5   6   7   8   9
+# K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z
+ 10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25
+# [   \   ]   ^   _   `   a   b   c   d   e   f   g   h   i   j
+ -1  -1  -1  -1  -1  -1  26  27  28  29  30  31  32  33  34  35
+# k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z
+ 36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51
+)
+function a2b6()
+{
+    if [ $1 -lt 43 -o $1 -gt 122 ]
+    then
+        echo -1
+    else
+        echo ${encodeTable[$(($1-43))]}
+    fi
+}
+
+function flush() {
+    for (( k=2; k>=4-CNT; k-- ))
+    do
+        (( b8=BUF>>(k*8)&255 ))
+        printf -v HEX %x $b8
+        printf \\x$HEX
+    done
+}
+
+while read INPUT
+do
+    for (( i=0; i<${#INPUT}; i++ ))
+    do
+        printf -v NUM %d "'${INPUT:$i:1}"
+        if (( NUM==61 ))
+        then
+            flush
+            exit 0
+        else
+            DEC=$( a2b6 $NUM )
+            if (( DEC>=0 ))
+            then
+                (( BUF|=DEC<<6*(3-CNT) ))
+                if (( ++CNT==4 ))
+                then
+                    flush
+                    (( CNT=0, BUF=0 ))
+                fi
+            fi
+        fi
+    done
+done