It can sometimes be useful to write information temporarily to file,
to read back later. These functions allow you to do so.
The dump file importer would use this to save a postimage from delta
application until the length is known and fast-import is ready to read
it.
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
---
vcs-svn/line_buffer.c | 24 ++++++++++++++++++++++++
vcs-svn/line_buffer.h | 7 ++++++-
vcs-svn/line_buffer.txt | 22 ++++++++++++++++++++++
3 files changed, 52 insertions(+), 1 deletions(-)
diff --git a/vcs-svn/line_buffer.c b/vcs-svn/line_buffer.c
index c54031b..f583623 100644
--- a/vcs-svn/line_buffer.c
+++ b/vcs-svn/line_buffer.c
@@ -42,6 +42,30 @@ int buffer_at_eof(struct line_buffer *buf)
return 0;
}
+int buffer_tmpfile_init(struct line_buffer *buf)
+{
+ buf->infile = tmpfile();
+ if (!buf->infile)
+ return error("cannot open temporary file: %s", strerror(errno));
+ return 0;
+}
+
+FILE *buffer_tmpfile_rewind(struct line_buffer *buf)
+{
+ rewind(buf->infile);
+ return buf->infile;
+}
+
+long buffer_tmpfile_prepare_to_read(struct line_buffer *buf)
+{
+ long pos = ftell(buf->infile);
+ if (pos < 0)
+ return error("ftell error: %s", strerror(errno));
+ if (fseek(buf->infile, 0, SEEK_SET))
+ return error("seek error: %s", strerror(errno));
+ return pos;
+}
+
int buffer_read_char(struct line_buffer *buf)
{
return fgetc(buf->infile);
diff --git a/vcs-svn/line_buffer.h b/vcs-svn/line_buffer.h
index 2375ee1..1db7434 100644
--- a/vcs-svn/line_buffer.h
+++ b/vcs-svn/line_buffer.h
@@ -16,12 +16,17 @@ int buffer_init(struct line_buffer *buf, const char *filename);
int buffer_deinit(struct line_buffer *buf);
int buffer_ferror(struct line_buffer *buf);
int buffer_at_eof(struct line_buffer *buf);
+void buffer_reset(struct line_buffer *buf);
+
+int buffer_tmpfile_init(struct line_buffer *buf);
+FILE *buffer_tmpfile_rewind(struct line_buffer *buf); /* prepare to write. */
+long buffer_tmpfile_prepare_to_read(struct line_buffer *buf);
+
char *buffer_read_line(struct line_buffer *buf);
char *buffer_read_string(struct line_buffer *buf, uint32_t len);
int buffer_read_char(struct line_buffer *buf);
void buffer_read_binary(struct strbuf *sb, uint32_t len, struct line_buffer *f);
void buffer_copy_bytes(struct line_buffer *buf, off_t len);
off_t buffer_skip_bytes(struct line_buffer *buf, off_t len);
-void buffer_reset(struct line_buffer *buf);
#endif
diff --git a/vcs-svn/line_buffer.txt b/vcs-svn/line_buffer.txt
index d06db24..344efc3 100644
--- a/vcs-svn/line_buffer.txt
+++ b/vcs-svn/line_buffer.txt
@@ -24,6 +24,28 @@ The calling program:
When finished, the caller can use `buffer_reset` to deallocate
resources.
+Using temporary files
+---------------------
+
+Sometimes a file is just a convenient place to stash data for
+later. A program
+
+ - initializes a `struct line_buffer` to LINE_BUFFER_INIT
+ - allocates a temporary file with `buffer_tmpfile_init`
+ - acquires an output handle by calling `buffer_tmpfile_rewind`
+ - uses standard I/O functions like `fprintf` and `fwrite` to fill
+ the temporary file
+ - declares writing is over with `buffer_tmpfile_prepare_to_read`
+ - can re-read what was written with `buffer_read_line`,
+ `buffer_read_string`, and so on
+ - can reuse the temporary file by calling `buffer_tmpfile_rewind`
+ again
+ - cleans up the temporary file with `buffer_deinit`, perhaps to
+ reuse the line_buffer for some other file.
+
+When finished, the program should use `buffer_reset` to deallocate
+resources.
+
Functions
---------
--
1.7.2.3
--
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