Extract binary to hex string conversion

app/src/hid/hid_event.h

@@ -12,4 +12,7 @@ struct sc_hid_event {
     uint8_t size;
 };
 
+char *
+sc_hid_event_to_string(const struct sc_hid_event *event, size_t max_data_bytes);
+
 #endif

app/src/usb/aoa_hid.c

@@ -5,6 +5,7 @@
 
 #include "aoa_hid.h"
 #include "util/log.h"
+#include "util/str.h"
 
 // See <https://source.android.com/devices/accessories/aoa2#hid-support>.
 #define ACCESSORY_REGISTER_HID 54
@@ -20,17 +21,12 @@ static void
 sc_hid_event_log(uint16_t accessory_id, const struct sc_hid_event *event) {
     // HID Event: [00] FF FF FF FF...
     assert(event->size);
-    unsigned buffer_size = event->size * 3 + 1;
-    char *buffer = malloc(buffer_size);
-    if (!buffer) {
-        LOG_OOM();
+    char *hex = sc_str_to_hex_string(event->data, event->size);
+    if (!hex) {
         return;
     }
-    for (unsigned i = 0; i < event->size; ++i) {
-        snprintf(buffer + i * 3, 4, " %02x", event->data[i]);
-    }
-    LOGV("HID Event: [%d]%s", accessory_id, buffer);
-    free(buffer);
+    LOGV("HID Event: [%d] %s", accessory_id, hex);
+    free(hex);
 }
 
 bool

app/src/util/str.c

@@ -3,6 +3,7 @@
 #include <assert.h>
 #include <errno.h>
 #include <limits.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -333,3 +334,22 @@ sc_str_remove_trailing_cr(char *s, size_t len) {
     }
     return len;
 }
+
+char *
+sc_str_to_hex_string(const uint8_t *data, size_t size) {
+    size_t buffer_size = size * 3 + 1;
+    char *buffer = malloc(buffer_size);
+    if (!buffer) {
+        LOG_OOM();
+        return NULL;
+    }
+
+    for (size_t i = 0; i < size; ++i) {
+        snprintf(buffer + i * 3, 4, "%02X ", data[i]);
+    }
+
+    // Remove the final space
+    buffer[size * 3] = '\0';
+
+    return buffer;
+}

app/src/util/str.h

@@ -138,4 +138,10 @@ sc_str_index_of_column(const char *s, unsigned col, const char *seps);
 size_t
 sc_str_remove_trailing_cr(char *s, size_t len);
 
+/**
+ * Convert binary data to hexadecimal string
+ */
+char *
+sc_str_to_hex_string(const uint8_t *data, size_t len);
+
 #endif