fix(libacron): infinite loop when wic_parse returns 0

This is a rather complicated way to fix backlogging issues. It asks the client to pass partial buffer, and the client also must retry with NULL buffer if ac_receive returns AC_E_AGAIN.

1 files changed, 52 insertions, 6 deletions

diff --git a/client/libacron/README.md b/client/libacron/README.md
index 14d37ad..736b44a 100644
--- a/client/libacron/README.md
+++ b/client/libacron/README.md
@@ -202,12 +202,22 @@ Then, the program can listen for responses or events.
 The client should do its own magic to receive from socket and 
 supply `ac_receive` with a buffer and size.
 
+Function `ac_receive` may only parse part of the buffer, so it is the client's responsibility to keep
+track of the bytes read:
+
 ```c
 ac_obj_t *obj = NULL;
 uint8_t buffer[1000U];
-size_t bytes;
-/* TODO: recv() */
-while (!(r = ac_receive(connection, buffer, bytes, &obj))) {
+size_t len;
+size_t pos = 0;
+size_t read;
+/* TODO: recv(): reset pos to 0 and set len. */
+while (1) {
+    if ((r = ac_receive(connection, buffer, pos, len, &obj, &read))) {
+        /* Handle error. */
+        break;
+    }
+    pos += read;
     /* The obj is now referencing to a library allocated event or response. */
     /* Do things with the event or response. */
     ac_obj_free(obj);
@@ -220,9 +230,45 @@ while (!(r = ac_receive(connection, buffer, bytes, &obj))) {
 > `ac_receive` will backlog the additional parsed messages, and they will return the second time
 > calling `ac_receive` with buffer = bytes = 0.
 > 
-> This will happen only `ac_receive` returns zero with a non-NULL obj output. If that is true,
-> the client must additionally call `ac_receive` infinite times with buffer = bytes = 0, until either
-> `ac_receive` returns an error or obj output is NULL.
+> This will happen only `ac_receive` returns `AC_E_AGAIN`. If that is true, the client must additionally
+> call `ac_receive` infinite times with buffer = bytes = 0, until either `ac_receive` returns an error or
+> returns `AC_E_OK`. See the code below:
+
+```c
+ac_obj_t *obj = NULL;
+uint8_t buffer[1000U];
+size_t len;
+size_t pos = 0;
+size_t read;
+/* TODO: recv(): reset pos to 0 and set len. */
+bool again = false;
+while (1) {
+    if ((r = ac_receive(connection, buffer, pos, len, &obj, &read))) {
+        if (r == AC_E_AGAIN) {
+            again = true;
+        } else {
+            /* Handle error. */
+            break;
+        }
+    }
+    pos += read;
+    /* The obj is now referencing to a library allocated event or response. */
+    /* Do things with the event or response. */
+    ac_obj_free(obj);
+    /* Clear backlog */
+    while (again) {
+        if ((r = ac_receive(connection, NULL, 0, 0, &obj, NULL))) {
+            if (r == AC_E_AGAIN) {
+                again = true;
+            } else {
+                /* Handle error. */
+                break;
+            }
+        }
+        ac_obj_free(obj);
+    }
+}
+```
 
 The program can make requests using `ac_request()`: