Add readv and writev for more efficient API packets (#2342)

esphome/components/socket/bsd_sockets_impl.cpp

@@ -6,6 +6,10 @@
 
 #include <cstring>
 
+#ifdef ARDUINO_ARCH_ESP32
+#include <esp_idf_version.h>
+#endif
+
 namespace esphome {
 namespace socket {
 
@@ -76,7 +80,51 @@ class BSDSocketImpl : public Socket {
   }
   int listen(int backlog) override { return ::listen(fd_, backlog); }
   ssize_t read(void *buf, size_t len) override { return ::read(fd_, buf, len); }
+  ssize_t readv(const struct iovec *iov, int iovcnt) override {
+#if defined(ARDUINO_ARCH_ESP32) && ESP_IDF_VERSION_MAJOR < 4
+    // esp-idf v3 doesn't have readv, emulate it
+    ssize_t ret = 0;
+    for (int i = 0; i < iovcnt; i++) {
+      ssize_t err = this->read(reinterpret_cast<uint8_t *>(iov[i].iov_base), iov[i].iov_len);
+      if (err == -1) {
+        if (ret != 0)
+          // if we already read some don't return an error
+          break;
+        return err;
+      }
+      ret += err;
+      if (err != iov[i].iov_len)
+        break;
+    }
+    return ret;
+#else
+    return ::readv(fd_, iov, iovcnt);
+#endif
+  }
   ssize_t write(const void *buf, size_t len) override { return ::write(fd_, buf, len); }
+  ssize_t send(void *buf, size_t len, int flags) { return ::send(fd_, buf, len, flags); }
+  ssize_t writev(const struct iovec *iov, int iovcnt) override {
+#if defined(ARDUINO_ARCH_ESP32) && ESP_IDF_VERSION_MAJOR < 4
+    // esp-idf v3 doesn't have writev, emulate it
+    ssize_t ret = 0;
+    for (int i = 0; i < iovcnt; i++) {
+      ssize_t err =
+          this->send(reinterpret_cast<uint8_t *>(iov[i].iov_base), iov[i].iov_len, i == iovcnt - 1 ? 0 : MSG_MORE);
+      if (err == -1) {
+        if (ret != 0)
+          // if we already wrote some don't return an error
+          break;
+        return err;
+      }
+      ret += err;
+      if (err != iov[i].iov_len)
+        break;
+    }
+    return ret;
+#else
+    return ::writev(fd_, iov, iovcnt);
+#endif
+  }
   int setblocking(bool blocking) override {
     int fl = ::fcntl(fd_, F_GETFL, 0);
     if (blocking) {