Flesh out the logging implementation.

Add PLOG and ensure we have CHECK_STREQ and CHECK_STRNE to go with
the existing non-functional DCHECK_STREQ and DCHECK_STRNE.

This also gives us two different logging implementations, one for
the host that just uses std::cerr, and one for Android that uses
the Android log.

Also bring in the StringPrintf family.

Change-Id: I8e190c2c58f26b22ee76a2a87d447df6eb0fa73b
diff --git a/src/stringprintf.cc b/src/stringprintf.cc
new file mode 100644
index 0000000..4f59fc1
--- /dev/null
+++ b/src/stringprintf.cc
@@ -0,0 +1,64 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+// Author: enh@google.com (Elliott Hughes)
+
+#include "stringprintf.h"
+
+#include <stdio.h>
+
+void 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 < 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 StringPrintf(const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  std::string result;
+  StringAppendV(&result, fmt, ap);
+  va_end(ap);
+  return result;
+}
+
+void StringAppendF(std::string* dst, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  StringAppendV(dst, format, ap);
+  va_end(ap);
+}