implement syslog via websocket with 1k buffer

firmware/log.cpp

@@ -0,0 +1,49 @@
+//
+// Created by jedi on 18.11.21.
+//
+
+#include "log.h"
+
+#include <espressif/esp_common.h>
+
+constexpr unsigned syslog_buffer_size = 1024;
+char syslog_buf[syslog_buffer_size];
+volatile unsigned head = 0;
+volatile unsigned streams = 0;
+
+extern "C" void syslog(const char *msg) {
+    printf("syslog> %s", msg);
+    while (char c = *msg++) {
+        syslog_buf[head++ % syslog_buffer_size] = c;
+    }
+    syslog_buf[head] = 0;
+}
+
+unsigned syslog_current_tail() {
+    if(head < syslog_buffer_size)
+        return 0;
+    return head + 1 - syslog_buffer_size;
+}
+
+unsigned syslog_data_after(unsigned local_tail) {
+    if(local_tail > head)
+        return 0;
+    return (head % syslog_buffer_size) - (local_tail % syslog_buffer_size);
+}
+
+extern "C" int syslog_copy_out(char *out, int len, unsigned local_tail) {
+    unsigned cnt = 0;
+    while (cnt < syslog_data_after(local_tail) && cnt < len) {
+        out[cnt] = syslog_buf[local_tail % syslog_buffer_size + cnt];
+        cnt++;
+    }
+    return cnt;
+}
+
+extern "C" void syslog_attach() {
+    streams++;
+}
+
+extern "C" void syslog_detach() {
+    streams--;
+}