From: Alan T. DeKok <aland@freeradius.org>
Date: Sat, 20 Nov 2021 16:09:35 +0000 (-0500)
Subject: subtraction is the inverse of addition
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=41df5a7dca3d05137b9a4354a760553708f94dec;p=thirdparty%2Ffreeradius-server.git

subtraction is the inverse of addition
---

diff --git a/src/lib/util/calc.c b/src/lib/util/calc.c
index 8f65ab0f05b..a9a0806313b 100644
--- a/src/lib/util/calc.c
+++ b/src/lib/util/calc.c
@@ -379,6 +379,31 @@ static int calc_octets(TALLOC_CTX *ctx, fr_value_box_t *dst, fr_value_box_t cons
 		fr_value_box_memdup_shallow(dst, dst->enumv, buf, len, a->tainted | b->tainted);
 		break;
 
+	case T_SUB:
+		/*
+		 *  The inverse of add!
+		 */
+		if (a->vb_length < b->vb_length) {
+			fr_strerror_const("Suffix to remove is longer than input string");
+			return -1;
+		}
+
+		if (memcmp(a->vb_octets + a->vb_length - b->vb_length, b->vb_strvalue, b->vb_length) != 0) {
+			fr_strerror_const("Right side is not a suffix of the input string");
+			return -1;
+		}
+
+		len = a->vb_length - b->vb_length;
+		buf = talloc_array(ctx, uint8_t, len);
+		if (!buf) goto oom;
+
+		memcpy(buf, a->vb_strvalue, len);
+		buf[len] = '\0';
+
+		fr_value_box_clear_value(dst);
+		fr_value_box_memdup_shallow(dst, dst->enumv, buf, len, a->tainted | b->tainted);
+		break;
+
 	default:
 		return ERR_INVALID;	/* invalid operator */
 	}
@@ -438,6 +463,31 @@ static int calc_string(TALLOC_CTX *ctx, fr_value_box_t *dst, fr_value_box_t cons
 		fr_value_box_strdup_shallow(dst, dst->enumv, buf, a->tainted | b->tainted);
 		break;
 
+	case T_SUB:
+		/*
+		 *  The inverse of add!
+		 */
+		if (a->vb_length < b->vb_length) {
+			fr_strerror_const("Suffix to remove is longer than input string");
+			return -1;
+		}
+
+		if (memcmp(a->vb_strvalue + a->vb_length - b->vb_length, b->vb_strvalue, b->vb_length) != 0) {
+			fr_strerror_const("Right side is not a suffix of the input string");
+			return -1;
+		}
+
+		len = a->vb_length - b->vb_length;
+		buf = talloc_array(ctx, char, len + 1);
+		if (!buf) goto oom;
+
+		memcpy(buf, a->vb_strvalue, len);
+		buf[len] = '\0';
+
+		fr_value_box_clear_value(dst);
+		fr_value_box_strdup_shallow(dst, dst->enumv, buf, a->tainted | b->tainted);
+		break;
+
 	default:
 		return ERR_INVALID;	/* invalid operator */
 	}
diff --git a/src/tests/unit/calc.txt b/src/tests/unit/calc.txt
index 0efe2323ad8..25537ca25cc 100644
--- a/src/tests/unit/calc.txt
+++ b/src/tests/unit/calc.txt
@@ -30,9 +30,22 @@ match 1
 calc string "a" . string "b" -> string
 match ab
 
-# string prepend
-calc string "a" ^ string "b" -> string
-match ba
+# string subtraction is the inverse of addition!
+calc string "ab" - string "b" -> string
+match a
+
+# octets prepend
+calc octets "a" ^ octets "b" -> octets
+match 0x6261
+
+# octets append
+calc octets "a" . octets "b" -> octets
+match 0x6162
+
+# octets subtraction is the inverse of addition!
+calc octets "ab" - octets "b" -> octets
+match 0x61
+
 
 # time deltas
 calc time_delta 1 + time_delta 2 -> time_delta
@@ -94,4 +107,4 @@ calc string "2" += string "test"
 match 2test
 
 count
-match 42
+match 48