tprintf: Add C++ stream for log messages

Signed-off-by: Stefan Weil <sw@weilnetz.de>

src/ccutil/tesserrstream.h

@@ -0,0 +1,67 @@
+// File:        tesserrstream.h
+// Description: C++ stream which enhances tprintf
+// Author:      Stefan Weil
+//
+// (C) Copyright 2024
+// 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 TESSERACT_CCUTIL_TESSERRSTREAM_H
+#define TESSERACT_CCUTIL_TESSERRSTREAM_H
+
+#include "tprintf.h"
+
+#include <ostream> // for std::ostream
+
+namespace tesseract {
+
+class TessStreamBuf : public std::streambuf {
+public:
+  TessStreamBuf() = default;
+
+protected:
+  virtual int_type overflow(int_type c) override {
+    if (c != EOF) {
+      if (debugfp == nullptr) {
+        debugfp = get_debugfp();
+      }
+      if (fputc(c, debugfp) == EOF) {
+        return EOF;
+      }
+    }
+    return c;
+  }
+
+  virtual std::streamsize xsputn(const char* s, std::streamsize n) override {
+    if (debugfp == nullptr) {
+      debugfp = get_debugfp();
+    }
+    return fwrite(s, 1, n, debugfp);
+  }
+
+private:
+  FILE *debugfp = nullptr;
+};
+
+class TessErrStream : public std::ostream {
+private:
+  TessStreamBuf buf;
+
+public:
+  TessErrStream() : std::ostream(nullptr), buf() {
+    rdbuf(&buf);
+  }
+};
+
+extern TessErrStream tesserr;
+
+} // namespace tesseract
+
+#endif // TESSERACT_CCUTIL_TESSERRSTREAM_H

src/ccutil/tprintf.cpp

@@ -21,6 +21,7 @@
 #  include "config_auto.h"
 #endif
 
+#include "tesserrstream.h"
 #include "tprintf.h"
 
 #include "params.h"
@@ -36,7 +37,7 @@ INT_VAR(log_level, INT_MAX, "Logging level");
 static STRING_VAR(debug_file, "", "File to send tprintf output to");
 
 // File for debug output.
-static FILE *debugfp;
+FILE *debugfp;
 
 // Set output for log messages.
 // The output is written to stderr if debug_file is empty.
@@ -49,7 +50,7 @@ static FILE *debugfp;
 // tprintf("write to /tmp/log\n");
 // debug_file = "";
 // tprintf("write to stderr\n");
-static void set_debugfp() {
+FILE *get_debugfp() {
   if (debug_file.empty()) {
     // Write to stderr.
     if (debugfp != stderr && debugfp != nullptr) {
@@ -66,15 +67,18 @@ static void set_debugfp() {
 #endif
     debugfp = fopen(debug_file.c_str(), "wb");
   }
+  return debugfp;
 }
 
 // Trace printf.
 void tprintf(const char *format, ...) {
-  set_debugfp();
+  FILE *f = get_debugfp();
   va_list args;           // variable args
   va_start(args, format); // variable list
-  vfprintf(debugfp, format, args);
+  vfprintf(f, format, args);
   va_end(args);
 }
 
+TessErrStream tesserr;
+
 } // namespace tesseract

src/ccutil/tprintf.h

@@ -36,6 +36,9 @@ extern TESS_API void tprintf( // Trace printf
     const char *format, ...)  // Message
     __attribute__((format(printf, 1, 2)));
 
+// Get file for debug output.
+FILE *get_debugfp();
+
 } // namespace tesseract
 
 #undef __attribute__