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git/run-command.h
Jeff King 96335bcf4d run-command: add pipe_command helper
We already have capture_command(), which captures the stdout
of a command in a way that avoids deadlocks. But sometimes
we need to do more I/O, like capturing stderr as well, or
sending data to stdin. It's easy to write code that
deadlocks racily in these situations depending on how fast
the command reads its input, or in which order it writes its
output.

Let's give callers an easy interface for doing this the
right way, similar to what capture_command() did for the
simple case.

The whole thing is backed by a generic poll() loop that can
feed an arbitrary number of buffers to descriptors, and fill
an arbitrary number of strbufs from other descriptors. This
seems like overkill, but the resulting code is actually a
bit cleaner than just handling the three descriptors
(because the output code for stdout/stderr is effectively
duplicated, so being able to loop is a benefit).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-06-17 17:03:56 -07:00

221 lines
7.4 KiB
C

#ifndef RUN_COMMAND_H
#define RUN_COMMAND_H
#ifndef NO_PTHREADS
#include <pthread.h>
#endif
#include "argv-array.h"
struct child_process {
const char **argv;
struct argv_array args;
struct argv_array env_array;
pid_t pid;
/*
* Using .in, .out, .err:
* - Specify 0 for no redirections (child inherits stdin, stdout,
* stderr from parent).
* - Specify -1 to have a pipe allocated as follows:
* .in: returns the writable pipe end; parent writes to it,
* the readable pipe end becomes child's stdin
* .out, .err: returns the readable pipe end; parent reads from
* it, the writable pipe end becomes child's stdout/stderr
* The caller of start_command() must close the returned FDs
* after it has completed reading from/writing to it!
* - Specify > 0 to set a channel to a particular FD as follows:
* .in: a readable FD, becomes child's stdin
* .out: a writable FD, becomes child's stdout/stderr
* .err: a writable FD, becomes child's stderr
* The specified FD is closed by start_command(), even in case
* of errors!
*/
int in;
int out;
int err;
const char *dir;
const char *const *env;
unsigned no_stdin:1;
unsigned no_stdout:1;
unsigned no_stderr:1;
unsigned git_cmd:1; /* if this is to be git sub-command */
unsigned silent_exec_failure:1;
unsigned stdout_to_stderr:1;
unsigned use_shell:1;
unsigned clean_on_exit:1;
};
#define CHILD_PROCESS_INIT { NULL, ARGV_ARRAY_INIT, ARGV_ARRAY_INIT }
void child_process_init(struct child_process *);
void child_process_clear(struct child_process *);
int start_command(struct child_process *);
int finish_command(struct child_process *);
int finish_command_in_signal(struct child_process *);
int run_command(struct child_process *);
/*
* Returns the path to the hook file, or NULL if the hook is missing
* or disabled. Note that this points to static storage that will be
* overwritten by further calls to find_hook and run_hook_*.
*/
extern const char *find_hook(const char *name);
LAST_ARG_MUST_BE_NULL
extern int run_hook_le(const char *const *env, const char *name, ...);
extern int run_hook_ve(const char *const *env, const char *name, va_list args);
#define RUN_COMMAND_NO_STDIN 1
#define RUN_GIT_CMD 2 /*If this is to be git sub-command */
#define RUN_COMMAND_STDOUT_TO_STDERR 4
#define RUN_SILENT_EXEC_FAILURE 8
#define RUN_USING_SHELL 16
#define RUN_CLEAN_ON_EXIT 32
int run_command_v_opt(const char **argv, int opt);
/*
* env (the environment) is to be formatted like environ: "VAR=VALUE".
* To unset an environment variable use just "VAR".
*/
int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env);
/**
* Execute the given command, sending "in" to its stdin, and capturing its
* stdout and stderr in the "out" and "err" strbufs. Any of the three may
* be NULL to skip processing.
*
* Returns -1 if starting the command fails or reading fails, and otherwise
* returns the exit code of the command. Any output collected in the
* buffers is kept even if the command returns a non-zero exit. The hint fields
* gives starting sizes for the strbuf allocations.
*
* The fields of "cmd" should be set up as they would for a normal run_command
