Add an exclusive create flag to IO::File

This flag is important in creating temp files, as it allows atomic
creation of a new file.  It also completes the set of create modes
available on Win32.

diff --git a/source/io/file.cpp b/source/io/file.cpp
index 862b607c9d00e08db7ce4e10bc2843ba1bd473ba..208371df8bff5b33bedb5ddbd72847dfc6fcf7d2 100644 (file)
--- a/source/io/file.cpp
+++ b/source/io/file.cpp
@@ -17,7 +17,9 @@ File::File(const string &fn, Mode m, CreateMode cm)
 {
        if(!(m&M_RDWR))
                throw invalid_argument("File::File mode");
-       if(cm&~(C_CREATE|C_TRUNCATE))
+       if(cm&~(C_CREATE|C_TRUNCATE|C_EXCLUSIVE))
+               throw invalid_argument("File::File create");
+       if((cm&C_EXCLUSIVE) && (!(cm&C_CREATE) || (cm&C_TRUNCATE)))
                throw invalid_argument("File::File create");
 
        mode = m;
@@ -38,6 +40,7 @@ File::File(const string &fn, Mode m, CreateMode cm)
                case C_CREATE:   create_flags = OPEN_ALWAYS; break;
                case C_TRUNCATE: create_flags = TRUNCATE_EXISTING; break;
                case C_CREATE+C_TRUNCATE: create_flags = CREATE_ALWAYS; break;
+               case C_CREATE+C_EXCLUSIVE: create_flags = CREATE_NEW; break;
                }
        }
 
@@ -47,6 +50,8 @@ File::File(const string &fn, Mode m, CreateMode cm)
                int err = GetLastError();
                if(err==ERROR_FILE_NOT_FOUND)
                        throw file_not_found(fn);
+               else if(err==ERROR_FILE_EXISTS)
+                       throw file_already_exists(fn);
                else
                        throw system_error(format("CreateFile(%s)", fn), err);
        }
@@ -66,6 +71,8 @@ File::File(const string &fn, Mode m, CreateMode cm)
                        flags |= O_CREAT;
                if(cm&C_TRUNCATE)
                        flags |= O_TRUNC;
+               if(cm&C_EXCLUSIVE)
+                       flags |= O_EXCL;
        }
        if(mode&M_APPEND)
                flags |= O_APPEND;
@@ -78,6 +85,8 @@ File::File(const string &fn, Mode m, CreateMode cm)
                int err = errno;
                if(err==ENOENT)
                        throw file_not_found(fn);
+               else if(err==EEXIST)
+                       throw file_already_exists(fn);
                else
                        throw system_error(format("open(%s)", fn), err);
        }

diff --git a/source/io/file.h b/source/io/file.h
index 430571f909d872854e64d11ac43917442541f121..4f8e5ddf8612b559f82ce5bfc7c2623ba5860cc9 100644 (file)
--- a/source/io/file.h
+++ b/source/io/file.h
@@ -17,6 +17,12 @@ public:
        file_not_found(const std::string &fn): std::runtime_error(fn) { }
 };
 
+class file_already_exists: public std::runtime_error
+{
+public:
+       file_already_exists(const std::string &fn): std::runtime_error(fn) { }
+};
+
 
 /**
 A class for reading and writing files.
@@ -30,7 +36,8 @@ public:
        {
                C_NONE = 0,
                C_CREATE = 1,
-               C_TRUNCATE = 2
+               C_TRUNCATE = 2,
+               C_EXCLUSIVE = 4
        };
 
 private: