Move detail::read_file() to test/test.cc (#2092)

The unit test code is the only user of the function.

read_file() now throws an exception if the file isn't found.

httplib.h

@@ -240,7 +240,6 @@ using socket_t = int;
 #include <errno.h>
 #include <exception>
 #include <fcntl.h>
-#include <fstream>
 #include <functional>
 #include <iomanip>
 #include <iostream>
@@ -2387,8 +2386,6 @@ std::string encode_query_param(const std::string &value);
 
 std::string decode_url(const std::string &s, bool convert_plus_to_space);
 
-void read_file(const std::string &path, std::string &out);
-
 std::string trim_copy(const std::string &s);
 
 void divide(
@@ -2916,15 +2913,6 @@ inline std::string decode_url(const std::string &s,
   return result;
 }
 
-inline void read_file(const std::string &path, std::string &out) {
-  std::ifstream fs(path, std::ios_base::binary);
-  fs.seekg(0, std::ios_base::end);
-  auto size = fs.tellg();
-  fs.seekg(0);
-  out.resize(static_cast<size_t>(size));
-  fs.read(&out[0], static_cast<std::streamsize>(size));
-}
-
 inline std::string file_extension(const std::string &path) {
   std::smatch m;
   static auto re = std::regex("\\.([a-zA-Z0-9]+)$");

test/test.cc

@@ -9,6 +9,7 @@
 
 #include <atomic>
 #include <chrono>
+#include <fstream>
 #include <future>
 #include <limits>
 #include <memory>
@@ -59,6 +60,16 @@ MultipartFormData &get_file_value(MultipartFormDataItems &files,
 #endif
 }
 
+static void read_file(const std::string &path, std::string &out) {
+  std::ifstream fs(path, std::ios_base::binary);
+  if (!fs) throw std::runtime_error("File not found: " + path);
+  fs.seekg(0, std::ios_base::end);
+  auto size = fs.tellg();
+  fs.seekg(0);
+  out.resize(static_cast<size_t>(size));
+  fs.read(&out[0], static_cast<std::streamsize>(size));
+}
+
 #ifndef _WIN32
 class UnixSocketTest : public ::testing::Test {
 protected:
@@ -729,7 +740,7 @@ TEST(ChunkedEncodingTest, FromHTTPWatch_Online) {
   ASSERT_TRUE(res);
 
   std::string out;
-  detail::read_file("./image.jpg", out);
+  read_file("./image.jpg", out);
 
   EXPECT_EQ(StatusCode::OK_200, res->status);
   EXPECT_EQ(out, res->body);
@@ -782,7 +793,7 @@ TEST(ChunkedEncodingTest, WithContentReceiver_Online) {
   ASSERT_TRUE(res);
 
   std::string out;
-  detail::read_file("./image.jpg", out);
+  read_file("./image.jpg", out);
 
   EXPECT_EQ(StatusCode::OK_200, res->status);
   EXPECT_EQ(out, body);
@@ -814,7 +825,7 @@ TEST(ChunkedEncodingTest, WithResponseHandlerAndContentReceiver_Online) {
   ASSERT_TRUE(res);
 
   std::string out;
-  detail::read_file("./image.jpg", out);
+  read_file("./image.jpg", out);
 
   EXPECT_EQ(StatusCode::OK_200, res->status);
   EXPECT_EQ(out, body);
@@ -6176,7 +6187,7 @@ TEST(SSLClientTest, ServerCertificateVerification4) {
 
 TEST(SSLClientTest, ServerCertificateVerification5_Online) {
   std::string cert;
-  detail::read_file(CA_CERT_FILE, cert);
+  read_file(CA_CERT_FILE, cert);
 
   SSLClient cli("google.com");
   cli.load_ca_cert_store(cert.data(), cert.size());