Improve handling of input path and map backend

src/TileGenerator.cpp

@@ -372,35 +372,51 @@ std::set<std::string> TileGenerator::getSupportedBackends()
 
 void TileGenerator::openDb(const std::string &input_path)
 {
+	if (dir_exists(input_path.c_str())) {
+		// ok
+	} else if (file_exists(input_path.c_str())) {
+		throw std::runtime_error("Input path is a file, it should point to the world folder instead");
+	} else {
+		throw std::runtime_error("Input path does not exist");
+	}
+
 	std::string input = input_path;
 	if (input.back() != PATH_SEPARATOR)
 		input += PATH_SEPARATOR;
 
-	std::string backend = m_backend;
-	if (backend.empty()) {
 	std::ifstream ifs(input + "world.mt");
-		if(!ifs.good())
+
+	std::string backend = m_backend;
+	if (backend.empty() && !ifs.good()) {
 		throw std::runtime_error("Failed to open world.mt");
+	} else if (backend.empty()) {
 		backend = read_setting_default("backend", ifs, "sqlite3");
-		ifs.close();
 	}
 
-	if (backend == "sqlite3")
+	if (backend == "dummy") {
+		throw std::runtime_error("This map uses the dummy backend and contains no data");
+	} else if (backend == "sqlite3") {
 		m_db = new DBSQLite3(input);
 #if USE_POSTGRESQL
-	else if (backend == "postgresql")
+	} else if (backend == "postgresql") {
 		m_db = new DBPostgreSQL(input);
 #endif
 #if USE_LEVELDB
-	else if (backend == "leveldb")
+	} else if (backend == "leveldb") {
 		m_db = new DBLevelDB(input);
 #endif
 #if USE_REDIS
-	else if (backend == "redis")
+	} else if (backend == "redis") {
 		m_db = new DBRedis(input);
 #endif
-	else
+	} else {
 		throw std::runtime_error(std::string("Unknown map backend: ") + backend);
+	}
+
+	if (!read_setting_default("readonly_backend", ifs, "").empty()) {
+		std::cerr << "Warning: Map with readonly_backend is not supported. "
+			"The result may be incomplete." << std::endl;
+	}
 
 	// Determine how we're going to traverse the database (heuristic)
 	if (m_exhaustiveSearch == EXH_AUTO) {

src/mapper.cpp

@@ -15,7 +15,7 @@ static void usage()
 {
 	const std::pair<const char*, const char*> options[] = {
 		{"-i/--input", "<world_path>"},
-		{"-o/--output", "<output_image.png>"},
+		{"-o/--output", "<output_image>"},
 		{"--bgcolor", "<color>"},
 		{"--scalecolor", "<color>"},
 		{"--playercolor", "<color>"},
@@ -38,7 +38,7 @@ static void usage()
 		{"--dumpblock", "x,y,z"},
 	};
 	const char *top_text =
-		"minetestmapper -i <world_path> -o <output_image.png> [options]\n"
+		"minetestmapper -i <world_path> -o <output_image> [options]\n"
 		"Generate an overview image of a Luanti map.\n"
 		"\n"
 		"Options:\n";

src/util.cpp

@@ -1,11 +1,15 @@
 #include <stdexcept>
 #include <sstream>
+#include <sys/types.h>
+#include <sys/stat.h>
 
 #include "util.h"
 
 static std::string trim(const std::string &s)
 {
-	auto isspace = [] (char c) -> bool { return c == ' ' || c == '\t' || c == '\r' || c == '\n'; };
+	auto isspace = [] (char c) {
+		return c == ' ' || c == '\t' || c == '\r' || c == '\n';
+	};
 
 	size_t front = 0;
 	while (isspace(s[front]))
@@ -20,6 +24,7 @@ static std::string trim(const std::string &s)
 std::string read_setting(const std::string &name, std::istream &is)
 {
 	char linebuf[512];
+	is.seekg(0);
 	while (is.good()) {
 		is.getline(linebuf, sizeof(linebuf));
 
@@ -53,3 +58,16 @@ std::string read_setting_default(const std::string &name, std::istream &is,
 		return def;
 	}
 }
+
+bool file_exists(const char *path)
+{
+	struct stat s{};
+	// check for !dir to allow symlinks or such
+	return stat(path, &s) == 0 && (s.st_mode & S_IFDIR) != S_IFDIR;
+}
+
+bool dir_exists(const char *path)
+{
+	struct stat s{};
+	return stat(path, &s) == 0 && (s.st_mode & S_IFDIR) == S_IFDIR;
+}

src/util.h

@@ -19,3 +19,7 @@ std::string read_setting(const std::string &name, std::istream &is);
 
 std::string read_setting_default(const std::string &name, std::istream &is,
 	const std::string &def);
+
+bool file_exists(const char *path);
+
+bool dir_exists(const char *path);