openpilot v0.3.7 release

old-commit-hash: daf54ad54d6356d35061ea2864d6397dc6184f3f

selfdrive/common/params.cc

@@ -0,0 +1,154 @@
+#include "selfdrive/common/params.h"
+
+#include "selfdrive/common/util.h"
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif  // _GNU_SOURCE
+
+#include <sys/file.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+namespace {
+
+template <typename T>
+T* null_coalesce(T* a, T* b) {
+  return a != NULL ? a : b;
+}
+
+static const char* default_params_path = null_coalesce(
+    const_cast<const char*>(getenv("PARAMS_PATH")), "/data/params");
+
+}  // namespace
+
+int write_db_value(const char* params_path, const char* key, const char* value,
+                   size_t value_size) {
+  int lock_fd = -1;
+  int tmp_fd = -1;
+  int result;
+  char tmp_path[1024];
+  char path[1024];
+  ssize_t bytes_written;
+
+  if (params_path == NULL) {
+    params_path = default_params_path;
+  }
+
+  // Write value to temp.
+  result =
+      snprintf(tmp_path, sizeof(tmp_path), "%s/.tmp_value_XXXXXX", params_path);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  tmp_fd = mkstemp(tmp_path);
+  bytes_written = write(tmp_fd, value, value_size);
+  if (bytes_written != value_size) {
+    result = -20;
+    goto cleanup;
+  }
+
+  result = snprintf(path, sizeof(path), "%s/.lock", params_path);
+  if (result < 0) {
+    goto cleanup;
+  }
+  lock_fd = open(path, 0);
+
+  result = snprintf(path, sizeof(path), "%s/d/%s", params_path, key);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  // Take lock.
+  result = flock(lock_fd, LOCK_EX);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  // fsync to force persist the changes.
+  result = fsync(tmp_fd);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  // Move temp into place.
+  result = rename(tmp_path, path);
+
+cleanup:
+  // Release lock.
+  if (lock_fd >= 0) {
+    close(lock_fd);
+  }
+  if (tmp_fd >= 0) {
+    if (result < 0) {
+      remove(tmp_path);
+    }
+    close(tmp_fd);
+  }
+  return result;
+}
+
+int read_db_value(const char* params_path, const char* key, char** value,
+                  size_t* value_sz) {
+  int lock_fd = -1;
+  int result;
+  char path[1024];
+
+  if (params_path == NULL) {
+    params_path = default_params_path;
+  }
+
+  result = snprintf(path, sizeof(path), "%s/.lock", params_path);
+  if (result < 0) {
+    goto cleanup;
+  }
+  lock_fd = open(path, 0);
+
+  result = snprintf(path, sizeof(path), "%s/d/%s", params_path, key);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  // Take lock.
+  result = flock(lock_fd, LOCK_EX);
+  if (result < 0) {
+    goto cleanup;
+  }
+
+  // Read value.
+  // TODO(mgraczyk): If there is a lot of contention, we can release the lock
+  //                 after opening the file, before reading.
+  *value = static_cast<char*>(read_file(path, value_sz));
+  if (*value == NULL) {
+    result = -22;
+    goto cleanup;
+  }
+
+  // Remove one for null byte.
+  if (value_sz != NULL) {
+    *value_sz -= 1;
+  }
+  result = 0;
+
+cleanup:
+  // Release lock.
+  if (lock_fd >= 0) {
+    close(lock_fd);
+  }
+  return result;
+}
+
+void read_db_value_blocking(const char* params_path, const char* key,
+                            char** value, size_t* value_sz) {
+  while (1) {
+    const int result = read_db_value(params_path, key, value, value_sz);
+    if (result == 0) {
+      return;
+    } else {
+      // Sleep for 0.1 seconds.
+      usleep(100000);
+    }
+  }
+}