Add StringPrintf() wrapper utility.

Adds an efficient wrapper around std::snprintf() that returns the
formatted result in a std::string.

Background: The issue of either 1) wanting to use absl::StrFormat()
without bloating our binary sizes, or 2) manually writing char[] buffer
code around std::snprintf() has come up several times over the past year
or so. So, this new utility is about reducing friction and improving
future developer velocity.
Change-Id: Ie898f91575852b06d59844dd564a0da03df1f7ed
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/2487768
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Brandon Tolsch <btolsch@chromium.org>

3 files changed, 30 insertions, 31 deletions

diff --git a/cast/standalone_receiver/main.cc b/cast/standalone_receiver/main.cc
index 0c9d3c1b..4e8c321c 100644
--- a/cast/standalone_receiver/main.cc
+++ b/cast/standalone_receiver/main.cc
@@ -116,16 +116,15 @@ std::unique_ptr<CastAgent> StartCastAgent(TaskRunnerImpl* task_runner,
 }
 
 void LogUsage(const char* argv0) {
-  std::cerr << R"(
-usage: )" << argv0
-            << R"( <options> <interface>
+  constexpr char kTemplate[] = R"(
+usage: %s <options> <interface>
 
-options:
     interface
         Specifies the network interface to bind to. The interface is
         looked up from the system interface registry.
         Mandatory, as it must be known for publishing discovery.
 
+options:
     -p, --private-key=path-to-key: Path to OpenSSL-generated private key to be
                     used for TLS authentication. If a private key is not
                     provided, a randomly generated one will be used for this
@@ -153,7 +152,9 @@ options:
     -v, --verbose: Enable verbose logging.
 
     -h, --help: Show this help message.
-  )";
+)";
+
+  std::cerr << StringPrintf(kTemplate, argv0);
 }
 
 InterfaceInfo GetInterfaceInfoFromName(const char* name) {
diff --git a/cast/standalone_sender/main.cc b/cast/standalone_sender/main.cc
index 8b0d9d08..470a6b52 100644
--- a/cast/standalone_sender/main.cc
+++ b/cast/standalone_sender/main.cc
@@ -42,24 +42,20 @@ IPEndpoint GetDefaultEndpoint() {
 }
 
 void LogUsage(const char* argv0) {
-  std::cerr << R"(
-    usage:)" << argv0
-            << R"( <options> <media_file>
+  constexpr char kTemplate[] = R"(
+usage: %s <options> <media_file>
 
       -r, --remote=addr[:port]
            Specify the destination (e.g., 192.168.1.22:9999 or [::1]:12345).
 
-           Default if not set: )"
-            << GetDefaultEndpoint() << R"(
+           Default if not set: %s
 
       -m, --max-bitrate=N
            Specifies the maximum bits per second for the media streams.
 
-           Default if not set: )"
-            << kDefaultMaxBitrate << "\n"
-
+           Default if not set: %d)"
 #if defined(CAST_ALLOW_DEVELOPER_CERTIFICATE)
-            << R"(
+                               R"(
       -d, --developer-certificate=path-to-cert
            Specifies the path to a self-signed developer certificate that will
            be permitted for use as a root CA certificate for receivers that
@@ -68,7 +64,7 @@ void LogUsage(const char* argv0) {
            Google-signed cast certificate chain will be permitted.
 )"
 #endif
-            << R"(
+                               R"(
       -a, --android-hack:
            Use the wrong RTP payload types, for compatibility with older Android
            TV receivers.
@@ -78,7 +74,11 @@ void LogUsage(const char* argv0) {
       -v, --verbose: Enable verbose logging.
 
       -h, --help: Show this help message.
-  )";
+)";
+
+  std::cerr << StringPrintf(kTemplate, argv0,
+                            GetDefaultEndpoint().ToString().c_str(),
+                            kDefaultMaxBitrate);
 }
 
 int StandaloneSenderMain(int argc, char* argv[]) {
diff --git a/cast/streaming/sender_session_unittest.cc b/cast/streaming/sender_session_unittest.cc
index d56a9f30..f5e1117b 100644
--- a/cast/streaming/sender_session_unittest.cc
+++ b/cast/streaming/sender_session_unittest.cc
@@ -17,6 +17,7 @@
 #include "platform/test/fake_clock.h"
 #include "platform/test/fake_task_runner.h"
 #include "util/chrono_helpers.h"
+#include "util/stringprintf.h"
 
 using ::testing::_;
 using ::testing::InSequence;
@@ -180,21 +181,18 @@ class SenderSessionTest : public ::testing::Test {
     const int video_index = video_stream["index"].asInt();
     const int video_ssrc = video_stream["ssrc"].asUInt();
 
-    constexpr size_t kAnswerSize = 512u;
-    char answer[kAnswerSize];
-    snprintf(answer, kAnswerSize, R"({ "type": "ANSWER",
-                           "seqNum": %d,
-                           "answer": {
-                             "castMode": "mirroring",
-                             "udpPort": 1234,
-                             "sendIndexes": [%d, %d],
-                             "ssrcs": [%d, %d]
-                           }
-                         })",
-             offer["seqNum"].asInt(), audio_index, video_index, audio_ssrc + 1,
-             video_ssrc + 1);
-
-    return std::string(answer);
+    constexpr char kAnswerTemplate[] = R"({
+        "type": "ANSWER",
+        "seqNum": %d,
+        "answer": {
+          "castMode": "mirroring",
+          "udpPort": 1234,
+          "sendIndexes": [%d, %d],
+          "ssrcs": [%d, %d]
+        }
+        })";
+    return StringPrintf(kAnswerTemplate, offer["seqNum"].asInt(), audio_index,
+                        video_index, audio_ssrc + 1, video_ssrc + 1);
   }
 
  protected: