Bug 29085: Refactor padding sent accounting out of callback.

This commit moves code that updates the state length and padding limit counts
out from the callback to its own function, for clarity.

It does not change functionality.

src/core/or/circuitpadding.c

@@ -830,6 +830,50 @@ check_machine_token_supply(circpad_machine_runtime_t *mi)
   return CIRCPAD_STATE_UNCHANGED;
 }
 
+/**
+ * Count that a padding packet was sent.
+ *
+ * This updates our state length count, our machine rate limit counts,
+ * and if token removal is used, decrements the histogram.
+ */
+static inline void
+circpad_machine_count_padding_sent(circpad_machine_runtime_t *mi)
+{
+  /* If we have a valid state length bound, consider it */
+  if (mi->state_length != CIRCPAD_STATE_LENGTH_INFINITE &&
+      !BUG(mi->state_length <= 0)) {
+    mi->state_length--;
+  }
+
+  /*
+   * Update non-padding counts for rate limiting: We scale at UINT16_MAX
+   * because we only use this for a percentile limit of 2 sig figs, and
+   * space is scare in the machineinfo struct.
+   */
+  mi->padding_sent++;
+  if (mi->padding_sent == UINT16_MAX) {
+    mi->padding_sent /= 2;
+    mi->nonpadding_sent /= 2;
+  }
+
+  circpad_global_padding_sent++;
+
+  /* If we have a mutable histogram, reduce the token count from
+   * the chosen padding bin (this assumes we always send padding
+   * when we intended to). */
+  if (mi->histogram && mi->histogram_len) {
+    /* Ensure that we have a token removal strategy set */
+    const circpad_state_t *state = circpad_machine_current_state(mi);
+    tor_assert_nonfatal(state->token_removal != CIRCPAD_TOKEN_REMOVAL_NONE);
+
+    /* Basic sanity check on the histogram before removing anything */
+    if (!BUG(mi->chosen_bin >= mi->histogram_len) &&
+        !BUG(mi->histogram[mi->chosen_bin] == 0)) {
+      mi->histogram[mi->chosen_bin]--;
+    }
+  }
+}
+
 /**
  * Count a nonpadding packet as being sent.
  *
@@ -1023,34 +1067,7 @@ circpad_send_padding_cell_for_callback(circpad_machine_runtime_t *mi)
     return CIRCPAD_STATE_CHANGED;
   }
 
-  /* If it's a histogram, reduce the token count */
-  if (mi->histogram && mi->histogram_len) {
-    /* Basic sanity check on the histogram before removing anything */
-    if (BUG(mi->chosen_bin >= mi->histogram_len) ||
-        BUG(mi->histogram[mi->chosen_bin] == 0)) {
-      return CIRCPAD_STATE_CHANGED;
-    }
-
-    mi->histogram[mi->chosen_bin]--;
-  }
-
-  /* If we have a valid state length bound, consider it */
-  if (mi->state_length != CIRCPAD_STATE_LENGTH_INFINITE &&
-      !BUG(mi->state_length <= 0)) {
-    mi->state_length--;
-  }
-
-  /*
-   * Update non-padding counts for rate limiting: We scale at UINT16_MAX
-   * because we only use this for a percentile limit of 2 sig figs, and
-   * space is scare in the machineinfo struct.
-   */
-  mi->padding_sent++;
-  if (mi->padding_sent == UINT16_MAX) {
-    mi->padding_sent /= 2;
-    mi->nonpadding_sent /= 2;
-  }
-  circpad_global_padding_sent++;
+  circpad_machine_count_padding_sent(mi);
 
   if (CIRCUIT_IS_ORIGIN(mi->on_circ)) {
     circpad_send_command_to_hop(TO_ORIGIN_CIRCUIT(mi->on_circ),