Merge branch 'js/gitdir-at-unc-root'
[git/git.git] / sub-process.h
1 #ifndef SUBPROCESS_H
2 #define SUBPROCESS_H
3
4 #include "git-compat-util.h"
5 #include "hashmap.h"
6 #include "run-command.h"
7
8 /*
9 * The sub-process API makes it possible to run background sub-processes
10 * for the entire lifetime of a Git invocation. If Git needs to communicate
11 * with an external process multiple times, then this can reduces the process
12 * invocation overhead. Git and the sub-process communicate through stdin and
13 * stdout.
14 *
15 * The sub-processes are kept in a hashmap by command name and looked up
16 * via the subprocess_find_entry function. If an existing instance can not
17 * be found then a new process should be created and started. When the
18 * parent git command terminates, all sub-processes are also terminated.
19 *
20 * This API is based on the run-command API.
21 */
22
23 /* data structures */
24
25 /* Members should not be accessed directly. */
26 struct subprocess_entry {
27 struct hashmap_entry ent; /* must be the first member! */
28 const char *cmd;
29 struct child_process process;
30 };
31
32 struct subprocess_capability {
33 const char *name;
34
35 /*
36 * subprocess_handshake will "|=" this value to supported_capabilities
37 * if the server reports that it supports this capability.
38 */
39 unsigned int flag;
40 };
41
42 /* subprocess functions */
43
44 /* Function to test two subprocess hashmap entries for equality. */
45 int cmd2process_cmp(const void *unused_cmp_data,
46 const void *e1,
47 const void *e2,
48 const void *unused_keydata);
49
50 /*
51 * User-supplied function to initialize the sub-process. This is
52 * typically used to negotiate the interface version and capabilities.
53 */
54 typedef int(*subprocess_start_fn)(struct subprocess_entry *entry);
55
56 /* Start a subprocess and add it to the subprocess hashmap. */
57 int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,
58 subprocess_start_fn startfn);
59
60 /* Kill a subprocess and remove it from the subprocess hashmap. */
61 void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry);
62
63 /* Find a subprocess in the subprocess hashmap. */
64 struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const char *cmd);
65
66 /* subprocess helper functions */
67
68 /* Get the underlying `struct child_process` from a subprocess. */
69 static inline struct child_process *subprocess_get_child_process(
70 struct subprocess_entry *entry)
71 {
72 return &entry->process;
73 }
74
75 /*
76 * Perform the version and capability negotiation as described in the
77 * "Handshake" section of long-running-process-protocol.txt using the
78 * given requested versions and capabilities. The "versions" and "capabilities"
79 * parameters are arrays terminated by a 0 or blank struct.
80 *
81 * This function is typically called when a subprocess is started (as part of
82 * the "startfn" passed to subprocess_start).
83 */
84 int subprocess_handshake(struct subprocess_entry *entry,
85 const char *welcome_prefix,
86 int *versions,
87 int *chosen_version,
88 struct subprocess_capability *capabilities,
89 unsigned int *supported_capabilities);
90
91 /*
92 * Helper function that will read packets looking for "status=<foo>"
93 * key/value pairs and return the value from the last "status" packet
94 */
95
96 int subprocess_read_status(int fd, struct strbuf *status);
97
98 #endif