From b1c9b798a6dd391aeaea31663a65164815701244 Mon Sep 17 00:00:00 2001 From: Jonathan Nieder Date: Sun, 2 Jan 2011 21:10:59 -0600 Subject: [PATCH] vcs-svn: teach line_buffer about temporary files It can sometimes be useful to write information temporarily to file, to read back later. These functions allow a program to use the line_buffer facilities when doing so. It works like this: 1. find a unique filename with buffer_tmpfile_init. 2. rewind with buffer_tmpfile_rewind. This returns a stdio handle for writing. 3. when finished writing, declare so with buffer_tmpfile_prepare_to_read. The return value indicates how many bytes were written. 4. read whatever portion of the file is needed. 5. if finished, remove the temporary file with buffer_deinit. otherwise, go back to step 2, The svn support would use this to buffer the postimage from delta application until the length is known and fast-import can receive the resulting blob. Based-on-patch-by: David Barr Signed-off-by: Jonathan Nieder --- vcs-svn/line_buffer.c | 24 ++++++++++++++++++++++++ vcs-svn/line_buffer.h | 7 ++++++- vcs-svn/line_buffer.txt | 22 ++++++++++++++++++++++ 3 files changed, 52 insertions(+), 1 deletion(-) diff --git a/vcs-svn/line_buffer.c b/vcs-svn/line_buffer.c index e29a81a53..aedf105b7 100644 --- a/vcs-svn/line_buffer.c +++ b/vcs-svn/line_buffer.c @@ -25,6 +25,14 @@ int buffer_fdinit(struct line_buffer *buf, int fd) return 0; } +int buffer_tmpfile_init(struct line_buffer *buf) +{ + buf->infile = tmpfile(); + if (!buf->infile) + return -1; + return 0; +} + int buffer_deinit(struct line_buffer *buf) { int err; @@ -35,6 +43,22 @@ int buffer_deinit(struct line_buffer *buf) return err; } +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 630d83c31..96ce966a2 100644 --- a/vcs-svn/line_buffer.h +++ b/vcs-svn/line_buffer.h @@ -15,12 +15,17 @@ struct line_buffer { 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); +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 line_buffer *buf, struct strbuf *sb, uint32_t len); void buffer_copy_bytes(struct line_buffer *buf, uint32_t len); void buffer_skip_bytes(struct line_buffer *buf, uint32_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 4e8fb719c..e89cc41d5 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 +--------------------- + +Temporary files provide a place to store data that should not outlive +the calling program. A program + + - initializes a `struct line_buffer` to LINE_BUFFER_INIT + - requests 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 + - removes the temporary file with `buffer_deinit`, perhaps to + reuse the line_buffer for some other file. + +When finished, the calling program can use `buffer_reset` to deallocate +resources. + Functions --------- -- 2.30.2