[FYI/PATCH] vcs-svn: give control over temporary file names

[Jonathan Nieder <jrnieder@gmail.com>]

Allow users of the line_buffer library to specify what directory and
filename to use for temporary files.  For example:

	struct line_buffer tmp = LINE_BUFFER_INIT;
	if (buffer_tmpfile_init(&tmp, ".git", "svnfe_blob.XXXXXX"))
		die_errno("opening temporary file");
	...
	if (buffer_deinit(&tmp))
		die_errno("removing temporary file");

On Windows, something like this is needed if users without write
permission to the root directory are to be able to use temporary
files.

Unlike the implementation using tmpfile, this would not take
care of automatically removing the temporary file on exit.  The
user is responsible for now for installing appropriate signal and
atexit handlers to take care of that.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
I have an odd feeling this will be necessary at some point but I'm not
sure if it's a good idea or not.  Although tmpfile(3) is a limited
interface, it's pretty much exactly what we want.

See [1] for tmpfile on Windows.

This is just to get the idea out there.  I don't think this patch's
moment has come (though I'd be interested in your thoughts either
way).

[1] http://msdn.microsoft.com/en-us/library/x8x7sakw.aspx

 vcs-svn/line_buffer.c |   35 ++++++++++++++++++++++++++++++-----
 vcs-svn/line_buffer.h |    6 ++++--
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/vcs-svn/line_buffer.c b/vcs-svn/line_buffer.c
index aedf105..4131e08 100644
--- a/vcs-svn/line_buffer.c
+++ b/vcs-svn/line_buffer.c
@@ -3,7 +3,7 @@
  * See LICENSE for details.
  */
 
-#include "git-compat-util.h"
+#include "cache.h"
 #include "line_buffer.h"
 #include "strbuf.h"
 
@@ -25,12 +25,33 @@ int buffer_fdinit(struct line_buffer *buf, int fd)
 	return 0;
 }
 
-int buffer_tmpfile_init(struct line_buffer *buf)
+int buffer_tmpfile_init(struct line_buffer *buf,
+			const char *dirname, const char *pattern)
 {
-	buf->infile = tmpfile();
-	if (!buf->infile)
-		return -1;
+	int fd, saved_errno;
+	int mode = 0444;	/* just remove write permission. */
+	strbuf_addstr(&buf->temp_filename, dirname);
+	strbuf_addch(&buf->temp_filename, '/');
+	strbuf_addstr(&buf->temp_filename, pattern);
+
+	fd = git_mkstemp_mode(buf->temp_filename.buf, mode);
+	if (fd < 0) {
+		saved_errno = errno;
+		goto fail_mktemp;
+	}
+	buf->infile = fdopen(fd, "r+");
+	if (!buf->infile) {
+		saved_errno = errno;
+		goto fail_fdopen;
+	}
 	return 0;
+
+fail_fdopen:
+	close(fd);
+fail_mktemp:
+	strbuf_reset(&buf->temp_filename);
+	errno = saved_errno;
+	return -1;
 }
 
 int buffer_deinit(struct line_buffer *buf)
@@ -40,6 +61,9 @@ int buffer_deinit(struct line_buffer *buf)
 		return ferror(buf->infile);
 	err = ferror(buf->infile);
 	err |= fclose(buf->infile);
+	if (buf->temp_filename.len)
+		err |= unlink_or_warn(buf->temp_filename.buf);
+	strbuf_reset(&buf->temp_filename);
 	return err;
 }
 
@@ -129,4 +153,5 @@ void buffer_skip_bytes(struct line_buffer *buf, uint32_t len)
 void buffer_reset(struct line_buffer *buf)
 {
 	strbuf_release(&buf->blob_buffer);
+	strbuf_release(&buf->temp_filename);
 }
diff --git a/vcs-svn/line_buffer.h b/vcs-svn/line_buffer.h
index 96ce966..bd1a621 100644
--- a/vcs-svn/line_buffer.h
+++ b/vcs-svn/line_buffer.h
@@ -9,15 +9,17 @@ struct line_buffer {
 	char line_buffer[LINE_BUFFER_LEN];
 	struct strbuf blob_buffer;
 	FILE *infile;
+	struct strbuf temp_filename;
 };
-#define LINE_BUFFER_INIT {"", STRBUF_INIT, NULL}
+#define LINE_BUFFER_INIT {"", STRBUF_INIT, NULL, STRBUF_INIT}
 
 int buffer_init(struct line_buffer *buf, const char *filename);
 int buffer_fdinit(struct line_buffer *buf, int fd);
 int buffer_deinit(struct line_buffer *buf);
 void buffer_reset(struct line_buffer *buf);
 
-int buffer_tmpfile_init(struct line_buffer *buf);
+int buffer_tmpfile_init(struct line_buffer *buf,
+		const char *directory, const char *pattern);
 FILE *buffer_tmpfile_rewind(struct line_buffer *buf);	/* prepare to write. */
 long buffer_tmpfile_prepare_to_read(struct line_buffer *buf);
 
-- 
1.7.4.rc2