2 files changed, 41 insertions, 0 deletions
diff --git a/misc/bstr.c b/misc/bstr.c
index 8c47b447d4..09eb6af25b 100644
--- a/misc/bstr.c
+++ b/misc/bstr.c
@@ -454,3 +454,40 @@ struct bstr bstr_get_ext(struct bstr s)
         return (struct bstr){NULL, 0};
     return bstr_splice(s, dotpos + 1, s.len);
 }
+
+static int h_to_i(unsigned char c)
+{
+    if (c >= '0' && c <= '9')
+        return c - '0';
+    if (c >= 'a' && c <= 'f')
+        return c - 'a' + 10;
+    if (c >= 'A' && c <= 'F')
+        return c - 'A' + 10;
+
+    return -1; // invalid char
+}
+
+bool bstr_decode_hex(void *talloc_ctx, struct bstr hex, struct bstr *out)
+{
+    if (!out)
+        return false;
+
+    char *arr = talloc_array(talloc_ctx, char, hex.len / 2);
+    int len = 0;
+
+    while (hex.len >= 2) {
+        int a = h_to_i(hex.start[0]);
+        int b = h_to_i(hex.start[1]);
+        hex = bstr_splice(hex, 2, hex.len);
+
+        if (a < 0 || b < 0) {
+            talloc_free(arr);
+            return false;
+        }
+
+        arr[len++] = (a << 4) | b;
+    }
+
+    *out = (struct bstr){ .start = arr, .len = len };
+    return true;
+}
diff --git a/misc/bstr.h b/misc/bstr.h
index 63865a4421..199f300ba1 100644
--- a/misc/bstr.h
+++ b/misc/bstr.h
@@ -80,6 +80,10 @@ double bstrtod(struct bstr str, struct bstr *rest);
 void bstr_lower(struct bstr str);
 int bstr_sscanf(struct bstr str, const char *format, ...);
 
+// Decode a string containing hexadecimal data. All whitespace will be silently
+// ignored. When successful, this allocates a new array to store the output.
+bool bstr_decode_hex(void *talloc_ctx, struct bstr hex, struct bstr *out);
+
 // Decode the UTF-8 code point at the start of the string, and return the
 // character.
 // After calling this function, *out_next will point to the next character.