Move base64_decode_atom into misc.c.

I'm about to need to refer to it from a source file that won't
necessarily always be linked against sshpubk.c, so it needs to live
somewhere less specialist. Now it sits alongside base64_encode_atom
(already in misc.c for another reason), which is neater anyway.

[originally from svn r10218]

misc.c

@@ -473,8 +473,7 @@ char *fgetline(FILE *fp)
 }
 
 /* ----------------------------------------------------------------------
- * Base64 encoding routine. This is required in public-key writing
+ * Core base64 encoding and decoding routines.
- * but also in HTTP proxy handling, so it's centralised here.
  */
 
 void base64_encode_atom(unsigned char *data, int n, char *out)
@@ -501,6 +500,54 @@ void base64_encode_atom(unsigned char *data, int n, char *out)
 	out[3] = '=';
 }
 
+int base64_decode_atom(char *atom, unsigned char *out)
+{
+    int vals[4];
+    int i, v, len;
+    unsigned word;
+    char c;
+
+    for (i = 0; i < 4; i++) {
+	c = atom[i];
+	if (c >= 'A' && c <= 'Z')
+	    v = c - 'A';
+	else if (c >= 'a' && c <= 'z')
+	    v = c - 'a' + 26;
+	else if (c >= '0' && c <= '9')
+	    v = c - '0' + 52;
+	else if (c == '+')
+	    v = 62;
+	else if (c == '/')
+	    v = 63;
+	else if (c == '=')
+	    v = -1;
+	else
+	    return 0;		       /* invalid atom */
+	vals[i] = v;
+    }
+
+    if (vals[0] == -1 || vals[1] == -1)
+	return 0;
+    if (vals[2] == -1 && vals[3] != -1)
+	return 0;
+
+    if (vals[3] != -1)
+	len = 3;
+    else if (vals[2] != -1)
+	len = 2;
+    else
+	len = 1;
+
+    word = ((vals[0] << 18) |
+	    (vals[1] << 12) | ((vals[2] & 0x3F) << 6) | (vals[3] & 0x3F));
+    out[0] = (word >> 16) & 0xFF;
+    if (len > 1)
+	out[1] = (word >> 8) & 0xFF;
+    if (len > 2)
+	out[2] = word & 0xFF;
+    return len;
+}
+
 /* ----------------------------------------------------------------------
  * Generic routines to deal with send buffers: a linked list of
  * smallish blocks, with the operations

misc.h

@@ -44,6 +44,7 @@ int toint(unsigned);
 char *fgetline(FILE *fp);
 
 void base64_encode_atom(unsigned char *data, int n, char *out);
+int base64_decode_atom(char *atom, unsigned char *out);
 
 struct bufchain_granule;
 typedef struct bufchain_tag {

sshpubk.c

@@ -513,54 +513,6 @@ static char *read_body(FILE * fp)
     }
 }
 
-int base64_decode_atom(char *atom, unsigned char *out)
-{
-    int vals[4];
-    int i, v, len;
-    unsigned word;
-    char c;
-
-    for (i = 0; i < 4; i++) {
-	c = atom[i];
-	if (c >= 'A' && c <= 'Z')
-	    v = c - 'A';
-	else if (c >= 'a' && c <= 'z')
-	    v = c - 'a' + 26;
-	else if (c >= '0' && c <= '9')
-	    v = c - '0' + 52;
-	else if (c == '+')
-	    v = 62;
-	else if (c == '/')
-	    v = 63;
-	else if (c == '=')
-	    v = -1;
-	else
-	    return 0;		       /* invalid atom */
-	vals[i] = v;
-    }
-
-    if (vals[0] == -1 || vals[1] == -1)
-	return 0;
-    if (vals[2] == -1 && vals[3] != -1)
-	return 0;
-
-    if (vals[3] != -1)
-	len = 3;
-    else if (vals[2] != -1)
-	len = 2;
-    else
-	len = 1;
-
-    word = ((vals[0] << 18) |
-	    (vals[1] << 12) | ((vals[2] & 0x3F) << 6) | (vals[3] & 0x3F));
-    out[0] = (word >> 16) & 0xFF;
-    if (len > 1)
-	out[1] = (word >> 8) & 0xFF;
-    if (len > 2)
-	out[2] = word & 0xFF;
-    return len;
-}
-
 static unsigned char *read_blob(FILE * fp, int nlines, int *bloblen)
 {
     unsigned char *blob;