* invocation. But note that there is no need to set the in, out, or err
* fields; pipe_command handles that automatically.
*/
int pipe_command(struct child_process *cmd,
const char *in, size_t in_len,
struct strbuf *out, size_t out_hint,
struct strbuf *err, size_t err_hint);
/**
* Convenience wrapper around pipe_command for the common case
* of capturing only stdout.
*/
static inline int capture_command(struct child_process *cmd,
struct strbuf *out,
size_t hint)
{
return pipe_command(cmd, NULL, 0, out, hint, NULL, 0);
}
/*
* The purpose of the following functions is to feed a pipe by running
* a function asynchronously and providing output that the caller reads.
*
* It is expected that no synchronization and mutual exclusion between
* the caller and the feed function is necessary so that the function
* can run in a thread without interfering with the caller.
*/
struct async {
/*
* proc reads from in; closes it before return
* proc writes to out; closes it before return
* returns 0 on success, non-zero on failure
*/
int (*proc)(int in, int out, void *data);
void *data;
int in; /* caller writes here and closes it */
int out; /* caller reads from here and closes it */
#ifdef NO_PTHREADS
pid_t pid;
#else
pthread_t tid;
int proc_in;
int proc_out;
#endif
int isolate_sigpipe;
};
int start_async(struct async *async);
int finish_async(struct async *async);
int in_async(void);
void NORETURN async_exit(int code);
/**
* This callback should initialize the child process and preload the
* error channel if desired. The preloading of is useful if you want to
* have a message printed directly before the output of the child process.
* pp_cb is the callback cookie as passed to run_processes_parallel.
* You can store a child process specific callback cookie in pp_task_cb.
*
* Even after returning 0 to indicate that there are no more processes,
* this function will be called again until there are no more running
* child processes.
*
* Return 1 if the next child is ready to run.
* Return 0 if there are currently no more tasks to be processed.
* To send a signal to other child processes for abortion,
* return the negative signal number.
*/
typedef int (*get_next_task_fn)(struct child_process *cp,
struct strbuf *out,
void *pp_cb,
void **pp_task_cb);
/**
* This callback is called whenever there are problems starting
* a new process.
*
* You must not write to stdout or stderr in this function. Add your
* message to the strbuf out instead, which will be printed without
* messing up the output of the other parallel processes.
*
* pp_cb is the callback cookie as passed into run_processes_parallel,
* pp_task_cb is the callback cookie as passed into get_next_task_fn.
*
* Return 0 to continue the parallel processing. To abort return non zero.
* To send a signal to other child processes for abortion, return
* the negative signal number.
*/
typedef int (*start_failure_fn)(struct strbuf *out,
void *pp_cb,
void *pp_task_cb);
/**
* This callback is called on every child process that finished processing.
*
* You must not write to stdout or stderr in this function. Add your
* message to the strbuf out instead, which will be printed without
* messing up the output of the other parallel processes.
*
* pp_cb is the callback cookie as passed into run_processes_parallel,
* pp_task_cb is the callback cookie as passed into get_next_task_fn.
*
* Return 0 to continue the parallel processing. To abort return non zero.
* To send a signal to other child processes for abortion, return
* the negative signal number.
*/
typedef int (*task_finished_fn)(int result,
struct strbuf *out,
void *pp_cb,
void *pp_task_cb);
/**
* Runs up to n processes at the same time. Whenever a process can be
* started, the callback get_next_task_fn is called to obtain the data
* required to start another child process.
*
* The children started via this function run in parallel. Their output
* (both stdout and stderr) is routed to stderr in a manner that output
* from different tasks does not interleave.
*
* start_failure_fn and task_finished_fn can be NULL to omit any
* special handling.
*/
int run_processes_parallel(int n,
get_next_task_fn,
start_failure_fn,
task_finished_fn,
void *pp_cb);
#endif