diff options
author | Erik Faye-Lund <kusmabite@gmail.com> | 2010-02-05 23:57:38 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2010-02-06 07:57:22 +0300 |
commit | ae6a5609c025d9ac79e54a3a052704e25d885314 (patch) | |
tree | c74d50beebc5c7bfe2f5ca9e335c45c534243af7 /Documentation/technical | |
parent | 4f41b611481bad08319966f7787fc7c4c7bfaa52 (diff) |
run-command: support custom fd-set in async
This patch adds the possibility to supply a set of non-0 file
descriptors for async process communication instead of the
default-created pipe.
Additionally, we now support bi-directional communiction with the
async procedure, by giving the async function both read and write
file descriptors.
To retain compatiblity and similar "API feel" with start_command,
we require start_async callers to set .out = -1 to get a readable
file descriptor. If either of .in or .out is 0, we supply no file
descriptor to the async process.
[sp: Note: Erik started this patch, and a huge bulk of it is
his work. All bugs were introduced later by Shawn.]
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/technical')
-rw-r--r-- | Documentation/technical/api-run-command.txt | 50 |
1 files changed, 40 insertions, 10 deletions
diff --git a/Documentation/technical/api-run-command.txt b/Documentation/technical/api-run-command.txt index a1280dd837..8994859c81 100644 --- a/Documentation/technical/api-run-command.txt +++ b/Documentation/technical/api-run-command.txt @@ -64,8 +64,8 @@ The functions above do the following: `start_async`:: Run a function asynchronously. Takes a pointer to a `struct - async` that specifies the details and returns a pipe FD - from which the caller reads. See below for details. + async` that specifies the details and returns a set of pipe FDs + for communication with the function. See below for details. `finish_async`:: @@ -180,17 +180,47 @@ The caller: struct async variable; 2. initializes .proc and .data; 3. calls start_async(); -4. processes the data by reading from the fd in .out; -5. closes .out; +4. processes communicates with proc through .in and .out; +5. closes .in and .out; 6. calls finish_async(). +The members .in, .out are used to provide a set of fd's for +communication between the caller and the callee as follows: + +. Specify 0 to have no file descriptor passed. The callee will + receive -1 in the corresponding argument. + +. Specify < 0 to have a pipe allocated; start_async() replaces + with the pipe FD in the following way: + + .in: Returns the writable pipe end into which the caller + writes; the readable end of the pipe becomes the function's + in argument. + + .out: Returns the readable pipe end from which the caller + reads; the writable end of the pipe becomes the function's + out argument. + + The caller of start_async() must close the returned FDs after it + has completed reading from/writing from them. + +. Specify a file descriptor > 0 to be used by the function: + + .in: The FD must be readable; it becomes the function's in. + .out: The FD must be writable; it becomes the function's out. + + The specified FD is closed by start_async(), even if it fails to + run the function. + The function pointer in .proc has the following signature: - int proc(int fd, void *data); + int proc(int in, int out, void *data); -. fd specifies a writable file descriptor to which the function must - write the data that it produces. The function *must* close this - descriptor before it returns. +. in, out specifies a set of file descriptors to which the function + must read/write the data that it needs/produces. The function + *must* close these descriptors before it returns. A descriptor + may be -1 if the caller did not configure a descriptor for that + direction. . data is the value that the caller has specified in the .data member of struct async. @@ -205,8 +235,8 @@ because this facility is implemented by a pipe to a forked process on UNIX, but by a thread in the same address space on Windows: . It cannot change the program's state (global variables, environment, - etc.) in a way that the caller notices; in other words, .out is the - only communication channel to the caller. + etc.) in a way that the caller notices; in other words, .in and .out + are the only communication channels to the caller. . It must not change the program's state that the caller of the facility also uses. |