988e7f5e95
We use the lockfile subsystem to write lockfiles for "tables.list". As with the tempfile subsystem, the lockfile subsystem also hooks into our infrastructure to prune stale locks via atexit(3p) or signal handlers. Furthermore, the lockfile subsystem also handles locking timeouts, which do add quite a bit of logic. Having to reimplement that in the context of Git wouldn't make a whole lot of sense, and it is quite likely that downstream users of the reftable library may have a better idea for how exactly to implement timeouts. So again, provide a thin wrapper for the lockfile subsystem instead such that the compatibility shim is fully self-contained. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
102 lines
3.2 KiB
C
102 lines
3.2 KiB
C
/*
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Copyright 2020 Google LLC
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file or at
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https://developers.google.com/open-source/licenses/bsd
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*/
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#ifndef SYSTEM_H
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#define SYSTEM_H
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/* This header glues the reftable library to the rest of Git */
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#include "git-compat-util.h"
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/*
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* An implementation-specific temporary file. By making this specific to the
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* implementation it becomes possible to tie temporary files into any kind of
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* signal or atexit handlers for cleanup on abnormal situations.
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*/
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struct reftable_tmpfile {
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const char *path;
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int fd;
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void *priv;
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};
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#define REFTABLE_TMPFILE_INIT ((struct reftable_tmpfile) { .fd = -1, })
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/*
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* Create a temporary file from a pattern similar to how mkstemp(3p) would.
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* The `pattern` shall not be modified. On success, the structure at `out` has
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* been initialized such that it is ready for use. Returns 0 on success, a
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* reftable error code on error.
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*/
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int tmpfile_from_pattern(struct reftable_tmpfile *out, const char *pattern);
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/*
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* Close the temporary file's file descriptor without removing the file itself.
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* This is a no-op in case the file has already been closed beforehand. Returns
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* 0 on success, a reftable error code on error.
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*/
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int tmpfile_close(struct reftable_tmpfile *t);
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/*
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* Close the temporary file and delete it. This is a no-op in case the file has
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* already been deleted or renamed beforehand. Returns 0 on success, a reftable
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* error code on error.
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*/
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int tmpfile_delete(struct reftable_tmpfile *t);
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/*
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* Rename the temporary file to the provided path. The temporary file must be
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* active. Return 0 on success, a reftable error code on error. Deactivates the
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* temporary file.
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*/
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int tmpfile_rename(struct reftable_tmpfile *t, const char *path);
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/*
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* An implementation-specific file lock. Same as with `reftable_tmpfile`,
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* making this specific to the implementation makes it possible to tie this
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* into signal or atexit handlers such that we know to clean up stale locks on
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* abnormal exits.
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*/
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struct reftable_flock {
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const char *path;
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int fd;
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void *priv;
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};
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#define REFTABLE_FLOCK_INIT ((struct reftable_flock){ .fd = -1, })
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/*
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* Acquire the lock for the given target path by exclusively creating a file
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* with ".lock" appended to it. If that lock exists, we wait up to `timeout_ms`
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* to acquire the lock. If `timeout_ms` is 0 we don't wait, if it is negative
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* we block indefinitely.
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*
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* Retrun 0 on success, a reftable error code on error.
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*/
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int flock_acquire(struct reftable_flock *l, const char *target_path,
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long timeout_ms);
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/*
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* Close the lockfile's file descriptor without removing the lock itself. This
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* is a no-op in case the lockfile has already been closed beforehand. Returns
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* 0 on success, a reftable error code on error.
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*/
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int flock_close(struct reftable_flock *l);
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/*
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* Release the lock by unlinking the lockfile. This is a no-op in case the
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* lockfile has already been released or committed beforehand. Returns 0 on
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* success, a reftable error code on error.
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*/
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int flock_release(struct reftable_flock *l);
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/*
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* Commit the lock by renaming the lockfile into place. Returns 0 on success, a
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* reftable error code on error.
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*/
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int flock_commit(struct reftable_flock *l);
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#endif
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