util: provide readFromFileToStr primitive, which doesn't throw except…

…ions

config.cc

@@ -34,6 +34,7 @@
 
 #include <fstream>
 #include <list>
+#include <sstream>
 #include <string>
 #include <vector>
 
@@ -321,13 +322,15 @@ static void flushLog() {
 bool parseFile(nsjconf_t* nsjconf, const char* file) {
 	LOG_D("Parsing configuration from '%s'", file);
 
-	std::ifstream ifs(file);
-	if (!ifs.is_open()) {
-		PLOG_W("Couldn't open config file '%s'", file);
+	std::string conf;
+	if (!util::readFromFileToStr(file, &conf)) {
+		LOG_E("Couldn't read config file '%s'", file);
+		return false;
+	}
+	if (conf.size() == 0) {
+		LOG_E("Config file '%s' is empty", file);
 		return false;
 	}
-
-	std::string conf((std::istreambuf_iterator<char>(ifs)), (std::istreambuf_iterator<char>()));
 
 	/* Use static so we can get c_str() pointers, and copy them into the nsjconf struct */
 	static nsjail::NsJailConfig json_nsc;

util.cc

@@ -40,6 +40,7 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <fstream>
 #include <iomanip>
 #include <sstream>
 #include <string>
@@ -89,6 +90,34 @@ bool writeToFd(int fd, const void* buf, size_t len) {
 	return true;
 }
 
+bool readFromFileToStr(const char* fname, std::string* str) {
+	std::fstream fs(fname, std::ios::in | std::ios::binary);
+	if (!fs.is_open()) {
+		PLOG_W("Couldn't open file '%s'", fname);
+		return false;
+	}
+
+	str->clear();
+
+	while (fs) {
+		char buf[4096];
+		fs.read(buf, sizeof(buf));
+		std::streamsize sz = fs.gcount();
+		if (sz > 0) {
+			str->append(buf, sz);
+		}
+		if (fs.eof()) {
+			return true;
+		}
+		if (fs.bad() || fs.fail()) {
+			PLOG_W("Reading from '%s' failed", fname);
+			return false;
+		}
+	}
+
+	return true;
+}
+
 bool writeBufToFile(
     const char* filename, const void* buf, size_t len, int open_flags, bool log_errors) {
 	int fd;

util.h

@@ -54,6 +54,7 @@ namespace util {
 
 ssize_t readFromFd(int fd, void* buf, size_t len);
 ssize_t readFromFile(const char* fname, void* buf, size_t len);
+bool readFromFileToStr(const char* fname, std::string* str);
 bool writeToFd(int fd, const void* buf, size_t len);
 bool writeBufToFile(
     const char* filename, const void* buf, size_t len, int open_flags, bool log_errors = true);