Add Google-style StringPrintf.

Change-Id: If333c28b8ed047346a2dd85e591c4bedbab874cc

include/utils/stringprintf.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://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.
+ */
+
+#ifndef UTILS_STRINGPRINTF_H_
+#define UTILS_STRINGPRINTF_H_
+
+#include <stdarg.h>
+#include <string>
+
+namespace android {
+
+// Returns a string corresponding to printf-like formatting of the arguments.
+std::string StringPrintf(const char* fmt, ...)
+        __attribute__((__format__(__printf__, 1, 2)));
+
+// Appends a printf-like formatting of the arguments to 'dst'.
+void StringAppendF(std::string* dst, const char* fmt, ...)
+        __attribute__((__format__(__printf__, 2, 3)));
+
+// Appends a printf-like formatting of the arguments to 'dst'.
+void StringAppendV(std::string* dst, const char* format, va_list ap);
+
+}  // namespace android
+
+#endif

libutils/Android.mk

@@ -41,6 +41,7 @@ commonSources:= \
 	VectorImpl.cpp \
 	file.cpp \
 	misc.cpp \
+	stringprintf.cpp \
 
 host_commonCflags := -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS) -Werror
 

libutils/stringprintf.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://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 <utils/stringprintf.h>
+
+#include <stdio.h>
+
+void android::StringAppendV(std::string* dst, const char* format, va_list ap) {
+  // First try with a small fixed size buffer
+  char space[1024];
+
+  // It's possible for methods that use a va_list to invalidate
+  // the data in it upon use.  The fix is to make a copy
+  // of the structure before using it and use that copy instead.
+  va_list backup_ap;
+  va_copy(backup_ap, ap);
+  int result = vsnprintf(space, sizeof(space), format, backup_ap);
+  va_end(backup_ap);
+
+  if (result < static_cast<int>(sizeof(space))) {
+    if (result >= 0) {
+      // Normal case -- everything fit.
+      dst->append(space, result);
+      return;
+    }
+
+    if (result < 0) {
+      // Just an error.
+      return;
+    }
+  }
+
+  // Increase the buffer size to the size requested by vsnprintf,
+  // plus one for the closing \0.
+  int length = result+1;
+  char* buf = new char[length];
+
+  // Restore the va_list before we use it again
+  va_copy(backup_ap, ap);
+  result = vsnprintf(buf, length, format, backup_ap);
+  va_end(backup_ap);
+
+  if (result >= 0 && result < length) {
+    // It fit
+    dst->append(buf, result);
+  }
+  delete[] buf;
+}
+
+std::string android::StringPrintf(const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  std::string result;
+  StringAppendV(&result, fmt, ap);
+  va_end(ap);
+  return result;
+}
+
+void android::StringAppendF(std::string* dst, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  StringAppendV(dst, format, ap);
+  va_end(ap);
+}

libutils/tests/Android.mk

@@ -30,6 +30,7 @@ LOCAL_SRC_FILES := \
     Looper_test.cpp \
     LruCache_test.cpp \
     String8_test.cpp \
+    stringprintf_test.cpp \
     Unicode_test.cpp \
     Vector_test.cpp \
 

libutils/tests/stringprintf_test.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://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 <utils/stringprintf.h>
+
+#include <gtest/gtest.h>
+
+TEST(StringPrintfTest, HexSizeT) {
+  size_t size = 0x00107e59;
+  EXPECT_EQ("00107e59", android::StringPrintf("%08zx", size));
+  EXPECT_EQ("0x00107e59", android::StringPrintf("0x%08zx", size));
+}
+
+TEST(StringPrintfTest, StringAppendF) {
+  std::string s("a");
+  android::StringAppendF(&s, "b");
+  EXPECT_EQ("ab", s);
+}
+
+TEST(StringPrintfTest, Errno) {
+  errno = 123;
+  android::StringPrintf("hello %s", "world");
+  EXPECT_EQ(123, errno);
+}
+
+void TestN(size_t n) {
+  char* buf = new char[n + 1];
+  memset(buf, 'x', n);
+  buf[n] = '\0';
+  std::string s(android::StringPrintf("%s", buf));
+  EXPECT_EQ(buf, s);
+  delete[] buf;
+}
+
+TEST(StringPrintfTest, At1023) {
+  TestN(1023);
+}
+
+TEST(StringPrintfTest, At1024) {
+  TestN(1024);
+}
+
+TEST(StringPrintfTest, At1025) {
+  TestN(1025);
+}