1 files changed, 50 insertions, 0 deletions
diff --git a/xmpp-vala/src/util.vala b/xmpp-vala/src/util.vala
new file mode 100644
index 00000000..34a05b7a
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+++ b/xmpp-vala/src/util.vala
@@ -0,0 +1,50 @@
+namespace Xmpp.Util {
+
+// Parse a number from a hexadecimal representation.
+//
+// Skips any whitespace at the start of the string, parses as many valid
+// characters as hexadecimal digits as possible (possibly zero) and returns
+// them as an integer value.
+//
+// ```
+// // 0x0
+// print("0x%lx\n", from_hex(""));
+//
+// // 0x123abc
+// print("0x%lx\n", from_hex("123abc"));
+//
+// // 0x0
+// print("0x%lx\n", from_hex("0x123abc"));
+//
+// // 0xa
+// print("0x%lx\n", from_hex("A quick brown fox jumps over the lazy dog."));
+//
+// // 0xfeed
+// print("0x%lx\n", from_hex("   FEED ME   "));
+// ```
+
+public long from_hex(string numeral) {
+    long result = 0;
+    bool skipping_whitespace = true;
+    foreach (uint8 byte in numeral.data) {
+        char c = (char)byte;
+        if (skipping_whitespace && c.isspace()) {
+            continue;
+        }
+        skipping_whitespace = false;
+        int digit;
+        if ('0' <= c && c <= '9') {
+            digit = c - '0';
+        } else if ('A' <= c && c <= 'F') {
+            digit = c - 'A' + 10;
+        } else if ('a' <= c && c <= 'f') {
+            digit = c - 'a' + 10;
+        } else {
+            break;
+        }
+        result = (result << 4) | digit;
+    }
+    return result;
+}
+
+}