Safer snprintf / vsnprintf functions
Provide a string::Format function that writes to a span. The snprintf
return value is interpreted and returned as a StatusWithSize.
Change-Id: Ib7fed684dc333d5feaef85c1bb558cb45e3936bd
diff --git a/pw_string/format_test.cc b/pw_string/format_test.cc
new file mode 100644
index 0000000..b1756a0
--- /dev/null
+++ b/pw_string/format_test.cc
@@ -0,0 +1,100 @@
+// Copyright 2019 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy
+// of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+#include "pw_string/format.h"
+
+#include <cstdarg>
+
+#include "gtest/gtest.h"
+#include "pw_span/span.h"
+
+namespace pw::string {
+namespace {
+
+TEST(Format, ValidFormatString_Succeeds) {
+ char buffer[32];
+ auto result = Format(buffer, "-_-");
+
+ EXPECT_EQ(Status::OK, result.status());
+ EXPECT_EQ(3u, result.size());
+ EXPECT_STREQ("-_-", buffer);
+}
+
+TEST(Format, ValidFormatStringAndArguments_Succeeds) {
+ char buffer[32];
+ auto result = Format(buffer, "%d4%s", 123, "5");
+
+ EXPECT_EQ(Status::OK, result.status());
+ EXPECT_EQ(5u, result.size());
+ EXPECT_STREQ("12345", buffer);
+}
+
+TEST(Format, InvalidConversionSpecifier_ReturnsInvalidArgumentAndTerminates) {
+ char buffer[32] = {'?', '?', '?', '?', '\0'};
+
+ // Make the format string volatile to prevent the compiler from potentially
+ // checking this as a format string.
+ const char* volatile fmt = "abc %9999999999999999999999999999999999d4%s";
+ auto result = Format(buffer, fmt, 123, "5");
+
+ EXPECT_EQ(Status::INVALID_ARGUMENT, result.status());
+ EXPECT_STREQ("", buffer);
+}
+
+TEST(Format, EmptyBuffer_ReturnsResourceExhausted) {
+ auto result = Format(span<char>(), "?");
+
+ EXPECT_EQ(Status::RESOURCE_EXHAUSTED, result.status());
+ EXPECT_EQ(0u, result.size());
+}
+
+TEST(Format, FormatLargerThanBuffer_ReturnsResourceExhausted) {
+ char buffer[5];
+ auto result = Format(buffer, "2big!");
+
+ EXPECT_EQ(Status::RESOURCE_EXHAUSTED, result.status());
+ EXPECT_EQ(4u, result.size());
+ EXPECT_STREQ("2big", buffer);
+}
+
+TEST(Format, ArgumentLargerThanBuffer_ReturnsResourceExhausted) {
+ char buffer[5];
+ auto result = Format(buffer, "%s", "2big!");
+
+ EXPECT_EQ(Status::RESOURCE_EXHAUSTED, result.status());
+ EXPECT_EQ(4u, result.size());
+ EXPECT_STREQ("2big", buffer);
+}
+
+StatusWithSize CallFormatWithVaList(span<char> buffer, const char* fmt, ...) {
+ va_list args;
+ va_start(args, fmt);
+
+ StatusWithSize result = Format(buffer, fmt, args);
+
+ va_end(args);
+ return result;
+}
+
+TEST(Format, CallFormatWithVaList_CallsCorrectFormatOverload) {
+ char buffer[8];
+ auto result = CallFormatWithVaList(buffer, "Yo%s", "?!");
+
+ EXPECT_EQ(Status::OK, result.status());
+ EXPECT_EQ(4u, result.size());
+ EXPECT_STREQ("Yo?!", buffer);
+}
+
+} // namespace
+} // namespace pw::string